emacs/doc/misc/modus-themes.org

#+title: Modus themes for GNU Emacs
#+author: Protesilaos Stavrou
#+email: info@protesilaos.com
#+language: en
#+options: ':t toc:nil author:t email:t num:t
#+startup: content

#+macro: stable-version 1.5.0
#+macro: release-date 2021-07-15
#+macro: development-version 1.6.0-dev
#+macro: file @@texinfo:@file{@@$1@@texinfo:}@@
#+macro: space @@texinfo:@: @@
#+macro: kbd @@texinfo:@kbd{@@$1@@texinfo:}@@

#+texinfo_filename: modus-themes.info
#+texinfo_dir_category: Emacs misc features
#+texinfo_dir_title: Modus Themes: (modus-themes)
#+texinfo_dir_desc: Highly accessible themes (WCAG AAA)
#+texinfo_header: @set MAINTAINERSITE @uref{https://protesilaos.com,maintainer webpage}
#+texinfo_header: @set MAINTAINER Protesilaos Stavrou
#+texinfo_header: @set MAINTAINEREMAIL @email{info@protesilaos.com}
#+texinfo_header: @set MAINTAINERCONTACT @uref{mailto:info@protesilaos.com,contact the maintainer}

#+texinfo: @insertcopying

This manual, written by Protesilaos Stavrou, describes the customization
options for the ~modus-operandi~ and ~modus-vivendi~ themes, and provides
every other piece of information pertinent to them.

The documentation furnished herein corresponds to stable version
{{{stable-version}}}, released on {{{release-date}}}.  Any reference to a newer
feature which does not yet form part of the latest tagged commit, is
explicitly marked as such.

Current development target is {{{development-version}}}.

#+toc: headlines 8 insert TOC here, with eight headline levels

* COPYING
:properties:
:copying: t
:custom_id: h:b14c3fcb-13dd-4144-9d92-2c58b3ed16d3
:end:

Copyright (C) 2020-2021  Free Software Foundation, Inc.

#+begin_quote
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and
with the Back-Cover Texts as in (a) below.  A copy of the license is
included in the section entitled “GNU Free Documentation License.”

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and
modify this GNU manual.”
#+end_quote

* Overview
:properties:
:custom_id: h:f0f3dbcb-602d-40cf-b918-8f929c441baf
:end:

The Modus themes are designed for accessible readability.  They conform
with the highest standard for color contrast between any given
combination of background and foreground values.  This corresponds to
the WCAG AAA standard, which specifies a minimum rate of distance in
relative luminance of 7:1.

Modus Operandi (~modus-operandi~) is a light theme, while Modus Vivendi
(~modus-vivendi~) is dark.  Each theme's color palette is designed to meet
the needs of the numerous interfaces that are possible in the Emacs
computing environment.

The overarching objective of this project is to always offer accessible
color combinations.  There shall never be a compromise on this
principle.  If there arises an inescapable trade-off between readability
and stylistic considerations, we will always opt for the former.

To ensure that users have a consistently accessible experience, the
themes strive to achieve as close to full face coverage as possible
([[#h:a9c8f29d-7f72-4b54-b74b-ddefe15d6a19][Face coverage]]).

Furthermore, the themes are designed to empower users with red-green
color deficiency (deuteranopia).  This is achieved through customization
options which have the effect of replacing all relevant instances of
green with a variant of blue ([[#h:bf1c82f2-46c7-4eb2-ad00-dd11fdd8b53f][Customization Options]]).

Starting with version 0.12.0 and onwards, the themes are built into GNU
Emacs.

** How do the themes look like
:properties:
:custom_id: h:69b92089-069c-4ba1-9d94-cc3415fc4f87
:end:
#+cindex: Screenshots

Check the web page with [[https://protesilaos.com/modus-themes-pictures/][the screen shots]].  There are lots of scenarios
on display that draw attention to details and important aspects in the
design of the themes.  They also showcase the numerous customization
options.

[[#h:bf1c82f2-46c7-4eb2-ad00-dd11fdd8b53f][Customization options]].

** Learn about the latest changes
:properties:
:custom_id: h:2cc37c36-6c1a-48b2-a010-1050b270ee18
:end:
#+cindex: Changelog

Please refer to the [[https://protesilaos.com/modus-themes-changelog][web page with the change log]].  It is comprehensive
and covers everything that goes into every tagged release of the themes.

* Installation
:properties:
:custom_id: h:1af85373-7f81-4c35-af25-afcef490c111
:end:

The Modus themes are distributed with Emacs starting with version 28.1.
On older versions of Emacs, they can be installed using Emacs' package
manager or manually from their code repository.  There also exist
packages for distributions of GNU/Linux.

** Install manually from source
:properties:
:custom_id: h:da3414b7-1426-46b8-8e76-47b845b76fd0
:end:

In the following example, we are assuming that your Emacs files are
stored in =~/.emacs.d= and that you want to place the Modus themes in
=~/.emacs.d/modus-themes=.

1. Get the source and store it in the desired path by running the
   following in the command line shell:

: $ git clone https://gitlab.com/protesilaos/modus-themes.git ~/.emacs.d/modus-themes

2. Add that path to your known Elisp libraries' list, by placing this
   snippet of Emacs Lisp in your init file (e.g. {{{file(init.el)}}}):

#+begin_src emacs-lisp
(add-to-list 'load-path "~/.emacs.d/modus-themes")
#+end_src

The themes are now ready to be used: [[#h:3f3c3728-1b34-437d-9d0c-b110f5b161a9][Enable and load]].

** Install from the archives
:properties:
:custom_id: h:c4b10085-149f-43e2-bd4d-347f33aee054
:end:

The ~modus-themes~ package is available from the GNU ELPA archive, which
is configured by default.

Prior to querying any package archive, make sure to have updated the
index, with {{{kbd(M-x package-refresh-contents)}}}.  Then all you need to do
is type {{{kbd(M-x package-install)}}} and specify the ~modus-themes~.

Note that older versions of the themes used to be distributed as
standalone packages.  This practice has been discontinued starting with
version 1.0.0 of this project.

Once installed, the themes are ready to be used: [[#h:3f3c3728-1b34-437d-9d0c-b110f5b161a9][Enable and load]].

** Install on GNU/Linux
:properties:
:custom_id: h:da640eb1-95dd-4e86-bb4e-1027b27885f0
:end:

The themes are also available from the archives of some distributions of
GNU/Linux.  These should correspond to a tagged release rather than
building directly from the latest Git commit.  It all depends on the
distro's packaging policies.

*** Debian 11 Bullseye
:properties:
:custom_id: h:7e570360-9ee6-4bc5-8c04-9dc11418a3e4
:end:

The themes are part of Debian 11 Bullseye.  Get them with:

#+begin_src sh
sudo apt install elpa-modus-themes
#+end_src

They are now ready to be used: [[#h:3f3c3728-1b34-437d-9d0c-b110f5b161a9][Enable and load]].

*** GNU Guix
:properties:
:custom_id: h:a4ca52cd-869f-46a5-9e16-4d9665f5b88e
:end:

Users of Guix can get the themes with this command:

#+begin_src sh
guix package -i emacs-modus-themes
#+end_src

They are now ready to be used: [[#h:3f3c3728-1b34-437d-9d0c-b110f5b161a9][Enable and load]].

* Enable and load
:properties:
:custom_id: h:3f3c3728-1b34-437d-9d0c-b110f5b161a9
:end:
#+findex: modus-themes-load-themes
#+findex: modus-themes-toggle
#+findex: modus-themes-load-operandi
#+findex: modus-themes-load-vivendi
#+cindex: Essential configuration
#+vindex: modus-themes-after-load-theme-hook

Users of the built-in themes can load and automatically enable the theme
of their preference by adding either form to their init file:

#+begin_src emacs-lisp
(load-theme 'modus-operandi)            ; Light theme
(load-theme 'modus-vivendi)             ; Dark theme
#+end_src

This is all one needs.

Users of packaged variants of the themes must add a few more lines to
ensure that everything works as intended.  First, one has to require the
main library before loading either theme:

#+begin_src emacs-lisp
(require 'modus-themes)
#+end_src

Then it is recommended to load the individual theme files with the
helper function ~modus-themes-load-themes~:

#+begin_src emacs-lisp
;; Load the theme files before enabling a theme (else you get an error).
(modus-themes-load-themes)
#+end_src

Once the libraries that define the themes are enabled, one can activate
a theme with either of the following expressions:

#+begin_src emacs-lisp
(modus-themes-load-operandi)            ; Light theme
;; OR
(modus-themes-load-vivendi)             ; Dark theme
#+end_src

Changes to the available customization options must always be evaluated
before loading a theme ([[#h:bf1c82f2-46c7-4eb2-ad00-dd11fdd8b53f][Customization Options]]).  An exception to this
norm is when using the various Custom interfaces or with commands like
{{{kbd(M-x customize-set-variable)}}}, which automatically reload the theme by
default ([[#h:9001527a-4e2c-43e0-98e8-3ef72d770639][Option for inhibiting theme reload]]).  This is how a basic setup
could look like:

#+begin_src emacs-lisp
(require 'modus-themes)

;; Your customisations here.  For example:
(setq modus-themes-bold-constructs t
      modus-themes-mode-line '3d)

;; Load the theme files before enabling a theme (else you get an error).
(modus-themes-load-themes)

;; Enable the theme of your preference:
(modus-themes-load-operandi)

;; Optionally add a key binding for the toggle between the themes:
(define-key global-map (kbd "<f5>") #'modus-themes-toggle)
#+end_src

[[#h:e979734c-a9e1-4373-9365-0f2cd36107b8][Sample configuration for use-package]].

With those granted, bear in mind a couple of technical points on
~modus-themes-load-operandi~ and ~modus-themes-load-vivendi~, as well as
~modus-themes-toggle~ which relies on them:

1. Those functions call ~load-theme~.  Some users prefer to opt for
 ~enable-theme~ instead ([[#h:e68560b3-7fb0-42bc-a151-e015948f8a35][Differences between loading and enabling]]).

2. The functions will run the ~modus-themes-after-load-theme-hook~ as
   their final step.  This can be employed for bespoke configurations
   ([[#h:f4651d55-8c07-46aa-b52b-bed1e53463bb][Advanced customization (do-it-yourself)]]).  Experienced users may not
   wish to rely on such a hook and the functions that run it: they may
   prefer a custom solution ([[#h:86f6906b-f090-46cc-9816-1fe8aeb38776][A theme-agnostic hook for theme loading]]).

** Sample configuration for use-package
:properties:
:custom_id: h:e979734c-a9e1-4373-9365-0f2cd36107b8
:end:
#+cindex: use-package configuration

It is common for Emacs users to rely on ~use-package~ for declaring
package configurations in their setup.  We use this as an example:

#+begin_src emacs-lisp
(use-package modus-themes
  :ensure                         ; omit this to use the built-in themes
  :init
  ;; Add all your customizations prior to loading the themes
  (setq modus-themes-italic-constructs t
        modus-themes-bold-constructs nil
        modus-themes-region '(bg-only no-extend))

  ;; Load the theme files before enabling a theme (else you get an error).
  (modus-themes-load-themes)
  :config
  ;; Load the theme of your choice:
  (modus-themes-load-operandi) ;; OR (modus-themes-load-vivendi)
  :bind ("<f5>" . modus-themes-toggle))
#+end_src

[[#h:e68560b3-7fb0-42bc-a151-e015948f8a35][Differences between loading and enabling]].

Note: make sure not to customize the variable ~custom-theme-load-path~
or ~custom-theme-directory~ after the themes' package declaration.  That
will lead to failures in loading the files.  If either or both of those
variables need to be changed, their values should be defined before the
package declaration of the themes.

** Differences between loading and enabling
:properties:
:custom_id: h:e68560b3-7fb0-42bc-a151-e015948f8a35
:end:
#+cindex: load-theme VS enable-theme

The reason we recommend ~load-theme~ instead of the other option of
~enable-theme~ is that the former does a kind of "reset" on the face
specs.  It quite literally loads (or re-loads) the theme.  Whereas the
latter simply puts an already loaded theme at the top of the list of
enabled items, re-using whatever state was last loaded.

As such, ~load-theme~ reads all customizations that may happen during
any given Emacs session: even after the initial setup of a theme.
Examples are calls to ~custom-set-faces~, as well as new values assigned
to the options the Modus themes provide ([[#h:bf1c82f2-46c7-4eb2-ad00-dd11fdd8b53f][Customization Options]]).

Our tests show that ~enable-theme~ does not read such variables anew, so
it might appear to the unsuspecting user that the themes are somehow
broken whenever they try to assign a new value to a customization option
or some face.

This "reset" that ~load-theme~ conducts does, however, come at the cost
of being somewhat slower than ~enable-theme~.  Users who have a stable
setup and who seldom update their variables during a given Emacs
session, are better off using something like this:

#+begin_src emacs-lisp
(require 'modus-themes)
(load-theme 'modus-operandi t t)
(load-theme 'modus-vivendi t t)

(enable-theme 'modus-operandi) ;; OR (enable-theme 'modus-vivendi)
#+end_src

[[#h:e979734c-a9e1-4373-9365-0f2cd36107b8][Sample configuration for use-package]].

With the above granted, other sections of the manual discuss how to
configure custom faces, where ~load-theme~ is expected, though
~enable-theme~ could still apply in stable setups:

[[#h:1487c631-f4fe-490d-8d58-d72ffa3bd474][Case-by-case face specs using the themes' palette]].

[[#h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae][Face specs at scale using the themes' palette]].

* Customization Options
:properties:
:custom_id: h:bf1c82f2-46c7-4eb2-ad00-dd11fdd8b53f
:end:

The Modus themes are highly configurable, though they should work well
without any further tweaks.  By default, all customization options are
set to nil, unless otherwise noted in this manual.

Remember that all customization options must be evaluated before loading
a theme ([[#h:3f3c3728-1b34-437d-9d0c-b110f5b161a9][Enable and load]]).

Below is a summary of what you will learn in the subsequent sections of
this manual.

#+begin_src emacs-lisp
(setq modus-themes-italic-constructs t
      modus-themes-bold-constructs nil
      modus-themes-no-mixed-fonts nil
      modus-themes-subtle-line-numbers nil
      modus-themes-success-deuteranopia t
      modus-themes-inhibit-reload t ; only applies to `customize-set-variable' and related

      modus-themes-fringes nil ; {nil,'subtle,'intense}

      ;; Options for `modus-themes-lang-checkers' are either nil (the
      ;; default), or a list of properties that may include any of those
      ;; symbols: `straight-underline', `text-also', `background',
      ;; `intense'
      modus-themes-lang-checkers nil

      ;; Options for `modus-themes-mode-line' are either nil, or a list
      ;; that can combine any of `3d' OR `moody', `borderless',
      ;; `accented'.  The variable's doc string shows all possible
      ;; combinations.
      modus-themes-mode-line '(3d accented)

      ;; Options for `modus-themes-syntax' are either nil (the default),
      ;; or a list of properties that may include any of those symbols:
      ;; `faint', `yellow-comments', `green-strings', `alt-syntax'
      modus-themes-syntax nil

      ;; Options for `modus-themes-hl-line' are either nil (the default),
      ;; or a list of properties that may include any of those symbols:
      ;; `accented', `underline', `intense'
      modus-themes-hl-line '(underline accented)

      ;; Options for `modus-themes-paren-match' are either nil (the
      ;; default), or a list of properties that may include any of those
      ;; symbols: `bold', `intense', `underline'
      modus-themes-paren-match '(bold intense)

      ;; Options for `modus-themes-links' are either nil (the default),
      ;; or a list of properties that may include any of those symbols:
      ;; `neutral-underline' OR `no-underline', `faint' OR `no-color',
      ;; `bold', `italic', `background'
      modus-themes-links '(neutral-underline background)

      ;; Options for `modus-themes-prompts' are either nil (the
      ;; default), or a list of properties that may include any of those
      ;; symbols: `background', `bold', `gray', `intense', `italic'
      modus-themes-prompts '(intense bold)

      modus-themes-completions 'moderate ; {nil,'moderate,'opinionated}

      modus-themes-mail-citations nil ; {nil,'faint,'monochrome}

      ;; Options for `modus-themes-region' are either nil (the default),
      ;; or a list of properties that may include any of those symbols:
      ;; `no-extend', `bg-only', `accented'
      modus-themes-region '(bg-only no-extend)

      ;; Options for `modus-themes-diffs': nil, 'desaturated,
      ;; 'bg-only, 'deuteranopia, 'fg-only-deuteranopia
      modus-themes-diffs 'fg-only-deuteranopia

      modus-themes-org-blocks 'gray-background ; {nil,'gray-background,'tinted-background}

      modus-themes-org-agenda ; this is an alist: read the manual or its doc string
      '((header-block . (variable-pitch scale-title))
        (header-date . (grayscale workaholic bold-today))
        (scheduled . uniform)
        (habit . traffic-light-deuteranopia))

      modus-themes-headings ; this is an alist: read the manual or its doc string
      '((1 . (overline background))
        (2 . (rainbow overline))
        (t . (no-bold)))

      modus-themes-variable-pitch-ui nil
      modus-themes-variable-pitch-headings t
      modus-themes-scale-headings t
      modus-themes-scale-1 1.1
      modus-themes-scale-2 1.15
      modus-themes-scale-3 1.21
      modus-themes-scale-4 1.27
      modus-themes-scale-title 1.33)
#+end_src

** Option for inhibiting theme reload
:properties:
:alt_title: Custom reload theme
:description: Toggle auto-reload of the theme when setting custom variables
:custom_id: h:9001527a-4e2c-43e0-98e8-3ef72d770639
:end:
#+vindex: modus-themes-inhibit-reload

Symbol: ~modus-themes-inhibit-reload~

Possible values:

1. ~nil~ 
2. ~t~ (default)

By default, customizing a theme-related user option through the Custom
interfaces or with {{{kbd(M-x customize-set-variable)}}} will not reload the
currently active Modus theme.

Enable this behaviour by setting this variable to ~nil~.

** Option for color-coding success state (deuteranopia)
:properties:
:alt_title: Success' color-code
:description: Toggle blue color for success or done states
:custom_id: h:3ed03a48-20d8-4ce7-b214-0eb7e4c79abe
:end:
#+vindex: modus-themes-success-deuteranopia

Symbol: ~modus-themes-success-deuteranopia~

Possible values:

1. ~nil~ (default)
2. ~t~

The default is to colorise all faces that denote "success", "done", or
similar with a variant of green.

With a non-nil value (~t~), use variants of blue instead of green.  This
is meant to empower users with red-green color deficiency.

The present customization option should apply to all contexts where
there can be a color-coded distinction between success and failure,
to-do and done, and so on.

