@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003,
+@c 2004, 2005, 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/windows
@node Windows, Frames, Buffers, Top
displayed in windows.
@menu
-* Basic Windows:: Basic information on using windows.
-* Splitting Windows:: Splitting one window into two windows.
-* Deleting Windows:: Deleting a window gives its space to other windows.
-* Selecting Windows:: The selected window is the one that you edit in.
-* Cyclic Window Ordering:: Moving around the existing windows.
-* Buffers and Windows:: Each window displays the contents of a buffer.
-* Displaying Buffers:: Higher-lever functions for displaying a buffer
- and choosing a window for it.
-* Choosing Window:: How to choose a window for displaying a buffer.
-* Window Point:: Each window has its own location of point.
-* Window Start:: The display-start position controls which text
- is on-screen in the window.
-* Vertical Scrolling:: Moving text up and down in the window.
-* Horizontal Scrolling:: Moving text sideways on the window.
-* Size of Window:: Accessing the size of a window.
-* Resizing Windows:: Changing the size of a window.
-* Coordinates and Windows::Converting coordinates to windows.
-* Window Configurations:: Saving and restoring the state of the screen.
+* Basic Windows:: Basic information on using windows.
+* Splitting Windows:: Splitting one window into two windows.
+* Deleting Windows:: Deleting a window gives its space to other windows.
+* Selecting Windows:: The selected window is the one that you edit in.
+* Cyclic Window Ordering:: Moving around the existing windows.
+* Buffers and Windows:: Each window displays the contents of a buffer.
+* Displaying Buffers:: Higher-level functions for displaying a buffer
+ and choosing a window for it.
+* Choosing Window:: How to choose a window for displaying a buffer.
+* Window Point:: Each window has its own location of point.
+* Window Start:: The display-start position controls which text
+ is on-screen in the window.
+* Textual Scrolling:: Moving text up and down through the window.
+* Vertical Scrolling:: Moving the contents up and down on the window.
+* Horizontal Scrolling:: Moving the contents sideways on the window.
+* Size of Window:: Accessing the size of a window.
+* Resizing Windows:: Changing the size of a window.
+* Coordinates and Windows:: Converting coordinates to windows.
+* Window Tree:: The layout and sizes of all windows in a frame.
+* Window Configurations:: Saving and restoring the state of the screen.
+* Window Hooks:: Hooks for scrolling, window size changes,
+ redisplay going past a certain point,
+ or window configuration changes.
@end menu
@node Basic Windows
In each frame, at any time, one and only one window is designated as
@dfn{selected within the frame}. The frame's cursor appears in that
-window. At ant time, one frame is the selected frame; and the window
-selected within that frame is @dfn{the selected window}. The selected
-window's buffer is usually the current buffer (except when
+window, but the other windows have ``non-selected'' cursors, normally
+less visible. At any time, one frame is the selected frame; and the
+window selected within that frame is @dfn{the selected window}. The
+selected window's buffer is usually the current buffer (except when
@code{set-buffer} has been used). @xref{Current Buffer}.
+@defvar cursor-in-non-selected-windows
+If this variable is @code{nil}, Emacs displays only one cursor,
+in the selected window. Other windows have no cursor at all.
+@end defvar
+
For practical purposes, a window exists only while it is displayed in
a frame. Once removed from the frame, the window is effectively deleted
and should not be used, @emph{even though there may still be references
@item
containing frame
-@item
+@item
window height
-@item
+@item
window width
-@item
+@item
window edges with respect to the screen or frame
-@item
+@item
the buffer it displays
-@item
+@item
position within the buffer at the upper left of the window
-@item
+@item
amount of horizontal scrolling, in columns
-@item
+@item
point
-@item
+@item
the mark
-@item
+@item
how recently the window was selected
+
+@item
+fringe settings
+
+@item
+display margins
+
+@item
+scroll-bar settings
@end itemize
@cindex multiple windows
@cindex tiled windows
Most window systems support arbitrarily located overlapping windows.
In contrast, Emacs windows are @dfn{tiled}; they never overlap, and
-together they fill the whole screen or frame. Because of the way
-in which Emacs creates new windows and resizes them, you can't create
-every conceivable tiling of windows on an Emacs frame. @xref{Splitting
-Windows}, and @ref{Size of Window}.
+together they fill the whole screen or frame. Because of the way in
+which Emacs creates new windows and resizes them, not all conceivable
+tilings of windows on an Emacs frame are actually possible.
+@xref{Splitting Windows}, and @ref{Size of Window}.
@xref{Display}, for information on how the contents of the
window's buffer are displayed in the window.
@defun windowp object
- This function returns @code{t} if @var{object} is a window.
+This function returns @code{t} if @var{object} is a window.
@end defun
@node Splitting Windows
part of its former screen area. The rest is occupied by a newly created
window which is returned as the value of this function.
- If @var{horizontal} is non-@code{nil}, then @var{window} splits into
+If @var{horizontal} is non-@code{nil}, then @var{window} splits into
two side by side windows. The original window @var{window} keeps the
leftmost @var{size} columns, and gives the rest of the columns to the
new window. Otherwise, it splits into windows one above the other, and
left-hand or upper of the two, and the new window is the right-hand or
lower.
- If @var{window} is omitted or @code{nil}, then the selected window is
+If @var{window} is omitted or @code{nil}, then the selected window is
split. If @var{size} is omitted or @code{nil}, then @var{window} is
divided evenly into two parts. (If there is an odd line, it is
allocated to the new window.) When @code{split-window} is called
interactively, all its arguments are @code{nil}.
- The following example starts with one window on a screen that is 50
-lines high by 80 columns wide; then the window is split.
+If splitting would result in making a window that is smaller than
+@code{window-min-height} or @code{window-min-width}, the function
+signals an error and does not split the window at all.
+
+The following example starts with one window on a screen that is 50
+lines high by 80 columns wide; then it splits the window.
@smallexample
@group
@group
;; @r{Returns window created}
-(setq w2 (split-window w 15))
+(setq w2 (split-window w 15))
@result{} #<window 28 on windows.texi>
@end group
@group
@smallexample
@group
- __________
- | | line 0
+ __________
+ | | line 0
| w |
|__________|
| | line 15
@end group
@end smallexample
-Next, the top window is split horizontally:
+Next, split the top window horizontally:
@smallexample
@group
@end smallexample
@need 3000
-Now, the screen looks like this:
+Now the screen looks like this:
@smallexample
@group
column 35
- __________
- | | | line 0
+ __________
+ | | | line 0
| w | w3 |
|___|______|
| | line 15
@end smallexample
Normally, Emacs indicates the border between two side-by-side windows
-with a scroll bar (@pxref{X Frame Parameters,Scroll Bars}) or @samp{|}
+with a scroll bar (@pxref{Layout Parameters,Scroll Bars}) or @samp{|}
characters. The display table can specify alternative border
characters; see @ref{Display Tables}.
@end deffn
-@deffn Command split-window-vertically size
-This function splits the selected window into two windows, one above
-the other, leaving the selected window with @var{size} lines.
+@deffn Command split-window-vertically &optional size
+This function splits the selected window into two windows, one above the
+other, leaving the upper of the two windows selected, with @var{size}
+lines. (If @var{size} is negative, then the lower of the two windows
+gets @minus{} @var{size} lines and the upper window gets the rest, but
+the upper window is still the one selected.) However, if
+@code{split-window-keep-point} (see below) is @code{nil}, then either
+window can be selected.
+
+In other respects, this function is similar to @code{split-window}.
+In particular, the upper window is the original one and the return
+value is the new, lower window.
+@end deffn
-This function is simply an interface to @code{split-windows}.
-Here is the complete function definition for it:
+@defopt split-window-keep-point
+If this variable is non-@code{nil} (the default), then
+@code{split-window-vertically} behaves as described above.
-@smallexample
-@group
-(defun split-window-vertically (&optional arg)
- "Split current window into two windows, one above the other."
- (interactive "P")
- (split-window nil (and arg (prefix-numeric-value arg))))
-@end group
-@end smallexample
-@end deffn
+If it is @code{nil}, then @code{split-window-vertically} adjusts point
+in each of the two windows to avoid scrolling. (This is useful on
+slow terminals.) It selects whichever window contains the screen line
+that point was previously on.
-@deffn Command split-window-horizontally size
+This variable only affects the behavior of @code{split-window-vertically}.
+It has no effect on the other functions described here.
+@end defopt
+
+@deffn Command split-window-horizontally &optional size
This function splits the selected window into two windows
-side-by-side, leaving the selected window with @var{size} columns.
+side-by-side, leaving the selected window on the left with @var{size}
+columns. If @var{size} is negative, the rightmost window gets
+@minus{} @var{size} columns, but the leftmost window still remains
+selected.
-This function is simply an interface to @code{split-windows}. Here is
-the complete definition for @code{split-window-horizontally} (except for
-part of the documentation string):
+This function is basically an interface to @code{split-window}.
+You could define a simplified version of the function like this:
@smallexample
@group
(defun split-window-horizontally (&optional arg)
"Split selected window into two windows, side by side..."
(interactive "P")
- (split-window nil (and arg (prefix-numeric-value arg)) t))
+@end group
+@group
+ (let ((size (and arg (prefix-numeric-value arg))))
+ (and size (< size 0)
+ (setq size (+ (window-width) size)))
+ (split-window nil size t)))
@end group
@end smallexample
@end deffn
This function returns non-@code{nil} if there is only one window. The
argument @var{no-mini}, if non-@code{nil}, means don't count the
minibuffer even if it is active; otherwise, the minibuffer window is
-included, if active, in the total number of windows, which is compared
-against one.
