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diff --git a/lispref/windows.texi b/lispref/windows.texi deleted file mode 100644 index 6f6431cf45d..00000000000 --- a/lispref/windows.texi +++ /dev/null @@ -1,2442 +0,0 @@ -@c -*-texinfo-*- -@c This is part of the GNU Emacs Lisp Reference Manual. -@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001, -@c 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc. -@c See the file elisp.texi for copying conditions. -@setfilename ../info/windows -@node Windows, Frames, Buffers, Top -@chapter Windows - - This chapter describes most of the functions and variables related to -Emacs windows. See @ref{Display}, for information on how text is -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-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 -@section Basic Concepts of Emacs Windows -@cindex window -@cindex selected window - - A @dfn{window} in Emacs is the physical area of the screen in which a -buffer is displayed. The term is also used to refer to a Lisp object that -represents that screen area in Emacs Lisp. It should be -clear from the context which is meant. - - Emacs groups windows into frames. A frame represents an area of -screen available for Emacs to use. Each frame always contains at least -one window, but you can subdivide it vertically or horizontally into -multiple nonoverlapping Emacs 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, but the other windows have ``non-selected'' cursors, normally -less visible. (@pxref{Cursor Parameters}, for customization of this.) -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}. - - 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 -to it} from other Lisp objects. Restoring a saved window configuration -is the only way for a window no longer on the screen to come back to -life. (@xref{Deleting Windows}.) - - Each window has the following attributes: - -@itemize @bullet -@item -containing frame - -@item -window height - -@item -window width - -@item -window edges with respect to the screen or frame - -@item -the buffer it displays - -@item -position within the buffer at the upper left of the window - -@item -amount of horizontal scrolling, in columns - -@item -point - -@item -the mark - -@item -how recently the window was selected - -@item -fringe settings - -@item -display margins - -@item -scroll-bar settings -@end itemize - -@cindex multiple windows - Users create multiple windows so they can look at several buffers at -once. Lisp libraries use multiple windows for a variety of reasons, but -most often to display related information. In Rmail, for example, you -can move through a summary buffer in one window while the other window -shows messages one at a time as they are reached. - - The meaning of ``window'' in Emacs is similar to what it means in the -context of general-purpose window systems such as X, but not identical. -The X Window System places X windows on the screen; Emacs uses one or -more X windows as frames, and subdivides them into -Emacs windows. When you use Emacs on a character-only terminal, Emacs -treats the whole terminal screen as one frame. - -@cindex terminal screen -@cindex screen of terminal -@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, 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. -@end defun - -@node Splitting Windows -@section Splitting Windows -@cindex splitting windows -@cindex window splitting - - The functions described here are the primitives used to split a window -into two windows. Two higher level functions sometimes split a window, -but not always: @code{pop-to-buffer} and @code{display-buffer} -(@pxref{Displaying Buffers}). - - The functions described here do not accept a buffer as an argument. -The two ``halves'' of the split window initially display the same buffer -previously visible in the window that was split. - -@deffn Command split-window &optional window size horizontal -This function splits a new window out of @var{window}'s screen area. -It returns the new window. - -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 -@var{window} keeps the upper @var{size} lines and gives the rest of the -lines to the new window. The original window is therefore the -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}, that stands for the selected -window. When you split the selected window, it remains selected. - -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}. - -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 -(setq w (selected-window)) - @result{} #<window 8 on windows.texi> -(window-edges) ; @r{Edges in order:} - @result{} (0 0 80 50) ; @r{left--top--right--bottom} -@end group - -@group -;; @r{Returns window created} -(setq w2 (split-window w 15)) - @result{} #<window 28 on windows.texi> -@end group -@group -(window-edges w2) - @result{} (0 15 80 50) ; @r{Bottom window;} - ; @r{top is line 15} -@end group -@group -(window-edges w) - @result{} (0 0 80 15) ; @r{Top window} -@end group -@end smallexample - -The screen looks like this: - -@smallexample -@group - __________ - | | line 0 - | w | - |__________| - | | line 15 - | w2 | - |__________| - line 50 - column 0 column 80 -@end group -@end smallexample - -Next, split the top window horizontally: - -@smallexample -@group -(setq w3 (split-window w 35 t)) - @result{} #<window 32 on windows.texi> -@end group -@group -(window-edges w3) - @result{} (35 0 80 15) ; @r{Left edge at column 35} -@end group -@group -(window-edges w) - @result{} (0 0 35 15) ; @r{Right edge at column 35} -@end group -@group -(window-edges w2) - @result{} (0 15 80 50) ; @r{Bottom window unchanged} -@end group -@end smallexample - -@need 3000 -Now the screen looks like this: - -@smallexample -@group - column 35 - __________ - | | | line 0 - | w | w3 | - |___|______| - | | line 15 - | w2 | - |__________| - line 50 - column 0 column 80 -@end group -@end smallexample - -Normally, Emacs