Diffs, which have a red/green dichotomy by default, can also be
configured to conform with deuteranopia.

[[#h:ea7ac54f-5827-49bd-b09f-62424b3b6427][Option for diff buffer looks]].

** Option for more bold constructs
:properties:
:alt_title: Bold constructs
:description: Toggle bold constructs in code
:custom_id: h:b25714f6-0fbe-41f6-89b5-6912d304091e
:end:
#+vindex: modus-themes-bold-constructs

Symbol: ~modus-themes-bold-constructs~

Possible values:

1. ~nil~ (default)
2. ~t~

The default is to use a bold typographic weight only when it is
required.

With a non-nil value (~t~) display several syntactic constructs in bold
weight.  This concerns keywords and other important aspects of code
syntax.  It also affects certain mode line indicators and command-line
prompts.

Advanced users may also want to configure the exact attributes of the
~bold~ face.

[[#h:2793a224-2109-4f61-a106-721c57c01375][Configure bold and italic faces]].

** Option for more italic constructs
:properties:
:alt_title: Italic constructs
:description: Toggle italic font constructs in code
:custom_id: h:977c900d-0d6d-4dbb-82d9-c2aae69543d6
:end:
#+vindex: modus-themes-italic-constructs

Symbol: ~modus-themes-italic-constructs~

Possible values:

1. ~nil~ (default)
2. ~t~

The default is to not use slanted text forms (italics) unless it is
absolutely necessary.

With a non-nil value (~t~) choose to render more faces in italics.  This
typically affects documentation strings and code comments.

Advanced users may also want to configure the exact attributes of the
~italic~ face.

[[#h:2793a224-2109-4f61-a106-721c57c01375][Configure bold and italic faces]].

** Option for syntax highlighting
:properties:
:alt_title: Syntax styles
:description: Choose the overall aesthetic of code syntax
:custom_id: h:c119d7b2-fcd4-4e44-890e-5e25733d5e52
:end:
#+vindex: modus-themes-syntax

Symbol: ~modus-themes-syntax~

Possible values are expressed as a list of properties (default is ~nil~ or
an empty list).  The list can include any of the following symbols:

+ ~faint~
+ ~yellow-comments~
+ ~green-strings~
+ ~alt-syntax~

The default (a ~nil~ value or an empty list) is to use a balanced
combination of colors on the cyan-blue-magenta side of the spectrum.
There is little to no use of greens, yellows, and reds.  Comments are
gray, strings are blue colored, doc strings are a shade of cyan, while
color combinations are designed to avoid exaggerations.

The property ~faint~ fades the saturation of all applicable colors, where
that is possible or appropriate.

The property ~yellow-comments~ applies a yellow color to comments.

The property ~green-strings~ applies a green color to strings and a green
tint to doc strings.

The property ~alt-syntax~ changes the combination of colors beyond strings
and comments, so that the effective palette is broadened to provide
greater variety relative to the default.

Combinations of any of those properties are expressed as a list, like in
these examples:

#+begin_src emacs-lisp
(faint)
(green-strings yellow-comments)
(alt-syntax green-strings yellow-comments)
(faint alt-syntax green-strings yellow-comments)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-syntax '(faint alt-syntax))
#+end_src

Independent of this variable, users may also control the use of a bold
weight or italic text: ~modus-themes-bold-constructs~ and
~modus-themes-italic-constructs~.

[[#h:b25714f6-0fbe-41f6-89b5-6912d304091e][Option for more bold constructs]].

[[#h:977c900d-0d6d-4dbb-82d9-c2aae69543d6][Option for more italic constructs]].

** Option for no font mixing
:properties:
:alt_title: No mixed fonts
:description: Toggle mixing of font families
:custom_id: h:115e6c23-ee35-4a16-8cef-e2fcbb08e28b
:end:
#+vindex: modus-themes-no-mixed-fonts

Symbol: ~modus-themes-no-mixed-fonts~

Possible values:

1. ~nil~ (default)
2. ~t~

By default, the themes configure some spacing-sensitive faces like Org
tables and code blocks to always inherit from the ~fixed-pitch~ face.
This is to ensure that those constructs remain monospaced even when
users opt for a mode that remaps typeface families, such as the built-in
{{{kbd(M-x variable-pitch-mode)}}}.  Otherwise the layout would appear
broken, due to how spacing is done.  To disable this behaviour, set the
option to ~t~.

Users may prefer to use another package for handling mixed typeface
configurations, rather than letting the theme do it, perhaps because a
purpose-specific package has extra functionality.  Two possible options
are ~org-variable-pitch~ and ~mixed-pitch~.

[[#h:defcf4fc-8fa8-4c29-b12e-7119582cc929][Font configurations for Org and others]].

** Option for links
:properties:
:alt_title: Link styles
:description: Choose among several styles, with or without underline
:custom_id: h:c119d7b2-fcd4-4e44-890e-5e25733d5e52
:end:
#+vindex: modus-themes-links

Symbol: ~modus-themes-links~

Possible values are expressed as a list of properties (default is ~nil~ or
an empty list).  The list can include any of the following symbols:

+ Underline style:
  - ~neutral-underline~
  - ~no-underline~
+ Text coloration:
  - ~faint~
  - ~no-color~
+ ~bold~
+ ~italic~
+ ~background~

The default (a ~nil~ value or an empty list) is a prominent text color,
typically blue, with an underline of the same color.

For the style of the underline, a ~neutral-underline~ property turns the
color of the line into a subtle gray, while the ~no-underline~ property
removes the line altogether.  If both of those are set, the latter takes
precedence.

For text coloration, a ~faint~ property desaturates the color of the text
and the underline, unless the underline is affected by the
aforementioned properties.  While a ~no-color~ property removes the color
from the text.  If both of those are set, the latter takes precedence.

A ~bold~ property applies a heavy typographic weight to the text of the
link.

An ~italic~ property adds a slant to the link's text (italic or oblique
forms, depending on the typeface).

A ~background~ property applies a subtle tinted background color.

In case both ~no-underline~ and ~no-color~ are set, then a subtle gray
background is applied to all links.  This can still be combined with the
~bold~ and ~italic~ properties.

Combinations of any of those properties are expressed as a list,
like in these examples:

#+begin_src emacs-lisp
(faint)
(no-underline faint)
(no-color no-underline bold)
(italic bold background no-color no-underline)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-links '(neutral-underline background))
#+end_src

The placement of the underline, meaning its proximity to the text, is
controlled by ~x-use-underline-position-properties~,
~x-underline-at-descent-line~, ~underline-minimum-offset~.  Please refer to
their documentation strings.

** Option for command prompt styles
:properties:
:alt_title: Command prompts
:description: Choose among plain, subtle, or intense prompts
:custom_id: h:db5a9a7c-2928-4a28-b0f0-6f2b9bd52ba1
:end:
#+vindex: modus-themes-prompts

Symbol: ~modus-themes-prompts~

Possible values are expressed as a list of properties (default is ~nil~ or
an empty list).  The list can include any of the following symbols:

+ ~background~
+ ~bold~
+ ~gray~
+ ~intense~
+ ~italic~

The default (a ~nil~ value or an empty list) means to only use a subtle
accented foreground color.

The property ~background~ applies a background color to the prompt's text.
By default, this is a subtle accented value.

The property ~intense~ makes the foreground color more prominent.  If the
~background~ property is also set, it amplifies the value of the
background as well.

The property ~gray~ changes the prompt's colors to grayscale.  This
affects the foreground and, if the ~background~ property is also set, the
background.  Its effect is subtle, unless it is combined with the
~intense~ property.

The property ~bold~ makes the text use a bold typographic weight.
Similarly, ~italic~ adds a slant to the font's forms (italic or oblique
forms, depending on the typeface).

Combinations of any of those properties are expressed as a list, like in
these examples:

#+begin_src emacs-lisp
(intense)
(bold intense)
(intense bold gray)
(intense background gray bold)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-prompts '(background gray))
#+end_src

** Option for mode line presentation
:properties:
:alt_title: Mode line
:description: Choose among several styles, with or without borders
:custom_id: h:27943af6-d950-42d0-bc23-106e43f50a24
:end:
#+vindex: modus-themes-mode-line

Symbol: ~modus-themes-mode-line~

Possible values, which can be expressed as a list of combinations of box
effect, color, and border visibility:

+ Overall style:
  - ~3d~
  - ~moody~
+ ~accented~
+ ~borderless~

The default (a nil value or an empty list) is a two-dimensional
rectangle with a border around it.  The active and the inactive
mode lines use different shades of grayscale values for the
background, foreground, border.

The ~3d~ property applies a three-dimensional effect to the
active mode line.  The inactive mode lines remain two-dimensional
and are toned down a bit, relative to the default style.

The ~moody~ property optimizes the mode line for use with the
library of the same name (hereinafter referred to as 'Moody').
In practice, it removes the box effect and replaces it with
underline and overline properties.  It also tones down the
inactive mode lines.  Despite its intended purpose, this option
can also be used without the Moody library (please consult the
themes' manual on this point for more details).  If both ~3d~ and
~moody~ properties are set, the latter takes precedence.

The ~borderless~ property removes the color of the borders.  It
does not actually remove the borders, but only makes their color
the same as the background, effectively creating some padding.

The ~accented~ property ensures that the active mode line uses a
colored background instead of the standard shade of gray.

Combinations of any of those properties are expressed as a list,
like in these examples:

#+begin_src emacs-lisp
(accented)
(borderless 3d)
(moody accented borderless)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-prompts '(borderless accented))
#+end_src

Note that Moody does not expose any faces that the themes could style
directly.  Instead it re-purposes existing ones to render its tabs and
ribbons.  As such, there may be cases where the contrast ratio falls
below the 7:1 target that the themes conform with (WCAG AAA).  To hedge
against this, we configure a fallback foreground for the ~moody~ property,
which will come into effect when the background of the mode line changes
to something less accessible, such as Moody ribbons (read the doc string
of ~set-face-attribute~, specifically ~:distant-foreground~).  This fallback
is activated when Emacs determines that the background and foreground of
the given construct are too close to each other in terms of color
distance.  In practice, users will need to experiment with the variable
~face-near-same-color-threshold~ to trigger the effect.  We find that a
value of =45000= shall suffice, contrary to the default =30000=.  Though for
the combinations that involve the ~accented~ and ~moody~ properties, as
mentioned above, that should be raised up to =70000=.  Do not set it too
high, because it has the adverse effect of always overriding the default
colors (which have been carefully designed to be highly accessible).

Furthermore, because Moody expects an underline and overline instead of
a box style, it is advised to set ~x-underline-at-descent-line~ to a
non-nil value.

** Option for completion framework aesthetics
:properties:
:alt_title: Completion UIs
:description: Choose among standard, moderate, or opinionated looks
:custom_id: h:f1c20c02-7b34-4c35-9c65-99170efb2882
:end:
#+vindex: modus-themes-completions

Symbol: ~modus-themes-completions~

Possible values:

1. ~nil~ (default)
2. ~moderate~
3. ~opinionated~

This is a special option that has different effects depending on the
completion UI.  The interfaces can be grouped in two categories, based
on their default aesthetics: (i) those that only or mostly use
foreground colors for their interaction model, and (ii) those that
combine background and foreground values for some of their metaphors.
The former category encompasses Icomplete, Ido, Selectrum, Vertico, as
well as pattern matching styles like Orderless and Flx.  The latter
covers Helm, Ivy, and Sallet.

A value of ~nil~ (the default) will simply respect the metaphors of each
completion framework.

Option ~moderate~ applies a combination of background and foreground that
is fairly subtle.  For Icomplete and friends this constitutes a
departure from their default aesthetics, however the difference is
small.  While Helm, Ivy et al appear slightly different than their
original looks, as they are toned down a bit.

Option ~opinionated~ uses color combinations that refashion the completion
UI.  For the Icomplete camp this means that intense background and
foreground combinations are used: in effect their looks emulate those of
Helm, Ivy and co. in their original style.  Whereas the other group of
packages will revert to an even more nuanced aesthetic with some
additional changes to the choice of hues.

To appreciate the scope of this customization option, you should spend
some time with every one of the ~nil~ (default), ~moderate~, and ~opinionated~
possibilities.

** Option for mail citations
:properties:
:alt_title: Mail citations
:description: Choose among colorful, desaturated, monochrome citations
:custom_id: h:5a12765d-0ba0-4a75-ab11-e35d3bbb317d
:end:
#+vindex: modus-themes-mail-citations

Symbol: ~modus-themes-mail-citations~

Possible values:

1. ~nil~ (default)
2. ~faint~
3. ~monochrome~

By default, citations in email-related buffers apply contrasting hues to
different levels of depth in cited text.  The colors are fairly easy to
tell apart.

A value of ~faint~ makes all citation levels less intense, while retaining
the default style of contrasting hues (albeit very subtle ones).

Option ~monochrome~ turns all citations in to a uniform shade of gray.

Whatever the value assigned to this variable, citations in emails are
controlled by typographic elements or indentation, which the themes do
not touch.

** Option for fringe visibility
:properties:
:alt_title: Fringes
:description: Choose among invisible, subtle, or intense fringe styles
:custom_id: h:1983c3fc-74f6-44f3-b917-967c403bebae
:end:
#+vindex: modus-themes-fringes

Symbol: ~modus-themes-fringes~

Possible values:

1. ~nil~ (default)
2. ~subtle~
3. ~intense~

The default is to use the same color as that of the main background,
meaning that the fringes are not obvious though they still occupy the
space given to them by ~fringe-mode~.

Options ~subtle~ and ~intense~ apply a gray background, making the fringes
visible.  The difference between the two is one of degree, as their
names imply.

** Option for language checkers
:properties:
:alt_title: Language checkers
:description: Control the style of language checkers/linters
:custom_id: h:4b13743a-8ebf-4d2c-a043-cceba10b1eb4
:end:
#+vindex: modus-themes-lang-checkers

Symbol: ~modus-themes-lang-checkers~

Possible values are expressed as a list of properties (default is ~nil~ or
an empty list).  The list can include any of the following symbols:

+ ~straight-underline~
+ ~text-also~
+ ~background~
+ ~intense~

The default (a ~nil~ value or an empty list) applies a color-coded
underline to the affected text, while it leaves the original foreground
intact.  If the display spec of Emacs has support for it, the
underline's style is that of a wave, otherwise it is a straight line.

The property ~straight-underline~ ensures that the underline under the
affected text is always drawn as a straight line.

The property ~text-also~ applies the same color of the underline to the
affected text.

The property ~background~ adds a color-coded background.

The property ~intense~ amplifies the applicable colors if ~background~
and/or ~text-only~ are set.  If ~intense~ is set on its own, then it implies
~text-only~.

To disable fringe indicators for Flymake or Flycheck, refer to variables
~flymake-fringe-indicator-position~ and ~flycheck-indication-mode~,
respectively.

Combinations of any of those properties can be expressed in a
list, as in those examples:

#+begin_src emacs-lisp
(background)
(straight-underline intense)
(background text-also straight-underline)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-lang-checkers '(text-also background))
#+end_src

NOTE: The placement of the straight underline, though not the wave
style, is controlled by the built-in variables ~underline-minimum-offset~,
~x-underline-at-descent-line~, ~x-use-underline-position-properties~.

** Option for line highlighting (hl-line-mode)
:properties:
:alt_title: Line highlighting
:description: Choose style of current line (hl-line-mode)
:custom_id: h:1dba1cfe-d079-4c13-a810-f768e8789177
:end:
#+vindex: modus-themes-hl-line

Symbol: ~modus-themes-hl-line~

Possible values are expressed as a list of properties (default is ~nil~ or
an empty list).  The list can include any of the following symbols:

+ ~accented~
+ ~intense~
+ ~underline~

The default (a ~nil~ value or an empty list) is a subtle gray background
color.

The property ~accented~ changes the background to a colored variant.

An ~underline~ property draws a line below the highlighted area.  Its
color is similar to the background, so gray by default or an accent
color when ~accented~ is also set.

An ~intense~ property amplifies the colors in use, which may be both the
background and the underline.

Combinations of any of those properties are expressed as a list, like in
these examples:

#+begin_src emacs-lisp
(intense)
(underline intense)
(accented intense underline)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-hl-line '(underline accented))
#+end_src

Set ~x-underline-at-descent-line~ to a non-nil value for better results
with underlines.

This style affects several packages that enable ~hl-line-mode~, such as
=elfeed=, =notmuch=, and =mu4e=.

** Option for line numbers (display-line-numbers-mode)
:properties:
:alt_title: Line numbers
:description: Toggle subtle style for line numbers
:custom_id: h:8c4a6230-2e43-4aa2-a631-3b7179392e09
:end:
#+vindex: modus-themes-subtle-line-numbers

Symbol: ~modus-themes-subtle-line-numbers~

Possible value:

1. ~nil~ (default)
2. ~t~

The default style for ~display-line-numbers-mode~ and its global variant
is to apply a subtle gray background to the line numbers.  The current
line has a more pronounced background and foreground combination to
bring more attention to itself.

Similarly, the faces for ~display-line-numbers-major-tick~ and its
counterpart ~display-line-numbers-minor-tick~ use appropriate styles that
involve a bespoke background and foreground combination.

With a non-nil value (~t~), line numbers have no background of their own.
Instead they retain the primary background of the theme, blending with
the rest of the buffer.  Foreground values for all relevant faces are
updated to accommodate this aesthetic.

** Option for parenthesis matching (show-paren-mode)
:properties:
:alt_title: Matching parentheses
:description: Choose between various styles for matching delimiters/parentheses
:custom_id: h:e66a7e4d-a512-4bc7-9f86-fbbb5923bf37
:end:
#+vindex: modus-themes-paren-match

Symbol: ~modus-themes-paren-match~

Possible values are expressed as a list of properties (default is ~nil~ or
an empty list).  The list can include any of the following symbols:

+ ~bold~
+ ~intense~
+ ~underline~

The default (a ~nil~ value or an empty list) is a subtle background color.

The ~bold~ property adds a bold weight to the characters of the matching
delimiters.

The ~intense~ property applies a more prominent background color to the
delimiters.

The ~underline~ property draws a straight line under the affected text.

Combinations of any of those properties are expressed as a list, like in
these examples:

#+begin_src emacs-lisp
(bold)
(underline intense)
(bold intense underline)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-paren-match '(bold intense))
#+end_src

This customization variable affects the built-in ~show-paren-mode~ and the
=smartparens= package.

