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This is Info file ../../info/lispref.info, produced by Makeinfo-1.63 from the input file lispref.texi. Edition History: GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp Programmer's Manual (for 19.13) Third Edition, July 1995 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. Copyright (C) 1995 Ben Wing. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English. File: lispref.info, Node: Cyclic Window Ordering, Next: Buffers and Windows, Prev: Selecting Windows, Up: Windows Cyclic Ordering of Windows ========================== When you use the command `C-x o' (`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 "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. - Function: next-window &optional WINDOW MINIBUF ALL-FRAMES This function returns the window following WINDOW in the cyclic ordering of windows. This is the window that `C-x o' would select if typed when WINDOW is selected. If WINDOW is the only window visible, then this function returns WINDOW. If omitted, WINDOW defaults to the selected window. The value of the argument MINIBUF determines whether the minibuffer is included in the window order. Normally, when MINIBUF is `nil', the minibuffer is included if it is currently active; this is the behavior of `C-x o'. (The minibuffer window is active while the minibuffer is in use. *Note Minibuffers::.) If MINIBUF is `t', then the cyclic ordering includes the minibuffer window even if it is not active. If MINIBUF is neither `t' nor `nil', then the minibuffer window is not included even if it is active. The argument ALL-FRAMES specifies which frames to consider. Here are the possible values and their meanings: `nil' Consider all the windows in WINDOW's frame, plus the minibuffer used by that frame even if it lies in some other frame. `t' Consider all windows in all existing frames. `visible' Consider all windows in all visible frames. (To get useful results, you must ensure WINDOW is in a visible frame.) 0 Consider all windows in all visible or iconified frames. anything else Consider precisely the windows in WINDOW's frame, and no others. This example assumes there are two windows, both displaying the buffer `windows.texi': (selected-window) => #<window 56 on windows.texi> (next-window (selected-window)) => #<window 52 on windows.texi> (next-window (next-window (selected-window))) => #<window 56 on windows.texi> - Function: previous-window &optional WINDOW MINIBUF ALL-FRAMES This function returns the window preceding WINDOW in the cyclic ordering of windows. The other arguments specify which windows to include in the cycle, as in `next-window'. - Command: other-window COUNT &optional FRAME This function selects the COUNTth following window in the cyclic order. If count is negative, then it selects the -COUNTth preceding window. It returns `nil'. In an interactive call, COUNT is the numeric prefix argument. The argument FRAME controls which set of windows are considered. * If it is `nil' or omitted, then windows on the selected frame are considered. * If it is a frame, then windows on that frame are considered. * If it is `t', then windows on all frames that currently exist (including invisible and iconified frames) are considered. * If it is the symbol `visible', then windows on all visible frames are considered. * If it is the number 0, then windows on all visible and iconified frames are considered. * If it is any other value, then the behavior is undefined. - Function: walk-windows PROC &optional MINIBUF ALL-FRAMES This function cycles through all windows, calling `proc' once for each window with the window as its sole argument. The optional arguments MINIBUF and ALL-FRAMES specify the set of windows to include in the scan. See `next-window', above, for details. File: lispref.info, Node: Buffers and Windows, Next: Displaying Buffers, Prev: Cyclic Window Ordering, Up: Windows Buffers and Windows =================== This section describes low-level functions to examine windows or to display buffers in windows in a precisely controlled fashion. *Note Displaying Buffers::, for 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. - Function: set-window-buffer WINDOW BUFFER-OR-NAME This function makes WINDOW display BUFFER-OR-NAME as its contents. It returns `nil'. (set-window-buffer (selected-window) "foo") => nil - Function: window-buffer &optional WINDOW This function returns the buffer that WINDOW is displaying. If WINDOW is omitted, this function returns the buffer for the selected window. (window-buffer) => #<buffer windows.texi> - Function: get-buffer-window BUFFER-OR-NAME &optional FRAME This function returns a window currently displaying BUFFER-OR-NAME, or `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. *Note Cyclic Window Ordering::. The argument ALL-FRAMES controls which windows to consider. * If it is `nil', consider windows on the selected frame. * If it is `t', consider windows on all frames. * If it is `visible', consider windows on all visible frames. * If it is 0, consider windows on all visible or iconified frames. * If it is a frame, consider windows on that frame. File: lispref.info, Node: Displaying Buffers, Next: Choosing Window, Prev: Buffers and Windows, Up: Windows Displaying Buffers in Windows ============================= 