+counted when it is active.
The argument @var{all-frames} specifies which frames to consider. Here
are the possible values and their meanings:
deletes any windows that aren't part of that configuration.
When you delete a window, the space it took up is given to one
-adjacent sibling. (In Emacs version 18, the space was divided evenly
-among all the siblings.)
+adjacent sibling.
@c Emacs 19 feature
@defun window-live-p window
@end defun
@deffn Command delete-window &optional window
-This function removes @var{window} from the display. If @var{window}
-is omitted, then the selected window is deleted. An error is signaled
-if there is only one window when @code{delete-window} is called.
-
-This function returns @code{nil}.
-
-When @code{delete-window} is called interactively, @var{window}
-defaults to the selected window.
+This function removes @var{window} from display, and returns @code{nil}.
+If @var{window} is omitted, then the selected window is deleted. An
+error is signaled if there is only one window when @code{delete-window}
+is called.
@end deffn
@deffn Command delete-other-windows &optional window
deleting the other windows in that frame. If @var{window} is omitted or
@code{nil}, then the selected window is used by default.
-The result is @code{nil}.
+The return value is @code{nil}.
@end deffn
-@deffn Command delete-windows-on buffer &optional frame
-This function deletes all windows showing @var{buffer}. If there are
-no windows showing @var{buffer}, it does nothing.
+@deffn Command delete-windows-on buffer-or-name &optional frame
+This function deletes all windows showing @var{buffer-or-name}. If
+there are no windows showing @var{buffer-or-name}, it does nothing.
+@var{buffer-or-name} must be a buffer or the name of an existing
+buffer.
@code{delete-windows-on} operates frame by frame. If a frame has
several windows showing different buffers, then those showing
-@var{buffer} are removed, and the others expand to fill the space. If
-all windows in some frame are showing @var{buffer} (including the case
-where there is only one window), then the frame reverts to having a
-single window showing another buffer chosen with @code{other-buffer}.
-@xref{The Buffer List}.
-
-The argument @var{frame} controls which frames to operate on:
+@var{buffer-or-name} are removed, and the others expand to fill the
+space. If all windows in some frame are showing @var{buffer-or-name}
+(including the case where there is only one window), then the frame
+winds up with a single window showing another buffer chosen with
+@code{other-buffer}. @xref{The Buffer List}.
+
+The argument @var{frame} controls which frames to operate on. This
+function does not use it in quite the same way as the other functions
+which scan all windows; specifically, the values @code{t} and @code{nil}
+have the opposite of their meanings in other functions. Here are the
+full details:
@itemize @bullet
@item
-If it is @code{nil}, operate on the selected frame.
+If it is @code{nil}, operate on all frames.
@item
-If it is @code{t}, operate on all frames.
+If it is @code{t}, operate on the selected frame.
@item
If it is @code{visible}, operate on all visible frames.
-@item 0
+@item
If it is 0, operate on all visible or iconified frames.
@item
If it is a frame, operate on that frame.
which the cursor appears and to which many commands apply.
@end defun
-@defun select-window window
+@defun select-window window &optional norecord
This function makes @var{window} the selected window. The cursor then
-appears in @var{window} (on redisplay). The buffer being displayed in
-@var{window} is immediately designated the current buffer.
+appears in @var{window} (on redisplay). Unless @var{window} was
+already selected, @code{select-window} makes @var{window}'s buffer the
+current buffer.
+
+Normally @var{window}'s selected buffer is moved to the front of the
+buffer list, but if @var{norecord} is non-@code{nil}, the buffer list
+order is unchanged.
The return value is @var{window}.
@end defun
@defmac save-selected-window forms@dots{}
-This macro records the selected window, executes @var{forms}
-in sequence, then restores the earlier selected window.
-It does not save or restore anything about the sizes, arrangement
-or contents of windows; therefore, if the @var{forms} change them,
-the changes are permanent.
+This macro records the selected frame, as well as the selected window
+of each frame, executes @var{forms} in sequence, then restores the
+earlier selected frame and windows. It also saves and restores the
+current buffer. It returns the value of the last form in @var{forms}.
+
+This macro does not save or restore anything about the sizes,
+arrangement or contents of windows; therefore, if the @var{forms}
+change them, the change persists. If the previously selected window
+of some frame is no longer live at the time of exit from @var{forms},
+that frame's selected window is left alone. If the previously
+selected window is no longer live, then whatever window is selected at
+the end of @var{forms} remains selected.
+@end defmac
+
+@defmac with-selected-window window forms@dots{}
+This macro selects @var{window} (without changing the buffer list),
+executes @var{forms} in sequence, then restores the previously
+selected window and current buffer. It is just like
+@code{save-selected-window}, except that it explicitly selects
+@var{window}, also without altering the buffer list sequence.
@end defmac
@cindex finding windows
The following functions choose one of the windows on the screen,
offering various criteria for the choice.
-@defun get-lru-window &optional frame
+@defun get-lru-window &optional frame dedicated
This function returns the window least recently ``used'' (that is,
-selected). The selected window is always the most recently used window.
+selected). If any full-width windows are present, it only considers
+these. The selected window is always the most recently used window.
The selected window can be the least recently used window if it is the
only window. A newly created window becomes the least recently used
-window until it is selected. A minibuffer window is never a candidate.
+window until it is selected. A minibuffer window is never a
+candidate. Dedicated windows are never candidates unless the
+@var{dedicated} argument is non-@code{nil}, so if all
+existing windows are dedicated, the value is @code{nil}.
The argument @var{frame} controls which windows are considered.
@end itemize
@end defun
-@defun get-largest-window &optional frame
+@defun get-largest-window &optional frame dedicated
This function returns the window with the largest area (height times
width). If there are no side-by-side windows, then this is the window
with the most lines. A minibuffer window is never a candidate.
+Dedicated windows are never candidates unless the
+@var{dedicated} argument is non-@code{nil}, so if all existing windows
+are dedicated, the value is @code{nil}.
-If there are two windows of the same size, then the function returns
-the window that is first in the cyclic ordering of windows (see
-following section), starting from the selected window.
+If there are two candidate windows of the same size, this function
+prefers the one that comes first in the cyclic ordering of windows
+(see following section), starting from the selected window.
-The argument @var{frame} controls which set of windows are
-considered. See @code{get-lru-window}, above.
+The argument @var{frame} controls which set of windows to
+consider. See @code{get-lru-window}, above.
+@end defun
+
+@cindex window that satisfies a predicate
+@cindex conditional selection of windows
+@defun get-window-with-predicate predicate &optional minibuf all-frames default
+This function returns a window satisfying @var{predicate}. It cycles
+through all visible windows using @code{walk-windows} (@pxref{Cyclic
+Window Ordering}), calling @var{predicate} on each one of them
+with that window as its argument. The function returns the first
+window for which @var{predicate} returns a non-@code{nil} value; if
+that never happens, it returns @var{default}.
+
+The optional arguments @var{minibuf} and @var{all-frames} specify the
+set of windows to include in the scan. See the description of
+@code{next-window} in @ref{Cyclic Window Ordering}, for details.
@end defun
@node Cyclic Window Ordering
@section Cyclic Ordering of Windows
@cindex cyclic ordering of windows
@cindex ordering of windows, cyclic
-@cindex window ordering, cyclic
+@cindex window ordering, cyclic
When you use the command @kbd{C-x o} (@code{other-window}) to select
the next window, it moves through all the windows on the screen in a
@table @asis
@item @code{nil}
Consider all the windows in @var{window}'s frame, plus the minibuffer
-used by that frame even if it lies in some other frame.
+used by that frame even if it lies in some other frame. If the
+minibuffer counts (as determined by @var{minibuf}), then all windows on
+all frames that share that minibuffer count too.
@item @code{t}
Consider all windows in all existing frames.
@item 0
Consider all windows in all visible or iconified frames.
+@item a frame
+Consider all windows on that frame.
+
@item anything else
Consider precisely the windows in @var{window}'s frame, and no others.
@end table
-This example assumes there are two windows, both displaying the
+This example assumes there are two windows, both displaying the
buffer @samp{windows.texi}:
@example
include in the cycle, as in @code{next-window}.
@end defun
-@deffn Command other-window count
+@deffn Command other-window count &optional all-frames
This function selects the @var{count}th following window in the cyclic
-order. If count is negative, then it selects the @minus{}@var{count}th
-preceding window. It returns @code{nil}.
+order. If count is negative, then it moves back @minus{}@var{count}
+windows in the cycle, rather than forward. It returns @code{nil}.
+
+The argument @var{all-frames} has the same meaning as in
+@code{next-window}, but the @var{minibuf} argument of @code{next-window}
+is always effectively @code{nil}.
In an interactive call, @var{count} is the numeric prefix argument.
@end deffn
@c Emacs 19 feature
@defun walk-windows proc &optional minibuf all-frames
-This function cycles through all windows, calling @code{proc}
-once for each window with the window as its sole argument.
+This function cycles through all windows. It calls the function
+@code{proc} once for each window, with the window as its sole
+argument.
The optional arguments @var{minibuf} and @var{all-frames} specify the
set of windows to include in the scan. See @code{next-window}, above,
for details.