** Option for active region
:properties:
:alt_title: Active region
:description: Choose between various styles for the active region
:custom_id: h:60798063-b4ad-45ea-b9a7-ff7b5c0ab74c
:end:
#+vindex: modus-themes-region

Symbol: ~modus-themes-region~

Possible values are expressed as a list of properties (default is ~nil~ or
an empty list).  The list can include any of the following symbols:

+ ~no-extend~
+ ~bg-only~
+ ~accented~

The default (a ~nil~ value or an empty list) is a prominent gray
background that overrides all foreground colors in the area it
encompasses.  Its reach extends to the edge of the window.

The ~no-extend~ property limits the region to the end of the line, so that
it does not reach the edge of the window.

The ~bg-only~ property makes the region's background color more subtle to
allow the underlying text to retain its foreground colors.

The ~accented~ property applies a more colorful background to the region.

Combinations of any of those properties are expressed as a list, like in
these examples:

#+begin_src emacs-lisp
(no-extend)
(bg-only accented)
(accented bg-only no-extend)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-region '(bg-only no-extend))
#+end_src

** Option for diff buffer looks
:properties:
:alt_title: Diffs
:description: Choose among intense, desaturated, or text-only diffs
:custom_id: h:ea7ac54f-5827-49bd-b09f-62424b3b6427
:end:
#+vindex: modus-themes-diffs

Symbol: ~modus-themes-diffs~

Possible values:

1. ~nil~ (default)
2. ~desaturated~
3. ~bg-only~
4. ~deuteranopia~
5. ~fg-only-deuteranopia~

The default (~nil~) uses fairly intense color combinations for diffs, by
applying prominently colored backgrounds, with appropriate foregrounds.

Option ~desaturated~ follows the same principles as with the default
(~nil~), though it tones down all relevant colors.

Option ~bg-only~ applies a background but does not override the text's
foreground.  This makes it suitable for a non-nil value passed to
~diff-font-lock-syntax~ (note: Magit does not support syntax highlighting
in diffs---last checked on 2021-04-21).

Option ~deuteranopia~ is like the default (~nil~) in terms of using
prominently colored backgrounds, except that it also accounts for
red-green color defficiency by replacing all instances of green with
colors on the blue side of the spectrum.  Other stylistic changes are
made in the interest of optimizing for such a use-case.

Option ~fg-only-deuteranopia~ removes all colored backgrounds, except from
word-wise or refined changes.  Instead, it only uses color-coded
foreground values to differentiate between added, removed, and changed
lines.  If a background is necessary to denote context, a subtle
grayscale value is applied.  The color used for added lines is a variant
of blue to account for red-green color defficiency but also because
green text alone is hard to discern in the diff's context (hard for our
accessibility purposes).  The ~fg-only~ option that existed in older
versions of the themes is now an alias of ~fg-only-deuteranopia~, in the
interest of backward compatibility.

** Option for org-mode block styles
:properties:
:alt_title: Org mode blocks
:description: Choose among plain, gray, or tinted backgrounds
:custom_id: h:b7e328c0-3034-4db7-9cdf-d5ba12081ca2
:end:
#+vindex: modus-themes-org-blocks

Symbol: ~modus-themes-org-blocks~

Possible values:

1. ~nil~ (default)
2. ~gray-background~ (value ~grayscale~ exists for backward compatibility)
3. ~tinted-background~ (value ~rainbow~ exists for backward compatibility)

The default means that the block has no distinct background of its own
and uses the one that applies to the rest of the buffer.

Option ~gray-background~ applies a subtle gray background to the block's
contents.  It also affects the begin and end lines of the block: their
background extends to the edge of the window for Emacs version >= 27
where the ~:extend~ keyword is recognized by ~set-face-attribute~ (this is
contingent on the variable ~org-fontify-whole-block-delimiter-line~).

Option ~tinted-background~ uses a slightly colored background for the
contents of the block.  The exact color will depend on the programming
language and is controlled by the variable ~org-src-block-faces~ (refer to
the theme's source code for the current association list).  For this to
take effect, Org must be restarted with {{{kbd(M-x org-mode-restart)}}}.

Code blocks use their major mode's colors only when the variable
~org-src-fontify-natively~ is non-nil.  While quote/verse blocks require
setting ~org-fontify-quote-and-verse-blocks~ to a non-nil value.

[[#h:f44cc6e3-b0f1-4a5e-8a90-9e48fa557b50][Update Org block delimiter fontification]].

Older versions of the themes provided options ~grayscale~ (or ~greyscale~)
and ~rainbow~.  Those will continue to work as they are aliases for
~gray-background~ and ~tinted-background~, respectively.

** Option for Org agenda constructs
:properties:
:alt_title: Org agenda
:description: Control each element in the presentation of the agenda
:custom_id: h:68f481bc-5904-4725-a3e6-d7ecfa7c3dbc
:end:
#+vindex: modus-themes-org-agenda

Symbol: ~modus-themes-org-agenda~

This is an alist that accepts a =(key . value)= combination.  Some values
are specified as a list.  Here is a sample, followed by a description of
all possible combinations:

#+begin_src emacs-lisp
(setq modus-themes-org-agenda
      '((header-block . (variable-pitch scale-title))
        (header-date . (grayscale workaholic bold-today))
        (scheduled . uniform)
        (habit . traffic-light)))
#+end_src

A ~header-block~ key applies to elements that concern the headings which
demarcate blocks in the structure of the agenda.  By default (a ~nil~
value) those are rendered in a bold typographic weight, plus a height
that is slightly taller than the default font size.  Acceptable values
come in the form of a list that can include either or both of those
properties:

- ~variable-pitch~ to use a proportionately spaced typeface;
- ~scale-title~ to increase the size to the number assigned to
 ~modus-themes-scale-title~ ([[#h:6868baa1-beba-45ed-baa5-5fd68322ccb3][Control the scale of headings]]) or ~no-scale~
  to make the font use the same height as the rest of the buffer.

In case both ~scale-title~ and ~no-scale~ are in the list, the latter takes
precedence.

Example usage:

#+begin_src emacs-lisp
(header-block . nil)
(header-block . (scale-title))
(header-block . (no-scale))
(header-block . (variable-pitch scale-title))
#+end_src

A ~header-date~ key covers date headings.  Dates use only a foreground
color by default (a ~nil~ value), with weekdays and weekends having a
slight difference in hueness.  The current date has an added gray
background.  This key accepts a list of values that can include any of
the following properties:

- ~grayscale~ to make weekdays use the main foreground color and
  weekends a more subtle gray;
- ~workaholic~ to make weekdays and weekends look the same in
  terms of color;
- ~bold-today~ to apply a bold typographic weight to the current
  date;
- ~bold-all~ to render all date headings in a bold weight.

For example:

#+begin_src emacs-lisp
(header-date . nil)
(header-date . (workaholic))
(header-date . (grayscale bold-all))
(header-date . (grayscale workaholic))
(header-date . (grayscale workaholic bold-today))
#+end_src

A ~scheduled~ key applies to tasks with a scheduled date.  By default (a
~nil~ value), those use varying shades of yellow to denote (i) a past or
current date and (ii) a future date.  Valid values are symbols:

- nil (default);
- ~uniform~ to make all scheduled dates the same color;
- ~rainbow~ to use contrasting colors for past, present, future
  scheduled dates.

For example:

#+begin_src emacs-lisp
(scheduled . nil)
(scheduled . uniform)
(scheduled . rainbow)
#+end_src

A ~habit~ key applies to the ~org-habit~ graph.  All possible value are
passed as a symbol.  Those are:

- The default (~nil~) is meant to conform with the original aesthetic of
 ~org-habit~.  It employs all four color codes that correspond to the
  org-habit states---clear, ready, alert, and overdue---while
  distinguishing between their present and future variants.  This
  results in a total of eight colors in use: red, yellow, green, blue,
  in tinted and shaded versions.  They cover the full set of information
  provided by the ~org-habit~ consistency graph.
- ~simplified~ is like the default except that it removes the dichotomy
  between current and future variants by applying uniform color-coded
  values.  It applies a total of four colors: red, yellow, green, blue.
  They produce a simplified consistency graph that is more legible (or
  less busy) than the default.  The intent is to shift focus towards the
  distinction between the four states of a habit task, rather than each
  state's present/future outlook.
- ~traffic-light~ further reduces the available colors to red, yellow, and
  green.  As in ~simplified~, present and future variants appear
  uniformly, but differently from it, the ~clear~ state is rendered in a
  green hue, instead of the original blue.  This is meant to capture the
  use-case where a habit task being too early is less important than it
  being too late.  The difference between ready and clear states is
  attenuated by painting both of them using shades of green.  This
  option thus highlights the alert and overdue states.
- ~traffic-light-deuteranopia~ is like the ~traffic-light~ except its three
  colors are red, yellow, and blue to be suitable for users with
  red-green color deficiency (deuteranopia).

For example:

#+begin_src emacs-lisp
(habit . nil)
(habit . simplified)
(habit . traffic-light)
#+end_src

Putting it all together, the alist can look like this:

#+begin_src emacs-lisp
'((header-block . (scale-title variable-pitch))
  (header-date . (grayscale workaholic bold-today))
  (scheduled . uniform)
  (habit . traffic-light))

;; Or else:
(setq modus-themes-org-agenda
      '((header-block . (scale-title variable-pitch))
        (header-date . (grayscale workaholic bold-today))
        (scheduled . uniform)
        (habit . traffic-light)))
#+end_src

** Option for the headings' overall style
:properties:
:alt_title: Heading styles
:description: Choose among several styles, also per heading level
:custom_id: h:271eff19-97aa-4090-9415-a6463c2f9ae1
:end:
#+vindex: modus-themes-headings

Symbol: ~modus-themes-headings~

This is an alist that accepts a =(key . list-of-values)= combination.  The
key is either a number, representing the heading's level or ~t~, which
pertains to the fallback style.  The list of values covers symbols that
refer to properties, as described below.  Here is a sample, followed by
a presentation of all available properties:

#+begin_src emacs-lisp
(setq modus-themes-headings
      '((1 . (background overline))
        (2 . (overline rainbow))
        (t . (monochrome))))
#+end_src

Properties:

+ ~rainbow~
+ ~overline~
+ ~background~
+ ~no-bold~
+ ~monochrome~

By default (a ~nil~ value for this variable), all headings have a bold
typographic weight and use a desaturated text color.

A ~rainbow~ property makes the text color more saturated.

An ~overline~ property draws a line above the area of the heading.

A ~background~ property adds a subtle tinted color to the background of
the heading.

A ~no-bold~ property removes the bold weight from the heading's text.

A ~monochrome~ property makes all headings the same base color, which is
that of the default for the active theme (black/white).  When ~background~
is also set, ~monochrome~ changes its color to gray.  If both ~monochrome~
and ~rainbow~ are set, the former takes precedence.

Combinations of any of those properties are expressed as a list, like in
these examples:

#+begin_src emacs-lisp
(no-bold)
(rainbow background)
(overline monochrome no-bold)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq modus-themes-headings
      '((1 . (background overline rainbow))
        (2 . (background overline))
        (t . (overline no-bold))))
#+end_src

When defining the styles per heading level, it is possible to pass a
non-nil value (~t~) instead of a list of properties.  This will retain the
original aesthetic for that level.  For example:

#+begin_src emacs-lisp
(setq modus-themes-headings
      '((1 . t)           ; keep the default style
        (2 . (background overline))
        (t . (rainbow)))) ; style for all other headings

(setq modus-themes-headings
      '((1 . (background overline))
        (2 . (rainbow no-bold))
        (t . t))) ; default style for all other levels
#+end_src

For Org users, the extent of the heading depends on the variable
~org-fontify-whole-heading-line~.  This affects the ~overline~ and
~background~ properties.  Depending on the version of Org, there may be
others, such as ~org-fontify-done-headline~.

[[#h:075eb022-37a6-41a4-a040-cc189f6bfa1f][Option for scaled headings]].

[[#h:97caca76-fa13-456c-aef1-a2aa165ea274][Option for variable-pitch font in headings]].

** Option for scaled headings
:properties:
:alt_title: Scaled headings
:description: Toggle scaling of headings
:custom_id: h:075eb022-37a6-41a4-a040-cc189f6bfa1f
:end:
#+vindex: modus-themes-scale-headings

Symbol: ~modus-themes-scale-headings~

Possible values:

1. ~nil~ (default)
2. ~t~

The default is to use the same size for headings and paragraph text.

With a non-nil value (~t~) make headings larger in height relative to the
main text.  This is noticeable in modes like Org, Markdown, and Info.

*** Control the scale of headings
:properties:
:alt_title: Scaled heading sizes
:description: Specify rate of increase for scaled headings
:custom_id: h:6868baa1-beba-45ed-baa5-5fd68322ccb3
:end:

In addition to the toggle for enabling scaled headings, users can also
specify a number of their own.

+ If it is a floating point, say, =1.5=, it is interpreted as a multiple
  of the base font size.  This is the recommended method, because it
  will always adapt to changes in the base font size, such as while
  using the ~text-scale-adjust~ command.

+ If it is an integer, it is read as an absolute font height that is
  1/10 of the typographic point size.  Thus a value of =18pt= must be
  expressed as =180=.  Setting an absolute value is discouraged, as it
  will break the layout in cases where the base font size must change,
  such as with the ~text-scale-adjust~ command ([[#h:defcf4fc-8fa8-4c29-b12e-7119582cc929][Font configurations]]).
  While we discourage using absolute values, we still provide for this
  option for users who do not need to perform text-scaling operations or
  who are content with whatever discrepancies in height.

Below are the variables in their default values, using the floating
point paradigm.  The numbers are very conservative, but one is free to
change them to their liking, such as =1.2=, =1.4=, =1.6=, =1.8=, =2.0=---or use a
resource for finding a consistent scale:

#+begin_src emacs-lisp
(setq modus-themes-scale-1 1.05
      modus-themes-scale-2 1.1
      modus-themes-scale-3 1.15
      modus-themes-scale-4 1.2
      modus-themes-scale-title 1.3)
#+end_src

As for the application of that scale, the variables that range from
~modus-themes-scale-1~ up to ~modus-themes-scale-4~ apply to regular
headings within the context of the given major mode.  The former is the
smallest, while the latter is the largest.  "Regular headings" are those
that have a standard syntax for their scale, such as Org mode's eight
levels of asterisks or Markdown's six columns.

Whereas ~modus-themes-scale-title~ is applied to special headings that do
not conform with the aforementioned syntax, yet which are expected to be
larger than the largest value on that implied scale or at least have
some unique purpose in the buffer.  Put concretely, Org's =#+title= meta
datum is not part of the eight levels of headings in an Org file, yet is
supposed to signify the primary header.  Similarly, the Org Agenda's
structure headings are not part of a recognisable scale and so they also
get ~modus-themes-scale-title~ ([[#h:68f481bc-5904-4725-a3e6-d7ecfa7c3dbc][Option for Org agenda constructs]]).

Users who wish to maintain scaled headings for the normal syntax while
preventing special headings from standing out, can assign a value of =1.0=
to ~modus-themes-scale-title~ to make it the same as body text (or
whatever value would render it indistinguishable from the desired point
of reference).

Note that in earlier versions of Org, scaling would only increase the
size of the heading, but not of keywords that were added to it, like
"TODO".  The issue has been fixed upstream:
<https://protesilaos.com/codelog/2020-09-24-org-headings-adapt/>.

** Option for variable-pitch font in UI elements
:properties:
:alt_title: UI typeface
:description: Toggle the use of variable-pitch across the User Interface
:custom_id: h:16cf666c-5e65-424c-a855-7ea8a4a1fcac
:end:
#+vindex: modus-themes-variable-pitch-ui

Symbol: ~modus-themes-variable-pitch-ui~

Possible values:

1. ~nil~ (default)
2. ~t~

This option concerns User Interface elements that are under the direct
control of Emacs.  In particular: the mode line, header line, tab bar,
and tab line.

The default is to use the same font as the rest of Emacs, which usually
is a monospaced family.

With a non-nil value (~t~) apply a proportionately spaced typeface.  This
is done by assigning the ~variable-pitch~ face to the relevant items.

[[#h:defcf4fc-8fa8-4c29-b12e-7119582cc929][Font configurations for Org and others]].

** Option for variable-pitch font in headings
:properties:
:alt_title: Headings' typeface
:description: Toggle the use of variable-pitch in headings
:custom_id: h:97caca76-fa13-456c-aef1-a2aa165ea274
:end:
#+vindex: modus-themes-variable-pitch-headings

Symbol: ~modus-themes-variable-pitch-headings~

Possible values:

1. ~nil~ (default)
2. ~t~

The default is to use the main font family, which typically is
monospaced.

With a non-nil value (~t~) apply a proportionately spaced typeface, else
"variable-pitch", to headings (such as in Org mode).

[[#h:defcf4fc-8fa8-4c29-b12e-7119582cc929][Font configurations for Org and others]].

* Advanced customization (do-it-yourself)
:properties:
:custom_id: h:f4651d55-8c07-46aa-b52b-bed1e53463bb
:end:

Unlike the predefined customization options which follow a clear pattern
of allowing the user to quickly specify their preference, the themes
also provide a more flexible, albeit difficult, mechanism to control
things with precision ([[#h:bf1c82f2-46c7-4eb2-ad00-dd11fdd8b53f][Customization Options]]).

This section is of interest only to users who are prepared to maintain
their own local tweaks and who are willing to deal with any possible
incompatibilities between versioned releases of the themes.  As such,
they are labelled as "do-it-yourself" or "DIY".

** Per-theme customization settings (DIY)
:properties:
:custom_id: h:a897b302-8e10-4a26-beab-3caaee1e1193
:end:

If you prefer to maintain different customization options between the
two themes, it is best you write your own functions that first set those
options and then load the relevant theme.  The following code does
exactly that by simply differentiating the two themes on the choice of
bold constructs in code syntax (enabled for one, disabled for the
other).

#+begin_src emacs-lisp
(defun my-demo-modus-operandi ()
  (interactive)
  (setq modus-themes-bold-constructs t) ; ENABLE bold
  (modus-themes-load-operandi))

(defun my-demo-modus-vivendi ()
  (interactive)
  (setq modus-themes-bold-constructs nil) ; DISABLE bold
  (modus-themes-load-vivendi))

(defun my-demo-modus-themes-toggle ()
  (if (eq (car custom-enabled-themes) 'modus-operandi)
      (my-demo-modus-vivendi)
    (my-demo-modus-operandi)))
#+end_src

Then assign ~my-demo-modus-themes-toggle~ to a key instead of the
equivalent the themes provide.

For a more elaborate design, it is better to inspect the source code of
~modus-themes-toggle~ and relevant functions.

