Merge from origin/emacs-26

b0da915 (origin/emacs-26, emacs-26) Fix a typo in ELisp manual
400907b Add option to disable help completion autoloading (Bug#28607)
122ba16 Don't segfault on force-window-update of deleted window
015b12e Fix typo in ELisp manual
eadf044 Remove repeated function call in picture.el
1228a90 ; Fix mm-destroy-parts docstring typo
6cfd68d Fix Hideshow key binding typo in Emacs manual

doc/emacs/building.texi

@@ -1521,6 +1521,12 @@ library lets Emacs properly set up the hyperlinks in the @file{*Help*}
 buffer).  To disable this feature, change the variable
 @code{help-enable-auto-load} to @code{nil}.
 
+@vindex help-enable-completion-auto-load
+Automatic loading also occurs when completing names for
+@code{describe-variable} and @code{describe-function}, based on the
+prefix being completed.  To disable this feature, change the variable
+@code{help-enable-completion-auto-load} to @code{nil}.
+
 @vindex load-dangerous-libraries
 @cindex Lisp files byte-compiled by XEmacs
   By default, Emacs refuses to load compiled Lisp files which were

doc/emacs/programs.texi

@@ -1298,8 +1298,11 @@ count as blocks.
 @findex hs-show-block
 @findex hs-show-region
 @findex hs-hide-level
+@findex hs-toggle-hiding
+@findex hs-mouse-toggle-hiding
 @kindex C-c @@ C-h
 @kindex C-c @@ C-s
+@kindex C-c @@ C-c
 @kindex C-c @@ C-M-h
 @kindex C-c @@ C-M-s
 @kindex C-c @@ C-r
@@ -1312,7 +1315,7 @@ Hide the current block (@code{hs-hide-block}).
 @item C-c @@ C-s
 Show the current block (@code{hs-show-block}).
 @item C-c @@ C-c
-@itemx C-x @@ C-e
+@itemx C-c @@ C-e
 Either hide or show the current block (@code{hs-toggle-hiding}).
 @item S-mouse-2
 Toggle hiding for the block you click on (@code{hs-mouse-toggle-hiding}).

doc/lispref/loading.texi

@@ -466,9 +466,11 @@ first call to the function automatically loads the proper library, in
 order to install the real definition and other associated code, then
 runs the real definition as if it had been loaded all along.
 Autoloading can also be triggered by looking up the documentation of
-the function or macro (@pxref{Documentation Basics}).
+the function or macro (@pxref{Documentation Basics}), and completion
+of variable and function names (@pxref{Autoload by Prefix} below).
 
 @menu
+* Autoload by Prefix:: Autoload by Prefix.
 * When to Autoload::   When to Use Autoload.
 @end menu
 
@@ -703,6 +705,25 @@ symbol's new function value.  If the value of the optional argument
 function, only a macro.
 @end defun
 
+@node Autoload by Prefix
+@subsection Autoload by Prefix
+@cindex autoload by prefix
+
+@vindex definition-prefixes
+@findex register-definition-prefixes
+@vindex autoload-compute-prefixes
+During completion for the commands @code{describe-variable} and
+@code{describe-function}, Emacs will try to load files which may
+contain definitions matching the prefix being completed.  The variable
+@code{definition-prefixes} holds a hashtable which maps a prefix to
+the corresponding list of files to load for it.  Entries to this
+mapping are added by calls to @code{register-definition-prefixes}
+which are generated by @code{update-file-autoloads}
+(@pxref{Autoload}).  Files which don't contain any definitions worth
+loading (test files, for examples), should set
+@code{autoload-compute-prefixes} to @code{nil} as a file-local
+variable.
+
 @node When to Autoload
 @subsection When to Use Autoload
 @cindex autoload, when to use

doc/lispref/sequences.texi

@@ -601,7 +601,7 @@ returned value is a list.
 @defun seq-mapn function &rest sequences
   This function returns the result of applying @var{function} to each
 element of @var{sequences}.  The arity (@pxref{What Is a Function,
-sub-arity}) of @var{function} must match the number of sequences.
+subr-arity}) of @var{function} must match the number of sequences.
 Mapping stops at the end of the shortest sequence, and the returned
 value is a list.
 

