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GNU Info File | 1994-08-02 | 50.2 KB | 1,219 lines

This is Info file elisp, produced by Makeinfo-1.55 from the input file elisp.texi. This version is newer than the second printed edition of the GNU Emacs Lisp Reference Manual. It corresponds to Emacs Version 19.19. Published by the Free Software Foundation 675 Massachusetts Avenue Cambridge, MA 02139 USA Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc. 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 Emacs 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 Emacs General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English. File: elisp, Node: Deleting Windows, Next: Selecting Windows, Prev: Splitting Windows, Up: Windows Deleting Windows ================ A window remains visible on its frame unless you "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 (*note 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. (In Emacs version 18, the space was divided evenly among all the siblings.) - Function: window-live-p WINDOW This function returns `nil' if WINDOW is deleted, and `t' otherwise. *Warning:* erroneous information or fatal errors may result from using a deleted window as if it were live. - Command: delete-window &optional WINDOW This function removes WINDOW from the display. If WINDOW is omitted, then the selected window is deleted. An error is signaled if there is only one window when `delete-window' is called. This function returns `nil'. When `delete-window' is called interactively, WINDOW defaults to the selected window. - Command: delete-other-windows &optional WINDOW This function makes WINDOW the only window on its frame, by deleting all the other windows. If WINDOW is omitted or `nil', then the selected window is used by default. The result is `nil'. - Command: delete-windows-on BUFFER &optional FRAME This function deletes all windows showing BUFFER. If there are no windows showing BUFFER, then this function does nothing. If all windows in some frame are showing BUFFER (including the case where there is only one window), then the frame reverts to having a single window showing the buffer chosen by `other-buffer'. *Note The Buffer List::. If there are several windows showing different buffers, then those showing BUFFER are removed, and the others are expanded to fill the void. If FRAME is a frame, then `delete-windows-on' considers just the windows on FRAME. If FRAME is `nil', all windows on all frames are considered. If FRAME is `t', that stands for the selected frame. This function always returns `nil'. File: elisp, Node: Selecting Windows, Next: Cyclic Window Ordering, Prev: Deleting Windows, Up: Windows Selecting Windows ================= When a window is selected, the buffer in the window becomes the current buffer, and the cursor will appear in it. - Function: selected-window This function returns the selected window. This is the window in which the cursor appears and to which many commands apply. - Function: select-window WINDOW This function makes WINDOW the selected window. The cursor then appears in WINDOW (on redisplay). The buffer being displayed in WINDOW is immediately designated the current buffer. The return value is WINDOW. (setq w (next-window)) (select-window w) => #<window 65 on windows.texi> The following functions choose one of the windows on the screen, offering various criteria for the choice. - Function: get-lru-window &optional ALL-FRAMES This function returns the window least recently "used" (that is, selected). 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. The minibuffer window is not considered a candidate. The argument ALL-FRAMES controls which set of windows are considered. If it is non-`nil', then all windows on all frames are considered. Otherwise, only windows in the selected frame are considered. - Function: get-largest-window &optional ALL-FRAMES 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. The minibuffer window is not considered a candidate. If there are two windows of the same size, then the function returns the window which is first in the cyclic ordering of windows (see following section), starting from the selected window. The argument ALL-FRAMES controls which set of windows are considered. If it is non-`nil', then all windows on all frames are considered. Otherwise, only windows in the selected frame are considered. File: elisp, Node: Cyclic Window Ordering, Next: Buffers and Windows, Prev: Selecting Windows, Up: Windows Cycling 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, 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 WINDOW &optional MINIBUF ALL-FRAMES This function returns the window following WINDOW in the cyclic ordering of windows. This is the window which `C-x o' would select if done when WINDOW is selected. If WINDOW is the only window visible, then this function returns 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'. 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 minibuffer window is active while the minibuffer is in use. *Note Minibuffers::.) When there are multiple frames, this functions normally cycles through all the windows in the selected frame, plus the minibuffer used by the selected frame even if it lies in some other frame. If ALL-FRAMES is `t', then it cycles through all the windows in all the frames that currently exist. If ALL-FRAMES is neither `t' nor `nil', then it cycles through precisely the windows in the selected frame, excluding the minibuffer in use if it lies in some other frame. This example shows two windows, which both happen to be displaying the same buffer: (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 WINDOW &optional MINIBUF ALL-FRAMES This function returns the window preceding WINDOW in the cyclic ordering of windows. The other