** Case-by-case face specs using the themes' palette (DIY)
:properties:
:custom_id: h:1487c631-f4fe-490d-8d58-d72ffa3bd474
:end:
#+findex: modus-themes-color
#+findex: modus-themes-color-alts
#+cindex: Extracting individual colors

This section is about tweaking individual faces.  If you plan to do
things at scale, consult the next section: [[#h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae][Set multiple faces]].

We already covered in previous sections how to toggle between the themes
and how to configure options prior to loading.  We also explained that
some of the functions made available to users will fire up a hook that
can be used to pass tweaks in the post-theme-load phase.

Now assume you wish to change a single face, say, the ~cursor~.  And you
would like to get the standard "blue" color value of the active Modus
theme, whether it is Modus Operandi or Modus Vivendi.  To do that, you
can use the ~modus-themes-color~ function.  It accepts a symbol that is
associated with a color in ~modus-themes-operandi-colors~ and
~modus-themes-vivendi-colors~.  Like this:

#+begin_src emacs-lisp
(modus-themes-color 'blue)
#+end_src

The function always extracts the color value of the active Modus theme.

#+begin_src emacs-lisp
(progn
  (load-theme 'modus-operandi t)
  (modus-themes-color 'blue))           ; "#0031a9" for `modus-operandi'

(progn
  (load-theme 'modus-vivendi t)
  (modus-themes-color 'blue))           ; "#2fafff" for `modus-vivendi'
#+end_src

Do {{{kbd(C-h v)}}} on the aforementioned variables to check all the available
symbols that can be passed to this function.

With that granted, let us expand the example to actually change the
~cursor~ face's background property.  We employ the built-in function of
~set-face-attribute~:

#+begin_src emacs-lisp
(set-face-attribute 'cursor nil :background (modus-themes-color 'blue))
#+end_src

If you evaluate this form, your cursor will become blue.  But if you
change themes, such as with ~modus-themes-toggle~, your edits will be
lost, because the newly loaded theme will override the ~:background~
attribute you had assigned to that face.

For such changes to persist, we need to make them after loading the
theme.  So we rely on ~modus-themes-after-load-theme-hook~, which gets
called from ~modus-themes-load-operandi~, ~modus-themes-load-vivendi~, as
well as the command ~modus-themes-toggle~.  Here is a sample function that
tweaks two faces and then gets added to the hook:

#+begin_src emacs-lisp
(defun my-modus-themes-custom-faces ()
  (set-face-attribute 'cursor nil :background (modus-themes-color 'blue))
  (set-face-attribute 'font-lock-type-face nil :foreground (modus-themes-color 'magenta-alt)))

(add-hook 'modus-themes-after-load-theme-hook #'my-modus-themes-custom-faces)
#+end_src

[[#h:86f6906b-f090-46cc-9816-1fe8aeb38776][A theme-agnostic hook for theme loading]].

Using this principle, it is possible to override the styles of faces
without having to find color values for each case.

Another application is to control the precise weight for bold
constructs.  This is particularly useful if your typeface has several
variants such as "heavy", "extrabold", "semibold".  All you have to do
is edit the ~bold~ face.  For example:

#+begin_src emacs-lisp
(set-face-attribute 'bold nil :weight 'semibold)
#+end_src

Remember to use the custom function and hook combo we demonstrated
above.  Because the themes do not hard-wire a specific weight, this
simple form is enough to change the weight of all bold constructs
throughout the interface.

Finally, there are cases where you want to tweak colors though wish to
apply different ones to each theme, say, a blue hue for Modus Operandi
and a shade of red for Modus Vivendi.  To this end, we provide
~modus-themes-color-alts~ as a convenience function to save you from the
trouble of writing separate wrappers for each theme.  It still returns a
single value by querying either of ~modus-themes-operandi-colors~ and
~modus-themes-vivendi-colors~, only here you pass the two keys you want,
first for ~modus-operandi~ then ~modus-vivendi~.

Take the previous example with the ~cursor~ face:

#+begin_src emacs-lisp
;; Blue for `modus-operandi' and red for `modus-vivendi'
(set-face-attribute 'cursor nil :background (modus-themes-color-alts 'blue 'red))
#+end_src

** Face specs at scale using the themes' palette (DIY)
:properties:
:custom_id: h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae
:end:
#+findex: modus-themes-with-colors
#+cindex: Extracting colors en masse

The examples here are for large scale operations.  For simple, one-off
tweaks, you may prefer the approach documented in the previous section
([[#h:1487c631-f4fe-490d-8d58-d72ffa3bd474][Case-by-case face specs using the themes' palette]]).

The ~modus-themes-with-colors~ macro lets you retrieve multiple color
values by employing the backquote/backtick and comma notation.  The
values are stored in the alists ~modus-themes-operandi-colors~ and
~modus-themes-vivendi-colors~, while the macro always queries that of the
active Modus theme.

Here is an abstract example that just returns a list of color values
while ~modus-operandi~ is enabled:

#+begin_src emacs-lisp
(modus-themes-with-colors
  (list fg-main
        blue-faint
        magenta
        magenta-alt-other
        cyan-alt-other
        fg-special-cold
        blue-alt
        magenta-faint
        cyan
        fg-main
        green-faint
        red-alt-faint
        blue-alt-faint
        fg-special-warm
        cyan-alt
        blue))
;; =>
;; ("#000000" "#002f88" "#721045" "#5317ac"
;;  "#005a5f" "#093060" "#2544bb" "#752f50"
;;  "#00538b" "#000000" "#104410" "#702f00"
;;  "#003f78" "#5d3026" "#30517f" "#0031a9")
#+end_src

Getting a list of colors may have its applications, though what you are
most likely interested in is how to use those variables to configure
several faces at once.  To do so we can rely on the built-in
~custom-set-faces~ function, which sets face specifications for the
special ~user~ theme.  That "theme" gets applied on top of regular themes
like ~modus-operandi~ and ~modus-vivendi~.

This is how it works:

#+begin_src emacs-lisp
(modus-themes-with-colors
  (custom-set-faces
   `(cursor ((,class :background ,blue)))
   `(mode-line ((,class :background ,yellow-nuanced-bg
                        :foreground ,yellow-nuanced-fg)))
   `(mode-line-inactive ((,class :background ,blue-nuanced-bg
                                 :foreground ,blue-nuanced-fg)))))
#+end_src

The above snippet will immediately refashion the faces it names once it
is evaluated.  However, if you switch between the Modus themes, say,
from ~modus-operandi~ to ~modus-vivendi~, the colors will not get updated to
match those of the new theme.  To make things work across the themes, we
need to employ the same technique we discussed in the previous section,
namely, to pass our changes at the post-theme-load phase via a hook.

The themes provide the ~modus-themes-after-load-theme-hook~, which gets
called from ~modus-themes-load-operandi~, ~modus-themes-load-vivendi~, as
well as the command ~modus-themes-toggle~.  With this knowledge, you can
wrap the macro in a function and then assign that function to the hook.
Thus:

#+begin_src emacs-lisp
(defun my-modus-themes-custom-faces ()
  (modus-themes-with-colors
    (custom-set-faces
     `(cursor ((,class :background ,blue)))
     `(mode-line ((,class :background ,yellow-nuanced-bg
                          :foreground ,yellow-nuanced-fg)))
     `(mode-line-inactive ((,class :background ,blue-nuanced-bg
                                   :foreground ,blue-nuanced-fg))))))

(add-hook 'modus-themes-after-load-theme-hook #'my-modus-themes-custom-faces)
#+end_src

[[#h:86f6906b-f090-46cc-9816-1fe8aeb38776][A theme-agnostic hook for theme loading]].

To discover the faces defined by all loaded libraries, you may do
{{{kbd(M-x list-faces-display)}}}.  Be warned that when you ~:inherit~ a face
you are introducing an implicit dependency, so try to avoid doing so for
libraries other than the built-in {{{file(faces.el)}}} (or at least understand
that things may break if you inherit from a yet-to-be-loaded face).

Also bear in mind that these examples are meant to work with the Modus
themes.  If you are cycling between multiple themes you may encounter
unforeseen issues, such as the colors of the Modus themes being applied
to a non-Modus item.

Finally, note that you can still use other functions where those make
sense.  For example, the ~modus-themes-color-alts~ that was discussed in
the previous section.  Adapt the above example like this:

#+begin_src emacs-lisp
...
(modus-themes-with-colors
  (custom-set-faces
   `(cursor ((,class :background ,(modus-themes-color-alts 'blue 'green))))
   ...))
#+end_src

** Remap face with local value (DIY)
:properties:
:custom_id: h:7a93cb6f-4eca-4d56-a85c-9dcd813d6b0f
:end:
#+cindex: Remapping faces

There are cases where we need to change the buffer-local attributes of a
face.  This might be because we have our own minor mode that re-uses a
face for a particular purpose, such as a line selection tool that
activates ~hl-line-mode~, but we wish to keep it distinct from other
buffers.  This is where ~face-remap-add-relative~ can be applied and may
be combined with ~modus-themes-with-colors~ to deliver consistent results.

[[#h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae][Face specs at scale using the themes' palette]].

In this example we will write a simple interactive function that adjusts
the background color of the ~region~ face.  This is the sample code:

#+begin_src emacs-lisp
(defvar my-rainbow-region-colors
  (modus-themes-with-colors
    `((red . ,red-subtle-bg)
      (green . ,green-subtle-bg)
      (yellow . ,yellow-subtle-bg)
      (blue . ,blue-subtle-bg)
      (magenta . ,magenta-subtle-bg)
      (cyan . ,cyan-subtle-bg)))
  "Sample list of color values for `my-rainbow-region'.")

(defun my-rainbow-region (color)
  "Remap buffer-local attribute of `region' using COLOR."
  (interactive
   (list
    (completing-read "Pick a color: " my-rainbow-region-colors)))
  (face-remap-add-relative
   'region
   `( :background ,(alist-get (intern color) my-rainbow-region-colors)
      :foreground ,(face-attribute 'default :foreground))))
#+end_src

When ~my-rainbow-region~ is called interactively, it prompts for a color
to use.  The list of candidates is drawn from the car of each
association in ~my-rainbow-region-colors~ (so "red", "green", etc.).

To extend this principle, we may write wrapper functions that pass a
color directly.  Those can be useful in tandem with hooks.  Consider
this example:

#+begin_src emacs-lisp
(defun my-rainbow-region-magenta ()
  (my-rainbow-region 'magenta))

(add-hook 'diff-mode-hook #'my-rainbow-region-magenta)
#+end_src

Whenever we enter a ~diff-mode~ buffer, we now get a magenta-colored
region.

Perhaps you may wish to generalise those findings in to a set of
functions that also accept an arbitrary face.  We shall leave the
experimentation up to you.

** Cycle through arbitrary colors (DIY)
:properties:
:custom_id: h:77dc4a30-b96a-4849-85a8-fee3c2995305
:end:
#+cindex: Cycle colors

Users may opt to customize individual faces of the themes to accommodate
their particular needs.  One such case is with the color intensity of
comments, specifically the foreground of ~font-lock-comment-face~.  The
Modus themes set that to a readable value, in accordance with their
accessibility objective, though users may prefer to lower the overall
contrast on an on-demand basis.

One way to achieve this is to design a command that cycles through three
distinct levels of intensity, though the following can be adapted to any
kind of cyclic behaviour, such as to switch between red, green, and
blue.

In the following example, we employ the ~modus-themes-color~ function
which reads a symbol that represents an entry in the active theme's
color palette ([[#h:1487c631-f4fe-490d-8d58-d72ffa3bd474][Case-by-case face specs using the themes' palette]]).
Those are stored in ~my-modus-themes-comment-colors~.

#+begin_src emacs-lisp
(defvar my-modus-themes-comment-colors
  ;; We are abusing the palette here, as those colors have their own
  ;; purpose in the palette, so please ignore the semantics of their
  ;; names.
  '((low . bg-region)
    (medium . bg-tab-inactive-alt)
    (high . fg-alt))
  "Alist of levels of intensity mapped to color palette entries.
The entries are found in `modus-themes-operandi-colors' or
`modus-themes-vivendi-colors'.")

(defvar my-modus-themes--adjust-comment-color-state nil
  "The cyclic state of `my-modus-themes-adjust-comment-color'.
For internal use.")

(defun my-modus-themes--comment-foreground (degree state)
  "Set `font-lock-comment-face' foreground.
Use `my-modus-themes-comment-colors' to extract the color value
for each level of intensity.

This is complementary to `my-modus-themes-adjust-comment-color'."
  (let ((palette-colors my-modus-themes-comment-colors))
    (set-face-foreground
     'font-lock-comment-face
     (modus-themes-color (alist-get degree palette-colors)))
    (setq my-modus-themes--adjust-comment-color-state state)
    (message "Comments are set to %s contrast" degree)))

(defun my-modus-themes-adjust-comment-color ()
  "Cycle through levels of intensity for comments.
The levels are determined by `my-modus-themes-comment-colors'."
  (interactive)
  (pcase my-modus-themes--adjust-comment-color-state
    ('nil
     (my-modus-themes--comment-foreground 'low 1))
    (1
     (my-modus-themes--comment-foreground 'medium 2))
    (_
     (my-modus-themes--comment-foreground 'high nil))))
#+end_src

With the above, {{{kbd(M-x my-modus-themes-adjust-comment-color)}}} will cycle
through the three levels of intensity that have been specified.

Another approach is to not read from the active theme's color palette
and instead provide explicit color values, either in hexadecimal RGB
notation (like =#123456=) or as the names that are displayed in the output
of {{{kbd(M-x list-colors-display)}}}.  In this case, the alist with the
colors will have to account for the active theme, so as to set the
appropriate colors.  While this introduces a bit more complexity, it
ultimately offers greater flexibility on the choice of colors for such a
niche functionality (so there is no need to abuse the palette of the
active Modus theme):

#+begin_src emacs-lisp
(defvar my-modus-themes-comment-colors
  '((light . ((low . "gray75")
              (medium . "gray50")
              (high . "#505050")))      ; the default for `modus-operandi'

    (dark . ((low . "gray25")
             (medium . "gray50")
             (high . "#a8a8a8"))))      ; the default for `modus-vivendi'
  "Alist of levels of intensity mapped to color values.
For such colors, consult the command `list-colors-display'.  Pass
the name of a color or its hex value.")

(defvar my-modus-themes--adjust-comment-color-state nil
  "The cyclic state of `my-modus-themes-adjust-comment-color'.
For internal use.")

(defun my-modus-themes--comment-foreground (degree state)
    "Set `font-lock-comment-face' foreground.
Use `my-modus-themes-comment-colors' to extract the color value
for each level of intensity.

This is complementary to `my-modus-themes-adjust-comment-color'."
  (let* ((colors my-modus-themes-comment-colors)
         (levels (pcase (car custom-enabled-themes)
                   ('modus-operandi (alist-get 'light colors))
                   ('modus-vivendi (alist-get 'dark colors)))))
    (set-face-foreground
     'font-lock-comment-face
     (alist-get degree levels))
    (setq my-modus-themes--adjust-comment-color-state state)
    (message "Comments are set to %s contrast" degree)))

(defun my-modus-themes-adjust-comment-color ()
  "Cycle through levels of intensity for comments.
The levels are determined by `my-modus-themes-comment-colors'."
  (interactive)
  (pcase my-modus-themes--adjust-comment-color-state
    ('nil
     (my-modus-themes--comment-foreground 'low 1))
    (1
     (my-modus-themes--comment-foreground 'medium 2))
    (_
     (my-modus-themes--comment-foreground 'high nil))))
#+end_src

The effect of the above configurations on ~font-lock-comment-face~ is
global.  To make it buffer-local, one must tweak the code to employ the
function ~face-remap-add-relative~ ([[#h:7a93cb6f-4eca-4d56-a85c-9dcd813d6b0f][Remap face with local value]]).

So this form in ~my-modus-themes--comment-foreground~:

#+begin_src emacs-lisp
;; example 1
(...
 (set-face-foreground
  'font-lock-comment-face
  (modus-themes-color (alist-get degree palette-colors)))
 ...)

;; example 2
(...
 (set-face-foreground
  'font-lock-comment-face
  (alist-get degree levels))
 ...)
#+end_src

Must become this:

#+begin_src emacs-lisp
;; example 1
(...
 (face-remap-add-relative
  'font-lock-comment-face
  `(:foreground ,(modus-themes-color (alist-get degree palette-colors))))
 ...)

;; example 2
(...
 (face-remap-add-relative
  'font-lock-comment-face
  `(:foreground ,(alist-get degree levels)))
 ...)
#+end_src

** Override colors (DIY)
:properties:
:custom_id: h:307d95dd-8dbd-4ece-a543-10ae86f155a6
:end:
#+vindex: modus-themes-operandi-color-overrides
#+vindex: modus-themes-vivendi-color-overrides
#+cindex: Change a theme's colors

The themes provide a mechanism for overriding their color values.  This
is controlled by the variables ~modus-themes-operandi-color-overrides~ and
~modus-themes-vivendi-color-overrides~, which are alists that should
mirror a subset of the associations in ~modus-themes-operandi-colors~ and
~modus-themes-vivendi-colors~ respectively.  As with all customisations,
overriding must be done before loading the affected theme.

Let us approach the present topic one step at a time.  Here is a
simplified excerpt of the default palette for Modus Operandi with some
basic background values that apply to buffers and the mode line
(remember to inspect the actual value to find out all the associations
that can be overridden):

#+begin_src emacs-lisp
(defconst modus-themes-operandi-colors
  '((bg-main . "#ffffff")
    (bg-dim . "#f8f8f8")
    (bg-alt . "#f0f0f0")
    (bg-active . "#d7d7d7")
    (bg-inactive . "#efefef")))
#+end_src

As one can tell, we bind a key to a hexadecimal RGB color value.  Now
say we wish to override those specific values and have our changes
propagate to all faces that use those keys.  We could write something
like this, which adds a subtle ochre tint:

#+begin_src emacs-lisp
(setq modus-themes-operandi-color-overrides
      '((bg-main . "#fefcf4")
        (bg-dim . "#faf6ef")
        (bg-alt . "#f7efe5")
        (bg-active . "#e8dfd1")
        (bg-inactive . "#f6ece5")))
#+end_src

Once this is evaluated, any subsequent loading of ~modus-operandi~ will
use those values instead of the defaults.  No further intervention is
required.

