Every major mode command should finish by running the mode-independent
normal hook change-major-mode-after-body-hook, its mode hook,
and the normal hook after-change-major-mode-hook.
It does this by calling run-mode-hooks. If the major mode is a
derived mode, that is if it calls another major mode (the parent mode)
in its body, it should do this inside delay-mode-hooks so that
the parent won’t run these hooks itself. Instead, the derived mode’s
call to run-mode-hooks runs the parent’s mode hook too.
See Major Mode Conventions.
Emacs versions before Emacs 22 did not have delay-mode-hooks.
Versions before 24 did not have change-major-mode-after-body-hook.
When user-implemented major modes do not use run-mode-hooks and
have not been updated to use these newer features, they won’t entirely
follow these conventions: they may run the parent’s mode hook too early,
or fail to run after-change-major-mode-hook. If you encounter
such a major mode, please correct it to follow these conventions.
When you define a major mode using define-derived-mode, it
automatically makes sure these conventions are followed. If you
define a major mode “by hand”, not using define-derived-mode,
use the following functions to handle these conventions automatically.
Major modes should run their mode hook using this function. It is
similar to run-hooks (see Hooks), but it also runs
change-major-mode-after-body-hook, hack-local-variables
(when the buffer is visiting a file) (see File Local Variables),
and after-change-major-mode-hook. The last thing it does is to
evaluate any :after-hook forms declared by parent modes
(see Defining Derived Modes).
When this function is called during the execution of a
delay-mode-hooks form, it does not run the hooks or
hack-local-variables or evaluate the forms immediately.
Instead, it arranges for the next call to run-mode-hooks to run
them.
When one major mode command calls another, it should do so inside of
delay-mode-hooks.
This macro executes body, but tells all run-mode-hooks
calls during the execution of body to delay running their hooks.
The hooks will actually run during the next call to
run-mode-hooks after the end of the delay-mode-hooks
construct.
This is a normal hook run by run-mode-hooks. It is run before
the mode hooks.
This is a normal hook run by run-mode-hooks. It is run at the
very end of every properly-written major mode command.