@end defun
+@defun window-list &optional frame minibuf window
+This function returns a list of the windows on @var{frame}, starting
+with @var{window}. If @var{frame} is @code{nil} or omitted,
+@code{window-list} uses the selected frame instead; if @var{window} is
+@code{nil} or omitted, it uses the selected window.
+
+The value of @var{minibuf} determines if the minibuffer window is
+included in the result list. If @var{minibuf} is @code{t}, the result
+always includes the minibuffer window. If @var{minibuf} is @code{nil}
+or omitted, that includes the minibuffer window if it is active. If
+@var{minibuf} is neither @code{nil} nor @code{t}, the result never
+includes the minibuffer window.
+@end defun
+
@node Buffers and Windows
@section Buffers and Windows
@cindex examining windows
@iftex
See the following section for
@end iftex
-@ifinfo
+@ifnottex
@xref{Displaying Buffers}, for
-@end ifinfo
+@end ifnottex
related functions that find a window to use and specify a buffer for it.
The functions described there are easier to use than these, but they
employ heuristics in choosing or creating a window; use these functions
when you need complete control.
-@defun set-window-buffer window buffer-or-name
+@defun set-window-buffer window buffer-or-name &optional keep-margins
This function makes @var{window} display @var{buffer-or-name} as its
-contents. It returns @code{nil}.
+contents. It returns @code{nil}. @var{buffer-or-name} must be a
+buffer, or the name of an existing buffer. This is the fundamental
+primitive for changing which buffer is displayed in a window, and all
+ways of doing that call this function.
@example
@group
@result{} nil
@end group
@end example
+
+Normally, displaying @var{buffer} in @var{window} resets the window's
+display margins, fringe widths, scroll bar settings, and position
+based on the local variables of @var{buffer}. However, if
+@var{keep-margins} is non-@code{nil}, the display margins and fringe
+widths of @var{window} remain unchanged. @xref{Fringes}.
@end defun
+@defvar buffer-display-count
+This buffer-local variable records the number of times a buffer is
+displayed in a window. It is incremented each time
+@code{set-window-buffer} is called for the buffer.
+@end defvar
+
@defun window-buffer &optional window
This function returns the buffer that @var{window} is displaying. If
@var{window} is omitted, this function returns the buffer for the
@end itemize
@end defun
+@defun get-buffer-window-list buffer-or-name &optional minibuf all-frames
+This function returns a list of all the windows currently displaying
+@var{buffer-or-name}.
+
+The two optional arguments work like the optional arguments of
+@code{next-window} (@pxref{Cyclic Window Ordering}); they are @emph{not}
+like the single optional argument of @code{get-buffer-window}. Perhaps
+we should change @code{get-buffer-window} in the future to make it
+compatible with the other functions.
+@end defun
+
+@defvar buffer-display-time
+This variable records the time at which a buffer was last made visible
+in a window. It is always local in each buffer; each time
+@code{set-window-buffer} is called, it sets this variable to
+@code{(current-time)} in the specified buffer (@pxref{Time of Day}).
+When a buffer is first created, @code{buffer-display-time} starts out
+with the value @code{nil}.
+@end defvar
+
@node Displaying Buffers
@section Displaying Buffers in Windows
@cindex switching to a buffer
@iftex
See the preceding section for
@end iftex
-@ifinfo
+@ifnottex
@xref{Buffers and Windows}, for
-@end ifinfo
-low-level functions that give you more precise control.
+@end ifnottex
+low-level functions that give you more precise control. All of these
+functions work by calling @code{set-window-buffer}.
Do not use the functions in this section in order to make a buffer
current so that a Lisp program can access or modify it; they are too
drastic for that purpose, since they change the display of buffers in
-windows, which is gratuitous and will surprise the user. Instead, use
-@code{set-buffer} (@pxref{Current Buffer}) and @code{save-excursion}
-(@pxref{Excursions}), which designate buffers as current for programmed
-access without affecting the display of buffers in windows.
+windows, which would be gratuitous and surprise the user. Instead, use
+@code{set-buffer} and @code{save-current-buffer} (@pxref{Current
+Buffer}), which designate buffers as current for programmed access
+without affecting the display of buffers in windows.
@deffn Command switch-to-buffer buffer-or-name &optional norecord
This function makes @var{buffer-or-name} the current buffer, and also
If @var{buffer-or-name} does not identify an existing buffer, then a new
buffer by that name is created. The major mode for the new buffer is
set according to the variable @code{default-major-mode}. @xref{Auto
-Major Mode}.
+Major Mode}. If @var{buffer-or-name} is @code{nil},
+@code{switch-to-buffer} chooses a buffer using @code{other-buffer}.
-Normally the specified buffer is put at the front of the buffer list.
-This affects the operation of @code{other-buffer}. However, if
+Normally the specified buffer is put at the front of the buffer list
+(both the selected frame's buffer list and the frame-independent buffer
+list). This affects the operation of @code{other-buffer}. However, if
@var{norecord} is non-@code{nil}, this is not done. @xref{The Buffer
List}.
The @code{switch-to-buffer} function is often used interactively, as
the binding of @kbd{C-x b}. It is also used frequently in programs. It
-always returns @code{nil}.
+returns the buffer that it switched to.
@end deffn
-@deffn Command switch-to-buffer-other-window buffer-or-name
+The next two functions are similar to @code{switch-to-buffer}, except
+for the described features.
+
+@deffn Command switch-to-buffer-other-window buffer-or-name &optional norecord
This function makes @var{buffer-or-name} the current buffer and
displays it in a window not currently selected. It then selects that
window. The handling of the buffer is the same as in
this purpose. If the selected window is already displaying the buffer,
then it continues to do so, but another window is nonetheless found to
display it in as well.
+
+This function updates the buffer list just like @code{switch-to-buffer}
+unless @var{norecord} is non-@code{nil}.
@end deffn
-@defun pop-to-buffer buffer-or-name &optional other-window
+@defun pop-to-buffer buffer-or-name &optional other-window norecord
This function makes @var{buffer-or-name} the current buffer and
switches to it in some window, preferably not the window previously
selected. The ``popped-to'' window becomes the selected window within
-its frame.
+its frame. The return value is the buffer that was switched to.
+If @var{buffer-or-name} is @code{nil}, that means to choose some
+other buffer, but you don't specify which.
If the variable @code{pop-up-frames} is non-@code{nil},
@code{pop-to-buffer} looks for a window in any visible frame already
buffer, a buffer by that name is created. The major mode for the new
buffer is set according to the variable @code{default-major-mode}.
@xref{Auto Major Mode}.
+
+This function updates the buffer list just like @code{switch-to-buffer}
+unless @var{norecord} is non-@code{nil}.
@end defun
-@deffn Command replace-buffer-in-windows buffer
-This function replaces @var{buffer} with some other buffer in all
-windows displaying it. The other buffer used is chosen with
+@deffn Command replace-buffer-in-windows buffer-or-name
+This function replaces @var{buffer-or-name} with some other buffer in all
+windows displaying it. It chooses the other buffer with
@code{other-buffer}. In the usual applications of this function, you
don't care which other buffer is used; you just want to make sure that
-@var{buffer} is no longer displayed.
+@var{buffer-or-name} is no longer displayed.
This function returns @code{nil}.
@end deffn
functions and commands use this subroutine. Here we describe how to use
@code{display-buffer} and how to customize it.
-@deffn Command display-buffer buffer-or-name &optional not-this-window
+@deffn Command display-buffer buffer-or-name &optional not-this-window frame
This command makes @var{buffer-or-name} appear in some window, like
@code{pop-to-buffer}, but it does not select that window and does not
make the buffer current. The identity of the selected window is
-unaltered by this function.
+unaltered by this function. @var{buffer-or-name} must be a buffer, or
+the name of an existing buffer.
If @var{not-this-window} is non-@code{nil}, it means to display the
specified buffer in a window other than the selected one, even if it is
@code{display-buffer} returns the window chosen to display
@var{buffer-or-name}.
+If the argument @var{frame} is non-@code{nil}, it specifies which frames
+to check when deciding whether the buffer is already displayed. If the
+buffer is already displayed in some window on one of these frames,
+@code{display-buffer} simply returns that window. Here are the possible
+values of @var{frame}:
+
+@itemize @bullet
+@item
+If it is @code{nil}, consider windows on the selected frame.
+(Actually, the last non-minibuffer frame.)
+@item
+If it is @code{t}, consider windows on all frames.
+@item
+If it is @code{visible}, consider windows on all visible frames.
+@item
+If it is 0, consider windows on all visible or iconified frames.
+@item
+If it is a frame, consider windows on that frame.
+@end itemize
+
Precisely how @code{display-buffer} finds or creates a window depends on
the variables described below.
@end deffn
+@defopt display-buffer-reuse-frames
+If this variable is non-@code{nil}, @code{display-buffer} searches
+existing frames for a window displaying the buffer. If the buffer is
+already displayed in a window in some frame, @code{display-buffer} makes
+the frame visible and raises it, to use that window. If the buffer is
+not already displayed, or if @code{display-buffer-reuse-frames} is
+@code{nil}, @code{display-buffer}'s behavior is determined by other
+variables, described below.
+@end defopt
+
@defopt pop-up-windows
This variable controls whether @code{display-buffer} makes new windows.
If it is non-@code{nil} and there is only one window, then that window
@code{pop-up-windows} is non-@code{nil}.