To reset the changes, we apply this and reload the theme:

#+begin_src emacs-lisp
(setq modus-themes-operandi-color-overrides nil)
#+end_src

Users who wish to leverage such a mechanism can opt to implement it
on-demand by means of a global minor mode.  The following snippet covers
both themes and expands to some more assosiations in the palette:

#+begin_src emacs-lisp
(define-minor-mode my-modus-themes-tinted
  "Tweak some Modus themes colors."
  :init-value nil
  :global t
  (if my-modus-themes-tinted
      (setq modus-themes-operandi-color-overrides
            '((bg-main . "#fefcf4")
              (bg-dim . "#faf6ef")
              (bg-alt . "#f7efe5")
              (bg-hl-line . "#f4f0e3")
              (bg-active . "#e8dfd1")
              (bg-inactive . "#f6ece5")
              (bg-region . "#c6bab1")
              (bg-header . "#ede3e0")
              (bg-tab-bar . "#dcd3d3")
              (bg-tab-active . "#fdf6eb")
              (bg-tab-inactive . "#c8bab8")
              (fg-unfocused . "#55556f"))
            modus-themes-vivendi-color-overrides
            '((bg-main . "#100b17")
              (bg-dim . "#161129")
              (bg-alt . "#181732")
              (bg-hl-line . "#191628")
              (bg-active . "#282e46")
              (bg-inactive . "#1a1e39")
              (bg-region . "#393a53")
              (bg-header . "#202037")
              (bg-tab-bar . "#262b41")
              (bg-tab-active . "#120f18")
              (bg-tab-inactive . "#3a3a5a")
              (fg-unfocused . "#9a9aab")))
    (setq modus-themes-operandi-color-overrides nil
          modus-themes-vivendi-color-overrides nil)))
#+end_src

With this in place, one can invoke {{{kbd(M-x my-modus-themes-tinted)}}} and
then load the Modus theme of their choice.  The new palette subset will
come into effect: subtle ochre tints for Modus Operandi and night sky
shades for Modus Vivendi.  Switching between the two themes, such as
with {{{kbd(M-x modus-themes-toggle)}}} will also use the overrides.

Given that this is a user-level customisation, one is free to implement
whatever color values they desire, even if the possible combinations
fall below the minimum 7:1 contrast ratio that governs the design of the
themes (the WCAG AAA legibility standard).  Alternatively, this can also
be done programmatically ([[#h:4589acdc-2505-41fc-9f5e-699cfc45ab00][Override color saturation]]).

For manual interventions it is advised to inspect the source code of
~modus-themes-operandi-colors~ and ~modus-themes-vivendi-colors~ for the
inline commentary: it explains what the intended use of each palette
subset is.

Furthermore, users may benefit from the ~modus-themes-contrast~ function
that we provide: [[#h:02e25930-e71a-493d-828a-8907fc80f874][test color combinations]].  It measures the contrast
ratio between two color values, so it can help in overriding the palette
(or a subset thereof) without making the end result inaccessible.

** Override color saturation (DIY)
:properties:
:custom_id: h:4589acdc-2505-41fc-9f5e-699cfc45ab00
:end:
#+cindex: Change a theme's color saturation

In the previous section we documented how one can override color values
manually ([[#h:307d95dd-8dbd-4ece-a543-10ae86f155a6][Override colors]]).  Here we use a programmatic approach which
leverages the built-in ~color-saturate-name~ function to adjust the
saturation of all color values used by the active Modus theme.  Our goal
is to prepare a counterpart of the active theme's palette that holds
modified color values, adjusted for a percent change in saturation.  A
positive number amplifies the effect, while a negative one will move
towards a grayscale spectrum.

We start with a function that can be either called from Lisp or invoked
interactively.  In the former scenario, we pass to it the rate of change
we want.  While in the latter, a minibuffer prompt asks for a number to
apply the desired effect.  In either case, we intend to assign anew the
value of ~modus-themes-operandi-color-overrides~ (light theme) and the
same for ~modus-themes-vivendi-color-overrides~ (dark theme).

#+begin_src emacs-lisp
(defun my-modus-themes-saturate (percent)
  "Saturate current Modus theme palette overrides by PERCENT."
  (interactive
   (list (read-number "Saturation by percent: ")))
  (let* ((theme (modus-themes--current-theme))
         (palette (pcase theme
                    ('modus-operandi modus-themes-operandi-colors)
                    ('modus-vivendi modus-themes-vivendi-colors)
                    (_ (error "No Modus theme is active"))))
         (overrides (pcase theme
                      ('modus-operandi 'modus-themes-operandi-color-overrides)
                      ('modus-vivendi 'modus-themes-vivendi-color-overrides)
                      (_ (error "No Modus theme is active")))))
    (let (name cons colors)
      (dolist (cons palette)
        (setq name (color-saturate-name (cdr cons) percent))
        (setq name (format "%s" name))
        (setq cons `(,(car cons) . ,name))
        (push cons colors))
      (set overrides colors))
    (pcase theme
      ('modus-operandi (modus-themes-load-operandi))
      ('modus-vivendi (modus-themes-load-vivendi)))))

;; sample Elisp calls (or call `my-modus-themes-saturate' interactively)
(my-modus-themes-saturate 50)
(my-modus-themes-saturate -75)
#+end_src

Using the above has an immediate effect, as it reloads the active Modus
theme.

The =my-modus-themes-saturate= function stores new color values in the
variables =modus-themes-operandi-color-overrides= and
=modus-themes-vivendi-color-overrides=, meaning that it undoes changes
implemented by the user on individual colors.  To have both automatic
saturation adjustment across the board and retain per-case edits to the
palette, some tweaks to the above function are required.  For example:

#+begin_src emacs-lisp
(defvar my-modus-themes-vivendi-extra-color-overrides
  '((fg-main . "#ead0c0")
    (bg-main . "#050515"))
  "My bespoke colors for `modus-vivendi'.")

(defvar my-modus-themes-operandi-extra-color-overrides
  '((fg-main . "#1a1a1a")
    (bg-main . "#fefcf4"))
  "My bespoke colors for `modus-operandi'.")

(defun my-modus-themes-saturate (percent)
  "Saturate current Modus theme palette overrides by PERCENT.
Preserve the color values stored in
`my-modus-themes-operandi-extra-color-overrides',
`my-modus-themes-vivendi-extra-color-overrides'."
  (interactive
   (list (read-number "Saturation by percent: ")))
  (let* ((theme (modus-themes--current-theme))
         (palette (pcase theme
                    ('modus-operandi modus-themes-operandi-colors)
                    ('modus-vivendi modus-themes-vivendi-colors)
                    (_ (error "No Modus theme is active"))))
         (overrides (pcase theme
                      ('modus-operandi 'modus-themes-operandi-color-overrides)
                      ('modus-vivendi 'modus-themes-vivendi-color-overrides)
                      (_ (error "No Modus theme is active"))))
         (extra-overrides (pcase theme
                            ('modus-operandi my-modus-themes-operandi-extra-color-overrides)
                            ('modus-vivendi my-modus-themes-vivendi-extra-color-overrides)
                            (_ (error "No Modus theme is active")))))
    (let (name cons colors)
      (dolist (cons palette)
        (setq name (color-saturate-name (cdr cons) percent))
        (setq name (format "%s" name))
        (setq cons `(,(car cons) . ,name))
        (push cons colors))
      (set overrides (append extra-overrides colors)))
    (pcase theme
      ('modus-operandi (modus-themes-load-operandi))
      ('modus-vivendi (modus-themes-load-vivendi)))))
#+end_src

To disable the effect, one must reset the aforementioned variables of
the themes to ~nil~.  Or specify a command for it, such as by taking
inspiration from the ~modus-themes-toggle~ we already provide:

#+begin_src emacs-lisp
(defun my-modus-themes-revert-overrides ()
  "Reset palette overrides and reload active Modus theme."
  (interactive)
  (setq modus-themes-operandi-color-overrides nil
        modus-themes-vivendi-color-overrides nil)
  (pcase (modus-themes--current-theme)
    ('modus-operandi (modus-themes-load-operandi))
    ('modus-vivendi (modus-themes-load-vivendi))))
#+end_src

** Font configurations for Org and others (DIY)
:properties:
:custom_id: h:defcf4fc-8fa8-4c29-b12e-7119582cc929
:end:
#+cindex: Font configurations

The themes are designed to cope well with mixed font configurations.

[[#h:115e6c23-ee35-4a16-8cef-e2fcbb08e28b][Option for no font mixing]].

This mostly concerns ~org-mode~ and ~markdown-mode~, though expect to find
it elsewhere like in ~Info-mode~.

In practice it means that the user can safely opt for a more
prose-friendly proportionately spaced typeface as their default, while
letting spacing-sensitive elements like tables and inline code always
use a monospaced font, by inheriting from the ~fixed-pitch~ face.

Users can try the built-in {{{kbd(M-x variable-pitch-mode)}}} to see the
effect in action.

To make everything use your desired font families, you need to configure
the ~variable-pitch~ (proportional spacing) and ~fixed-pitch~ (monospaced)
faces respectively.  It may also be convenient to set your main typeface
by configuring the ~default~ face the same way.

Put something like this in your initialization file (also consider
reading the doc string of ~set-face-attribute~):

#+begin_src emacs-lisp
;; Main typeface
(set-face-attribute 'default nil :family "DejaVu Sans Mono" :height 110)

;; Proportionately spaced typeface
(set-face-attribute 'variable-pitch nil :family "DejaVu Serif" :height 1.0)

;; Monospaced typeface
(set-face-attribute 'fixed-pitch nil :family "DejaVu Sans Mono" :height 1.0)
#+end_src

The next section shows how to make those work in a more elaborate setup
that is robust to changes between the Modus themes.

[[#h:2793a224-2109-4f61-a106-721c57c01375][Configure bold and italic faces]].

Note the differences in the ~:height~ property.  The ~default~ face must
specify an absolute value, which is the point size × 10.  So if you want
to use a font at point size =11=, you set the height to =110=.[fn:: ~:height~
values do not need to be rounded to multiples of ten: the likes of =115=
are perfectly valid—some typefaces will change to account for those
finer increments.]  Whereas every other face must have a value that is
relative to the default, represented as a floating point (if you use an
integer, then that means an absolute height).  This is of paramount
importance: it ensures that all fonts can scale gracefully when using
something like the ~text-scale-adjust~ command which only operates on the
base font size (i.e. the ~default~ face's absolute height).

[[#h:e6c5451f-6763-4be7-8fdb-b4706a422a4c][Note for EWW and Elfeed fonts (SHR fonts)]].

** Configure bold and italic faces (DIY)
:properties:
:custom_id: h:2793a224-2109-4f61-a106-721c57c01375
:end:
#+cindex: Bold and italic fonts

The Modus themes do not hardcode a ~:weight~ or ~:slant~ attribute in the
thousands of faces they cover.  Instead, they configure the generic
faces called ~bold~ and ~italic~ to use the appropriate styles and then
instruct all relevant faces that require emphasis to inherit from them.

This practically means that users can change the particularities of what
it means for a construct to be bold/italic, by tweaking the ~bold~ and
~italic~ faces.  Cases where that can be useful include:

+ The default typeface does not have a variant with slanted glyphs
  (e.g. Fira Mono/Code as of this writing on 2021-07-07), so the user
  wants to add another family for the italics, such as Hack.

+ The typeface of choice provides a multitude of weights and the user
  prefers the light one by default.  To prevent the bold weight from
  being too heavy compared to the light one, they opt to make ~bold~ use a
  semibold weight.

+ The typeface distinguishes between oblique and italic forms by
  providing different font variants (the former are just slanted
  versions of the upright forms, while the latter have distinguishing
  features as well).  In this case, the user wants to specify the font
  that applies to the ~italic~ face.

To achieve those effects, one must first be sure that the fonts they use
have support for those features.  It then is a matter of following the
instructions for all face tweaks.

[[#h:defcf4fc-8fa8-4c29-b12e-7119582cc929][Font configurations for Org and others]].

In this example, we set the default font family to Fira Code, while we
choose to render italics in the Hack typeface (obviously you need to
pick fonts that work well together):

#+begin_src emacs-lisp
(set-face-attribute 'default nil :family "Fira Code" :height 110)
(set-face-attribute 'italic nil :family "Hack")
#+end_src

And here we play with different weights, using Source Code Pro:

#+begin_src emacs-lisp
(set-face-attribute 'default nil :family "Source Code Pro" :height 110 :weight 'light)
(set-face-attribute 'bold nil :weight 'semibold)
#+end_src

To reset the font family, one can use this:

#+begin_src emacs-lisp
(set-face-attribute 'italic nil :family 'unspecified)
#+end_src

To ensure that the effects persist after switching between the Modus
themes (such as with {{{kbd(M-x modus-themes-toggle)}}}), the user needs to
write their configurations to a function and hook it up to the
~modus-themes-after-load-theme-hook~.  This is necessary because the
themes set the default styles of faces (otherwise changing themes would
not be possible).

[[#h:86f6906b-f090-46cc-9816-1fe8aeb38776][A theme-agnostic hook for theme loading]].

This is a minimal setup to preserve font configurations across theme
load phases.  For a more permanent setup, it is better to employ the
~custom-set-faces~ function: ~set-face-attribute~ works just fine, though it
is more convenient for quick previews or for smaller scale operations
(~custom-set-faces~ follows the format used in the source code of the
themes).

#+begin_src emacs-lisp
;; our generic function
(defun my-modes-themes-bold-italic-faces ()
  (set-face-attribute 'default nil :family "Source Code Pro" :height 110)
  (set-face-attribute 'bold nil :weight 'semibold))

;; or use this if you configure a lot of face and attributes and
;; especially if you plan to use `modus-themes-with-colors', as shown
;; elsewhere in the manual
(defun my-modes-themes-bold-italic-faces ()
  (custom-set-faces
   '(default ((t :family "Source Code Pro" :height 110)))
   '(bold ((t :weight semibold)))))

;; and here is the hook
(add-hook 'modus-themes-after-load-theme-hook #'my-modes-themes-bold-italic-faces)
#+end_src

** Custom Org user faces (DIY)
:properties:
:custom_id: h:89f0678d-c5c3-4a57-a526-668b2bb2d7ad
:end:
#+cindex: Org extra faces

Users of ~org-mode~ have the option to configure various keywords and
priority cookies to better match their workflow.  User options are
~org-todo-keyword-faces~ and ~org-priority-faces~.

As those are meant to be custom faces, it is futile to have the themes
guess what each user wants to use, which keywords to target, and so on.
Instead, we can provide guidelines on how to customize things to one's
liking with the intent of retaining the overall aesthetic of the themes.

Please bear in mind that the end result of those is not controlled by
the active Modus theme but by how Org maps faces to its constructs.
Editing those while ~org-mode~ is active requires re-initialization of the
mode with {{{kbd(M-x org-mode-restart)}}} for changes to take effect.

Let us assume you wish to visually differentiate your keywords.  You
have something like this:

#+begin_src emacs-lisp
(setq org-todo-keywords
      '((sequence "TODO(t)" "|" "DONE(D)" "CANCEL(C)")
        (sequence "MEET(m)" "|" "MET(M)")
        (sequence "STUDY(s)" "|" "STUDIED(S)")
        (sequence "WRITE(w)" "|" "WROTE(W)")))
#+end_src

You could then use a variant of the following to inherit from a face
that uses the styles you want and also to preserve the properties
applied by the ~org-todo~ face (in case there is a difference between the
two):

#+begin_src emacs-lisp
(setq org-todo-keyword-faces
      '(("MEET" . '(font-lock-preprocessor-face org-todo))
        ("STUDY" . '(font-lock-variable-name-face org-todo))
        ("WRITE" . '(font-lock-type-face org-todo))))
#+end_src

This will refashion the keywords you specify, while letting the other
items in ~org-todo-keywords~ use their original styles (which are defined
in the ~org-todo~ and ~org-done~ faces).

If you want back the defaults, try specifying just the ~org-todo~ face:

#+begin_src emacs-lisp
(setq org-todo-keyword-faces
      '(("MEET" . org-todo)
        ("STUDY" . org-todo)
        ("WRITE" . org-todo)))
#+end_src

When you inherit from multiple faces, you need to quote the list as
shown further above.  The order is significant: the first entry is
applied on top of the second, overriding any properties that are
explicitly set for both of them: any property that is not specified is
not overridden, so, for example, if ~org-todo~ has a background and a
foreground, while ~font-lock-type-face~ only has a foreground, the merged
face will include the background of the former and the foreground of the
latter.  If you do not want to blend multiple faces, you do not need a
quoted list.  A pattern of =keyword . face= will suffice.

Both approaches can be used simultaneously, as illustrated in this
configuration of the priority cookies:

#+begin_src emacs-lisp
(setq org-priority-faces
      '((?A . '(org-scheduled-today org-priority))
        (?B . org-priority)
        (?C . '(shadow org-priority))))
#+end_src

To find all the faces that are loaded in your current Emacs session, use
{{{kbd(M-x list-faces-display)}}}.  Try {{{kbd(M-x describe-variable)}}} as well and
then specify the name of each of those Org variables demonstrated above.
Their documentation strings will offer you further guidance.

Recall that the themes let you retrieve a color from their palette.  Do
it if you plan to control face attributes.

[[#h:1487c631-f4fe-490d-8d58-d72ffa3bd474][Custom face specs using the themes' palette]].

[[#h:02e25930-e71a-493d-828a-8907fc80f874][Check color combinations]].

** Update Org block delimiter fontification (DIY)
:properties:
:custom_id: h:f44cc6e3-b0f1-4a5e-8a90-9e48fa557b50
:end:

As noted in the section about ~modus-themes-org-blocks~, Org contains a
variable that determines whether the block's begin and end lines are
extended to the edge of the window ([[#h:b7e328c0-3034-4db7-9cdf-d5ba12081ca2][Option for org-mode block styles]]).
The variable is ~org-fontify-whole-block-delimiter-line~.

Users who change the style of Org blocks from time to time may prefer to
automatically update delimiter line fontification, such as with the
following setup:

#+begin_src emacs-lisp
(defun my-modus-themes-org-fontify-block-delimiter-lines ()
  "Match `org-fontify-whole-block-delimiter-line' to theme style.
Run this function at the post theme load phase, such as with the
`modus-themes-after-load-theme-hook'."
  (if (eq modus-themes-org-blocks 'gray-background)
      (setq org-fontify-whole-block-delimiter-line t)
    (setq org-fontify-whole-block-delimiter-line nil)))

(add-hook 'modus-themes-after-load-theme-hook
          #'my-modus-themes-org-fontify-block-delimiter-lines)
#+end_src

Then {{{kbd(M-x org-mode-restart)}}} for changes to take effect, though manual
intervention can be circumvented by tweaking the function thus:

#+begin_src emacs-lisp
(defun my-modus-themes-org-fontify-block-delimiter-lines ()
  "Match `org-fontify-whole-block-delimiter-line' to theme style.
Run this function at the post theme load phase, such as with the
`modus-themes-after-load-theme-hook'."
  (if (eq modus-themes-org-blocks 'gray-background)
      (setq org-fontify-whole-block-delimiter-line t)
    (setq org-fontify-whole-block-delimiter-line nil))
  (when (derived-mode-p 'org-mode)
    (font-lock-flush)))
#+end_src

** Measure color contrast (DIY)
:properties:
:custom_id: h:02e25930-e71a-493d-828a-8907fc80f874
:end:
#+findex: modus-themes-contrast
#+findex: modus-themes-wcag-formula
#+cindex: Color contrast

The themes provide the functions ~modus-themes-wcag-formula~ and
~modus-themes-contrast~.  The former is a direct implementation of the
WCAG formula: <https://www.w3.org/TR/WCAG20-TECHS/G18.html>.  It
calculates the relative luminance of a color value that is expressed in
hexadecimal RGB notation.  While the latter function is just a
convenient wrapper for comparing the relative luminance between two
colors.

