This is ../info/lispref.info, produced by makeinfo version 4.0b from lispref/lispref.texi. INFO-DIR-SECTION XEmacs Editor START-INFO-DIR-ENTRY * Lispref: (lispref). XEmacs Lisp Reference Manual. END-INFO-DIR-ENTRY Edition History: GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp Reference Manual (for 19.15 and 20.1, 20.2, 20.3) v3.2, April, May, November 1997 XEmacs Lisp Reference Manual (for 21.0) v3.3, April 1998 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995, 1996 Ben Wing. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English.  File: lispref.info, Node: Creating Buffers, Next: Killing Buffers, Prev: The Buffer List, Up: Buffers Creating Buffers ================ This section describes the two primitives for creating buffers. `get-buffer-create' creates a buffer if it finds no existing buffer with the specified name; `generate-new-buffer' always creates a new buffer and gives it a unique name. Other functions you can use to create buffers include `with-output-to-temp-buffer' (*note Temporary Displays::) and `create-file-buffer' (*note Visiting Files::). Starting a subprocess can also create a buffer (*note Processes::). - Function: get-buffer-create name This function returns a buffer named NAME. It returns an existing buffer with that name, if one exists; otherwise, it creates a new buffer. The buffer does not become the current buffer--this function does not change which buffer is current. An error is signaled if NAME is not a string. (get-buffer-create "foo") => # The major mode for the new buffer is set to Fundamental mode. The variable `default-major-mode' is handled at a higher level. *Note Auto Major Mode::. - Function: generate-new-buffer name This function returns a newly created, empty buffer, but does not make it current. If there is no buffer named NAME, then that is the name of the new buffer. If that name is in use, this function adds suffixes of the form `' to NAME, where N is an integer. It tries successive integers starting with 2 until it finds an available name. An error is signaled if NAME is not a string. (generate-new-buffer "bar") => # (generate-new-buffer "bar") => #> (generate-new-buffer "bar") => #> The major mode for the new buffer is set to Fundamental mode. The variable `default-major-mode' is handled at a higher level. *Note Auto Major Mode::. See the related function `generate-new-buffer-name' in *Note Buffer Names::.  File: lispref.info, Node: Killing Buffers, Next: Indirect Buffers, Prev: Creating Buffers, Up: Buffers Killing Buffers =============== "Killing a buffer" makes its name unknown to XEmacs and makes its text space available for other use. The buffer object for the buffer that has been killed remains in existence as long as anything refers to it, but it is specially marked so that you cannot make it current or display it. Killed buffers retain their identity, however; two distinct buffers, when killed, remain distinct according to `eq'. If you kill a buffer that is current or displayed in a window, XEmacs automatically selects or displays some other buffer instead. This means that killing a buffer can in general change the current buffer. Therefore, when you kill a buffer, you should also take the precautions associated with changing the current buffer (unless you happen to know that the buffer being killed isn't current). *Note Current Buffer::. If you kill a buffer that is the base buffer of one or more indirect buffers, the indirect buffers are automatically killed as well. The `buffer-name' of a killed buffer is `nil'. To test whether a buffer has been killed, you can either use this feature or the function `buffer-live-p'. - Function: buffer-live-p object This function returns `t' if OBJECT is an editor buffer that has not been deleted, `nil' otherwise. - Command: kill-buffer buffer-or-name This function kills the buffer BUFFER-OR-NAME, freeing all its memory for use as space for other buffers. (Emacs version 18 and older was unable to return the memory to the operating system.) It returns `nil'. The argument BUFFER-OR-NAME may be a buffer or the name of one. Any processes that have this buffer as the `process-buffer' are sent the `SIGHUP' signal, which normally causes them to terminate. (The basic meaning of `SIGHUP' is that a dialup line has been disconnected.) *Note Deleting Processes::. If the buffer is visiting a file and contains unsaved changes, `kill-buffer' asks the user to confirm before the buffer is killed. It does this even if not called interactively. To prevent the request for confirmation, clear the modified flag before calling `kill-buffer'. *Note Buffer Modification::. Killing a buffer that is already dead has no effect. (kill-buffer "foo.unchanged") => nil (kill-buffer "foo.changed") ---------- Buffer: Minibuffer ---------- Buffer foo.changed modified; kill anyway? (yes or no) yes ---------- Buffer: Minibuffer ---------- => nil - Variable: kill-buffer-query-functions After confirming unsaved changes, `kill-buffer' calls the functions in the list `kill-buffer-query-functions', in order of appearance, with no arguments. The buffer being killed is the current buffer when they are called. The idea is that these functions ask for confirmation from the user for various nonstandard reasons. If any of them returns `nil', `kill-buffer' spares the buffer's life. - Variable: kill-buffer-hook This is a normal hook run by `kill-buffer' after asking all the questions it is going to ask, just before actually killing the buffer. The buffer to be killed is current when the hook functions run. *Note Hooks::. - Variable: buffer-offer-save This variable, if non-`nil' in a particular buffer, tells `save-buffers-kill-emacs' and `save-some-buffers' to offer to save that buffer, just as they offer to save file-visiting buffers. The variable `buffer-offer-save' automatically becomes buffer-local when set for any reason. *Note Buffer-Local Variables::.  