indicates the border between two side-by-side windows -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 &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 - -@defopt split-window-keep-point -If this variable is non-@code{nil} (the default), then -@code{split-window-vertically} behaves as described above. - -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. - -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 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 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") -@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 - -@defun one-window-p &optional no-mini all-frames -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 -counted when it is active. - -The argument @var{all-frames} specifies which frames to consider. Here -are the possible values and their meanings: - -@table @asis -@item @code{nil} -Count the windows in the selected frame, plus the minibuffer used -by that frame even if it lies in some other frame. - -@item @code{t} -Count all windows in all existing frames. - -@item @code{visible} -Count all windows in all visible frames. - -@item 0 -Count all windows in all visible or iconified frames. - -@item anything else -Count precisely the windows in the selected frame, and no others. -@end table -@end defun - -@node Deleting Windows -@section Deleting Windows -@cindex deleting windows - -A window remains visible on its frame unless you @dfn{delete} it by -calling certain functions that delete windows. A deleted window cannot -appear on the screen, but continues to exist as a Lisp object until -there are no references to it. There is no way to cancel the deletion -of a window aside from restoring a saved window configuration -(@pxref{Window Configurations}). Restoring a window configuration also -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. - -@c Emacs 19 feature -@defun window-live-p window -This function returns @code{nil} if @var{window} is deleted, and -@code{t} otherwise. - -@strong{Warning:} Erroneous information or fatal errors may result from -using a deleted window as if it were live. -@end defun - -@deffn Command delete-window &optional 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 -This function makes @var{window} the only window on its frame, by -deleting the other windows in that frame. If @var{window} is omitted or -@code{nil}, then the selected window is used by default. - -The return value is @code{nil}. -@end deffn - -@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-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 all frames. -@item -If it is @code{t}, operate on the selected frame. -@item -If it is @code{visible}, operate on all visible frames. -@item -If it is 0, operate on all visible or iconified frames. -@item -If it is a frame, operate on that frame. -@end itemize - -This function always returns @code{nil}. -@end deffn - -@node Selecting Windows -@section Selecting Windows -@cindex selecting a window - - When a window is selected, the buffer in the window becomes the current -buffer, and the cursor will appear in it. - -@defun selected-window -This function returns the selected window. This is the window in -which the cursor appears and to which many commands apply. -@end defun - -@defun select-window window &optional norecord -This function makes @var{window} the selected window. The cursor then -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}. - -@example -@group -(setq w (next-window)) -(select-window w) - @result{} #<window 65 on windows.texi> -@end group -@end example -@end defun - -@defmac save-selected-window forms@dots{} -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 dedicated -This function returns the window least recently ``used'' (that is, -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. 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. - -@itemize @bullet -@item -If it is @code{nil}, consider windows on the selected 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 -@end defun - -@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 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 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 -@comment node-name, next, previous, up -@section Cyclic Ordering of Windows -@cindex cyclic ordering of windows -@cindex ordering of windows, 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 -specific cyclic order. For any given configuration of windows, this -order never varies. It is called the @dfn{cyclic ordering of windows}. - - This ordering generally goes from top to bottom, and from left to -right. But it may go down first or go right first, depending on the -order in which the windows were split. - - If the first split was vertical (into windows one above each other), -and then the subwindows were split horizontally, then the ordering is -left to right in the top of the frame, and then left to right in the -next lower part of the frame, and so on. If the first split was -horizontal, the ordering is top to bottom in the left part, and so on. -In general, within each set of siblings at any level in the window tree, -the order is left to right, or top to bottom. - -@defun next-window &optional window minibuf all-frames -@cindex minibuffer window, and @code{next-window} -This function returns the window following @var{window} in the cyclic -ordering of windows. This is the window that @kbd{C-x o} would select -if typed when @var{window} is selected. If @var{window} is the only -window visible, then this function returns @var{window}. If omitted, -@var{window} defaults to the selected window. - -The value of the argument @var{minibuf} determines whether the -minibuffer is included in the window order. Normally, when -@var{minibuf} is @code{nil}, the minibuffer is included if it is -currently active; this is the behavior of @kbd{C-x o}. (The minibuffer -window is active while the minibuffer is in use. @xref{Minibuffers}.) - -If @var{minibuf} is @code{t}, then the cyclic ordering includes the -minibuffer window even if it is not active. - -If @var{minibuf} is neither @code{t} nor @code{nil}, then the minibuffer -window is not included even if it is active. - -The argument @var{all-frames} specifies which frames to consider. Here -are the possible values and their meanings: - -@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. 