In practice, one needs to work only with ~modus-themes-contrast~.  It
accepts two color values and returns their contrast ratio.  Values range
from 1 to 21 (lowest to highest).  The themes are designed to always be
equal or higher than 7 for each combination of background and foreground
that they use (this is the WCAG AAA standard---the most demanding of its
kind).

A couple of examples (rounded numbers):

#+begin_src emacs-lisp
;; Pure white with pure green
(modus-themes-contrast "#ffffff" "#00ff00")
;; => 1.37
;; That is an outright inaccessible combo

;; Pure black with pure green
(modus-themes-contrast "#000000" "#00ff00")
;; => 15.3
;; That is is a highly accessible combo
#+end_src

It does not matter which color value comes first.  The ratio is always
the same.

If one does not wish to read all the decimal points, it is possible to
try something like this:

#+begin_src emacs-lisp
(format "%0.2f" (modus-themes-contrast "#000000" "#00ff00"))
#+end_src

While it is fine to perform such calculations on a case-by-case basis,
it is preferable to implement formulas and tables for more demanding
tasks.  Such instruments are provided by ~org-mode~ or ~orgtbl-mode~, both
of which are built into Emacs.  Below is such a table that derives the
contrast ratio of all colors in the first column (pure red, green, blue)
relative to the color specified in the first row of the second column
(pure white) and rounds the results:

#+begin_example
|         | #ffffff |
|---------+---------|
| #ff0000 |    4.00 |
| #00ff00 |    1.37 |
| #0000ff |    8.59 |
#+tblfm: $2='(modus-themes-contrast $1 @1$2);%0.2f
#+end_example

To measure color contrast one needs to start from a known value.  This
typically is the background.  The Modus themes define an expanded
palette in large part because certain colors are only meant to be used
in combination with some others.  Consult the source code for the
minutia and relevant commentary.

Such knowledge may prove valuable while attempting to override some of
the themes' colors: [[#h:307d95dd-8dbd-4ece-a543-10ae86f155a6][Override colors]].

** Load theme depending on time of day (DIY)
:properties:
:custom_id: h:1d1ef4b4-8600-4a09-993c-6de3af0ddd26
:end:

While we do provide ~modus-themes-toggle~ to manually switch between the
themes, users may also set up their system to perform such a task
automatically at sunrise and sunset.

This can be accomplished by specifying the coordinates of one's location
using the built-in {{{file(solar.el)}}} and then configuring the =circadian=
package:

#+begin_src emacs-lisp
(use-package solar                      ; built-in
  :config
  (setq calendar-latitude 35.17
        calendar-longitude 33.36))

(use-package circadian                  ; you need to install this
  :ensure
  :after solar
  (setq circadian-themes '((:sunrise . modus-operandi)
                           (:sunset  . modus-vivendi)))
  (circadian-setup))
#+end_src

** Backdrop for pdf-tools (DIY)
:properties:
:custom_id: h:ff69dfe1-29c0-447a-915c-b5ff7c5509cd
:end:
#+cindex: Remapping pdf-tools backdrop

Most PDF files use a white background for their page, making it
impossible to discern the file's boundaries in the buffer while using
the Modus Operandi theme.  To introduce a distinction between the
buffer's backdrop and the PDF page's background, the former must be
rendered as some shade of gray.  Ideally, ~pdf-tools~ would provide a face
that the themes could support directly, though this does not seem to be
the case for the time being.  We must thus employ the face remapping
technique that is documented elsewhere in this document to change the
buffer-local value of the ~default~ face.

[[#h:7a93cb6f-4eca-4d56-a85c-9dcd813d6b0f][Remap face with local value]].

To remap the buffer's backdrop, we start with a function like this one:

#+begin_src emacs-lisp
(defun my-pdf-tools-backdrop ()
  (face-remap-add-relative
   'default
   `(:background ,(modus-themes-color 'bg-alt))))

(add-hook 'pdf-tools-enabled-hook #'my-pdf-tools-backdrop)
#+end_src

The idea is to assign that function to a hook that gets called when
~pdf-tools~ renders the document: ~pdf-tools-enabled-hook~.  This is enough
when you only use one theme.  However it has the downside of setting the
background color value only at render time.  In other words, the face
remapping function does not get evaluated anew whenever the theme
changes, such as upon invoking {{{kbd(M-x modus-themes-toggle)}}}.

To have our face remapping adapt gracefully while switching between the
Modus themes, we need to also account for the current theme and control
the activation of ~pdf-view-midnight-minor-mode~.  To which end we arrive
at something like the following, which builds on the above example:

#+begin_src emacs-lisp
(defun my-pdf-tools-backdrop ()
  (face-remap-add-relative
   'default
   `(:background ,(modus-themes-color 'bg-alt))))

(defun my-pdf-tools-midnight-mode-toggle ()
  (when (derived-mode-p 'pdf-view-mode)
    (if (eq (car custom-enabled-themes) 'modus-vivendi)
        (pdf-view-midnight-minor-mode 1)
      (pdf-view-midnight-minor-mode -1))
    (my-pdf-tools-backdrop)))

(add-hook 'pdf-tools-enabled-hook #'my-pdf-tools-midnight-mode-toggle)
(add-hook 'modus-themes-after-load-theme-hook #'my-pdf-tools-midnight-mode-toggle)
#+end_src

With those in place, PDFs have a distinct backdrop for their page, while
they automatically switch to their dark mode when ~modus-themes-toggle~ is
called from inside a buffer whose major-mode is ~pdf-view-mode~.

** A theme-agnostic hook for theme loading (DIY)
:properties:
:custom_id: h:86f6906b-f090-46cc-9816-1fe8aeb38776
:end:

The themes are designed with the intent to be useful to Emacs users of
varying skill levels, from beginners to experts.  This means that we try
to make things easier by not expecting anyone reading this document to
be proficient in Emacs Lisp or programming in general.

Such a case is with the use of the ~modus-themes-after-load-theme-hook~,
which runs after ~modus-themes-toggle~, ~modus-themes-load-operandi~, or
~modus-themes-load-vivendi~ is evaluated.  We recommend using that hook
for advanced customizations, because (1) we know for sure that it is
available once the themes are loaded, and (2) anyone consulting this
manual, especially the sections on enabling and loading the themes, will
be in a good position to benefit from that hook.

Advanced users who have a need to switch between the Modus themes and
other items will find that such a hook does not meet their requirements:
it only works with the Modus themes and only with the aforementioned
functions.

A theme-agnostic setup can be configured thus:

#+begin_src emacs-lisp
(defvar after-enable-theme-hook nil
   "Normal hook run after enabling a theme.")

(defun run-after-enable-theme-hook (&rest _args)
   "Run `after-enable-theme-hook'."
   (run-hooks 'after-enable-theme-hook))

(advice-add 'enable-theme :after #'run-after-enable-theme-hook)
#+end_src

This creates the ~after-enable-theme-hook~ and makes it run after each
call to ~enable-theme~, which means that it will work for all themes and
also has the benefit that it does not depend on functions such as
~modus-themes-toggle~ and the others mentioned above. ~enable-theme~ is
called internally by ~load-theme~, so the hook works everywhere.

Now this specific piece of Elisp may be simple for experienced users,
but it is not easy to read for newcomers, including the author of the
Modus themes for the first several months of their time as an Emacs
user.  Hence our hesitation to recommend it as part of the standard
setup of the Modus themes (it is generally a good idea to understand
what the implications are of advising a function).

* Face coverage
:properties:
:custom_id: h:a9c8f29d-7f72-4b54-b74b-ddefe15d6a19
:end:

The Modus themes try to provide as close to full face coverage as
possible.  This is necessary to ensure a consistently accessible reading
experience across all available interfaces.

** Full support for packages or face groups
:properties:
:alt_title: Supported packages
:description: Full list of covered face groups
:custom_id: h:60ed4275-60d6-49f8-9287-9a64e54bea0e
:end:
#+cindex: Explicitly supported packages

This list will always be updated to reflect the current state of the
project.  The idea is to offer an overview of the known status of all
affected face groups.  The items with an appended asterisk =*= tend to
have lots of extensions, so the "full support" may not be 100% true…

+ ace-window
+ ag
+ alert
+ all-the-icons
+ annotate
+ anzu
+ apropos
+ apt-sources-list
+ artbollocks-mode
+ auctex and TeX
+ auto-dim-other-buffers
+ avy
+ awesome-tray
+ bbdb
+ binder
+ bm
+ bongo
+ boon
+ bookmark
+ breakpoint (provided by the built-in {{{file(gdb-mi.el)}}} library)
+ buffer-expose
+ calendar and diary
+ calfw
+ centaur-tabs
+ cfrs
+ change-log and log-view (such as ~vc-print-log~, ~vc-print-root-log~)
+ cider
+ circe
+ color-rg
+ column-enforce-mode
+ company-mode*
+ company-posframe
+ compilation-mode
+ completions
+ consult
+ corfu
+ counsel*
+ counsel-css
+ counsel-org-capture-string
+ cov
+ cperl-mode
+ css-mode
+ csv-mode
+ ctrlf
+ custom (what you get with {{{kbd(M-x customize)}}})
+ dap-mode
+ dashboard (emacs-dashboard)
+ deadgrep
+ debbugs
+ define-word
+ deft
+ dictionary
+ diff-hl
+ diff-mode
+ dim-autoload
+ dir-treeview
+ dired
+ dired-async
+ dired-git
+ dired-git-info
+ dired-narrow
+ dired-subtree
+ diredc
+ diredfl
+ diredp (dired+)
+ disk-usage
+ display-fill-column-indicator-mode
+ doom-modeline
+ dynamic-ruler
+ easy-jekyll
+ easy-kill
+ ebdb
+ ediff
+ eglot
+ el-search
+ eldoc-box
+ elfeed
+ elfeed-score
+ embark
+ emms
+ enh-ruby-mode (enhanced-ruby-mode)
+ epa
+ equake
+ erc
+ eros
+ ert
+ eshell
+ eshell-fringe-status
+ eshell-git-prompt
+ eshell-prompt-extras (epe)
+ eshell-syntax-highlighting
+ evil* (evil-mode)
+ evil-goggles
+ evil-snipe
+ evil-visual-mark-mode
+ eww
+ exwm
+ eyebrowse
+ fancy-dabbrev
+ flycheck
+ flycheck-color-mode-line
+ flycheck-indicator
+ flycheck-posframe
+ flymake
+ flyspell
+ flyspell-correct
+ flx
+ freeze-it
+ frog-menu
+ focus
+ fold-this
+ font-lock (generic syntax highlighting)
+ forge
+ fountain (fountain-mode)
+ geiser
+ git-commit
+ git-gutter (and variants)
+ git-lens
+ git-rebase
+ git-timemachine
+ git-walktree
+ gnus
+ gotest
+ golden-ratio-scroll-screen
+ helm*
+ helm-ls-git
+ helm-switch-shell
+ helm-xref
+ helpful
+ highlight-blocks
+ highlight-defined
+ highlight-escape-sequences (~hes-mode~)
+ highlight-indentation
+ highlight-numbers
+ highlight-symbol
+ highlight-tail
+ highlight-thing
+ hl-defined
+ hl-fill-column
+ hl-line-mode
+ hl-todo
+ hydra
+ hyperlist
+ ibuffer
+ icomplete
+ icomplete-vertical
+ ido-mode
+ iedit
+ iflipb
+ imenu-list
+ indium
+ info
+ info-colors
+ interaction-log
+ ioccur
+ isearch, occur, etc.
+ isl (isearch-light)
+ ivy*
+ ivy-posframe
+ jira (org-jira)
+ journalctl-mode
+ js2-mode
+ julia
+ jupyter
+ kaocha-runner
+ keycast
+ ledger-mode
+ line numbers (~display-line-numbers-mode~ and global variant)
+ lsp-mode
+ lsp-ui
+ macrostep
+ magit
+ magit-imerge
+ make-mode
+ man
+ marginalia
+ markdown-mode
+ markup-faces (~adoc-mode~)
+ mentor
+ messages
+ minibuffer-line
+ minimap
+ mmm-mode
+ mode-line
+ mood-line
+ moody
+ mpdel
+ mu4e
+ mu4e-conversation
+ multiple-cursors
+ neotree
+ no-emoji
+ notmuch
+ num3-mode
+ nxml-mode
+ objed
+ orderless
+ org*
+ org-journal
+ org-noter
+ org-pomodoro
+ org-recur
+ org-roam
+ org-superstar
+ org-table-sticky-header
+ org-tree-slide
+ org-treescope
+ origami
+ outline-mode
+ outline-minor-faces
+ package (what you get with {{{kbd(M-x list-packages)}}})
+ page-break-lines
+ pandoc-mode
+ paradox
+ paren-face
+ parrot
+ pass
+ pdf-tools
+ persp-mode
+ perspective
+ phi-grep
+ phi-search
+ pkgbuild-mode
+ pomidor
+ popup
+ powerline
+ powerline-evil
+ prism ([[#h:a94272e0-99da-4149-9e80-11a7e67a2cf2][Note for prism.el]])
+ proced
+ prodigy
+ pulse
+ quick-peek
+ racket-mode
+ rainbow-blocks
+ rainbow-identifiers
+ rainbow-delimiters
+ rcirc
+ recursion-indicator
+ regexp-builder (also known as ~re-builder~)
+ rg (rg.el)
+ ripgrep
+ rmail
+ ruler-mode
+ sallet
+ selectrum
+ selectrum-prescient
+ semantic
+ sesman
+ shell-script-mode
+ shortdoc
+ show-paren-mode
+ shr
+ side-notes
+ sieve-mode
+ skewer-mode
+ smart-mode-line
+ smartparens
+ smerge
+ solaire
+ spaceline
+ speedbar
+ spell-fu
+ spray
+ stripes
+ suggest
+ switch-window
+ swiper
+ swoop
+ sx
+ symbol-overlay
+ syslog-mode
+ tab-bar-groups
+ tab-bar-mode
+ tab-line-mode
+ table (built-in table.el)
+ telega
+ telephone-line
+ terraform-mode
+ term
+ tomatinho
+ transient (pop-up windows such as Magit's)
+ trashed
+ treemacs
+ tty-menu
+ tuareg
+ typescript
+ undo-tree
+ vc (vc-dir.el, vc-hooks.el)
+ vc-annotate (the output of {{{kbd(C-x v g)}}})
+ vdiff
+ vertico
+ vimish-fold
+ visible-mark
+ visual-regexp
+ volatile-highlights
+ vterm
+ wcheck-mode
+ web-mode
+ wgrep
+ which-function-mode
+ which-key
+ whitespace-mode
+ window-divider-mode
+ winum
+ writegood-mode
+ woman
+ xah-elisp-mode
+ xref
+ xterm-color (and ansi-colors)
+ yaml-mode
+ yasnippet
+ ztree

Plus many other miscellaneous faces that are provided by the upstream
GNU Emacs distribution.

** Indirectly covered packages
:properties:
:custom_id: h:2cb359c7-3a84-4262-bab3-dcdc1d0034d7
:end:
#+cindex: Implicitly supported packages

These do not require any extra styles because they are configured to
inherit from some basic faces or their dependencies which are directly
supported by the themes.

+ counsel-notmuch
+ edit-indirect
+ evil-owl
+ fortran-mode
+ goggles
+ i3wm-config-mode
+ perl-mode
+ php-mode
+ rjsx-mode
+ swift-mode
+ tab-bar-echo-area

* Notes on individual packages
:properties:
:custom_id: h:4c4d901a-84d7-4f20-bd99-0808c2b06eba
:end:

This section covers information that may be of interest to users of
individual packages.

** Note on avy hints
:properties:
:custom_id: h:2fdce705-6de7-44e6-ab7f-18f59af99e01
:end:

Hints can appear everywhere, in wildly varying contexts, hence, their
appearance, by necessity, is a compromise.  However, there are various
options for making them stand out. First is dimming the surroundings:

#+begin_src emacs-lisp
(setq avy-background t)
#+end_src

Dimming works well when you find it difficult to spot hints, any hint.
Second is limiting the number of faces used by hints:

#+begin_src emacs-lisp
(setq avy-lead-faces
      '(avy-lead-face
        avy-lead-face-1
        avy-lead-face-1
        avy-lead-face-1
        avy-lead-face-1))
#+end_src

Limiting the number of faces works well with longer hints when you find
it difficult to identify individual hints, especially with hints
touching each other.  The first character of the hint will have an
intense color, the remaining ones the same neutral color.

Third is preferring commands that produce fewer candidates.  Fewer hints
is less noise: ~avy-goto-char-timer~ is an excellent alternative to
~avy-goto-char~.

** Note on calendar.el weekday and weekend colors
:properties:
:custom_id: h:b2db46fb-32f4-44fd-8e11-d2b261cf51ae
:end:

By default, the {{{kbd(M-x calendar)}}} interface differentiates weekdays from
weekends by applying a gray color to the former and a faint red to the
latter.  The idea for this approach is that the weekend should serve as
a subtle warning that no work is supposed to be done on that day, per
the design of traditional calendars.

Users who prefer all days to look the same can configure the variable
~calendar-weekend-days~ to either use gray of weekdays or the faint red of
weekends uniformly.

#+begin_src emacs-lisp
;; All are treated like weekdays (gray color)
(setq calendar-weekend-days nil)

;; All are treated like weekends (red-faint color)
(setq calendar-weekend-days (number-sequence 0 6))

;; The default marks the Saturday and Sunday as the weekend
(setq calendar-weekend-days '(0 6))
#+end_src

For changes to take effect, the Calendar buffer needs to be generated
anew.

** Note on underlines in compilation buffers
:properties:
:custom_id: h:420f5a33-c7a9-4112-9b04-eaf2cbad96bd
:end:

Various buffers that produce compilation results or run tests on code
apply an underline to the file names they reference or to relevant
messages.  Users may consider this unnecessary or excessive.