arguments affect which windows are included in the cycle, as in `next-window'. - Command: other-window COUNT This function selects the COUNTth next 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. - Function: walk-windows PROC &optional MINIBUF ALL-FRAMES This function cycles through all visible windows, calling `proc' once for each window with the window as its sole argument. The optional argument MINIBUF says whether to include minibuffer windows. A value of `t' means count the minibuffer window even if not active. A value of `nil' means count it only if active. Any other value means not to count the minibuffer even if it is active. If the optional third argument ALL-FRAMES is `t', that means include all windows in all frames. If ALL-FRAMES is `nil', it means to cycle within the selected frame, but include the minibuffer window (if MINIBUF says so) that that frame uses, even if it is on another frame. If ALL-FRAMES is neither `nil' nor `t', `walk-windows' sticks strictly to the selected frame. File: elisp, 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 show 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, then this function returns the buffer for the selected window. (window-buffer) => #<buffer windows.texi> - Function: get-buffer-window BUFFER-OR-NAME &optional ALL-FRAMES 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 set of windows are considered. * If it is `nil', 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 visible frames are considered. * If it is some other non-`nil' value, then all windows on all frames are considered. - 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: elisp, 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. 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 previously selected window is absolutely never used to display the buffer. 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 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. If the variable `pop-up-frames' is non-`nil', `pop-to-buffer' creates a new frame to display the buffer in. Otherwise, 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. If BUFFER-OR-NAME is a string that does not name an existing buffer, a buffer by that name is created. An example use of this function is found at the end of *Note Filter Functions::. File: elisp, Node: Choosing Window, Next: Window Point, Prev: Displaying Buffers, Up: Windows Choosing a Window ================= This section describes the basic facility which 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. - Function: display-buffer BUFFER-OR-NAME &optional NOT-THIS-WINDOW This function 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 that the specified buffer should be displayed 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 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 FLAGS is non-`nil', and nondedicated otherwise. - 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 rather replaces its buffer. - User Option: split-height-threshold This variable determines when `display-buffer' may split a window, if there are multiple windows. `display-buffer' splits the largest window if it has at least this many lines. If there is only one window, it is split regardless of this value, provided `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' makes a new frame. If it is `nil', then `display-buffer' either splits a window or reuses one. If this is non-`nil', the variables `pop-up-windows' and `split-height-threshold' do not matter. *Note Frames::, for more information. - Variable: pop-up-frame-function This variable specifies how to make a new frame if `pop-up-frame' 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 which 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: 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. File: elisp, Node: Window Point, Next: Window Start, Prev: Choosing Window, Up: Windows Window 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 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: elisp, 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 which 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. (window-start) => 7058 For a more complicated example of use, 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. - Function: set-window-start WINDOW POSITION &optional NOFORCE This function sets the display-start position of WINDOW to POSITION in WINDOW's buffer. 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 with `nil' for NOFORCE, it means you want display to start at POSITION even if that would put the location of point off the screen. What the display routines do in this case is move point instead, to the left margin on the middle line in the window. For example, if point is 1 and you attempt to set the start of the window to 2, then the position of point would be "above" the top of the window. The display routines would 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))) ;; 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 ---------- => 2 However, when NOFORCE is non-`nil', `set-window-start' does nothing if the specified start position would make point invisible. This function returns POSITION, regardless of whether the NOFORCE option caused that position to be overruled. - 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. It returns `t' if POSITION is out of view only because WINDOW has been scrolled horizontally. *Note Horizontal Scrolling::. File: elisp, 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') will 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 mode line). `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. `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'. The window that is scrolled is normally the one following the selected window in the cyclic ordering of windows--the window that `next-window' would return. *Note Cyclic Window Ordering::. If the selected window is the minibuffer, the next window is normally the one at the top left corner. However, you can specify the window to scroll by binding 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 the text is scrolled so that point is centered vertically in the window. If the value is a positive integer N, then if it is possible to bring point back on screen by scrolling N lines in either direction, that is done; otherwise, point is centered vertically as usual. 