* Windows and Frames:: Relating windows to the frame they appear on.
* Window Sizes:: Accessing a window's size.
* Resizing Windows:: Changing the sizes of windows.
+* Preserving Window Sizes:: Preserving the size of windows.
* Splitting Windows:: Creating a new window.
* Deleting Windows:: Removing a window from its frame.
* Recombining Windows:: Preserving the frame layout when splitting and
margins, fringes, a scroll bar and a right divider, if present.
@end defopt
-@defvar window-size-fixed
-If this buffer-local variable is non-@code{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 its size, if
-there is no choice.
-
-If the value is @code{height}, then only the window's height is fixed;
-if the value is @code{width}, then only the window's width is fixed.
-Any other non-@code{nil} value fixes both the width and the height.
-
-If this variable is @code{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 @code{window-resizable}.
-@xref{Resizing Windows}.
-@end defvar
-
The following function tells how small a specific window can get taking
into account the sizes of its areas and the values of
@code{window-min-height}, @code{window-min-width} and
The following commands resize windows in more specific ways. When
called interactively, they act on the selected window.
-@deffn Command fit-window-to-buffer &optional window max-height min-height max-width min-width
+@deffn Command fit-window-to-buffer &optional window max-height min-height max-width min-width preserve-size
This command adjusts the height or width of @var{window} to fit the text
in it. It returns non-@code{nil} if it was able to resize @var{window},
and @code{nil} otherwise. If @var{window} is omitted or @code{nil}, it
specified in columns and include fringes, margins and scrollbars, if
any.
+The optional argument @var{preserve-size}, if non-@code{nil}, will
+install a parameter to preserve the size of @var{window} during future
+resize operations (@pxref{Preserving Window Sizes}).
+
If the option @code{fit-frame-to-buffer} (see below) is non-@code{nil},
this function will try to resize the frame of @var{window} to fit its
contents by calling @code{fit-frame-to-buffer} (@pxref{Size and
function.
@end defopt
+
+@node Preserving Window Sizes
+@section Preserving Window Sizes
+@cindex preserving window sizes
+
+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 (@pxref{Splitting
+Windows}, @pxref{Deleting Windows}) or when resizing the window's frame
+(@pxref{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 @dfn{preserve} the size of that
+window. There are two basic ways to do that.
+
+@defvar window-size-fixed
+If this buffer-local variable is non-@code{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 @code{height}, then only the window's height is fixed;
+if the value is @code{width}, then only the window's width is fixed.
+Any other non-@code{nil} value fixes both the width and the height.
+
+If this variable is @code{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 @code{window-resizable}.
+@xref{Resizing Windows}.
+@end defvar
+
+Often @code{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:
+
+@defun window-preserve-size &optional window horizontal preserve
+This function (un-)marks the height of window @var{window} as preserved
+for future resize operations. @var{window} must be a live window and
+defaults to the selected one. If the optional argument @var{horizontal}
+is non-@code{nil}, it (un-)marks the width of @var{window} as preserved.
+
+If the optional argument @var{preserve} is @code{t}, this means to
+preserve the current height/width of @var{window}'s body. The
+height/width of @var{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 @var{preserve} is @code{nil}, this means to stop preserving the
+height/width of @var{window}, lifting any respective restraint induced
+by a previous call of this function for @var{window}. Calling
+@code{enlarge-window}, @code{shrink-window} or
+@code{fit-window-to-buffer} with @var{window} as argument may also
+remove the respective restraint.
+@end defun
+
+@code{window-preserve-size} is currently invoked by the following
+functions:
+
+@table @code
+@item fit-window-to-buffer
+If the optional argument @var{preserve-size} of that function
+(@pxref{Resizing Windows}) is non-@code{nil}, the size established by
+that function is preserved.
+
+@item display-buffer
+If the @var{alist} argument of that function (@pxref{Choosing Window})
+contains a @code{preserve-size} entry, the size of the window produced
+by that function is preserved.
+@end table
+
+ @code{window-preserve-size} installs a window parameter (@pxref{Window
+Parameters}) called @code{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
+@code{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:
+
+@defun window-preserved-size &optional window horizontal
+This function returns the preserved height of window @var{window} in
+pixels. @var{window} must be a live window and defaults to the selected
+one. If the optional argument @var{horizontal} is non-@code{nil}, it
+returns the preserved width of @var{window}. It returns @code{nil} if
+the size of @var{window} is not preserved.
+@end defun
+
+
@node Deleting Windows
@section Deleting Windows
@cindex deleting windows
of the window; its return value is ignored.
@end itemize
+If @var{alist} contains a @code{preserve-size} entry, Emacs will try to
+preserve the size of the new window during future resize operations
+(@pxref{Preserving Window Sizes}). The @sc{cdr} of that entry must be a
+cons cell whose @sc{car}, if non-@code{nil}, means to preserve the width
+of the window and whose @sc{cdr}, if non-@code{nil}, means to preserve
+the height of the window.
+
This function can fail if no window splitting can be performed for some
reason (e.g., if the selected frame has an @code{unsplittable} frame
parameter; @pxref{Buffer Parameters}).
from. It is installed by @code{window-state-get} (@pxref{Window
Configurations}).
+@item @code{preserved-size}
+This parameter specifies a buffer, a direction where @code{nil} means
+vertical and @code{t} horizontal, and a size in pixels. If this window
+displays the specified buffer and its size in the indicated direction
+equals the size specified by this parameter, then Emacs will try to
+preserve the size of this window in the indicated direction. This
+parameter is installed and updated by the function
+@code{window-preserve-size} (@pxref{Preserving Window Sizes}).
+
@item @code{quit-restore}
This parameter is installed by the buffer display functions
(@pxref{Choosing Window}) and consulted by @code{quit-restore-window}
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