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 @code{visible} -Consider all windows in all visible frames. (To get useful results, you -must ensure @var{window} is in a visible frame.) - -@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 -buffer @samp{windows.texi}: - -@example -@group -(selected-window) - @result{} #<window 56 on windows.texi> -@end group -@group -(next-window (selected-window)) - @result{} #<window 52 on windows.texi> -@end group -@group -(next-window (next-window (selected-window))) - @result{} #<window 56 on windows.texi> -@end group -@end example -@end defun - -@defun previous-window &optional window minibuf all-frames -This function returns the window preceding @var{window} in the cyclic -ordering of windows. The other arguments specify which windows to -include in the cycle, as in @code{next-window}. -@end defun - -@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 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. 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 -@cindex windows, controlling precisely -@cindex buffers, controlled in windows - - This section describes low-level functions to examine windows or to -display buffers in windows in a precisely controlled fashion. -@iftex -See the following section for -@end iftex -@ifnottex -@xref{Displaying Buffers}, for -@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 &optional keep-margins -This function makes @var{window} display @var{buffer-or-name} as its -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 -(set-window-buffer (selected-window) "foo") - @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 -selected window. - -@example -@group -(window-buffer) - @result{} #<buffer windows.texi> -@end group -@end example -@end defun - -@defun get-buffer-window buffer-or-name &optional all-frames -This function returns a window currently displaying -@var{buffer-or-name}, or @code{nil} if there is none. If there are -several such windows, then the function returns the first one in the -cyclic ordering of windows, starting from the selected window. -@xref{Cyclic Window Ordering}. - -The argument @var{all-frames} controls which windows to consider. - -@itemize @bullet -@item -If it is @code{nil}, consider windows on the selected 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 -@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 -@cindex displaying a buffer - - In this section we describe convenient functions that choose a window -automatically and use it to display a specified buffer. These functions -can also split an existing window in certain circumstances. We also -describe variables that parameterize the heuristics used for choosing a -window. -@iftex -See the preceding section for -@end iftex -@ifnottex -@xref{Buffers and Windows}, for -@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 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 -displays the buffer in the selected window. This means that a human can -see the buffer and subsequent keyboard commands will apply to it. -Contrast this with @code{set-buffer}, which makes @var{buffer-or-name} -the current buffer but does not display it in the selected window. -@xref{Current Buffer}. - -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}. 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 -(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 -returns the buffer that it switched to. -@end deffn - -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 -@code{switch-to-buffer}. - -The currently selected window is absolutely never used to do the job. -If it is the only window, then it is split to make a distinct window for -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 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. 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 -displaying the buffer; if there is one, it returns that window and makes -it be selected within its frame. If there is none, it creates a new -frame and displays the buffer in it. - -If @code{pop-up-frames} is @code{nil}, then @code{pop-to-buffer} -operates entirely within the selected frame. (If the selected frame has -just a minibuffer, @code{pop-to-buffer} operates within the most -recently selected frame that was not just a minibuffer.) - -If the variable @code{pop-up-windows} is non-@code{nil}, windows may -be split to create a new window that is different from the original -window. For details, see @ref{Choosing Window}. - -If @var{other-window} is non-@code{nil}, @code{pop-to-buffer} finds or -creates another window even if @var{buffer-or-name} is already visible -in the selected window. Thus @var{buffer-or-name} could end up -displayed in two windows. On the other hand, if @var{buffer-or-name} is -already displayed in the selected window and @var{other-window} is -@code{nil}, then the selected window is considered sufficient display -for @var{buffer-or-name}, so that nothing needs to be done. - -All the variables that affect @code{display-buffer} affect -@code{pop-to-buffer} as well. @xref{Choosing Window}. - -If @var{buffer-or-name} is a string that does not name an existing -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-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-or-name} is no longer displayed. - -This function returns @code{nil}. -@end deffn - -@node Choosing Window -@section Choosing a Window for Display - - This section describes