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. *Note Buffers and Windows::, for low-level functions that give you more precise control. Do not use the functions in this section in order to make a buffer current so that a Lisp program can access or modify it; they are too drastic for that purpose, since they change the display of buffers in windows, which is gratuitous and will surprise the user. Instead, use `set-buffer' (*note Current Buffer::.) and `save-excursion' (*note Excursions::.), which designate buffers as current for programmed access without affecting the display of buffers in windows. - Command: switch-to-buffer BUFFER-OR-NAME &optional NORECORD This function makes 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 `set-buffer', which makes BUFFER-OR-NAME the current buffer but does not display it in the selected window. *Note Current Buffer::. If 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 `default-major-mode'. *Note Auto Major Mode::. Normally the specified buffer is put at the front of the buffer list. This affects the operation of `other-buffer'. However, if NORECORD is non-`nil', this is not done. *Note The Buffer List::. The `switch-to-buffer' function is often used interactively, as the binding of `C-x b'. It is also used frequently in programs. It always returns `nil'. - Command: switch-to-buffer-other-window BUFFER-OR-NAME This function makes 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 `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. - Function: pop-to-buffer BUFFER-OR-NAME &optional OTHER-WINDOW ON-FRAME This function makes 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. If the variable `pop-up-windows' is non-`nil', windows may be split to create a new window that is different from the original window. For details, see *Note Choosing Window::. If OTHER-WINDOW is non-`nil', `pop-to-buffer' finds or creates another window even if BUFFER-OR-NAME is already visible in the selected window. Thus BUFFER-OR-NAME could end up displayed in two windows. On the other hand, if BUFFER-OR-NAME is already displayed in the selected window and OTHER-WINDOW is `nil', then the selected window is considered sufficient display for BUFFER-OR-NAME, so that nothing needs to be done. All the variables that affect `display-buffer' affect `pop-to-buffer' as well. *Note Choosing Window::. If 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 `default-major-mode'. *Note Auto Major Mode::. If ON-FRAME is non-`nil', it is the frame to pop to this buffer on. An example use of this function is found at the end of *Note Filter Functions::. - Command: replace-buffer-in-windows BUFFER This function replaces BUFFER with some other buffer in all windows displaying it. The other buffer used is chosen with `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 BUFFER is no longer displayed. This function returns `nil'. File: lispref.info, Node: Choosing Window, Next: Window Point, Prev: Displaying Buffers, Up: Windows Choosing a Window for Display ============================= This section describes the basic facility that chooses a window to display a buffer in--`display-buffer'. All the higher-level functions and commands use this subroutine. Here we describe how to use `display-buffer' and how to customize it. - Command: display-buffer BUFFER-OR-NAME &optional NOT-THIS-WINDOW This command makes BUFFER-OR-NAME appear in some window, like `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. If NOT-THIS-WINDOW is non-`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 BUFFER-OR-NAME is already being displayed in any window, that is good enough, so this function does nothing. `display-buffer' returns the window chosen to display BUFFER-OR-NAME. Precisely how `display-buffer' finds or creates a window depends on the variables described below. A window can be marked as "dedicated" to a particular buffer. Then XEmacs will not automatically change which buffer appears in the window, such as `display-buffer' might normally do. - Function: window-dedicated-p WINDOW This function returns WINDOW's dedicated object, usually `t' or `nil'. - Function: set-window-buffer-dedicated WINDOW BUFFER This function makes WINDOW display BUFFER and be dedicated to that buffer. Then XEmacs will not automatically change which buffer appears in WINDOW. If BUFFER is `nil', this function makes WINDOW not be dedicated (but doesn't change which buffer appears in it currently). - User Option: pop-up-windows This variable controls whether `display-buffer' makes new windows. If it is non-`nil' and there is only one window, then that window is split. If it is `nil', then `display-buffer' does not split the single window, but uses it whole. - User Option: split-height-threshold This variable determines when `display-buffer' may split a window, if there are multiple windows. `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 `pop-up-windows' is non-`nil'. - User Option: pop-up-frames This variable controls whether `display-buffer' makes new frames. If it is non-`nil', `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 `pop-up-windows' and `split-height-threshold' do not matter if `pop-up-frames' is non-`nil'. If `pop-up-frames' is `nil', then `display-buffer' either splits a window or reuses one. *Note Frames::, for more information. - Variable: pop-up-frame-function This variable specifies how to make a new frame if `pop-up-frames' is non-`nil'. Its value should be a function of no arguments. When `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 `pop-up-frame-alist'. - Variable: pop-up-frame-alist This variable holds an alist specifying frame parameters used when `display-buffer' makes a new frame. *Note Frame Parameters::, for more information about frame parameters. - Variable: 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, `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 CAR of the list is the buffer name, and the rest of the list says how to create the frame. There are two possibilities for the rest of the list. It can be an alist, specifying frame parameters, or it can contain a function and arguments to give to it. (The function's first argument is always the buffer to be displayed; the arguments from the list come after that.) - Variable: 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, `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 CAR of the list is the regular expression, and the rest of the list says how to create the frame. See above, under `special-display-buffer-names'. - Variable: 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 `special-display-popup-frame'. - Function: special-display-popup-frame BUFFER This function makes BUFFER visible in a frame of its own. If 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 BUFFER. This function uses an existing window displaying 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 BUFFER was created, then presumably the window was previously made by this function. - User Option: special-display-frame-alist This variable holds frame parameters for `special-display-popup-frame' to use when it creates a frame. - Variable: 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, `display-buffer' handles the buffer by switching to it in the selected window. - Variable: 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, `display-buffer' handles the buffer by switching to it in the selected window. - Variable: display-buffer-function This variable is the most flexible way to customize the behavior of `display-buffer'. If it is non-`nil', it should be a function that `display-buffer' calls to do the work. The function should accept two arguments, the same two arguments that `display-buffer' received. It should choose or create a window, display the specified buffer, and then return the window. This hook takes precedence over all the other options and hooks described above. A window can be marked as "dedicated" to its buffer. Then `display-buffer' does not try to use that window. - Function: window-dedicated-p WINDOW This function returns `t' if WINDOW is marked as dedicated; otherwise `nil'. - Function: set-window-dedicated-p WINDOW FLAG This function marks WINDOW as dedicated if FLAG is non-`nil', and nondedicated otherwise. File: lispref.info, Node: Window Point, Next: Window Start, Prev: Choosing Window, Up: Windows Windows and Point ================= 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. * 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. * Selecting a window sets the value of point in its buffer to the window's value of point. Conversely, deselecting a window sets the window's value of point from that of the buffer. Thus, when you switch between windows that display a given buffer, the point value for the selected window is in effect in the buffer, while the point values for the other windows are stored in those windows. * 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. * *Note Positions::, for more details on buffer positions. 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. - Function: window-point WINDOW This function returns the current position of point in WINDOW. For a nonselected window, this is the value point would have (in that window's buffer) if that window were selected. When 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 `save-excursion' forms. But that value is hard to find. - Function: set-window-point WINDOW POSITION This function positions point in WINDOW at position POSITION in WINDOW's buffer. File: lispref.info, Node: Window Start, Next: Vertical Scrolling, Prev: Window Point, Up: Windows The 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 "display-start" position of the window (or just the "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. - Function: window-start &optional WINDOW This function returns the display-start position of window WINDOW. If WINDOW is `nil', the selected window is used. For example, (window-start) => 7058 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. For a realistic example, see the description of `count-lines' in *Note Text Lines::. - Function: window-end &optional WINDOW This function returns the position of the end of the display in window WINDOW. If WINDOW is `nil', the selected window is used. Simply changing the buffer text or moving point does not update the value that `window-end' returns. The value is updated only when Emacs redisplays and redisplay actually finishes. If the last redisplay of WINDOW was preempted, and did not finish, Emacs does not know the position of the end of display in that window. In that case, this function returns a value that is not correct. In a future version, `window-end' will return `nil' in that case. - Function: set-window-start WINDOW POSITION &optional NOFORCE This function sets the display-start position of WINDOW to POSITION in WINDOW's buffer. It returns 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 `nil' for NOFORCE, it means you want display to start at 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 is 1 and you set the start of the window 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: ;; Here is what `foo' looks like before executing ;; the `set-window-start' expression. ---------- Buffer: foo ---------- -!