doc/lispref/variables.texi

@@ -2009,7 +2009,7 @@ all files in those directories.  The list in @var{variables} can be of
 one of the two forms: @code{(@var{major-mode} . @var{alist})} or
 @code{(@var{directory} . @var{list})}.  With the first form, if the
 file's buffer turns on a mode that is derived from @var{major-mode},
-then the all the variables in the associated @var{alist} are applied;
+then all the variables in the associated @var{alist} are applied;
 @var{alist} should be of the form @code{(@var{name} . @var{value})}.
 A special value @code{nil} for @var{major-mode} means the settings are
 applicable to any mode.  In @var{alist}, you can use a special

etc/NEWS

@@ -153,6 +153,12 @@ after Emacs has finished initialization and is ready for use.
 emacs.service file to eg "~/.config/systemd/user/", you will need to copy
 the new version of the file again.)
 
++++
+** New option 'help-enable-completion-auto-load'.
+This allows disabling the new feature introduced in Emacs 26.1 which
+loads files during completion of 'C-h f' and 'C-h v' according to
+'definition-prefixes'.
+
 
 * Changes in Emacs 27.1
 

lisp/gnus/mm-decode.el

@@ -1111,7 +1111,7 @@ external if displayed external."
 	  (mm-remove-part handle)))))))
 
 (defun mm-destroy-parts (handles)
-  "Remove the displayed MIME parts represented by HANDLES."
+  "Destroy the displayed MIME parts represented by HANDLES."
   (if (and (listp handles)
 	   (bufferp (car handles)))
       (mm-destroy-part handles)

lisp/help-fns.el

@@ -103,11 +103,23 @@ and the output should go to `standard-output'.")
         (with-demoted-errors "while loading: %S"
           (load file 'noerror 'nomessage))))))
 
+(defcustom help-enable-completion-auto-load t
+  "Whether completion for Help commands can perform autoloading.
+If non-nil, whenever invoking completion for `describe-function'
+or `describe-variable' load files that might contain definitions
+with the current prefix.  The files are chosen according to
+`definition-prefixes'."
+  :type 'boolean
+  :group 'help
+  :version "26.3")
+
 (defun help--symbol-completion-table (string pred action)
-  (let ((prefixes (radix-tree-prefixes (help-definition-prefixes) string)))
-    (help--load-prefixes prefixes))
+  (when help-enable-completion-auto-load
+    (let ((prefixes (radix-tree-prefixes (help-definition-prefixes) string)))
+      (help--load-prefixes prefixes)))
   (let ((prefix-completions
-         (mapcar #'intern (all-completions string definition-prefixes))))
+         (and help-enable-completion-auto-load
+              (mapcar #'intern (all-completions string definition-prefixes)))))
     (complete-with-action action obarray string
                           (if pred (lambda (sym)
                                      (or (funcall pred sym)

lisp/textmodes/picture.el

@@ -623,7 +623,6 @@ Leaves the region surrounding the rectangle."
 
 (defvar picture-mode-map
   (let ((map (make-keymap)))
-    (define-key map [remap self-insert-command] 'picture-self-insert)
     (define-key map [remap self-insert-command] 'picture-self-insert)
     (define-key map [remap completion-separator-self-insert-command]
 			  'picture-self-insert)

src/window.c

@@ -4089,7 +4089,7 @@ displaying that buffer.  */)
       return Qt;
     }
 
-  if (WINDOWP (object))
+  if (WINDOW_LIVE_P (object))
     {
       struct window *w = XWINDOW (object);
       mark_window_display_accurate (object, false);