the basic facility that chooses a window to -display a buffer in---@code{display-buffer}. All the higher-level -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 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. @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 -already on display in the selected window. This can cause the buffer to -appear in two windows at once. Otherwise, if @var{buffer-or-name} is -already being displayed in any window, that is good enough, so this -function does nothing. - -@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 -is split. If it is @code{nil}, then @code{display-buffer} does not -split the single window, but uses it whole. -@end defopt - -@defopt split-height-threshold -This variable determines when @code{display-buffer} may split a window, -if there are multiple windows. @code{display-buffer} always splits the -largest window if it has at least this many lines. If the largest -window is not this tall, it is split only if it is the sole window and -@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. -If it is non-@code{nil}, @code{display-buffer} looks for an existing -window already displaying the desired buffer, on any visible frame. If -it finds one, it returns that window. Otherwise it makes a new frame. -The variables @code{pop-up-windows} and @code{split-height-threshold} do -not matter if @code{pop-up-frames} is non-@code{nil}. - -If @code{pop-up-frames} is @code{nil}, then @code{display-buffer} either -splits a window or reuses one. - -@xref{Frames}, for more information. -@end defopt - -@c Emacs 19 feature -@defopt pop-up-frame-function -This variable specifies how to make a new frame if @code{pop-up-frames} -is non-@code{nil}. - -Its value should be a function of no arguments. When -@code{display-buffer} makes a new frame, it does so by calling that -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 defopt - -@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 defopt - -@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 (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 - -@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 -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 regular expression, and the rest of the list says how to -create the frame. See above, under @code{special-display-buffer-names}. -@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. -It receives the buffer as an argument, and should return the window in -which it is displayed. - -The default value of this variable is -@code{special-display-popup-frame}. -@end defvar - -@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}. This -function returns the window it used. - -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 - -@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 defopt - -@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 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 first two arguments that @code{display-buffer} -received. It should choose or create a window, display the specified -buffer in it, and then return the window. - -This hook takes precedence over all the other options and hooks -described above. -@end defvar - -@c Emacs 19 feature -@cindex dedicated window -A window can be marked as ``dedicated'' to its buffer. Then -@code{display-buffer} will not try to use that window to display any -other buffer. - -@defun window-dedicated-p window -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 -This function marks @var{window} as dedicated if @var{flag} is -non-@code{nil}, and nondedicated otherwise. -@end defun - -@node Window Point -@section Windows and Point -@cindex window position -@cindex window point -@cindex position in window -@cindex point in window - - Each window has its own value of point, independent of the value of -point in other windows displaying the same buffer. This makes it useful -to have multiple windows showing one buffer. - -@itemize @bullet -@item -The window point is established when a window is first created; it is -initialized from the buffer's point, or from the window point of another -window opened on the buffer if such a window exists. - -@item -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 - -@noindent -@xref{Positions}, for more details on buffer positions. - -@cindex cursor - 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 &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. 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. - -Strictly speaking, it would be more correct to return the -``top-level'' value of point, outside of any @code{save-excursion} -forms. But that value is hard to find. -@end defun - -@defun set-window-point window position -This function positions point in @var{window} at position -@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 -@section The Window Start Position -@cindex window start position - - Each window contains a marker used to keep track of a buffer position -that specifies where in the buffer display should start. This position -is called the @dfn{display-start} position of the window (or just the -@dfn{start}). The character after this position is the one that appears -at the upper left corner of the window. It is usually, but not -inevitably, at the beginning of a text line. - -@defun window-start &optional window -@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, - -@example -@group -(window-start) - @result{} 7058 -@end group -@end example - -When you create a window, or display a different buffer in it, the -display-start position is set to a display-start position recently used -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)---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}. @xref{Definition of count-lines}. -@end defun - -@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 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 @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 -This function sets the display-start position of @var{window} to -@var{position} in @var{window}'s buffer. It returns @var{position}. - -The display routines insist that the position of point be visible when a -buffer is displayed. Normally, they change the display-start position -(that is, scroll the window) whenever necessary to make point visible. -However, if you specify the start position with this function using -@code{nil} for @var{noforce}, it means you want display to start at -@var{position} even if that would put the location of point off the -screen. If this does place point off screen, the display routines move -point to the left margin on the middle line in the window. - -For example, if point @w{is 1} and you set the start of the window @w{to -2}, then point would be ``above'' the top of the window. The display -routines will automatically move point if it is still 1 when redisplay -occurs. Here is an example: - -@example -@group -;; @r{Here is what @samp{foo} looks like before executing} -;; @r{the @code{set-window-start} expression.} -@end group - -@group ----------- Buffer: foo ---------- -@point{}This is the contents of buffer foo. -2 -3 -4 -5 -6 ----------- Buffer: foo ---------- -@end group - -@group -(set-window-start - (selected-window) - (1+ (window-start))) -@result{} 2 -@end group - -@group -;; @r{Here is what @samp{foo} looks like after executing} -;; @r{the @code{set-window-start} expression.} ----------- Buffer: foo ---------- -his is the contents of buffer foo. -2 -3 -@point{}4 -5 -6 ----------- Buffer: foo ---------- -@end group -@end example - -If @var{noforce} is non-@code{nil}, and @var{position} would place point -off screen at the next redisplay, then redisplay computes a new window-start -position that works well with point, and thus @var{position} is not used. -@end defun - -@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. - -If @var{position} is @code{t}, that means to check the last visible -position in @var{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}, and the character after @var{position} is fully -visible, it returns a list of the form @code{(@var{x} @var{y})}, where -@var{x} and @var{y} are the pixel coordinates relative to the top left -corner of the window; otherwise it returns an extended list of the -form @code{(@var{x} @var{y} @var{rtop} @var{rbot} @var{rowh} -@var{vpos})}, where the @var{rtop} and @var{rbot} specify the number -of off-window pixels at the top and bottom of the row at -@var{position}, @var{rowh} specifies the visible height of that row, -and @var{vpos} specifies the vertical position (zero-based row number) -of that row. - -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 -@end defun - -@defun window-line-height &optional line window -This function returns information about text line @var{line} in @var{window}. -If @var{line} is one of @code{header-line} or @code{mode-line}, -@code{window-line-height} returns information about the corresponding -line of the window. Otherwise, @var{line} is a text line number -starting from 0. A negative number counts from the end of the window. -The argument @var{line} defaults to the current line in @var{window}; -@var{window}, to the selected window. - -If the display is not up to date, @code{window-line-height} returns -@code{nil}. In that case, @code{pos-visible-in-window-p} may be used -to obtain related information. - -If there is no line corresponding to the specified @var{line}, -@code{window-line-height} returns @code{nil}. Otherwise, it returns -a list @code{(@var{height} @var{vpos} @var{ypos} @var{offbot})}, -where @var{height} is the height in pixels of the visible part of the -line, @var{vpos} and @var{ypos} are the vertical position in lines and -pixels of the line relative to the top of the first text line, and -@var{offbot} is the number of off-window pixels at the bottom of the -text line. If there are off-window pixels at the top of the (first) -text line, @var{ypos} is negative. -@end defun - -@node Textual Scrolling -@section Textual Scrolling -@cindex textual scrolling -@cindex scrolling textually - - @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 -you are looking through the window. Imagine that the text is -written on a long roll of paper and that the scrolling commands move the -paper up and down. Thus, if you are looking at text in the middle of a -buffer and repeatedly call @code{scroll-down}, you will eventually see -the beginning of the buffer. - - Some people have urged that the opposite convention be used: they -imagine that the window moves over text that remains in place. Then -``down'' commands would take you to the end of the buffer. This view is -more consistent with the actual relationship between windows and the -text in the buffer, but it is less like what the user sees. The -position of a window on the terminal does not move, and short scrolling -commands clearly move the text up or down on the screen. We have chosen -names that fit the user's point of view. - - 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 presence 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 -@var{count} lines. If @var{count} is negative, scrolling is actually -downward. - -If @var{count} is @code{nil} (or omitted), then the length of scroll -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}, unless it gets an error -because it can't scroll any further. -@end deffn - -@deffn Command scroll-down &optional count -This function scrolls the text in the selected window downward -@var{count} lines. If @var{count} is negative, scrolling is actually -upward. - -If @var{count} is omitted or @code{nil}, then the length of the scroll -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}, unless it gets an error because -it can't scroll any further. -@end deffn - -@deffn Command scroll-other-window &optional count -This function scrolls the text in another window upward @var{count} -lines. Negative values of @var{count}, or @code{nil}, are handled -as in @code{scroll-up}. - -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. 