To outright disable the effect, use this:

#+begin_src emacs-lisp
(setq compilation-message-face nil)
#+end_src

If some element of differentiation is still desired, a good option is to
render the affected text using the ~italic~ face:

#+begin_src emacs-lisp
(setq compilation-message-face 'italic)
#+end_src

[[#h:2793a224-2109-4f61-a106-721c57c01375][Configure bold and italic faces]].

** Note on inline Latex in Org buffers
:properties:
:custom_id: h:dd8478da-f56a-45cd-b199-b836c85c3c5a
:end:

Org can work with inline latex and related syntax.  To actually fontify
those constructs, set the variable ~org-highlight-latex-and-related~ to
the desired list of values (per its doc string).  For example:

#+begin_src emacs-lisp
(setq org-highlight-latex-and-related '(latex script))
#+end_src

Remember to use {{{kbd(M-x org-mode-restart)}}} for changes to take effect.

** Note on dimmer.el
:properties:
:custom_id: h:8eb4b758-d318-4480-9ead-357a571beb93
:end:

The {{{file(dimmer.el)}}} library by Neil Okamoto can be configured to
automatically dim the colors of inactive Emacs windows.  To guarantee
consistent results with the Modus themes, we suggest some tweaks to the
default styles, such as in this minimal setup:

#+begin_src emacs-lisp
(use-package dimmer
  :config
  (setq dimmer-fraction 0.3)
  (setq dimmer-adjustment-mode :foreground)
  (setq dimmer-use-colorspace :rgb)

  (dimmer-mode 1))
#+end_src

Of the above, we strongly recommend the RGB color space because it is
the one that remains faithful to the hueness of the colors used by the
themes.  Whereas the default CIELAB space has a tendency to distort
colors in addition to applying the dim effect, which can be somewhat
disorienting.

The value of the ~dimmer-fraction~ has been selected empirically.  Users
might prefer to tweak it further (increasing it makes the dim effect
more pronounced).

Changing the ~dimmer-adjustment-mode~ is a matter of preference.  Though
because the Modus themes use black and white as their base colors, any
other value for that variable will turn the main background gray.  This
inadvertently leads to the opposite of the intended utility of this
package: it draws too much attention to unfocused windows.

** Note on display-fill-column-indicator-mode
:properties:
:custom_id: h:2a602816-bc1b-45bf-9675-4cbbd7bf6cab
:end:

While designing the style for ~display-fill-column-indicator-mode~, we
stayed close to the mode's defaults: to apply a subtle foreground color
to the ~fill-column-indicator~ face, which blends well with the rest of
theme and is consistent with the role of that mode.  This is to not
upset the expectations of users.

Nevertheless, ~display-fill-column-indicator-mode~ has some known
limitations pertaining to its choice of using typographic characters to
draw its indicator.  What should be a continuous vertical line might
appear as a series of dashes in certain contexts or under specific
conditions: a non-default value for ~line-spacing~, scaled and/or
variable-pitch headings have been observed to cause this effect.

Given that we cannot control such factors, it may be better for affected
users to deviate from the default style of the ~fill-column-indicator~
face.  Instead of setting a foreground color, one could use a background
and have the foreground be indistinguishable from it.  For example:

#+begin_src emacs-lisp
(modus-themes-with-colors
  (custom-set-faces
   `(fill-column-indicator ((,class :background ,bg-inactive
                                    :foreground ,bg-inactive)))))
#+end_src

[[#h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae][Face specs at scale using the themes' palette]].

** Note on mmm-mode.el background colors
:properties:
:custom_id: h:99cf0d6c-e478-4e26-9932-3bf3427d13f6
:end:

The faces used by {{{file(mmm-mode.el)}}} are expected to have a colorful
background, while they should not touch any foreground value.  The idea
is that they must not interfere with existing fontification.  Those
background colors need to be distinct from each other, such as an
unambiguous red juxtaposed with a clear blue.

While this design may be internally consistent with the raison d'être of
that library, it inevitably produces inaccessible color combinations.

There are two competing goals at play:

1. Legibility of the text, understood as the contrast ratio between the
   background and the foreground.

2. Semantic precision of each face which entails faithfulness to
   color-coding of the underlying background.

As the Modus themes are designed with the express purpose of conforming
with the first point, we have to forgo the apparent color-coding of the
background elements.  Instead we use subtle colors that do not undermine
the legibility of the affected text while they still offer a sense of
added context.

Users who might prefer to fall below the minimum 7:1 contrast ratio in
relative luminance (the accessibility target we conform with), can opt
to configure the relevant faces on their own.

[[#h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae][Face specs at scale using the themes' palette]].

This example uses more vivid background colors, though it comes at the
very high cost of degraded legibility.

#+begin_src emacs-lisp
(modus-themes-with-colors
  (custom-set-faces
   `(mmm-cleanup-submode-face ((,class :background ,yellow-refine-bg)))
   `(mmm-code-submode-face ((,class :background ,bg-active)))
   `(mmm-comment-submode-face ((,class :background ,blue-refine-bg)))
   `(mmm-declaration-submode-face ((,class :background ,cyan-refine-bg)))
   `(mmm-default-submode-face ((,class :background ,bg-alt)))
   `(mmm-init-submode-face ((,class :background ,magenta-refine-bg)))
   `(mmm-output-submode-face ((,class :background ,red-refine-bg)))
   `(mmm-special-submode-face ((,class :background ,green-refine-bg)))))
#+end_src

** Note on prism.el
:properties:
:alt_title: Note for prism
:custom_id: h:a94272e0-99da-4149-9e80-11a7e67a2cf2
:end:

This package by Adam Porter, aka "alphapapa" or "github-alphapapa",
implements an alternative to the typical coloration of code.  Instead of
highlighting the syntactic constructs, it applies color to different
levels of depth in the code structure.

As {{{file(prism.el)}}} offers a broad range of customisations, we cannot
style it directly at the theme level: that would run contrary to the
spirit of the package.  Instead, we may offer preset color schemes.
Those should offer a starting point for users to adapt to their needs.

In the following code snippets, we employ the ~modus-themes-with-colors~
macro: [[#h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae][Face specs at scale using the themes' palette]].

These are the minimum recommended settings with 16 colors:

#+begin_src emacs-lisp
(setq prism-num-faces 16)

(prism-set-colors
  :desaturations '(0) ; do not change---may lower the contrast ratio
  :lightens '(0)      ; same
  :colors (modus-themes-with-colors
            (list fg-main
                  magenta
                  cyan-alt-other
                  magenta-alt-other
                  blue
                  magenta-alt
                  cyan-alt
                  red-alt-other
                  green
                  fg-main
                  cyan
                  yellow
                  blue-alt
                  red-alt
                  green-alt-other
                  fg-special-warm)))
#+end_src

With 8 colors:

#+begin_src emacs-lisp
(setq prism-num-faces 8)

(prism-set-colors
  :desaturations '(0) ; do not change---may lower the contrast ratio
  :lightens '(0)      ; same
  :colors (modus-themes-with-colors
            (list fg-special-cold
                  magenta
                  magenta-alt-other
                  cyan-alt-other
                  fg-main
                  blue-alt
                  red-alt-other
                  cyan)))
#+end_src

And this is with 4 colors, which produces results that are the closest
to the themes' default aesthetic:

#+begin_src emacs-lisp
(setq prism-num-faces 4)

(prism-set-colors
  :desaturations '(0) ; do not change---may lower the contrast ratio
  :lightens '(0)      ; same
  :colors (modus-themes-with-colors
            (list fg-main
                  cyan-alt-other
                  magenta-alt-other
                  magenta)))
#+end_src

If you need to apply desaturation and lightening, you can use what the
{{{file(prism.el)}}} documentation recommends, like this (adapting to the
examples with the 4, 8, 16 colors):

#+begin_src emacs-lisp
(prism-set-colors
  :desaturations (cl-loop for i from 0 below 16 collect (* i 2.5))
  :lightens (cl-loop for i from 0 below 16 collect (* i 2.5))
  :colors (modus-themes-with-colors
            (list fg-main
                  cyan-alt-other
                  magenta-alt-other
                  magenta)))
#+end_src

** Note on god-mode.el
:properties:
:alt_title: Note for god-mode
:custom_id: h:4da1d515-3e05-47ef-9e45-8251fc7e986a
:end:

The ~god-mode~ library does not provide faces that could be configured by
the Modus themes.  Users who would like to get some visual feedback on
the status of {{{kbd(M-x god-mode)}}} are instead encouraged by upstream to
set up their own configurations, such as by changing the ~mode-line~ face
([[#h:f4651d55-8c07-46aa-b52b-bed1e53463bb][Advanced customization (do-it-yourself)]]).  This is an adaptation of the
approach followed in the upstream README:

#+begin_src emacs-lisp
(defun my-god-mode-update-mode-line ()
  "Make `mode-line' blue if God local mode is active."
  (modus-themes-with-colors
    (if god-local-mode
        (set-face-attribute 'mode-line nil
                            :foreground blue-active
                            :background bg-active-accent
                            :box blue)
      (set-face-attribute 'mode-line nil
                          :foreground fg-active
                          :background bg-active
                          :box fg-alt))))

(add-hook 'post-command-hook 'my-god-mode-update-mode-line)
#+end_src

We employ the ~modus-themes-with-colors~ which provides access to color
variables defined by the active theme.  Its use is covered elsewhere in
this manual ([[#h:51ba3547-b8c8-40d6-ba5a-4586477fd4ae][Face specs at scale using the themes' palette]]).  As for the
attributes that can be passed to each face, start by consulting the
documentation string of ~set-face-attribute~.

** Note on company-mode overlay pop-up
:properties:
:custom_id: h:20cef8c4-d11f-4053-8b2c-2872925780b1
:end:

By default, the ~company-mode~ pop-up that lists completion candidates is
drawn using an overlay.  This creates alignment issues every time it is
placed above a piece of text that has a different height than the
default.

The solution recommended by the project's maintainer is to use an
alternative front-end for drawing the pop-up which draws child frames
instead of overlays.[fn::
https://github.com/company-mode/company-mode/issues/1010][fn::
https://github.com/tumashu/company-posframe/]

** Note on ERC escaped color sequences
:properties:
:custom_id: h:98bdf319-1e32-4469-8a01-771200fba65c
:end:

The built-in IRC client ~erc~ has the ability to colorise any text using
escape sequences that start with =^C= (inserted with {{{kbd(C-q C-c)}}}) and are
followed by a number for the foreground and background.[fn:: This page
explains the basics, though it is not specific to Emacs:
https://www.mirc.com/colors.html] Possible numbers are 0-15, with the
first entry being the foreground and the second the background,
separated by a comma.  Like this =^C1,6=.  The minimum setup is this:

#+begin_src emacs-lisp
(add-to-list 'erc-modules 'irccontrols)
(setq erc-interpret-controls-p t
      erc-interpret-mirc-color t)
#+end_src

As this allows users the chance to make arbitrary combinations, it is
impossible to guarantee a consistently high contrast ratio.  All we can
we do is provide guidance on the combinations that satisfy the
accessibility standard of the themes:

+ Modus Operandi :: Use foreground color 1 for all backgrounds from
  2-15.  Like so: {{{kbd(C-q C-c1,N)}}} where =N= is the background.

+ Modus Vivendi :: Use foreground color 0 for all backgrounds from
  2-13.  Use foreground =1= for backgrounds 14, 15.

Colors 0 and 1 are white and black respectively.  So combine them
together, if you must.

** Note on powerline or spaceline
:properties:
:custom_id: h:9130a8ba-d8e3-41be-a58b-3cb1eb7b6d17
:end:

Both Powerline and Spaceline package users will likely need to use the
command ~powerline-reset~ whenever they make changes to their themes
and/or mode line setup.

** Note on SHR colors
:properties:
:custom_id: h:4cc767dc-ffef-4c5c-9f10-82eb7b8921bf
:end:

Emacs' HTML rendering library ({{{file(shr.el)}}}) may need explicit
configuration to respect the theme's colors instead of whatever
specifications the webpage provides.

Consult {{{kbd(C-h v shr-use-colors)}}}.

** Note on EWW and Elfeed fonts (SHR fonts)
:properties:
:custom_id: h:e6c5451f-6763-4be7-8fdb-b4706a422a4c
:end:

EWW and Elfeed rely on the Simple HTML Renderer to display their
content.  The {{{file(shr.el)}}} library contains the variable ~shr-use-fonts~
that controls whether the text in the buffer is set to a ~variable-pitch~
typeface (proportionately spaced) or if just retains whatever the
default font family is.  Its default value is non-nil, which means that
~variable-pitch~ is applied.

[[#h:defcf4fc-8fa8-4c29-b12e-7119582cc929][Font configurations for Org and others]].

** Note on Helm grep
:properties:
:custom_id: h:d28879a2-8e4b-4525-986e-14c0f873d229
:end:

There is one face from the Helm package that is meant to highlight the
matches of a grep or grep-like command (=ag= or =ripgrep=).  It is
~helm-grep-match~.  However, this face can only apply when the user does
not pass =--color=always= as a command-line option for their command.

Here is the docstring for that face, which is defined in the
{{{file(helm-grep.el)}}} library (you can always visit the source code with
{{{kbd(M-x find-library)}}}).

#+begin_quote
Face used to highlight grep matches.  Have no effect when grep backend
use "--color="
#+end_quote

The user must either remove =--color= from the flags passed to the grep
function, or explicitly use =--color=never= (or equivalent).  Helm
provides user-facing customization options for controlling the grep
function's parameters, such as ~helm-grep-default-command~ and
~helm-grep-git-grep-command~.

When =--color=always= is in effect, the grep output will use red text in
bold letter forms to present the matching part in the list of
candidates.  That style still meets the contrast ratio target of >= 7:1
(accessibility standard WCAG AAA), because it draws the reference to
ANSI color number 1 (red) from the already-supported array of
~ansi-color-names-vector~.

** Note on vc-annotate-background-mode
:properties:
:custom_id: h:5095cbd1-e17a-419c-93e8-951c186362a3
:end:

Due to the unique way ~vc-annotate~ ({{{kbd(C-x v g)}}}) applies colors, support
for its background mode (~vc-annotate-background-mode~) is disabled at the
theme level.

Normally, such a drastic measure should not belong in a theme: assuming
the user's preferences is bad practice.  However, it has been deemed
necessary in the interest of preserving color contrast accessibility
while still supporting a useful built-in tool.

If there actually is a way to avoid such a course of action, without
prejudice to the accessibility standard of this project, then please
report as much or send patches ([[#h:9c3cd842-14b7-44d7-84b2-a5c8bc3fc3b1][Contributing]]).

** Note on pdf-tools link hints
:properties:
:custom_id: h:2659d13e-b1a5-416c-9a89-7c3ce3a76574
:end:

Hints are drawn by [[https://imagemagick.org/][ImageMagick]], not Emacs, i.e., ImageMagick doesn't
know about the hint face unless you tell ImageMagick about it. By
default, only the foreground and background color attributes are
passed. The below snippet adds to those the various font attributes.  As
it queries various faces, specifically ~pdf-links-read-link~ and the faces
it inherits, it needs to be added to your initialization file after
you've customized any faces.

#+begin_src emacs-lisp
(use-package pdf-links
  :config
  (let ((spec
         (apply #'append
                (mapcar
                 (lambda (name)
                   (list name
                         (face-attribute 'pdf-links-read-link
                                         name nil 'default)))
                 '(:family :width :weight :slant)))))
    (setq pdf-links-read-link-convert-commands
          `("-density"    "96"
            "-family"     ,(plist-get spec :family)
            "-stretch"    ,(let* ((width (plist-get spec :width))
                                  (name (symbol-name width)))
                             (replace-regexp-in-string "-" ""
                                                       (capitalize name)))
            "-weight"     ,(pcase (plist-get spec :weight)
                             ('ultra-light "Thin")
                             ('extra-light "ExtraLight")
                             ('light       "Light")
                             ('semi-bold   "SemiBold")
                             ('bold        "Bold")
                             ('extra-bold  "ExtraBold")
                             ('ultra-bold  "Black")
                             (_weight      "Normal"))
            "-style"      ,(pcase (plist-get spec :slant)
                             ('italic  "Italic")
                             ('oblique "Oblique")
                             (_slant   "Normal"))
            "-pointsize"  "%P"
            "-undercolor" "%f"
            "-fill"       "%b"
            "-draw"       "text %X,%Y '%c'"))))
#+end_src

* Frequently Asked Questions (FAQ)
:properties:
:custom_id: h:b3384767-30d3-4484-ba7f-081729f03a47
:end:
#+cindex: Frequently Asked Questions (FAQ)

In this section we provide answers related to some aspects of the Modus
themes' design and application.

** Is the contrast ratio about adjacent colors?
:properties:
:custom_id: h:5ce7ae2e-9348-4e55-b4cf-9302345b1826
:end:
#+cindex: Contrast between adjacent colors

The minimum contrast ratio in relative luminance that the themes conform
with always refers to any given combination of background and foreground
colors.  If we have some blue colored text next to a magenta one, both
against a white background, we do not mean to imply that blue:magenta is
7:1 in terms of relative luminance.  Rather, we state that blue:white
and magenta:white each are 7:1 or higher.

The point of reference is always the background.  Because colors have
about the same minimum distance in luminance from their backdrop, they
necessarily are fairly close to each other in this measure.  A possible
blue:magenta combination would naturally be around 1:1 in contrast of
the sort here considered.

To differentiate between sequential colors, we rely on hueness by
mapping contrasting hues to adjacent constructs, while avoiding
exaggerations.  A blue next to a magenta can be told apart regardless of
their respective contrast ratio against their common background.
Exceptions would be tiny characters in arguably not so realistic cases,
such as two dots drawn side-by-side which for some reason would need to
be colored differently.  They would still be legible though, which is
the primary objective of the Modus themes.

** What does it mean to avoid exaggerations?
:properties:
:custom_id: h:44284e1f-fab8-4c4f-92f0-544728a7c91e
:end:
#+cindex: Avoiding exaggerations in design

The Modus themes are designed with restraint, so that their default
looks do not overdo it with the application of color.

[[#h:bf1c82f2-46c7-4eb2-ad00-dd11fdd8b53f][Customization Options]].

This is the non-quantifiable aspect of the themes' design: the artistic
part, if you will.  There are a lot of cases where color can be used
inconsiderately, without accounting for layout, typographic, or other
properties of the presentation.  For example, two headings with distinct
markers, such as leading asterisks in Org buffers, do not have to have
highly contrasting hues between them in order to be told apart: the
added element of contrast in hueness does not contribute significantly
more to the distinction between the headings than colors whose hues are
relatively closer to each other in the color space.

