elisp: Preserving Window Sizes
27.5 Preserving Window Sizes
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A window can get resized explicitly by using one of the functions from
the preceding section or implicitly, for example, when resizing an
adjacent window, when splitting or deleting a window (
Splitting
Windows, Deleting Windows) or when resizing the window’s frame
(Size and Position).
It is possible to avoid implicit resizing of a specific window when
there are one or more other resizable windows on the same frame. For
this purpose, Emacs must be advised to “preserve” the size of that
window. There are two basic ways to do that.
-- Variable: window-size-fixed
If this buffer-local variable is non-‘nil’, the size of any window
displaying the buffer cannot normally be changed. Deleting a
window or changing the frame’s size may still change the window’s
size, if there is no choice.
If the value is ‘height’, then only the window’s height is fixed;
if the value is ‘width’, then only the window’s width is fixed.
Any other non-‘nil’ value fixes both the width and the height.
If this variable is ‘nil’, this does not necessarily mean that any
window showing the buffer can be resized in the desired direction.
To determine that, use the function ‘window-resizable’.
Resizing Windows.
Often ‘window-size-fixed’ is overly aggressive because it inhibits
any attempt to explicitly resize or split an affected window as well.
This may even happen after the window has been resized implicitly, for
example, when deleting an adjacent window or resizing the window’s
frame. The following function tries hard to never disallow resizing
such a window explicitly:
-- Function: window-preserve-size &optional window horizontal preserve
This function (un-)marks the height of window WINDOW as preserved
for future resize operations. WINDOW must be a live window and
defaults to the selected one. If the optional argument HORIZONTAL
is non-‘nil’, it (un-)marks the width of WINDOW as preserved.
If the optional argument PRESERVE is ‘t’, this means to preserve
the current height/width of WINDOW’s body. The height/width of
WINDOW will change only if Emacs has no better choice. Resizing a
window whose height/width is preserved by this function never
throws an error.
If PRESERVE is ‘nil’, this means to stop preserving the
height/width of WINDOW, lifting any respective restraint induced by
a previous call of this function for WINDOW. Calling
‘enlarge-window’, ‘shrink-window’ or ‘fit-window-to-buffer’ with
WINDOW as argument may also remove the respective restraint.
‘window-preserve-size’ is currently invoked by the following
functions:
‘fit-window-to-buffer’
If the optional argument PRESERVE-SIZE of that function (
Resizing Windows) is non-‘nil’, the size established by that
function is preserved.
‘display-buffer’
If the ALIST argument of that function (Choosing Window)
contains a ‘preserve-size’ entry, the size of the window produced
by that function is preserved.
Parameters::) called ‘preserved-size’ which is consulted by the window
resizing functions. This parameter will not prevent resizing the window
when the window shows another buffer than the one when
‘window-preserve-size’ was invoked or if its size has changed since
then.
The following function can be used to check whether the height of a
particular window is preserved:
-- Function: window-preserved-size &optional window horizontal
This function returns the preserved height of window WINDOW in
pixels. WINDOW must be a live window and defaults to the selected
one. If the optional argument HORIZONTAL is non-‘nil’, it returns
the preserved width of WINDOW. It returns ‘nil’ if the size of
WINDOW is not preserved.
Info Catalog
elisp: Resizing Windows
elisp: Windows
elisp: Splitting Windows