elisp: Window Hooks
27.27 Hooks for Window Scrolling and Changes
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This section describes how a Lisp program can take action whenever a
window displays a different part of its buffer or a different buffer.
There are three actions that can change this: scrolling the window,
switching buffers in the window, and changing the size of the window.
The first two actions run ‘window-scroll-functions’; the last runs
‘window-size-change-functions’.
-- Variable: window-scroll-functions
This variable holds a list of functions that Emacs should call
before redisplaying a window with scrolling. Displaying a
different buffer in the window also runs these functions.
This variable is not a normal hook, because each function is called
with two arguments: the window, and its new display-start position.
These functions must take care when using ‘window-end’ (
Window Start and End); if you need an up-to-date value, you must
use the UPDATE argument to ensure you get it.
*Warning:* don’t use this feature to alter the way the window is
scrolled. It’s not designed for that, and such use probably won’t
work.
-- Variable: window-size-change-functions
This variable holds a list of functions to be called if the size of
any window changes for any reason. The functions are called at the
beginning of a redisplay cycle, and just once for each frame on
which size changes have occurred.
Each function receives the frame as its sole argument. There is no
direct way to find out which windows on that frame have changed
size, or precisely how. However, if a size-change function
records, at each call, the existing windows and their sizes, it can
also compare the present sizes and the previous sizes.
Creating or deleting windows counts as a size change, and therefore
causes these functions to be called. Changing the frame size also
counts, because it changes the sizes of the existing windows.
You may use ‘save-selected-window’ in these functions (
Selecting Windows). However, do not use ‘save-window-excursion’
(Window Configurations); exiting that macro counts as a
size change, which would cause these functions to be called over
and over.
-- Variable: window-configuration-change-hook
A normal hook that is run every time you change the window
configuration of an existing frame. This includes splitting or
deleting windows, changing the sizes of windows, or displaying a
different buffer in a window.
The buffer-local part of this hook is run once for each window on
the affected frame, with the relevant window selected and its
buffer current. The global part is run once for the modified
frame, with that frame selected.
In addition, you can use ‘jit-lock-register’ to register a Font Lock
fontification function, which will be called whenever parts of a buffer
are (re)fontified because a window was scrolled or its size changed.
Other Font Lock Variables.
Info Catalog
elisp: Window Parameters
elisp: Windows