@end defopt
+@defopt even-window-heights
+This variable determines if @code{display-buffer} should even out window
+heights if the buffer gets displayed in an existing window, above or
+beneath another existing window. If @code{even-window-heights} is
+@code{t}, the default, window heights will be evened out. If
+@code{even-window-heights} is @code{nil}, the original window heights
+will be left alone.
+@end defopt
+
@c Emacs 19 feature
@defopt pop-up-frames
This variable controls whether @code{display-buffer} makes new frames.
@end defopt
@c Emacs 19 feature
-@defvar pop-up-frame-function
+@defopt pop-up-frame-function
This variable specifies how to make a new frame if @code{pop-up-frames}
is non-@code{nil}.
function, which should return a frame. The default value of the
variable is a function that creates a frame using parameters from
@code{pop-up-frame-alist}.
-@end defvar
+@end defopt
-@defvar pop-up-frame-alist
+@defopt pop-up-frame-alist
This variable holds an alist specifying frame parameters used when
@code{display-buffer} makes a new frame. @xref{Frame Parameters}, for
more information about frame parameters.
-@end defvar
+@end defopt
-@defvar special-display-buffer-names
+@defopt special-display-buffer-names
A list of buffer names for buffers that should be displayed specially.
If the buffer's name is in this list, @code{display-buffer} handles the
buffer specially.
By default, special display means to give the buffer a dedicated frame.
If an element is a list, instead of a string, then the @sc{car} of the
-list is the buffer name, and the rest of the list says how to create the
-frame. There are two possibilities for the rest of the list. It can be
-an alist, specifying frame parameters, or it can contain a function and
-arguments to give to it. (The function's first argument is always the
-buffer to be displayed; the arguments from the list come after that.)
-@end defvar
+list is the buffer name, and the rest of the list says how to create
+the frame. There are two possibilities for the rest of the list (its
+@sc{cdr}). It can be an alist, specifying frame parameters, or it can
+contain a function and arguments to give to it. (The function's first
+argument is always the buffer to be displayed; the arguments from the
+list come after that.)
+
+For example:
+
+@example
+(("myfile" (minibuffer) (menu-bar-lines . 0)))
+@end example
+
+@noindent
+specifies to display a buffer named @samp{myfile} in a dedicated frame
+with specified @code{minibuffer} and @code{menu-bar-lines} parameters.
+
+The list of frame parameters can also use the phony frame parameters
+@code{same-frame} and @code{same-window}. If the specified frame
+parameters include @code{(same-window . @var{value})} and @var{value}
+is non-@code{nil}, that means to display the buffer in the current
+selected window. Otherwise, if they include @code{(same-frame .
+@var{value})} and @var{value} is non-@code{nil}, that means to display
+the buffer in a new window in the currently selected frame.
+@end defopt
-@defvar special-display-regexps
+@defopt special-display-regexps
A list of regular expressions that specify buffers that should be
displayed specially. If the buffer's name matches any of the regular
expressions in this list, @code{display-buffer} handles the buffer
If an element is a list, instead of a string, then the @sc{car} of the
list is the regular expression, and the rest of the list says how to
create the frame. See above, under @code{special-display-buffer-names}.
-@end defvar
+@end defopt
+
+@defun special-display-p buffer-name
+This function returns non-@code{nil} if displaying a buffer
+named @var{buffer-name} with @code{display-buffer} would
+create a special frame. The value is @code{t} if it would
+use the default frame parameters, or else the specified list
+of frame parameters.
+@end defun
@defvar special-display-function
This variable holds the function to call to display a buffer specially.
@code{special-display-popup-frame}.
@end defvar
-@defun special-display-popup-frame buffer
+@defun special-display-popup-frame buffer &optional args
This function makes @var{buffer} visible in a frame of its own. If
@var{buffer} is already displayed in a window in some frame, it makes
the frame visible and raises it, to use that window. Otherwise, it
-creates a frame that will be dedicated to @var{buffer}.
+creates a frame that will be dedicated to @var{buffer}. This
+function returns the window it used.
-This function uses an existing window displaying @var{buffer} whether or
-not it is in a frame of its own; but if you set up the above variables
-in your init file, before @var{buffer} was created, then presumably the
-window was previously made by this function.
+If @var{args} is an alist, it specifies frame parameters for the new
+frame.
+
+If @var{args} is a list whose @sc{car} is a symbol, then @code{(car
+@var{args})} is called as a function to actually create and set up the
+frame; it is called with @var{buffer} as first argument, and @code{(cdr
+@var{args})} as additional arguments.
+
+This function always uses an existing window displaying @var{buffer},
+whether or not it is in a frame of its own; but if you set up the above
+variables in your init file, before @var{buffer} was created, then
+presumably the window was previously made by this function.
@end defun
@defopt special-display-frame-alist
+@anchor{Definition of special-display-frame-alist}
This variable holds frame parameters for
@code{special-display-popup-frame} to use when it creates a frame.
@end defopt
-@defvar same-window-buffer-names
+@defopt same-window-buffer-names
A list of buffer names for buffers that should be displayed in the
selected window. If the buffer's name is in this list,
@code{display-buffer} handles the buffer by switching to it in the
selected window.
-@end defvar
+@end defopt
-@defvar same-window-regexps
+@defopt same-window-regexps
A list of regular expressions that specify buffers that should be
displayed in the selected window. If the buffer's name matches any of
the regular expressions in this list, @code{display-buffer} handles the
buffer by switching to it in the selected window.
-@end defvar
+@end defopt
+
+@defun same-window-p buffer-name
+This function returns @code{t} if displaying a buffer
+named @var{buffer-name} with @code{display-buffer} would
+put it in the selected window.
+@end defun
@c Emacs 19 feature
@defvar display-buffer-function
This variable is the most flexible way to customize the behavior of
@code{display-buffer}. If it is non-@code{nil}, it should be a function
that @code{display-buffer} calls to do the work. The function should
-accept two arguments, the same two arguments that @code{display-buffer}
+accept two arguments, the first two arguments that @code{display-buffer}
received. It should choose or create a window, display the specified
-buffer, and then return the window.
+buffer in it, and then return the window.
This hook takes precedence over all the other options and hooks
described above.
@c Emacs 19 feature
@cindex dedicated window
A window can be marked as ``dedicated'' to its buffer. Then
-@code{display-buffer} does not try to use that window.
+@code{display-buffer} will not try to use that window to display any
+other buffer.
@defun window-dedicated-p window
-This function returns @code{t} if @var{window} is marked as dedicated;
-otherwise @code{nil}.
+This function returns non-@code{nil} if @var{window} is marked as
+dedicated; otherwise @code{nil}.
@end defun
@defun set-window-dedicated-p window flag
window opened on the buffer if such a window exists.
@item
-Selecting a window sets the value of point in its buffer to the window's
-value of point. Conversely, deselecting a window sets the window's
-value of point from that of the buffer. Thus, when you switch between
-windows that display a given buffer, the point value for the selected
-window is in effect in the buffer, while the point values for the other
-windows are stored in those windows.
+Selecting a window sets the value of point in its buffer from the
+window's value of point. Conversely, deselecting a window sets the
+window's value of point from that of the buffer. Thus, when you switch
+between windows that display a given buffer, the point value for the
+selected window is in effect in the buffer, while the point values for
+the other windows are stored in those windows.
@item
As long as the selected window displays the current buffer, the window's
point and the buffer's point always move together; they remain equal.
+@end itemize
-@item
+@noindent
@xref{Positions}, for more details on buffer positions.
-@end itemize
As far as the user is concerned, point is where the cursor is, and
when the user switches to another buffer, the cursor jumps to the
position of point in that buffer.
-@defun window-point window
+@defun window-point &optional window
This function returns the current position of point in @var{window}.
For a nonselected window, this is the value point would have (in that
-window's buffer) if that window were selected.
+window's buffer) if that window were selected. If @var{window} is
+@code{nil}, the selected window is used.
When @var{window} is the selected window and its buffer is also the
current buffer, the value returned is the same as point in that buffer.
@defun set-window-point window position
This function positions point in @var{window} at position
-@var{position} in @var{window}'s buffer.
+@var{position} in @var{window}'s buffer. It returns @var{position}.
+
+If @var{window} is selected, and its buffer is current,
+this simply does @code{goto-char}.
@end defun
@node Window Start
@cindex window top line
This function returns the display-start position of window
@var{window}. If @var{window} is @code{nil}, the selected window is
-used. For example,
+used. For example,
@example
@group
for the same buffer, or 1 if the buffer doesn't have any.
Redisplay updates the window-start position (if you have not specified
-it explicitly since the previous redisplay) so that point appears on the
-screen. Nothing except redisplay automatically changes the window-start
-position; if you move point, do not expect the window-start position to
-change in response until after the next redisplay.
+it explicitly since the previous redisplay)---for example, to make sure
+point appears on the screen. Nothing except redisplay automatically
+changes the window-start position; if you move point, do not expect the
+window-start position to change in response until after the next
+redisplay.
For a realistic example of using @code{window-start}, see the
-description of @code{count-lines} in @ref{Text Lines}.
+description of @code{count-lines}. @xref{Definition of count-lines}.
@end defun
-@defun window-end &optional window
+@defun window-end &optional window update
This function returns the position of the end of the display in window
@var{window}. If @var{window} is @code{nil}, the selected window is
used.
Simply changing the buffer text or moving point does not update the
value that @code{window-end} returns. The value is updated only when
-Emacs redisplays and redisplay actually finishes.
+Emacs redisplays and redisplay completes without being preempted.