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, -@code{scroll-other-window} attempts to scroll the minibuffer. If the -minibuffer contains just one line, it has nowhere to scroll to, so the -line reappears after the echo area momentarily displays the message -@samp{Beginning of buffer}. -@end deffn - -@c Emacs 19 feature -@defvar other-window-scroll-buffer -If this variable is non-@code{nil}, it tells @code{scroll-other-window} -which buffer to scroll. -@end defvar - -@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 (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 -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 -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 -The value of this variable is the number of lines of continuity to -retain when scrolling by full screens. For example, @code{scroll-up} -with an argument of @code{nil} scrolls so that this many lines at the -bottom of the window appear instead at the top. The default value is -@code{2}. -@end defopt - -@deffn Command recenter &optional count -@cindex centering point -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, 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 -selected frame. - -When @code{recenter} is called interactively, @var{count} is the raw -prefix argument. Thus, typing @kbd{C-u} as the prefix sets the -@var{count} to a non-@code{nil} list, while typing @kbd{C-u 4} sets -@var{count} to 4, which positions the current line four lines from the -top. - -With an argument of zero, @code{recenter} positions the current line at -the top of the window. This action is so handy that some people make a -separate key binding to do this. For example, - -@example -@group -(defun line-to-top-of-window () - "Scroll current line to top of window. -Replaces three keystroke sequence C-u 0 C-l." - (interactive) - (recenter 0)) - -(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 presence of large images. -@end defvar - -@node Horizontal Scrolling -@section Horizontal Scrolling -@cindex horizontal scrolling - - @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 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 default -for @var{count} is the window width, minus 2. - -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 -This function returns the total leftward horizontal scrolling of -@var{window}---the number of columns by which the text in @var{window} -is scrolled left past the left margin. - -The value is never negative. It is zero when no horizontal scrolling -has been done in @var{window} (which is usually the case). - -If @var{window} is @code{nil}, the selected window is used. - -@example -@group -(window-hscroll) - @result{} 0 -@end group -@group -(scroll-left 5) - @result{} 5 -@end group -@group -(window-hscroll) - @result{} 5 -@end group -@end example -@end defun - -@defun set-window-hscroll window columns -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 -(set-window-hscroll (selected-window) 10) - @result{} 10 -@end group -@end example -@end defun - - Here is how you can determine whether a given position @var{position} -is off the screen due to horizontal scrolling: - -@example -@group -(defun hscroll-on-screen (window position) - (save-excursion - (goto-char position) - (and - (>= (- (current-column) (window-hscroll window)) 0) - (< (- (current-column) (window-hscroll window)) - (window-width window))))) -@end group -@end example - -@node Size of Window -@section The Size of a Window -@cindex window size -@cindex size of window - - An Emacs window is rectangular, and its size information consists of -the height (the number of lines) and the width (the number of character -positions in each line). The mode line is included in the height. But -the width does not count the scroll bar or the column of @samp{|} -characters that separates side-by-side windows. - - The following three functions return size information about a window: - -@defun window-height &optional window -This function returns the number of lines in @var{window}, including -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. - -@example -@group -(window-height) - @result{} 23 -@end group -@group -(split-window-vertically) - @result{} #<window 4 on windows.texi> -@end group -@group -(window-height) - @result{} 11 -@end group -@end example -@end defun - -@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 -@code{frame-width} on that frame. The width does not include the -window's scroll bar or the column of @samp{|} characters that separates -side-by-side windows. - -If @var{window} is @code{nil}, the function uses the selected window. - -@example -@group -(window-width) - @result{} 80 -@end group -@end example -@end defun - -@defun window-full-width-p &optional window -This function returns non-@code{nil} if @var{window} is as wide as -the frame that contains it; otherwise @code{nil}. -If @var{window} is @code{nil}, the function uses the selected window. -@end defun - -@defun window-edges &optional window -This function returns a list of the edge coordinates of @var{window}. -If @var{window} is @code{nil}, the selected window is used. - -The order of the list is @code{(@var{left} @var{top} @var{right} -@var{bottom})}, all elements relative to 0, 0 at the top left corner of -the frame. The element @var{right} of the value is one more than the -rightmost column used by @var{window}, and @var{bottom} is one more than -the bottommost row used by @var{window} and its mode-line. - -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 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 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. -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 | | - | | - | | - | | - xxxxxxxxx 4 - - 7 -@end group -@end example - -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 - - 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 -@section Changing the Size of a Window -@cindex window resizing -@cindex resize window -@cindex changing window size -@cindex window size, changing - - The window size functions fall into two classes: high-level commands -that change the size of windows and low-level functions that access -window size. Emacs does not permit overlapping windows or gaps between -windows, so resizing one window affects other windows. - -@deffn Command enlarge-window size &optional horizontal -This function makes the selected window @var{size} lines taller, -stealing lines from neighboring windows. It takes the lines from one -window at a time until that window is used up, then takes from another. -If a window from which lines are stolen shrinks below -@code{window-min-height} lines, that window disappears. - -If @var{horizontal} is non-@code{nil}, this function makes -@var{window} wider by @var{size} columns, stealing columns instead of -lines. If a window from which columns are stolen shrinks below -@code{window-min-width} columns, that window disappears. - -If the requested size would exceed that of the window's frame, then the -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}. -@end deffn - -@deffn Command enlarge-window-horizontally columns -This function makes the selected window @var{columns} wider. -It could be defined as follows: - -@example -@group -(defun enlarge-window-horizontally (columns) - (interactive "p") - (enlarge-window columns t)) -@end group -@end example -@end deffn - -@deffn Command shrink-window size &optional horizontal -This function is like @code{enlarge-window} but negates the argument -@var{size}, making the selected window smaller by giving lines (or -columns) to the other windows. If the window shrinks below -@code{window-min-height} or @code{window-min-width}, then it disappears. - -If @var{size} is negative, the window is enlarged by @minus{}@var{size} -lines or columns. -@end deffn - -@deffn Command shrink-window-horizontally columns -This function makes the selected window @var{columns} narrower. -It could be defined as follows: - -@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 - -@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-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 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 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 default value is 10. - -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 section describes how to relate screen coordinates to windows. - -@defun window-at x y &optional frame -This function returns the window containing the specified cursor -position in the frame @var{frame}. The coordinates @var{x} and @var{y} -are measured in characters and count from the top left corner of the -frame. If they are out of range, @code{window-at} returns @code{nil}. - -If you omit @var{frame}, the selected frame is used. -@end defun - -@defun coordinates-in-window-p coordinates window -This function checks whether a particular frame position falls within -the window @var{window}. - -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. - -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}) -The coordinates are inside @var{window}. The numbers @var{relx} and -@var{rely} are the equivalent window-relative coordinates for the -specified position, counting from 0 at the top left corner of the -window. - -@item mode-line -The coordinates are in the mode line of @var{window}. - -@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 -have a scroll bar; positions in a scroll bar are considered outside the -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}. -@end table - -The function @code{coordinates-in-window-p} does not require a frame as -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 one -frame---all windows, their sizes, which buffers they contain, how -those buffers are scrolled, and their 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}. As a -special exception, the window configuration does not record the value -of point in the selected window for the current buffer. - - 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 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}: - -@example -@group -(let ((config (current-window-configuration))) - (unwind-protect - (progn (split-window-vertically nil) - @dots{}) - (set-window-configuration config))) -@end group -@end example -@end defun - -@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, 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 sufficient. - -Exit from @code{save-window-excursion} always triggers execution of the -@code{window-size-change-functions}. (It doesn't know how to tell -whether the restored configuration actually differs from the one in -effect at the end of the @var{forms}.) - -The return value is the value of the final form in @var{forms}. -For example: - -@example -@group -(split-window) - @result{} #<window 25 on control.texi> -@end group -@group -(setq w (selected-window)) - @result{} #<window 19 on control.texi> -@end group -@group -(save-window-excursion - (delete-other-windows w) - (switch-to-buffer "foo") - 'do-something) - @result{} do-something - ;; @r{The screen is now split again.} -@end group -@end example -@end defspec - -@defun window-configuration-p object -This function returns @code{t} if @var{object} is a window configuration. -@end defun - -@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 -@cindex hooks for window operations - -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. - -@strong{Warning:} don't use this feature to alter the way the window -is scrolled. It's not designed for that, and such use probably won't -work. -@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 |