-This is the contents of buffer foo. 2 3 4 5 6 ---------- Buffer: foo ---------- (set-window-start (selected-window) (1+ (window-start))) => 2 ;; Here is what `foo' looks like after executing ;; the `set-window-start' expression. ---------- Buffer: foo ---------- his is the contents of buffer foo. 2 3 -!-4 5 6 ---------- Buffer: foo ---------- If NOFORCE is non-`nil', and 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 POSITION is not used. - Function: pos-visible-in-window-p &optional POSITION WINDOW This function returns `t' if POSITION is within the range of text currently visible on the screen in WINDOW. It returns `nil' if POSITION is scrolled vertically out of view. The argument POSITION defaults to the current position of point; WINDOW, to the selected window. Here is an example: (or (pos-visible-in-window-p (point) (selected-window)) (recenter 0)) The `pos-visible-in-window-p' function considers only vertical scrolling. If POSITION is out of view only because WINDOW has been scrolled horizontally, `pos-visible-in-window-p' returns `t'. *Note Horizontal Scrolling::. File: lispref.info, Node: Vertical Scrolling, Next: Horizontal Scrolling, Prev: Window Start, Up: Windows Vertical Scrolling ================== Vertical scrolling means moving the text up or down in a window. It works by changing the value of the window's display-start location. It may also change the value of `window-point' to keep it on the screen. In the commands `scroll-up' and `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 `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 scrolling functions (aside from `scroll-other-window') have unpredictable results if the current buffer is different from the buffer that is displayed in the selected window. *Note Current Buffer::. - Command: scroll-up &optional COUNT This function scrolls the text in the selected window upward COUNT lines. If COUNT is negative, scrolling is actually downward. If COUNT is `nil' (or omitted), then the length of scroll is `next-screen-context-lines' lines less than the usable height of the window (not counting its modeline). `scroll-up' returns `nil'. - Command: scroll-down &optional COUNT This function scrolls the text in the selected window downward COUNT lines. If COUNT is negative, scrolling is actually upward. If COUNT is omitted or `nil', then the length of the scroll is `next-screen-context-lines' lines less than the usable height of the window (not counting its mode line). `scroll-down' returns `nil'. - Command: scroll-other-window &optional COUNT This function scrolls the text in another window upward COUNT lines. Negative values of COUNT, or `nil', are handled as in `scroll-up'. You can specify a buffer to scroll with the variable `other-window-scroll-buffer'. When the selected window is the minibuffer, the next window is normally the one at the top left corner. You can specify a different window to scroll with the variable `minibuffer-scroll-window'. This variable has no effect when any other window is selected. *Note Minibuffer Misc::. 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, `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 "Beginning of buffer". - Variable: other-window-scroll-buffer If this variable is non-`nil', it tells `scroll-other-window' which buffer to scroll. - User Option: scroll-step This variable controls how scrolling is done automatically when point moves off the screen. If the value is zero, then redisplay scrolls the text to center point vertically in the window. If the value is a positive integer N, then redisplay brings point back on screen by scrolling N lines in either direction, if possible; otherwise, it centers point. The default value is zero. - User Option: 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, `scroll-up' with an argument of `nil' scrolls so that this many lines at the bottom of the window appear instead at the top. The default value is `2'. - Command: recenter &optional COUNT This function scrolls the selected window to put the text where point is located at a specified vertical position within the window. If COUNT is a nonnegative number, it puts the line containing point COUNT lines down from the top of the window. If COUNT is a negative number, then it counts upward from the bottom of the window, so that -1 stands for the last usable line in the window. If COUNT is a non-`nil' list, then it stands for the line in the middle of the window. If COUNT is `nil', `recenter' puts the line containing point in the middle of the window, then clears and redisplays the entire selected frame. When `recenter' is called interactively, COUNT is the raw prefix argument. Thus, typing `C-u' as the prefix sets the COUNT