If the last redisplay of @var{window} was preempted, and did not finish,
Emacs does not know the position of the end of display in that window.
-In that case, this function returns a value that is not correct. In a
-future version, @code{window-end} will return @code{nil} in that case.
-@ignore
-in that case, this function returns @code{nil}. You can compute where
-the end of the window @emph{would} have been, if redisplay had finished,
-like this:
-
-@example
-(save-excursion
- (goto-char (window-start window))
- (vertical-motion (1- (window-height window))
- window)
- (point))
-@end example
-@end ignore
+In that case, this function returns @code{nil}.
+
+If @var{update} is non-@code{nil}, @code{window-end} always returns an
+up-to-date value for where the window ends, based on the current
+@code{window-start} value. If the saved value is valid,
+@code{window-end} returns that; otherwise it computes the correct
+value by scanning the buffer text.
+
+Even if @var{update} is non-@code{nil}, @code{window-end} does not
+attempt to scroll the display if point has moved off the screen, the
+way real redisplay would do. It does not alter the
+@code{window-start} value. In effect, it reports where the displayed
+text will end if scrolling is not required.
@end defun
@defun set-window-start window position &optional noforce
position that works well with point, and thus @var{position} is not used.
@end defun
-@defun pos-visible-in-window-p &optional position window
-This function returns @code{t} if @var{position} is within the range
-of text currently visible on the screen in @var{window}. It returns
-@code{nil} if @var{position} is scrolled vertically out of view. The
-argument @var{position} defaults to the current position of point;
-@var{window}, to the selected window. Here is an example:
+@defun pos-visible-in-window-p &optional position window partially
+This function returns non-@code{nil} if @var{position} is within the
+range of text currently visible on the screen in @var{window}. It
+returns @code{nil} if @var{position} is scrolled vertically out of
+view. Locations that are partially obscured are not considered
+visible unless @var{partially} is non-@code{nil}. The argument
+@var{position} defaults to the current position of point in
+@var{window}; @var{window}, to the selected window.
+
+The @code{pos-visible-in-window-p} function considers only vertical
+scrolling. If @var{position} is out of view only because @var{window}
+has been scrolled horizontally, @code{pos-visible-in-window-p} returns
+non-@code{nil} anyway. @xref{Horizontal Scrolling}.
+
+If @var{position} is visible, @code{pos-visible-in-window-p} returns
+@code{t} if @var{partially} is @code{nil}; if @var{partially} is
+non-@code{nil}, it returns a list of the form @code{(@var{x} @var{y}
+@var{partial})}, where @var{x} and @var{y} are the pixel coordinates
+relative to the top left corner of the window, and @var{partial} is
+@code{nil} if the character after @var{position} is fully visible;
+otherwise it is a cons @code{(@var{rtop} . @var{rbot})} where the
+@var{rtop} and @var{rbot} specify the number of invisible pixels at
+the top and bottom of the row at @var{position}.
+
+Here is an example:
@example
@group
+;; @r{If point is off the screen now, recenter it now.}
(or (pos-visible-in-window-p
(point) (selected-window))
(recenter 0))
@end group
@end example
-
-The @code{pos-visible-in-window-p} function considers only vertical
-scrolling. If @var{position} is out of view only because @var{window}
-has been scrolled horizontally, @code{pos-visible-in-window-p} returns
-@code{t}. @xref{Horizontal Scrolling}.
@end defun
-@node Vertical Scrolling
-@section Vertical Scrolling
-@cindex vertical scrolling
-@cindex scrolling vertically
+@node Textual Scrolling
+@section Textual Scrolling
+@cindex textual scrolling
+@cindex scrolling textually
- Vertical scrolling means moving the text up or down in a window. It
-works by changing the value of the window's display-start location. It
-may also change the value of @code{window-point} to keep it on the
-screen.
+ @dfn{Textual scrolling} means moving the text up or down through a
+window. It works by changing the value of the window's display-start
+location. It may also change the value of @code{window-point} to keep
+point on the screen.
+
+ Textual scrolling was formerly called ``vertical scrolling,'' but we
+changed its name to distinguish it from the new vertical fractional
+scrolling feature (@pxref{Vertical Scrolling}).
In the commands @code{scroll-up} and @code{scroll-down}, the directions
``up'' and ``down'' refer to the motion of the text in the buffer at which
commands clearly move the text up or down on the screen. We have chosen
names that fit the user's point of view.
- The scrolling functions (aside from @code{scroll-other-window}) have
-unpredictable results if the current buffer is different from the buffer
-that is displayed in the selected window. @xref{Current Buffer}.
+ The textual scrolling functions (aside from
+@code{scroll-other-window}) have unpredictable results if the current
+buffer is different from the buffer that is displayed in the selected
+window. @xref{Current Buffer}.
+
+ If the window contains a row which is taller than the height of the
+window (for example in the presense of a large image), the scroll
+functions will adjust the window vscroll to scroll the partially
+visible row. To disable this feature, Lisp code may bind the variable
+`auto-window-vscroll' to @code{nil} (@pxref{Vertical Scrolling}).
@deffn Command scroll-up &optional count
This function scrolls the text in the selected window upward
is @code{next-screen-context-lines} lines less than the usable height of
the window (not counting its mode line).
-@code{scroll-up} returns @code{nil}.
+@code{scroll-up} returns @code{nil}, unless it gets an error
+because it can't scroll any further.
@end deffn
@deffn Command scroll-down &optional count
is @code{next-screen-context-lines} lines less than the usable height of
the window (not counting its mode line).
-@code{scroll-down} returns @code{nil}.
+@code{scroll-down} returns @code{nil}, unless it gets an error because
+it can't scroll any further.
@end deffn
@deffn Command scroll-other-window &optional count
lines. Negative values of @var{count}, or @code{nil}, are handled
as in @code{scroll-up}.
-You can specify a buffer to scroll with the variable
-@code{other-window-scroll-buffer}. When the selected window is the
-minibuffer, the next window is normally the one at the top left corner.
-You can specify a different window to scroll with the variable
+You can specify which buffer to scroll by setting the variable
+@code{other-window-scroll-buffer} to a buffer. If that buffer isn't
+already displayed, @code{scroll-other-window} displays it in some
+window.
+
+When the selected window is the minibuffer, the next window is normally
+the one at the top left corner. You can specify a different window to
+scroll, when the minibuffer is selected, by setting the variable
@code{minibuffer-scroll-window}. This variable has no effect when any
-other window is selected. @xref{Minibuffer Misc}.
+other window is selected. When it is non-@code{nil} and the
+minibuffer is selected, it takes precedence over
+@code{other-window-scroll-buffer}. @xref{Definition of
+minibuffer-scroll-window}.
When the minibuffer is active, it is the next window if the selected
window is the one at the bottom right corner. In this case,
which buffer to scroll.
@end defvar
-@defopt scroll-step
+@defopt scroll-margin
+This option specifies the size of the scroll margin---a minimum number
+of lines between point and the top or bottom of a window. Whenever
+point gets within this many lines of the top or bottom of the window,
+redisplay scrolls the text automatically (if possible) to move point
+out of the margin, closer to the center of the window.
+@end defopt
+
+@defopt scroll-conservatively
This variable controls how scrolling is done automatically when point
-moves off the screen. If the value is zero, then redisplay scrolls the
-text to center point vertically in the window. If the value is a
-positive integer @var{n}, then redisplay brings point back on screen by
-scrolling @var{n} lines in either direction, if possible; otherwise, it
-centers point. The default value is zero.
+moves off the screen (or into the scroll margin). If the value is a
+positive integer @var{n}, then redisplay scrolls the text up to
+@var{n} lines in either direction, if that will bring point back into
+proper view. This action is called @dfn{conservative scrolling}.
+Otherwise, scrolling happens in the usual way, under the control of
+other variables such as @code{scroll-up-aggressively} and
+@code{scroll-down-aggressively}.
+
+The default value is zero, which means that conservative scrolling
+never happens.
+@end defopt
+
+@defopt scroll-down-aggressively
+@tindex scroll-down-aggressively
+The value of this variable should be either @code{nil} or a fraction
+@var{f} between 0 and 1. If it is a fraction, that specifies where on
+the screen to put point when scrolling down. More precisely, when a
+window scrolls down because point is above the window start, the new
+start position is chosen to put point @var{f} part of the window
+height from the top. The larger @var{f}, the more aggressive the
+scrolling.
+
+A value of @code{nil} is equivalent to .5, since its effect is to center
+point. This variable automatically becomes buffer-local when set in any
+fashion.
+@end defopt
+
+@defopt scroll-up-aggressively
+@tindex scroll-up-aggressively
+Likewise, for scrolling up. The value, @var{f}, specifies how far
+point should be placed from the bottom of the window; thus, as with
+@code{scroll-up-aggressively}, a larger value scrolls more aggressively.
+@end defopt
+
+@defopt scroll-step
+This variable is an older variant of @code{scroll-conservatively}. The
+difference is that it if its value is @var{n}, that permits scrolling
+only by precisely @var{n} lines, not a smaller number. This feature
+does not work with @code{scroll-margin}. The default value is zero.
+@end defopt
+
+@defopt scroll-preserve-screen-position
+If this option is @code{t}, scrolling which would move the current
+point position out of the window chooses the new position of point
+so that the vertical position of the cursor is unchanged, if possible.
+
+If it is non-@code{nil} and not @code{t}, then the scrolling functions
+always preserve the vertical position of point, if possible.