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, when `scroll-up' executes, this many lines that were visible at the bottom of the window move to the top of the window. 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', then it puts the line containing point in the middle of the window, then clears and redisplays the entire selected frame. When `recenter' is called interactively, Emacs sets COUNT to 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. Typing `C-u 0 C-l' positions the current line at the top of the window. This action is so handy that some people bind the command to a function key. 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 "\C-cl" 'line-to-top-of-window) File: elisp, 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 it is not allowed. Scrolling to the left is allowed; it causes the first columns of text to go 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'. - 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'. 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 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: (save-excursion (goto-char POSITION) (and (>= (- (current-column) (window-hscroll WINDOW)) 0) (< (- (current-column) (window-hscroll WINDOW)) (window-width WINDOW)))) File: elisp, Node: Size of Window, Next: Resizing Windows, Prev: Horizontal Scrolling, Up: Windows The Size of a 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. For a window that does not abut the right hand edge of the screen, the column of `|' characters that separates it from the window on the right is included in the width. The following three functions return size information about a window: - Function: window-height &optional WINDOW This function returns the number of lines in WINDOW, including its mode line. If WINDOW fills its entire frame, this is one less than the value of `frame-height' on that frame (since the last line is always reserved for the minibuffer). If WINDOW is `nil', the function uses the selected window. (window-height) => 23 (split-window-vertically) => #<window 4 on windows.texi> (window-height) => 11 - Function: window-width &optional WINDOW This function returns the number of columns in WINDOW. If WINDOW fills its entire frame, this is the same as the value of `frame-width' on that frame. If WINDOW is `nil', the function uses the selected window. (window-width) => 80 - Function: window-edges &optional WINDOW This function returns a list of the 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 column used by WINDOW, and BOTTOM is one more than the bottommost row used by WINDOW and its mode-line. Here is the result obtained on a typical 24-line terminal with just one window: (window-edges (selected-window)) => (0 0 80 23) If WINDOW is at the upper left corner of its frame, RIGHT and BOTTOM are the same as the values returned by `(window-width)' and `(window-height)' respectively, and TOP and BOTTOM are zero. For example, the edges of the following window are `0 0 5 8'. Assuming that the frame has more than 8 columns, the last column of the window (column 7) holds a border rather than text. The last row (row 4) holds the mode line, shown here with `xxxxxxxxx'. 0 _______ 0 | | | | | | | | xxxxxxxxx 4 7 When there are side-by-side windows, any window not at the right edge of its frame has a border in its last column. This border counts as one column in the width of the window. A window never includes a border on its left, since the border there belongs to the window to the left. In the following example, let's imagine that the frame is 7 columns wide. Then the edges of the left window are `0 0 4 3' and the edges of the right window are `4 0 7 3'. ___ ___ | | | | | | xxxxxxxxx 0 34 7 File: elisp, Node: Resizing Windows, Next: Coordinates and Windows, Prev: Size 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. Emacs 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 bigger, 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, then that window disappears. If HORIZONTAL is non-`nil', then 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, then that window disappears. If the window's frame is smaller than SIZE lines (or columns), 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. If it becomes shorter than `window-min-height', it disappears. `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. - 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 disappears. A window disappears when it becomes smaller than `window-min-height', and no window may be created that is smaller. The absolute minimum height is two (allowing one line for the mode line, and one line for the buffer display). Actions which 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 disappears. A window disappears when it becomes narrower than `window-min-width', and no window may be created that is narrower. The absolute minimum width is one; any value below that is ignored. The default value is 10. File: elisp, Node: Coordinates and Windows, Next: Window Configurations, Prev: Resizing Windows, Up: Windows Coordinates and Windows ======================= This section describes how to compare screen coordinates with windows. - Function: window-at X Y &optional FRAME This function returns the window containing the specified cursor