to a non-`nil' list, while typing `C-u 4' sets COUNT to 4, which positions the current line four lines from the top. With an argument of zero, `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, (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) File: lispref.info, Node: Horizontal Scrolling, Next: Size of Window, Prev: Vertical Scrolling, Up: Windows Horizontal Scrolling ==================== Because we read English first from top to bottom and second from left to right, horizontal scrolling is not like vertical scrolling. Vertical scrolling involves selection of a contiguous portion of text to display. Horizontal scrolling causes part of each line to go off screen. The amount of horizontal scrolling is therefore specified as a number of columns rather than as a position in the buffer. It has nothing to do with the display-start position returned by `window-start'. Usually, no horizontal scrolling is in effect; then the leftmost column is at the left edge of the window. In this state, scrolling to the right is meaningless, since there is no data to the left of the screen to be revealed by it; so this is not allowed. Scrolling to the left is allowed; it scrolls the first columns of text off the edge of the window and can reveal additional columns on the right that were truncated before. Once a window has a nonzero amount of leftward horizontal scrolling, you can scroll it back to the right, but only so far as to reduce the net horizontal scroll to zero. There is no limit to how far left you can scroll, but eventually all the text will disappear off the left edge. - Command: scroll-left COUNT This function scrolls the selected window COUNT columns to the left (or to the right if COUNT is negative). The return value is the total amount of leftward horizontal scrolling in effect after the change--just like the value returned by `window-hscroll' (below). - Command: scroll-right COUNT This function scrolls the selected window COUNT columns to the right (or to the left if COUNT is negative). The return value is the total amount of leftward horizontal scrolling in effect after the change--just like the value returned by `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. - Function: window-hscroll &optional WINDOW This function returns the total leftward horizontal scrolling of WINDOW--the number of columns by which the text in WINDOW is scrolled left past the left margin. The value is never negative. It is zero when no horizontal scrolling has been done in WINDOW (which is usually the case). If WINDOW is `nil', the selected window is used. (window-hscroll) => 0 (scroll-left 5) => 5 (window-hscroll) => 5 - Function: set-window-hscroll WINDOW COLUMNS This function sets the number of columns from the left margin that WINDOW is scrolled to the value of COLUMNS. The argument COLUMNS should be zero or positive; if not, it is taken as zero. The value returned is COLUMNS. (set-window-hscroll (selected-window) 10) => 10 Here is how you can determine whether a given position POSITION is off the screen due to horizontal scrolling: (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))))) File: lispref.info, Node: Size of Window, Next: Position of Window, Prev: Horizontal Scrolling, Up: Windows The Size of a Window ==================== An Emacs window is rectangular, and its size information consists of the height (in lines or pixels) and the width (in character positions or pixels). The modeline is included in the height. The pixel width and height values include scrollbars and margins, while the line/character-position values do not. Note that the height in lines, and the width in characters, are determined by dividing the corresponding pixel value by the height or width of the default font in that window (if this is a variable-width font, the average width is used). The resulting values may or may not represent the actual number of lines in the window, or the actual number of character positions in any particular line, esp. if there are pixmaps or various different fonts in the window. The following functions return size information about a window: - Function: window-height &optional WINDOW This function returns the number of lines in WINDOW, including its modeline but not including the horizontal scrollbar, if any (this is different from `window-pixel-height'). If WINDOW is `nil', the function uses the selected window. (window-height) => 40 (split-window-vertically) => #<window on "windows.texi" 0x679b> (window-height) => 20 - Function: window-width &optional WINDOW This function returns the number of columns in WINDOW, not including any left margin, right margin, or vertical scrollbar (this is different from `window-pixel-width'). If WINDOW is `nil', the function uses the selected window. (window-width) => 80 (window-height) => 40 (split-window-horizontally) => #<window on "windows.texi" 0x7538> (window-width) => 39 Note that after splitting the window into two side-by-side windows, the width of each window is less the half the width of the original window because a vertical scrollbar appeared between the windows, occupying two columns worth of space. Also, the height shrunk by one because horizontal scrollbars appeared that weren't there before. (Horizontal scrollbars appear only when lines are truncated, not when they wrap. This is usually