File: lispref.info, Node: Indirect Buffers, Prev: Killing Buffers, Up: Buffers Indirect Buffers ================ An "indirect buffer" shares the text of some other buffer, which is called the "base buffer" of the indirect buffer. In some ways it is the analogue, for buffers, of a symbolic link among files. The base buffer may not itself be an indirect buffer. One base buffer may have several "indirect children". The text of the indirect buffer is always identical to the text of its base buffer; changes made by editing either one are visible immediately in the other. But in all other respects, the indirect buffer and its base buffer are completely separate. They have different names, different values of point and mark, different narrowing, different markers and extents (though inserting or deleting text in either buffer relocates the markers and extents for both), different major modes, and different local variables. Unlike in FSF Emacs, XEmacs indirect buffers do not automatically share text properties among themselves and their base buffer. An indirect buffer cannot visit a file, but its base buffer can. If you try to save the indirect buffer, that actually works by saving the base buffer. Killing an indirect buffer has no effect on its base buffer. Killing the base buffer kills all its indirect children. - Command: make-indirect-buffer base-buffer name This creates an indirect buffer named NAME whose base buffer is BASE-BUFFER. The argument BASE-BUFFER may be a buffer or a string. If BASE-BUFFER is an indirect buffer, its base buffer is used as the base for the new buffer. (make-indirect-buffer "*scratch*" "indirect") => # - Function: buffer-base-buffer &optional buffer This function returns the base buffer of BUFFER. If BUFFER is not indirect, the value is `nil'. Otherwise, the value is another buffer, which is never an indirect buffer. If BUFFER is not supplied, it defaults to the current buffer. (buffer-base-buffer (get-buffer "indirect")) => # - Function: buffer-indirect-children &optional buffer This function returns a list of all indirect buffers whose base buffer is BUFFER. If BUFFER is indirect, the return value will always be `nil'; see `make-indirect-buffer'. If BUFFER is not supplied, it defaults to the current buffer. (buffer-indirect-children (get-buffer "*scratch*")) => (#)  File: lispref.info, Node: Windows, Next: Frames, Prev: Buffers, Up: Top Windows ******* This chapter describes most of the functions and variables related to Emacs windows. See *Note Display::, for information on how text is displayed in windows. * Menu: * Basic Windows:: Basic information on using windows. * Splitting Windows:: Splitting one window into two windows. * Deleting Windows:: Deleting a window gives its space to other windows. * Selecting Windows:: The selected window is the one that you edit in. * Cyclic Window Ordering:: Moving around the existing windows. * Buffers and Windows:: Each window displays the contents of a buffer. * Displaying Buffers:: Higher-lever functions for displaying a buffer and choosing a window for it. * Choosing Window:: How to choose a window for displaying a buffer. * Window Point:: Each window has its own location of point. * Window Start:: The display-start position controls which text is on-screen in the window. * Vertical Scrolling:: Moving text up and down in the window. * Horizontal Scrolling:: Moving text sideways on the window. * Size of Window:: Accessing the size of a window. * Position of Window:: Accessing the position of a window. * Resizing Windows:: Changing the size of a window. * Window Configurations:: Saving and restoring the state of the screen.  File: lispref.info, Node: Basic Windows, Next: Splitting Windows, Up: Windows Basic Concepts of Emacs Windows =============================== A "window" in XEmacs is the physical area of the screen in which a buffer is displayed. The term is also used to refer to a Lisp object that represents that screen area in XEmacs Lisp. It should be clear from the context which is meant. XEmacs groups windows into frames. A frame represents an area of screen available for XEmacs to use. Each frame always contains at least one window, but you can subdivide it vertically or horizontally into multiple nonoverlapping Emacs windows. In each frame, at any time, one and only one window is designated as "selected within the frame". The frame's cursor appears in that window. At ant time, one frame is the selected frame; and the window selected within that frame is "the selected window". The selected window's buffer is usually the current buffer (except when `set-buffer' has been used). *Note Current Buffer::. For practical purposes, a window exists only while it is displayed in a frame. Once removed from the frame, the window is effectively deleted and should not be used, _even though there may still be references to it_ from other Lisp objects. