This is Info file elisp, produced by Makeinfo-1.63 from the input file elisp.texi. This version is the edition 2.4b of the GNU Emacs Lisp Reference Manual. It corresponds to Emacs Version 19.34. Published by the Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996 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. 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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. 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 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-frames' is non-`nil', `pop-to-buffer' looks for a window in any visible frame already displaying the buffer; if there is one, it returns that window and makes it be selected within its frame. If there is none, it creates a new frame and displays the buffer in it. If `pop-up-frames' is `nil', then `pop-to-buffer' operates entirely within the selected frame. (If the selected frame has just a minibuffer, `pop-to-buffer' operates within the most recently selected frame that was not just a minibuffer.) 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::. - 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: 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. - 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. - User Option: 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. - User Option: 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: elisp, 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: 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 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. Redisplay updates the window-start position (if you have not specified it explicitly since the previous redisplay) so that point appears on the screen. Nothing except redisplay automatically changes the window-start position; if you move point, do not expect the window-start position to change in response until after the next redisplay. For a realistic example of using `window-start', 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: elisp, Node: Vertical Scrolling, Next: Scrolling Hooks, 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 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 (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: elisp, Node: Scrolling Hooks, Next: Horizontal Scrolling, Prev: Vertical Scrolling, Up: Windows Hooks for Vertical Scrolling ============================ This section describes how a Lisp program can take action whenever a window displays a different part of its buffer or a different buffer. There are three actions that can change this: scrolling the window, switching buffers in the window, and changing the size of the window. The first two actions run `window-scroll-functions'; the last runs `window-size-change-functions'. The paradigmatic use of these hooks is Lazy Lock mode; see *Note Lazy Lock: (emacs)Support Modes. - Variable: window-scroll-functions This variable holds a list of functions that Emacs should call before redisplaying a window with scrolling. It is not a normal hook, because each function is called with two arguments: the window, and its new display-start position. Displaying a different buffer in the window also runs these functions. These functions cannot expect `window-end' (*note Window Start::.) to return a meaningful value, because that value is updated only by redisplaying the buffer. So if one of these functions needs to know the last character that will fit in the window with its current display-start position, it has to find that character using `vertical-motion' (*note Screen Lines::.). - 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 on that frame have changed size, or precisely how. However, if a size-change function records, at each call, the existing windows and their sizes, it can also compare the present sizes and the previous sizes. Creating or deleting windows counts as a size change, and therefore causes these functions to be called. Changing the frame size also counts, because it changes the sizes of the existing windows. It is not a good idea to use `save-window-excursion' (*note Window Configurations::.) in these functions, because that always counts as a size change, and it would cause these functions to be called over and over. In most cases, `save-selected-window' (*note Selecting Windows::.) is what you need here.  File: elisp, Node: Horizontal Scrolling, Next: Size of Window, Prev: Scrolling Hooks, 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: 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. But the width does not count the scroll bar or the column of `|' characters that separates side-by-side windows. 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-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. The width does not include the window's scroll bar or the column of `|' characters that separates side-by-side windows. 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. When you have side-by-side windows, the right edge value for a window with a neighbor on the right includes the width of the separator between the window and that neighbor. This separator may be a column of `|' characters or it may be a scroll bar. Since the width of the window does not include this separator, the width does not equal the difference between the right and left edges in this case. Here is the result obtained on a typical 24-line terminal with just one window: (window-edges (selected-window)) => (0 0 80 23) The bottom edge is at line 23 because the last line is the echo area. If WINDOW is at the upper left corner of its frame, then BOTTOM is the same as the value of `(window-height)', RIGHT is almost the same as the value of `(window-width)'(1), and TOP and LEFT 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 separator in its last column or columns. The separator counts as one or two columns in the width of the window. A window never includes a separator on its left, since that belongs to the window to the left. In the following example, let's suppose that the frame is 7 columns wide. Then the edges of the left window are `0 0 4 3' and the edges of the right window are `4 0 7 3'. ___ ___ | | | | | | xxxxxxxxx 0 34 7 ---------- Footnotes ---------- (1) They are not exactly equal because RIGHT includes the vertical separator line or scroll bar, while `(window-width)' does not.  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 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.  File: elisp, Node: Coordinates and Windows, Next: Window Configurations, Prev: Resizing Windows, Up: Windows Coordinates and Windows ======================= This section describes how to relate screen coordinates to 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 frame. If they are out of range, `window-at' returns `nil'. 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. This value occurs only if the window doesn't have a scroll bar; positions in a scroll bar are considered outside the window. `nil' The coordinates are not in any part of WINDOW. The function `coordinates-in-window-p' does not require a frame as argument because it always uses the frame that 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'. 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) => # (setq w (selected-window)) => # (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 starts with one "terminal frame". If you create additional ones, Emacs displays one and only one at any given time--on the terminal screen, of course. When Emacs communicates directly with an X server, it does not have a terminal 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. * Multiple Displays:: Creating frames on other X displays. * 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 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. * Dialog Boxes:: Displaying a box to ask yes or no. * Pointer Shapes:: Specifying the shape of the mouse pointer. * X Selections:: Transferring text to and from other X clients. * Color Names:: Getting the definitions of color names. * Resources:: Getting resource values from the server. * Server Data:: Getting info about the X server. *Note Display::, for related information.  File: elisp, Node: Creating Frames, Next: Multiple Displays, Up: Frames Creating Frames =============== To create a new frame, call the function `make-frame'. - Function: make-frame &optional ALIST This function creates a new frame. If you are using X, it makes an X window frame; otherwise, it makes a terminal frame. 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 even there 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 frames. *Note X Frame Parameters::, for documentation of individual parameters you can specify. - Variable: before-make-frame-hook A normal hook run by `make-frame' before it actually creates the frame. - Variable: after-make-frame-hook A normal hook run by `make-frame' after it creates the frame.  File: elisp, Node: Multiple Displays, Next: Frame Parameters, Prev: Creating Frames, Up: Frames Multiple Displays ================= A single Emacs can talk to more than one X Windows display. Initially, Emacs uses just one display--the one chosen with the `DISPLAY' environment variable or with the `--display' option (*note Initial Options: (emacs)Initial Options.). To connect to another display, use the command `make-frame-on-display' or specify the `display' frame parameter when you create the frame. Emacs treats each X server as a separate terminal, giving each one its own selected frame and its own minibuffer windows. A few Lisp variables have values local to the current terminal (that is, the terminal corresponding to the currently selected frame): these are `default-minibuffer-frame', `defining-kbd-macro', `last-kbd-macro', and `system-key-alist'. These variables are always terminal-local and can never be buffer-local. A single X server can handle more than one screen. A display name `HOST.SERVER.SCREEN' has three parts; the last part specifies the screen number for a given server. When you use two screens belonging to one server, Emacs knows by the similarity in their names that they share a single keyboard, and it treats them as a single terminal. - Command: make-frame-on-display DISPLAY &optional PARAMETERS This creates a new frame on display DISPLAY, taking the other frame parameters from PARAMETERS. Aside from the DISPLAY argument, it is like `make-frame' (*note Creating Frames::.). - Function: x-display-list This returns a list that indicates which X displays Emacs has a connection to. The elements of the list are strings, and each one is a display name. - Function: x-open-connection DISPLAY &optional XRM-STRING This function opens a connection to the X display DISPLAY. It does not create a frame on that display, but it permits you to check that communication can be established with that display. The optional argument RESOURCE-STRING, if not `nil', is a string of resource names and values, in the same format used in the `.Xresources' file. The values you specify override the resource values recorded in the X server itself; they apply to all Emacs frames created on this display. Here's an example of what this string might look like: "*BorderWidth: 3\n*InternalBorder: 2\n" *Note Resources::. - Function: x-close-connection DISPLAY This function closes the connection to display DISPLAY. Before you can do this, you must first delete all the frames that were open on that display (*note Deleting Frames::.).