@end defopt
@defopt next-screen-context-lines
@deffn Command recenter &optional count
@cindex centering point
-This function scrolls the selected window to put the text where point
-is located at a specified vertical position within the window.
+This function scrolls the text in the selected window so that point is
+displayed at a specified vertical position within the window. It does
+not ``move point'' with respect to the text.
-If @var{count} is a nonnegative number, it puts the line containing
-point @var{count} lines down from the top of the window. If @var{count}
-is a negative number, then it counts upward from the bottom of the
-window, so that @minus{}1 stands for the last usable line in the window.
-If @var{count} is a non-@code{nil} list, then it stands for the line in
-the middle of the window.
+If @var{count} is a nonnegative number, that puts the line containing
+point @var{count} lines down from the top of the window. If
+@var{count} is a negative number, then it counts upward from the
+bottom of the window, so that @minus{}1 stands for the last usable
+line in the window. If @var{count} is a non-@code{nil} list, then it
+stands for the line in the middle of the window.
If @var{count} is @code{nil}, @code{recenter} puts the line containing
point in the middle of the window, then clears and redisplays the entire
(defun line-to-top-of-window ()
"Scroll current line to top of window.
Replaces three keystroke sequence C-u 0 C-l."
- (interactive)
+ (interactive)
(recenter 0))
-(global-set-key [kp-multiply] 'line-to-top-of-window)
+(global-set-key [kp-multiply] 'line-to-top-of-window)
@end group
@end example
@end deffn
+@node Vertical Scrolling
+@section Vertical Fractional Scrolling
+@cindex Vertical Fractional Scrolling
+
+ @dfn{Vertical fractional scrolling} means shifting the image in the
+window up or down by a specified multiple or fraction of a line.
+Each window has a @dfn{vertical scroll position},
+which is a number, never less than zero. It specifies how far to raise
+the contents of the window. Raising the window contents generally makes
+all or part of some lines disappear off the top, and all or part of some
+other lines appear at the bottom. The usual value is zero.
+
+ The vertical scroll position is measured in units of the normal line
+height, which is the height of the default font. Thus, if the value is
+.5, that means the window contents are scrolled up half the normal line
+height. If it is 3.3, that means the window contents are scrolled up
+somewhat over three times the normal line height.
+
+ What fraction of a line the vertical scrolling covers, or how many
+lines, depends on what the lines contain. A value of .5 could scroll a
+line whose height is very short off the screen, while a value of 3.3
+could scroll just part of the way through a tall line or an image.
+
+@defun window-vscroll &optional window pixels-p
+This function returns the current vertical scroll position of
+@var{window}. If @var{window} is @code{nil}, the selected window is
+used. If @var{pixels-p} is non-@code{nil}, the return value is
+measured in pixels, rather than in units of the normal line height.
+
+@example
+@group
+(window-vscroll)
+ @result{} 0
+@end group
+@end example
+@end defun
+
+@defun set-window-vscroll window lines &optional pixels-p
+This function sets @var{window}'s vertical scroll position to
+@var{lines}. The argument @var{lines} should be zero or positive; if
+not, it is taken as zero.
+
+If @var{window} is @code{nil}, the selected window is used.
+
+The actual vertical scroll position must always correspond
+to an integral number of pixels, so the value you specify
+is rounded accordingly.
+
+The return value is the result of this rounding.
+
+@example
+@group
+(set-window-vscroll (selected-window) 1.2)
+ @result{} 1.13
+@end group
+@end example
+
+If @var{pixels-p} is non-@code{nil}, @var{lines} specifies a number of
+pixels. In this case, the return value is @var{lines}.
+@end defun
+
+@defvar auto-window-vscroll
+If this variable is non-@code{nil}, the line-move, scroll-up, and
+scroll-down functions will automatically modify the window vscroll to
+scroll through display rows that are taller that the height of the
+window, for example in the presense of large images.
+@end defvar
+
@node Horizontal Scrolling
@section Horizontal Scrolling
@cindex horizontal scrolling
- Because we read English first from top to bottom and second from left
-to right, horizontal scrolling is not like vertical scrolling. Vertical
-scrolling involves selection of a contiguous portion of text to display.
-Horizontal scrolling causes part of each line to go off screen. The
-amount of horizontal scrolling is therefore specified as a number of
-columns rather than as a position in the buffer. It has nothing to do
-with the display-start position returned by @code{window-start}.
+ @dfn{Horizontal scrolling} means shifting the image in the window left
+or right by a specified multiple of the normal character width. Each
+window has a @dfn{horizontal scroll position}, which is a number, never
+less than zero. It specifies how far to shift the contents left.
+Shifting the window contents left generally makes all or part of some
+characters disappear off the left, and all or part of some other
+characters appear at the right. The usual value is zero.
+
+ The horizontal scroll position is measured in units of the normal
+character width, which is the width of space in the default font. Thus,
+if the value is 5, that means the window contents are scrolled left by 5
+times the normal character width. How many characters actually
+disappear off to the left depends on their width, and could vary from
+line to line.
+
+ Because we read from side to side in the ``inner loop'', and from top
+to bottom in the ``outer loop'', the effect of horizontal scrolling is
+not like that of textual or vertical scrolling. Textual scrolling
+involves selection of a portion of text to display, and vertical
+scrolling moves the window contents contiguously; but horizontal
+scrolling causes part of @emph{each line} to go off screen.
Usually, no horizontal scrolling is in effect; then the leftmost
column is at the left edge of the window. In this state, scrolling to
-the right is meaningless, since there is no data to the left of the
-screen to be revealed by it; so this is not allowed. Scrolling to the
-left is allowed; it scrolls the first columns of text off the edge of
-the window and can reveal additional columns on the right that were
-truncated before. Once a window has a nonzero amount of leftward
-horizontal scrolling, you can scroll it back to the right, but only so
-far as to reduce the net horizontal scroll to zero. There is no limit
-to how far left you can scroll, but eventually all the text will
-disappear off the left edge.
-
-@deffn Command scroll-left count
+the right is meaningless, since there is no data to the left of the edge
+to be revealed by it; so this is not allowed. Scrolling to the left is
+allowed; it scrolls the first columns of text off the edge of the window
+and can reveal additional columns on the right that were truncated
+before. Once a window has a nonzero amount of leftward horizontal
+scrolling, you can scroll it back to the right, but only so far as to
+reduce the net horizontal scroll to zero. There is no limit to how far
+left you can scroll, but eventually all the text will disappear off the
+left edge.
+
+@vindex auto-hscroll-mode
+ If @code{auto-hscroll-mode} is set, redisplay automatically alters
+the horizontal scrolling of a window as necessary to ensure that point
+is always visible. However, you can still set the horizontal
+scrolling value explicitly. The value you specify serves as a lower
+bound for automatic scrolling, i.e. automatic scrolling will not
+scroll a window to a column less than the specified one.
+
+@deffn Command scroll-left &optional count set-minimum
This function scrolls the selected window @var{count} columns to the
-left (or to the right if @var{count} is negative). The return value is
-the total amount of leftward horizontal scrolling in effect after the
-change---just like the value returned by @code{window-hscroll} (below).
-@end deffn
+left (or to the right if @var{count} is negative). The default
+for @var{count} is the window width, minus 2.
-@deffn Command scroll-right count
-This function scrolls the selected window @var{count} columns to the
-right (or to the left if @var{count} is negative). The return value is
-the total amount of leftward horizontal scrolling in effect after the
-change---just like the value returned by @code{window-hscroll} (below).
+The return value is the total amount of leftward horizontal scrolling in
+effect after the change---just like the value returned by
+@code{window-hscroll} (below).
Once you scroll a window as far right as it can go, back to its normal
position where the total leftward scrolling is zero, attempts to scroll
any farther right have no effect.
+
+If @var{set-minimum} is non-@code{nil}, the new scroll amount becomes
+the lower bound for automatic scrolling; that is, automatic scrolling
+will not scroll a window to a column less than the value returned by
+this function. Interactive calls pass non-@code{nil} for
+@var{set-minimum}.
+@end deffn
+
+@deffn Command scroll-right &optional count set-minimum
+This function scrolls the selected window @var{count} columns to the
+right (or to the left if @var{count} is negative). The default
+for @var{count} is the window width, minus 2. Aside from the direction
+of scrolling, this works just like @code{scroll-left}.
@end deffn
@defun window-hscroll &optional window
@end defun
@defun set-window-hscroll window columns
-This function sets the number of columns from the left margin that
-@var{window} is scrolled to the value of @var{columns}. The argument
-@var{columns} should be zero or positive; if not, it is taken as zero.
+This function sets horizontal scrolling of @var{window}. The value of
+@var{columns} specifies the amount of scrolling, in terms of columns
+from the left margin. The argument @var{columns} should be zero or
+positive; if not, it is taken as zero. Fractional values of
+@var{columns} are not supported at present.
+
+Note that @code{set-window-hscroll} may appear not to work if you test
+it by evaluating a call with @kbd{M-:} in a simple way. What happens
+is that the function sets the horizontal scroll value and returns, but
+then redisplay adjusts the horizontal scrolling to make point visible,
+and this overrides what the function did. You can observe the
+function's effect if you call it while point is sufficiently far from
+the left margin that it will remain visible.
The value returned is @var{columns}.