position in the frame FRAME. The coordinates X and Y are measured in characters and count from the top left corner of the screen or frame. If you omit FRAME, the selected frame is used. - Function: coordinates-in-window-p COORDINATES WINDOW This function checks whether a particular frame position falls within the window WINDOW. The argument COORDINATES is a cons cell of this form: (X . Y) The coordinates X and Y are measured in characters, and count from the top left corner of the screen or frame. The value of `coordinates-in-window-p' is non-`nil' if the coordinates are inside WINDOW. The value also indicates what part of the window the position is in, as follows: `(RELX . RELY)' The coordinates are inside WINDOW. The numbers RELX and RELY are the equivalent window-relative coordinates for the specified position, counting from 0 at the top left corner of the window. `mode-line' The coordinates are in the mode line of WINDOW. `vertical-split' The coordinates are in the vertical line between WINDOW and its neighbor to the right. `nil' The coordinates are not in any sense within WINDOW. The function `coordinates-in-window-p' does not require a frame as argument because it always uses the frame that window WINDOW is on. File: elisp, Node: Window Configurations, Prev: Coordinates and 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. If you want to record all frames instead of just one, use a frame configuration instead of a window configuration. *Note Frame Configurations::. - Function: current-window-configuration This function returns a new object representing Emacs's current window configuration, namely the number of windows, their sizes and current buffers, which window is the selected window, and for each window the displayed buffer, the display-start position, and the positions of point and the mark. An exception is made for point in the current buffer, whose value is not saved. - Function: set-window-configuration CONFIGURATION This function restores the configuration of Emacs'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'. 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 executes FORMS in sequence, preserving window sizes and contents, including the value of point and the portion of the buffer which is visible. It also preserves the choice of selected window. However, it does not restore the value of point in the current buffer; use `save-excursion' for that. 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 screen 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: elisp, Node: Frames, Next: Positions, 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 Emacs runs on a text-only terminal, it has just one frame, a "terminal frame". There is no way to create another terminal frame after startup. If Emacs has an X display, it does not make a terminal frame; instead, it initially creates a single "X window frame". You can create more; see *Note Creating Frames::. - Function: framep OBJECT This predicate returns `t' if OBJECT is a frame, and `nil' otherwise. * Menu: * Creating Frames:: Creating additional X Window frames. * Frame Parameters:: Controlling frame size, position, font, etc. * 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:: What is this?? * 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 Configurations:: Saving the state of all frames. * Mouse Tracking:: Getting events that say when the mouse moves. * Mouse Position:: Asking where the mouse is, or moving it. * Pop-Up Menus:: Displaying a menu for the user to select from. * X Selections:: Transferring text to and from other X clients. * X Server:: *Note Display::, for related information. File: elisp, Node: Creating Frames, Next: Frame Parameters, Up: Frames Creating Frames =============== To create a new frame, call the function `make-frame'. - Function: make-frame ALIST This function creates a new frame, if the display mechanism permits creation of frames. (An X server does; an ordinary terminal does not.) The argument is an alist specifying frame parameters. Any parameters not mentioned in ALIST default according to the value of the variable `default-frame-alist'; parameters not specified there either default from the standard X defaults file and X resources. The set of possible parameters depends in principle on what kind of window system Emacs uses to display its the frames. *Note X Frame Parameters::, for documentation of individual parameters you can specify when creating an X window frame. - Variable: default-frame-alist An alist specifying default values of frame parameters. Each element has the form: (PARAMETER . VALUE) If you use options that specify window appearance when you invoke Emacs, they take effect by adding elements to `default-frame-alist'. File: elisp, Node: Frame Parameters, Next: Deleting Frames, Prev: Creating Frames, Up: Frames Frame Parameters ================ A frame has many parameters that control how it displays. * Menu: * Parameter Access:: How to change a frame's parameters. * Initial Parameters:: Specifying frame parameters when you make a frame. * X Frame Parameters:: Individual parameters documented. * Size And Position:: Changing the size and position of a frame. File: elisp, Node: Parameter Access, Next: Initial Parameters, Up: Frame Parameters Access to Frame Parameters -------------------------- These functions let you read and change the parameter values of a frame. - Function: frame-parameters FRAME The function `frame-parameters' returns an alist of all the parameters of FRAME. - Function: modify-frame-parameters FRAME ALIST This function alters the parameters of frame FRAME based on the elements of ALIST. Each element of ALIST has the form `(PARM . VALUE)', where PARM is a symbol naming a parameter. If you don't mention a parameter in ALIST, its value doesn't change.