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(Major Mode Conventions): Note that specialness is inherited.

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This commit is contained in:
Chong Yidong 2009-03-28 13:38:55 +00:00
parent 3c25a5a986
commit 4163374057
1 changed files with 20 additions and 14 deletions
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34
doc/lispref/modes.texi
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@ -157,13 +157,13 @@ If @var{function} has a non-@code{nil} property
changing major modes) won't delete it from the hook variable's local
value.
It is best to design your hook functions so that the order in which they
are executed does not matter. Any dependence on the order is ``asking
for trouble.'' However, the order is predictable: normally,
It is best to design your hook functions so that the order in which
they are executed does not matter. Any dependence on the order is
asking for trouble. However, the order is predictable: normally,
@var{function} goes at the front of the hook list, so it will be
executed first (barring another @code{add-hook} call). If the optional
argument @var{append} is non-@code{nil}, the new hook function goes at
the end of the hook list and will be executed last.
executed first (barring another @code{add-hook} call). If the
optional argument @var{append} is non-@code{nil}, the new hook
function goes at the end of the hook list and will be executed last.
@code{add-hook} can handle the cases where @var{hook} is void or its
value is a single function; it sets or changes the value to a list of
@ -231,11 +231,11 @@ writing a minor mode, which is often difficult).
If the new mode is similar to an old one, it is often unwise to
modify the old one to serve two purposes, since it may become harder
to use and maintain. Instead, copy and rename an existing major mode
definition and alter the copy---or use @code{define-derived-mode} to
define a @dfn{derived mode} (@pxref{Derived Modes}). For example,
Rmail Edit mode is a major mode that is very similar to Text mode
except that it provides two additional commands. Its definition is
distinct from that of Text mode, but uses that of Text mode.
definition and alter the copy---or use the @code{define-derived-mode}
macro to define a @dfn{derived mode} (@pxref{Derived Modes}). For
example, Rmail Edit mode is a major mode that is very similar to Text
mode except that it provides two additional commands. Its definition
is distinct from that of Text mode, but uses that of Text mode.
Even if the new mode is not an obvious derivative of any other mode,
it is convenient to use @code{define-derived-mode} with a @code{nil}
@ -460,9 +460,9 @@ and then runs the normal hook @code{after-change-major-mode-hook}.
The major mode command may start by calling some other major mode
command (called the @dfn{parent mode}) and then alter some of its
settings. A mode that does this is called a @dfn{derived mode}. The
recommended way to define one is to use @code{define-derived-mode},
but this is not required. Such a mode should call the parent mode
command inside a @code{delay-mode-hooks} form. (Using
recommended way to define one is to use the @code{define-derived-mode}
macro, but this is not required. Such a mode should call the parent
mode command inside a @code{delay-mode-hooks} form. (Using
@code{define-derived-mode} does this automatically.) @xref{Derived
Modes}, and @ref{Mode Hooks}.
@ -488,6 +488,12 @@ in Funny mode should not inherit Funny mode, in case
@code{default-major-mode} is @code{nil}. Modes such as Dired, Rmail,
and Buffer List use this feature.
The @code{define-derived-mode} macro automatically marks the derived
mode as special if the parent mode is special. The special mode
@code{special-mode} provides a convenient parent for other special
modes to inherit from; it sets @code{buffer-read-only} to @code{t},
and does nothing else.
@item
If you want to make the new mode the default for files with certain
recognizable names, add an element to @code{auto-mode-alist} to select