@example
@group
(defun hscroll-on-screen (window position)
- (save-excursion
+ (save-excursion
(goto-char position)
- (and
+ (and
(>= (- (current-column) (window-hscroll window)) 0)
(< (- (current-column) (window-hscroll window))
(window-width window)))))
@defun window-height &optional window
This function returns the number of lines in @var{window}, including
-its mode line. If @var{window} fills its entire frame, this is one less
-than the value of @code{frame-height} on that frame (since the last line
-is always reserved for the minibuffer).
+its mode line and header line, if any. If @var{window} fills its
+entire frame except for the echo area, this is typically one less than
+the value of @code{frame-height} on that frame.
If @var{window} is @code{nil}, the function uses the selected window.
@end example
@end defun
+@tindex window-body-height
+@defun window-body-height &optional window
+Like @code{window-height} but the value does not include the
+mode line (if any) or the header line (if any).
+@end defun
+
@defun window-width &optional window
This function returns the number of columns in @var{window}. If
@var{window} fills its entire frame, this is the same as the value of
rightmost column used by @var{window}, and @var{bottom} is one more than
the bottommost row used by @var{window} and its mode-line.
-When you have side-by-side windows, the right edge value for a window
-with a neighbor on the right includes the width of the separator between
-the window and that neighbor. This separator may be a column of
-@samp{|} characters or it may be a scroll bar. Since the width of the
-window does not include this separator, the width does not equal the
-difference between the right and left edges in this case.
+The edges include the space used by the window's scroll bar, display
+margins, fringes, header line, and mode line, if it has them. Also,
+if the window has a neighbor on the right, its right edge value
+includes the width of the separator line between the window and that
+neighbor. Since the width of the window does not include this
+separator, the width does not usually equal the difference between the
+right and left edges.
+@end defun
+
+@defun window-inside-edges &optional window
+This is similar to @code{window-edges}, but the edge values
+it returns include only the text area of the window. They
+do not include the header line, mode line, scroll bar or
+vertical separator, fringes, or display margins.
+@end defun
-Here is the result obtained on a typical 24-line terminal with just one
-window:
+Here are the results obtained on a typical 24-line terminal with just
+one window, with menu bar enabled:
@example
@group
(window-edges (selected-window))
- @result{} (0 0 80 23)
+ @result{} (0 1 80 23)
+@end group
+@group
+(window-inside-edges (selected-window))
+ @result{} (0 1 80 22)
@end group
@end example
@noindent
The bottom edge is at line 23 because the last line is the echo area.
-
-If @var{window} is at the upper left corner of its frame, @var{right}
-and @var{bottom} are the same as the values returned by
-@code{(window-width)} and @code{(window-height)} respectively, and
-@var{top} and @var{bottom} are zero. For example, the edges of the
-following window are @w{@samp{0 0 5 8}}. Assuming that the frame has
-more than 8 columns, the last column of the window (column 7) holds a
-border rather than text. The last row (row 4) holds the mode line,
-shown here with @samp{xxxxxxxxx}.
+The bottom inside edge is at line 22, which is the window's mode line.
+
+If @var{window} is at the upper left corner of its frame, and there is
+no menu bar, then @var{bottom} returned by @code{window-edges} is the
+same as the value of @code{(window-height)}, @var{right} is almost the
+same as the value of @code{(window-width)}, and @var{top} and
+@var{left} are zero. For example, the edges of the following window
+are @w{@samp{0 0 8 5}}. Assuming that the frame has more than 8
+columns, the last column of the window (column 7) holds a border
+rather than text. The last row (row 4) holds the mode line, shown
+here with @samp{xxxxxxxxx}.
@example
@group
- 0
+ 0
_______
- 0 | |
- | |
- | |
- | |
+ 0 | |
+ | |
+ | |
+ | |
xxxxxxxxx 4
- 7
+ 7
@end group
@end example
-When there are side-by-side windows, any window not at the right edge of
-its frame has a separator in its last column or columns. The separator
-counts as one or two columns in the width of the window. A window never
-includes a separator on its left, since that belongs to the window to
-the left.
-
In the following example, let's suppose that the frame is 7
columns wide. Then the edges of the left window are @w{@samp{0 0 4 3}}
and the edges of the right window are @w{@samp{4 0 7 3}}.
+The inside edges of the left window are @w{@samp{0 0 3 2}},
+and the inside edges of the right window are @w{@samp{4 0 7 2}},
@example
@group
___ ___
- | | |
- | | |
- xxxxxxxxx
+ | | |
+ | | |
+ xxxxxxxxx
0 34 7
@end group
@end example
+
+@defun window-pixel-edges &optional window
+This function is like @code{window-edges} except that, on a graphical
+display, the edge values are measured in pixels instead of in
+character lines and columns.
+@end defun
+
+@defun window-inside-pixel-edges &optional window
+This function is like @code{window-inside-edges} except that, on a
+graphical display, the edge values are measured in pixels instead of
+in character lines and columns.
@end defun
@node Resizing Windows
function makes the window occupy the entire height (or width) of the
frame.
+If there are various other windows from which lines or columns can be
+stolen, and some of them specify fixed size (using
+@code{window-size-fixed}, see below), they are left untouched while
+other windows are ``robbed.'' If it would be necessary to alter the
+size of a fixed-size window, @code{enlarge-window} gets an error
+instead.
+
If @var{size} is negative, this function shrinks the window by
@minus{}@var{size} lines or columns. If that makes the window smaller
than the minimum size (@code{window-min-height} and
@code{window-min-width}), @code{enlarge-window} deletes the window.
-@code{enlarge-window} returns @code{nil}.
+@code{enlarge-window} returns @code{nil}.
@end deffn
@deffn Command enlarge-window-horizontally columns
@example
@group
(defun enlarge-window-horizontally (columns)
+ (interactive "p")
(enlarge-window columns t))
@end group
@end example
@example
@group
(defun shrink-window-horizontally (columns)
+ (interactive "p")
(shrink-window columns t))
@end group
@end example
@end deffn
+@defun adjust-window-trailing-edge window delta horizontal
+This function makes the selected window @var{delta} lines taller or
+@var{delta} columns wider, by moving the bottom or right edge. This
+function does not delete other windows; if it cannot make the
+requested size adjustment, it signals an error. On success, this
+function returns @code{nil}.
+@end defun
+
+@defun fit-window-to-buffer &optional window max-height min-height
+This function makes @var{window} the right height to display its
+contents exactly. If @var{window} is omitted or @code{nil}, it uses
+the selected window.
+
+The argument @var{max-height} specifies the maximum height the window
+is allowed to be; @code{nil} means use the frame height. The argument
+@var{min-height} specifies the minimum height for the window;
+@code{nil} means use @code{window-min-height}. All these height
+values include the mode-line and/or header-line.
+@end defun
+
+@deffn Command shrink-window-if-larger-than-buffer &optional window
+This command shrinks @var{window} vertically to be as small as
+possible while still showing the full contents of its buffer---but not
+less than @code{window-min-height} lines. If @var{window} is not
+given, it defaults to the selected window.
+
+However, the command does nothing if the window is already too small to
+display the whole text of the buffer, or if part of the contents are
+currently scrolled off screen, or if the window is not the full width of
+its frame, or if the window is the only window in its frame.
+
+This command returns non-@code{nil} if it actually shrank the window
+and @code{nil} otherwise.
+@end deffn
+
+@tindex window-size-fixed
+@defvar window-size-fixed
+If this variable is non-@code{nil}, in any given buffer,
+then the size of any window displaying the buffer remains fixed
+unless you explicitly change it or Emacs has no other 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.
+
+This variable automatically becomes buffer-local when set.
+
+Explicit size-change functions such as @code{enlarge-window}
+get an error if they would have to change a window size which is fixed.
+Therefore, when you want to change the size of such a window,
+you should bind @code{window-size-fixed} to @code{nil}, like this:
+
+@example
+(let ((window-size-fixed nil))
+ (enlarge-window 10))
+@end example
+
+Note that changing the frame size will change the size of a
+fixed-size window, if there is no other alternative.
+@end defvar
+
@cindex minimum window size
- The following two variables constrain the window-size-changing
+ The following two variables constrain the window-structure-changing
functions to a minimum height and width.
@defopt window-min-height
The value of this variable determines how short a window may become
before it is automatically deleted. Making a window smaller than
-@code{window-min-height} automatically deletes it, and no window may be
-created shorter than this. The absolute minimum height is two (allowing
-one line for the mode line, and one line for the buffer display).
-Actions that change window sizes reset this variable to two if it is
-less than two. The default value is 4.
+@code{window-min-height} automatically deletes it, and no window may
+be created shorter than this. The default value is 4.
+
+The absolute minimum window height is one; actions that change window
+sizes reset this variable to one if it is less than one.
@end defopt
@defopt window-min-width
The value of this variable determines how narrow a window may become
-before it automatically deleted. Making a window smaller than
+before it is automatically deleted. Making a window smaller than
@code{window-min-width} automatically deletes it, and no window may be
-created narrower than this. The absolute minimum width is one; any
-value below that is ignored. The default value is 10.
-@end defopt
+created narrower than this. The default value is 10.
-@defvar 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 just once per
-redisplay, 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 changed size, or precisely how;
-however, if your size-change function keeps track, after each change, of
-the windows that interest you, you can figure out what has changed by
-comparing the old size data with the new.
-
-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.
-
-It is not a good idea to use @code{save-window-excursion} in these
-functions, because that always counts as a size change, and it would
-cause these functions to be called over and over. In most cases,
-@code{save-selected-window} is what you need here.