the case for horizontally split windows but not for full-frame windows. You can change this using the variables `truncate-lines' and `truncate-partial-width-windows'.) - Function: window-pixel-height &optional WINDOW This function returns the height of WINDOW in pixels, including its modeline and horizontal scrollbar, if any. If WINDOW is `nil', the function uses the selected window. (window-pixel-height) => 600 (split-window-vertically) => #<window on "windows.texi" 0x68a6> (window-pixel-height) => 300 - Function: window-pixel-width &optional WINDOW This function returns the width of WINDOW in pixels, including any left margin, right margin, or vertical scrollbar that may be displayed alongside it. If WINDOW is `nil', the function uses the selected window. (window-pixel-width) => 735 (window-pixel-height) => 600 (split-window-horizontally) => #<window on "windows.texi" 0x7538> (window-pixel-width) => 367 (window-pixel-height) => 600 File: lispref.info, Node: Position of Window, Next: Resizing Windows, Prev: Size of Window, Up: Windows The Position of a Window ======================== XEmacs provides functions to determine the absolute location of windows within a frame, and the relative location of a window in comparison to other windows in the same frame. - Function: window-pixel-edges &optional WINDOW This function returns a list of the pixel edge coordinates of WINDOW. If WINDOW is `nil', the selected window is used. The order of the list is `(LEFT TOP RIGHT BOTTOM)', all elements relative to 0, 0 at the top left corner of the frame. The element RIGHT of the value is one more than the rightmost pixel used by WINDOW (including any left margin, right margin, or vertical scrollbar displayed alongside it), and BOTTOM is one more than the bottommost pixel used by WINDOW (including any modeline or horizontal scrollbar displayed above or below it). The frame area does not include any frame menubars or toolbars that may be displayed; thus, for example, if there is only one window on the frame, the values for LEFT and TOP will always be 0. If WINDOW is at the upper left corner of its frame, RIGHT and BOTTOM are the same as the values returned by `(window-pixel-width)' and `(window-pixel-height)' respectively, and TOP and BOTTOM are zero. There is no longer a function `window-edges' because it does not make sense in a world with variable-width and variable-height lines, as are allowed in XEmacs. - Function: window-highest-p WINDOW This function returns non-`nil' if WINDOW is along the top of its frame. - Function: window-lowest-p WINDOW This function returns non-`nil' if WINDOW is along the bottom of its frame. File: lispref.info, Node: Resizing Windows, Next: Window Configurations, Prev: Position of Window, Up: Windows Changing the Size of a Window ============================= 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. XEmacs does not permit overlapping windows or gaps between windows, so resizing one window affects other windows. - Command: enlarge-window SIZE &optional HORIZONTAL This function makes the selected window 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 `window-min-height' lines, that window disappears. If HORIZONTAL is non-`nil', this function makes WINDOW wider by SIZE columns, stealing columns instead of lines. If a window from which columns are stolen shrinks below `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 SIZE is negative, this function shrinks the window by -SIZE lines or columns. If that makes the window smaller than the minimum size (`window-min-height' and `window-min-width'), `enlarge-window' deletes the window. `enlarge-window' returns `nil'. - Command: enlarge-window-horizontally COLUMNS This function makes the selected window COLUMNS wider. It could be defined as follows: (defun enlarge-window-horizontally (columns) (enlarge-window columns t)) - Command: shrink-window SIZE &optional HORIZONTAL This function is like `enlarge-window' but negates the argument SIZE, making the selected window smaller by giving lines (or columns) to the other windows. If the window shrinks below `window-min-height' or `window-min-width', then it disappears. If SIZE is negative, the window is enlarged by -SIZE lines or columns. - Command: shrink-window-horizontally COLUMNS This function makes the selected window COLUMNS narrower. It could be defined as follows: (defun shrink-window-horizontally (columns) (shrink-window columns t)) The following two variables constrain the window-size-changing functions to a minimum height and width. - User Option: 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 `window-min-height' automatically deletes it, and no window may be created shorter than this. The absolute minimum height is two (allowing one line for the mode line, and one line for the buffer display). Actions that change window sizes reset this variable to two if it is less than two. The default value is 4. - User Option: window-min-width The value of this variable determines how narrow a window may become before it automatically deleted. Making a window smaller than `window-min-width' automatically deletes it, and no window may be created narrower than this. The absolute minimum width is one; any value below that is ignored. The default value is 10. - Variable: window-size-change-functions This variable holds