Exaggerations can be hard to anticipate or identify.  Multiple shades of
blue and magenta in the same context may not seem optimal: one might
think that it would be better to use highly contrasting hues to ensure
that all colors stand out, such as by placing blue next to yellow, next
to magenta, and green.  That would, however, be a case of design for its
own sake; a case where color is being applied without consideration of
its end results in the given context.  Too many contrasting hues in
close proximity force an erratic rate to how the eye jumps from one
piece of text to the next.  Whereas multiple shades of, say, blue and
magenta can suffice to tell things apart and avoid excess coloration: a
harmonious rhythm.

** Why are colors mostly variants of blue, magenta, cyan?
:properties:
:custom_id: h:0b26cb47-9733-4cb1-87d9-50850cb0386e
:end:
#+cindex: Innate color qualities of the palette

Due to the innate properties of color, some options are better than
others for the accessibility purposes of the themes, the stylistic
consistency between ~modus-operandi~ and ~modus-vivendi~, and the avoidance
of exaggerations in design.

[[#h:44284e1f-fab8-4c4f-92f0-544728a7c91e][What does it mean to avoid exaggerations?]]

What we describe as color is a function of three distinct channels of
light: red, green, blue.  In hexadecimal RGB notation, a color value is
read as three pairs of red, green, and blue light: =#RRGGBB=.  Of those
three, the most luminant is green, while the least luminant is blue.

The three basic colors represent each of the channels of light.  They
can be intermixed to give us six colors: red and green derive yellow,
green and blue make cyan, red and blue turn into magenta.

We can test the luminance of each of those against white and black to
get a sense of how not all colors are equally good for accessibility
(white is =#ffffff=, which means that all three light channels are fully
luminated, while black is =#000000= meaning that no light is present
(notwithstanding display technology)).

#+begin_example
| Name    |         | #ffffff | #000000 |
|---------+---------+---------+---------|
| red     | #ff0000 |    4.00 |    5.25 |
| yellow  | #ffff00 |    1.07 |   19.56 |
| green   | #00ff00 |    1.37 |   15.30 |
| cyan    | #00ffff |    1.25 |   16.75 |
| blue    | #0000ff |    8.59 |    2.44 |
| magenta | #ff00ff |    3.14 |    6.70 |
#+end_example

[[#h:02e25930-e71a-493d-828a-8907fc80f874][Measure color contrast]].

By reading this table we learn that every color that has a high level of
green light (green, yellow, cyan) is virtually unreadable against a
white background and, conversely, can be easily read against black.

We can then infer that red and blue, in different combinations, with
green acting as calibrator for luminance, will give us fairly moderate
colors that pass the 7:1 target.  Blue with a bit of green produce
appropriate variants of cyan.  Similarly, blue combined with some red
and hints of green give us suitable shades of purple.

Due to the need of maintaining some difference in hueness between
adjacent colors, it is not possible to make red, green, and yellow the
primary colors, because blue could not be used to control their
luminance and, thus the relevant space would shrink considerably.

[[#h:5ce7ae2e-9348-4e55-b4cf-9302345b1826][Is the contrast ratio about adjacent colors?]]

This phenomenon is best illustrated by the following table that measures
the relative luminance of shades of red, yellow, magenta against white:

#+begin_example
|         | #ffffff |
|---------+---------|
| #990000 |    8.92 |
| #995500 |    5.75 |
| #990099 |    7.46 |
#+end_example

We notice that equal values of red and blue light in =#990099= (magenta
shade) do not lead to a considerable change in luminance compared with
=#990000= (red variant).  Whereas less amount of green light in =#995500=
leads to a major drop in luminance relative to white.  It follows that
using the green channel of light to calibrate the luminance of colors is
more effective than trying to do the same with either red or blue (the
latter is the least effective in that regard).

When we need to work with several colors, it is always better to have
sufficient manoeuvring space, especially since we cannot pick arbitrary
colors but only those that satisfy the accessibility objectives of the
themes.

As for why we do not mostly use green, yellow, cyan for the dark theme,
it is because those colors are far more luminant than their counterparts
on the other side of the spectrum, so to ensure that they all have about
the same contrast ratios we would have to alter their hueness
considerably.  In short, the effect would not be optimal as it would
lead to exaggerations.  Plus, it would make ~modus-vivendi~ look
completely different than ~modus-operandi~, to the effect that the two
could not be properly considered part of the same project.

** What is the best setup for legibility?
:properties:
:custom_id: h:f60cc2ae-129d-47c0-9849-4f6bbd87d8be
:end:
#+cindex: General setup for readability

The Modus themes can be conceptually simplified as combinations of color
values that account for relative luminance and inner harmony.  Those
qualities do not guarantee that every end-user will have the same
experience, due to differences between people, but also because of
variances in hardware capabilities and configurations.  For the purposes
of this document, we may only provide suggestions pertaining to the
latter case.

~modus-operandi~ is best used outdoors or in a room that either gets
direct sunlight or has plenty of light.  Whereas ~modus-vivendi~ works
better when there is not a lot of sunshine or the room has a source of
light, preferably a faint or warm one.  It is possible to use
~modus-operandi~ at night and ~modus-vivendi~ during the day, though that
will depend on several variables, such as one's overall perception of
color, the paint on the walls and how that contributes to the impression
of lightness in the room, the sense of space within the eye's peripheral
vision, hardware specifications, and environmental factors.

In general, an additional source of light other than that of the monitor
can help reduce eye strain: the eyes are more relaxed when they do not
have to focus on one point to gather light.

The monitor's display settings must be accounted for. Gamma values, in
particular, need to be calibrated to neither amplify nor distort the
perception of black. Same principle for sharpness, brightness, and
contrast as determined by the hardware, which all have an effect on how
text is read on the screen.

There are software level methods on offer, such as the XrandR utility
for the X Window System (X.org), which can make gamma corrections for
each of the three channels of light (red, green, blue).  For example:

: xrandr --output LVDS1 --brightness 1.0 --gamma 0.76:0.75:0.68

Typography is another variable.  Some font families are blurry at small
point sizes.  Others may have a regular weight that is lighter (thiner)
than that of their peers which may, under certain circumstances, cause a
halo effect around each glyph.

The gist is that legibility cannot be fully solved at the theme level.
The color combinations may have been optimized for accessibility, though
the remaining contributing factors in each case need to be considered in
full.

* Contributing
:properties:
:custom_id: h:9c3cd842-14b7-44d7-84b2-a5c8bc3fc3b1
:end:

This section documents the canonical sources of the themes and the ways
in which you can contribute to their ongoing development.

** Sources of the themes
:properties:
:custom_id: h:89504f1c-c9a1-4bd9-ab39-78fd0eddb47c
:end:
#+cindex: Sources of the themes

The ~modus-operandi~ and ~modus-vivendi~ themes are built into Emacs.
Currently they are in Emacs' git main branch (trunk), which is tracking
the next development release target.

The source code of the themes is [[https://gitlab.com/protesilaos/modus-themes/][available on Gitlab]], for the time
being.  A [[https://github.com/protesilaos/modus-themes/][mirror on Github]] is also on offer.

An HTML version of this manual is provided as an extension of the
[[https://protesilaos.com/modus-themes/][author's personal website]] (does not rely on any non-free code).

** Issues you can help with
:properties:
:custom_id: h:6536c8d5-3f98-43ab-a787-b94120e735e8
:end:
#+cindex: Contributing

A few tasks you can help with:

+ Suggest refinements to packages that are covered.
+ Report packages not covered thus far.
+ Report bugs, inconsistencies, shortcomings.
+ Help expand the documentation of covered-but-not-styled packages.
+ Suggest refinements to the color palette.
+ Help expand this document or any other piece of documentation.
+ Merge requests for code refinements.

[[#h:111773e2-f26f-4b68-8c4f-9794ca6b9633][Patches require copyright assignment to the FSF]].

It is preferable that your feedback includes some screenshots, GIFs, or
short videos, as well as further instructions to reproduce a given
setup.  Though this is not a requirement.

Whatever you do, bear in mind the overarching objective of the Modus
themes: to keep a contrast ratio that is greater or equal to 7:1 between
background and foreground colors.  If a compromise is ever necessary
between aesthetics and accessibility, it shall always be made in the
interest of the latter.

** Patches require copyright assignment to the FSF
:properties:
:custom_id: h:111773e2-f26f-4b68-8c4f-9794ca6b9633
:end:

Code contributions are most welcome.  For any major edit (more than 15
lines, or so, in aggregate per person), you need to make a copyright
assignment to the Free Software Foundation.  This is necessary because
the themes are part of the upstream Emacs distribution: the FSF must at
all times be in a position to enforce the GNU General Public License.

Copyright assignment is a simple process.  Check the request form below
(please adapt it accordingly).  You must write an email to the address
mentioned in the form and then wait for the FSF to send you a legal
agreement.  Sign the document and file it back to them.  This could all
happen via email and take about a week.  You are encouraged to go
through this process.  You only need to do it once.  It will allow you
to make contributions to Emacs in general.

#+begin_example text
Please email the following information to assign@gnu.org, and we
will send you the assignment form for your past and future changes.

Please use your full legal name (in ASCII characters) as the subject
line of the message.
----------------------------------------------------------------------
REQUEST: SEND FORM FOR PAST AND FUTURE CHANGES

[What is the name of the program or package you're contributing to?]

GNU Emacs

[Did you copy any files or text written by someone else in these changes?
Even if that material is free software, we need to know about it.]

Copied a few snippets from the same files I edited.  Their author,
Protesilaos Stavrou, has already assigned copyright to the Free Software
Foundation.

[Do you have an employer who might have a basis to claim to own
your changes?  Do you attend a school which might make such a claim?]


[For the copyright registration, what country are you a citizen of?]


[What year were you born?]


[Please write your email address here.]


[Please write your postal address here.]





[Which files have you changed so far, and which new files have you written
so far?]

#+end_example

* Acknowledgements
:properties:
:custom_id: h:95c3da23-217f-404e-b5f3-56c75760ebcf
:end:
#+cindex: Contributors

The Modus themes are a collective effort.  Every bit of work matters.

+ Author/maintainer :: Protesilaos Stavrou.

+ Contributions to code or documentation :: Anders Johansson, Basil
  L.{{{space()}}} Contovounesios, Carlo Zancanaro, Eli Zaretskii, Fritz Grabo,
  Kostadin Ninev, Madhavan Krishnan, Markus Beppler, Matthew Stevenson,
  Mauro Aranda, Nicolas De Jaeghere, Philip Kaludercic, Rudolf
  Adamkovič, Shreyas Ragavan, Stefan Kangas, Vincent Murphy, Xinglu
  Chen.

+ Ideas and user feedback :: Aaron Jensen, Adam Spiers, Adrian Manea,
  Alex Griffin, Alex Peitsinis, Alexey Shmalko, Alok Singh, Anders
  Johansson, André Alexandre Gomes, Arif Rezai, Basil L.{{{space()}}}
  Contovounesios, Burgess Chang, Christian Tietze, Christopher Dimech,
  Damien Cassou, Daniel Mendler, Dario Gjorgjevski, David Edmondson,
  Davor Rotim, Divan Santana, Emanuele Michele Alberto Monterosso,
  Farasha Euker, Gautier Ponsinet, Gerry Agbobada, Gianluca Recchia,
  Gustavo Barros, Hörmetjan Yiltiz, Ilja Kocken, Iris Garcia, Jeremy
  Friesen, Jerry Zhang, John Haman, Joshua O'Connor, Kevin Fleming,
  Kévin Le Gouguec, Kostadin Ninev, Len Trigg, Manuel Uberti, Mark
  Burton, Markus Beppler, Mauro Aranda, Michael Goldenberg, Morgan
  Smith, Murilo Pereira, Nicky van Foreest, Nicolas De Jaeghere, Paul
  Poloskov, Pengji Zhang, Pete Kazmier, Peter Wu, Philip Kaludercic,
  Pierre Téchoueyres, Roman Rudakov, Ryan Phillips, Rudolf Adamkovič,
  Sam Kleinman, Shreyas Ragavan, Simon Pugnet, Tassilo Horn, Thibaut
  Verron, Thomas Heartman, Trey Merkley, Togan Muftuoglu, Toon Claes,
  Uri Sharf, Utkarsh Singh, Vincent Foley.  As well as users: Ben,
  CsBigDataHub1, Emacs Contrib, Eugene, Fourchaux, Fredrik, Moesasji,
  Nick, TheBlob42, Trey, bepolymathe, doolio, fleimgruber, iSeeU,
  jixiuf, okamsn, pRot0ta1p.

+ Packaging :: Basil L.{{{space()}}} Contovounesios, Eli Zaretskii, Glenn
  Morris, Mauro Aranda, Richard Stallman, Stefan Kangas (core Emacs),
  Stefan Monnier (GNU Elpa), André Alexandre Gomes, Dimakakos Dimos,
  Morgan Smith, Nicolas Goaziou (Guix), Dhavan Vaidya (Debian).

+ Inspiration for certain features :: Bozhidar Batsov (zenburn-theme),
  Fabrice Niessen (leuven-theme).

Special thanks, in no particular order, to Manuel Uberti, Gustavo
Barros, and Omar Antolín Camarena for their long time contributions and
insightful commentary.

* Meta
:properties:
:custom_id: h:13752581-4378-478c-af17-165b6e76bc1b
:end:
#+cindex: Development notes

If you are curious about the principles that govern the development of
this project read the essay [[https://protesilaos.com/codelog/2020-03-17-design-modus-themes-emacs/][On the design of the Modus themes]]
(2020-03-17).

Here are some more publications for those interested in the kind of work
that goes into this project (sometimes the commits also include details
of this sort):

+ [[https://protesilaos.com/codelog/2020-05-10-modus-operandi-palette-review/][Modus Operandi theme subtle palette review]] (2020-05-10)
+ [[https://protesilaos.com/codelog/2020-06-13-modus-vivendi-palette-review/][Modus Vivendi theme subtle palette review]] (2020-06-13)
+ [[https://protesilaos.com/codelog/2020-07-04-modus-themes-faint-colours/][Modus themes: new "faint syntax" option]] (2020-07-04)
+ [[https://protesilaos.com/codelog/2020-07-08-modus-themes-nuanced-colours/][Modus themes: major review of "nuanced" colours]] (2020-07-08)
+ [[https://protesilaos.com/codelog/2020-09-14-modus-themes-review-blues/][Modus themes: review of blue colours]] (2020-09-14)
+ [[https://protesilaos.com/codelog/2020-12-27-modus-themes-review-rainbow-delimiters/][Modus themes: review rainbow-delimiters faces]] (2020-12-27)
+ [[https://protesilaos.com/codelog/2021-01-11-modus-themes-review-select-faint-colours/][Modus themes: review of select "faint" colours]] (2021-01-11)
+ [[https://protesilaos.com/codelog/2021-02-25-modus-themes-diffs-deuteranopia/][The Modus themes now cover deuteranopia in diffs]] (2021-02-25)

And here are the canonical sources of this project's documentation:

+ Manual :: <https://protesilaos.com/modus-themes>
+ Change Log :: <https://protesilaos.com/modus-themes-changelog>
+ Screenshots :: <https://protesilaos.com/modus-themes-pictures>

* GNU Free Documentation License
:properties:
:appendix: t
:custom_id: h:3077c3d2-7f90-4228-8f0a-73124f4026f6
:end:

#+texinfo: @include doclicense.texi

#+begin_export html
<pre>

                GNU Free Documentation License
                 Version 1.3, 3 November 2008


 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     <https://fsf.org/>
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.

This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
license designed for free software.

We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book.  We recommend this License
principally for works whose purpose is instruction or reference.


1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License.  Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein.  The "Document", below,
refers to any such manual or work.  Any member of the public is a
licensee, and is addressed as "you".  You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.

A "Modified Version" of the Document means any work containing the
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A "Secondary Section" is a named appendix or a front-matter section of
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The "Invariant Sections" are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.  If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant.  The Document may contain zero
Invariant Sections.  If the Document does not identify any Invariant
Sections then there are none.

The "Cover Texts" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License.  A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.

A "Transparent" copy of the Document means a machine-readable copy,
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or discourage subsequent modification by readers is not Transparent.
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Examples of suitable formats for Transparent copies include plain
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A section "Entitled XYZ" means a named subunit of the Document whose
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The Document may include Warranty Disclaimers next to the notice which
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no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either
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If you publish printed copies (or copies in media that commonly have
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If the required texts for either cover are too voluminous to fit
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If you publish or distribute Opaque copies of the Document numbering
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It is requested, but not required, that you contact the authors of the
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4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
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and modification of the Modified Version to whoever possesses a copy
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B. List on the Title Page, as authors, one or more persons or entities
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E. Add an appropriate copyright notice for your modifications
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   giving the public permission to use the Modified Version under the
   terms of this License, in the form shown in the Addendum below.
G. Preserve in that license notice the full lists of Invariant Sections
   and required Cover Texts given in the Document's license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title, and add
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M. Delete any section Entitled "Endorsements".  Such a section
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N. Do not retitle any existing section to be Entitled "Endorsements"
   or to conflict in title with any Invariant Section.
O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
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These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
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You may add a passage of up to five words as a Front-Cover Text, and a
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permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
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imply endorsement of any Modified Version.


5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
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list them all as Invariant Sections of your combined work in its
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The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
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Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History"
in the various original documents, forming one section Entitled
"History"; likewise combine any sections Entitled "Acknowledgements",
and any sections Entitled "Dedications".  You must delete all sections
Entitled "Endorsements".


6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the rules
of this License for verbatim copying of each of the documents in all
other respects.

You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert a
copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.


7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
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If the Cover Text requirement of section 3 is applicable to these
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the entire aggregate, the Document's Cover Texts may be placed on
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8. TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
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Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.


9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License.  Any attempt
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will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license
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Moreover, your license from a particular copyright holder is
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Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
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not give you any rights to use it.


10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the
GNU Free Documentation License from time to time.  Such new versions
will be similar in spirit to the present version, but may differ in
detail to address new problems or concerns.  See
https://www.gnu.org/licenses/.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
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following the terms and conditions either of that specified version or
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11. RELICENSING

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
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"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
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"Incorporate" means to publish or republish a Document, in whole or in
part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole or
in part into the MMC, (1) had no cover texts or invariant sections, and
(2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.


ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:

    Copyright (c)  YEAR  YOUR NAME.
    Permission is granted to copy, distribute and/or modify this document
    under the terms of the GNU Free Documentation License, Version 1.3
    or any later version published by the Free Software Foundation;
    with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
    A copy of the license is included in the section entitled "GNU
    Free Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this:

    with the Invariant Sections being LIST THEIR TITLES, with the
    Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
</pre>
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