-@end defvar
+The absolute minimum window width is two; actions that change window
+sizes reset this variable to two if it is less than two.
+@end defopt
@node Coordinates and Windows
@section Coordinates and Windows
This function checks whether a particular frame position falls within
the window @var{window}.
-@need 3000
-The argument @var{coordinates} is a cons cell of this form:
+The argument @var{coordinates} is a cons cell of the form @code{(@var{x}
+. @var{y})}. The coordinates @var{x} and @var{y} are measured in
+characters, and count from the top left corner of the screen or frame.
-@example
-(@var{x} . @var{y})
-@end example
-
-@noindent
-The coordinates @var{x} and @var{y} are measured in characters, and
-count from the top left corner of the screen or frame.
-
-The value of @code{coordinates-in-window-p} is non-@code{nil} if the
-coordinates are inside @var{window}. The value also indicates what part
-of the window the position is in, as follows:
+The value returned by @code{coordinates-in-window-p} is non-@code{nil}
+if the coordinates are inside @var{window}. The value also indicates
+what part of the window the position is in, as follows:
@table @code
@item (@var{relx} . @var{rely})
@item mode-line
The coordinates are in the mode line of @var{window}.
-@item vertical-split
+@item header-line
+The coordinates are in the header line of @var{window}.
+
+@item vertical-line
The coordinates are in the vertical line between @var{window} and its
-neighbor to the right. This value occurs only if the window doesn't
+neighbor to the right. This value occurs only if the window doesn't
have a scroll bar; positions in a scroll bar are considered outside the
-window.
+window for these purposes.
+
+@item left-fringe
+@itemx right-fringe
+The coordinates are in the left or right fringe of the window.
+
+@item left-margin
+@itemx right-margin
+The coordinates are in the left or right margin of the window.
@item nil
The coordinates are not in any part of @var{window}.
argument because it always uses the frame that @var{window} is on.
@end defun
+@node Window Tree
+@section The Window Tree
+@cindex window tree
+
+ A @dfn{window tree} specifies the layout, size, and relationship
+between all windows in one frame.
+
+@defun window-tree &optional frame
+This function returns the window tree for frame @var{frame}.
+If @var{frame} is omitted, the selected frame is used.
+
+The return value is a list of the form @code{(@var{root} @var{mini})},
+where @var{root} represents the window tree of the frame's
+root window, and @var{mini} is the frame's minibuffer window.
+
+If the root window is not split, @var{root} is the root window itself.
+Otherwise, @var{root} is a list @code{(@var{dir} @var{edges} @var{w1}
+@var{w2} ...)} where @var{dir} is @code{nil} for a horizontal split,
+and @code{t} for a vertical split, @var{edges} gives the combined size and
+position of the subwindows in the split, and the rest of the elements
+are the subwindows in the split. Each of the subwindows may again be
+a window or a list representing a window split, and so on. The
+@var{edges} element is a list @code{(@var{left}@var{ top}@var{ right}@var{ bottom})}
+similar to the value returned by @code{window-edges}.
+@end defun
+
@node Window Configurations
@section Window Configurations
@cindex window configurations
@cindex saving window information
- A @dfn{window configuration} records the entire layout of a
-frame---all windows, their sizes, which buffers they contain, what part
-of each buffer is displayed, and the values of point and the mark. You
-can bring back an entire previous layout by restoring a window
-configuration previously saved.
-
- If you want to record all frames instead of just one, use a frame
-configuration instead of a window configuration. @xref{Frame
-Configurations}.
-
-@defun current-window-configuration
-This function returns a new object representing Emacs's current window
-configuration, namely the number of windows, their sizes and current
-buffers, which window is the selected window, and for each window the
-displayed buffer, the display-start position, and the positions of point
-and the mark. An exception is made for point in the current buffer,
-whose value is not saved.
+ A @dfn{window configuration} records the entire layout of one
+frame---all windows, their sizes, which buffers they contain, what
+part of each buffer is displayed, and the values of point and the
+mark; also their fringes, margins, and scroll bar settings. It also
+includes the values of @code{window-min-height},
+@code{window-min-width} and @code{minibuffer-scroll-window}. An
+exception is made for point in the selected window for the current
+buffer; its value is not saved in the window configuration.
+
+ You can bring back an entire previous layout by restoring a window
+configuration previously saved. If you want to record all frames
+instead of just one, use a frame configuration instead of a window
+configuration. @xref{Frame Configurations}.
+
+@defun current-window-configuration &optional frame
+This function returns a new object representing @var{frame}'s current
+window configuration. If @var{frame} is omitted, the selected frame
+is used.
@end defun
@defun set-window-configuration configuration
-This function restores the configuration of Emacs's windows and
-buffers to the state specified by @var{configuration}. The argument
-@var{configuration} must be a value that was previously returned by
-@code{current-window-configuration}.
-
-This function always counts as a window size change and triggers
-execution of the @code{window-size-change-functions}. (It doesn't know
-how to tell whether the new configuration actually differs from the old
-one.)
+This function restores the configuration of windows and buffers as
+specified by @var{configuration}, for the frame that @var{configuration}
+was created for.
+
+The argument @var{configuration} must be a value that was previously
+returned by @code{current-window-configuration}. This configuration is
+restored in the frame from which @var{configuration} was made, whether
+that frame is selected or not. This always counts as a window size
+change and triggers execution of the @code{window-size-change-functions}
+(@pxref{Window Hooks}), because @code{set-window-configuration} doesn't
+know how to tell whether the new configuration actually differs from the
+old one.
+
+If the frame which @var{configuration} was saved from is dead, all this
+function does is restore the three variables @code{window-min-height},
+@code{window-min-width} and @code{minibuffer-scroll-window}. In this
+case, the function returns @code{nil}. Otherwise, it returns @code{t}.
Here is a way of using this function to get the same effect
as @code{save-window-excursion}:
@defspec save-window-excursion forms@dots{}
This special form records the window configuration, executes @var{forms}
in sequence, then restores the earlier window configuration. The window
-configuration includes the value of point and the portion of the buffer
-that is visible. It also includes the choice of selected window.
-However, it does not include the value of point in the current buffer;
-use @code{save-excursion} if you wish to preserve that.
+configuration includes, for each window, the value of point and the
+portion of the buffer that is visible. It also includes the choice of
+selected window. However, it does not include the value of point in
+the current buffer; use @code{save-excursion} also, if you wish to
+preserve that.
-Don't use this construct when @code{save-selected-window} is all you need.
+Don't use this construct when @code{save-selected-window} is sufficient.
Exit from @code{save-window-excursion} always triggers execution of the
@code{window-size-change-functions}. (It doesn't know how to tell
This function returns @code{t} if @var{object} is a window configuration.
@end defun
- Primitives to look inside of window configurations would make sense,
-but none are implemented. It is not clear they are useful enough to be
-worth implementing.
+@defun compare-window-configurations config1 config2
+This function compares two window configurations as regards the
+structure of windows, but ignores the values of point and mark and the
+saved scrolling positions---it can return @code{t} even if those
+aspects differ.
+
+The function @code{equal} can also compare two window configurations; it
+regards configurations as unequal if they differ in any respect, even a
+saved point or mark.
+@end defun
+
+@defun window-configuration-frame config
+This function returns the frame for which the window configuration
+@var{config} was made.
+@end defun
+
+ Other primitives to look inside of window configurations would make
+sense, but are not implemented because we did not need them. See the
+file @file{winner.el} for some more operations on windows
+configurations.
+
+@node Window Hooks
+@section Hooks for Window Scrolling and Changes
+
+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 @code{window-scroll-functions}; the last runs
+@code{window-size-change-functions}.
+
+@defvar window-scroll-functions
+This variable holds a list of functions that Emacs should call before
+redisplaying a window with scrolling. It is not a normal hook, because
+each function is called with two arguments: the window, and its new
+display-start position.
+
+Displaying a different buffer in the window also runs these functions.
+
+These functions must be careful in using @code{window-end}
+(@pxref{Window Start}); if you need an up-to-date value, you must use
+the @var{update} argument to ensure you get it.
+@end defvar
+
+@defvar 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 just once per
+redisplay, 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.
+
+It is not a good idea to use @code{save-window-excursion} (@pxref{Window
+Configurations}) in these functions, because that always counts as a
+size change, and it would cause these functions to be called over and
+over. In most cases, @code{save-selected-window} (@pxref{Selecting
+Windows}) is what you need here.
+@end defvar
+
+@defvar redisplay-end-trigger-functions
+This abnormal hook is run whenever redisplay in a window uses text that
+extends past a specified end trigger position. You set the end trigger
+position with the function @code{set-window-redisplay-end-trigger}. The
+functions are called with two arguments: the window, and the end trigger
+position. Storing @code{nil} for the end trigger position turns off the
+feature, and the trigger value is automatically reset to @code{nil} just
+after the hook is run.
+@end defvar
+
+@defun set-window-redisplay-end-trigger window position
+This function sets @var{window}'s end trigger position at
+@var{position}.
+@end defun
+
+@defun window-redisplay-end-trigger &optional window
+This function returns @var{window}'s current end trigger position.
+If @var{window} is @code{nil} or omitted, it uses the selected window.
+@end defun
+
+@defvar 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 frame whose window configuration has changed is the
+selected frame when this hook runs.
+@end defvar
+
+@ignore
+ arch-tag: 3f6c36e8-df49-4986-b757-417feed88be3
+@end ignore