a list of functions to be called if the size of any window changes for any reason. The functions are called just once per redisplay, and just once for each frame on which size changes have occurred. Each function receives the frame as its sole argument. There is no direct way to find out which windows changed size, or precisely how; however, if your size-change function keeps track, after each change, of the windows that interest you, you can figure out what has changed by comparing the old size data with the new. Creating or deleting windows counts as a size change, and therefore causes these functions to be called. Changing the frame size also counts, because it changes the sizes of the existing windows. It is not a good idea to use `save-window-excursion' in these functions, because that always counts as a size change, and it would cause these functions to be called over and over. In most cases, `save-selected-window' is what you need here. File: lispref.info, Node: Window Configurations, Prev: Resizing Windows, Up: Windows Window Configurations ===================== A "window configuration" records the entire layout of a frame--all windows, their sizes, which buffers they contain, what part of each buffer is displayed, and the values of point and the mark. You can bring back an entire previous layout by restoring a window configuration previously saved. - Function: current-window-configuration This function returns a new object representing XEmacs's current window configuration, namely the number of windows, their sizes and current buffers, which window is the selected window, and for each window the displayed buffer, the display-start position, and the positions of point and the mark. An exception is made for point in the current buffer, whose value is not saved. - Function: set-window-configuration CONFIGURATION This function restores the configuration of XEmacs's windows and buffers to the state specified by CONFIGURATION. The argument CONFIGURATION must be a value that was previously returned by `current-window-configuration'. This function always counts as a window size change and triggers execution of the `window-size-change-functions'. (It doesn't know how to tell whether the new configuration actually differs from the old one.) Here is a way of using this function to get the same effect as `save-window-excursion': (let ((config (current-window-configuration))) (unwind-protect (progn (split-window-vertically nil) ...) (set-window-configuration config))) - Special Form: save-window-excursion FORMS... This special form records the window configuration, executes FORMS in sequence, then restores the earlier window configuration. The window configuration includes the value of point and the portion of the buffer that is visible. It also includes the choice of selected window. However, it does not include the value of point in the current buffer; use `save-excursion' if you wish to preserve that. Don't use this construct when `save-selected-window' is all you need. Exit from `save-window-excursion' always triggers execution of the `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 FORMS.) The return value is the value of the final form in FORMS. For example: (split-window) => #<window 25 on control.texi> (setq w (selected-window)) => #<window 19 on control.texi> (save-window-excursion (delete-other-windows w) (switch-to-buffer "foo") 'do-something) => do-something ;; The frame is now split again. - Function: window-configuration-p OBJECT This function returns `t' if OBJECT is a window configuration. Primitives to look inside of window configurations would make sense, but none are implemented. It is not clear they are useful enough to be worth implementing. File: lispref.info, Node: Frames, Next: Devices, Prev: Windows, Up: Top Frames ****** A FRAME is a rectangle on the screen that contains one or more Emacs windows. A frame initially contains a single main window (plus perhaps a minibuffer window), which you can subdivide vertically or horizontally into smaller windows. When XEmacs runs on a text-only terminal, it starts with one "TTY frame". If you create additional ones, XEmacs displays one and only one at any given time--on the terminal screen, of course. When XEmacs communicates directly with an X server, it does not have a TTY frame; instead, it starts with a single "X window frame". It can display multiple X window frames at the same time, each in its own X window. - Function: framep OBJECT This predicate returns `t' if OBJECT is a frame, and `nil' otherwise. * Menu: * Creating Frames:: Creating additional frames. * Frame Parameters:: Controlling frame size, position, font, etc. * Frame Titles:: Automatic updating of frame titles. * Deleting Frames:: Frames last until explicitly deleted. * Finding All Frames:: How to examine all existing frames. * Frames and Windows:: A frame contains windows; display of text always works through windows. * Minibuffers and Frames:: How a frame finds the minibuffer to use. * Input Focus:: Specifying the selected frame. * Visibility of Frames:: Frames may be visible or invisible, or icons. * Raising and Lowering:: Raising a frame makes it hide other X windows; lowering it makes the others hide them. * Frame Hooks:: Hooks for customizing frame behavior. *Note Display::, for related information.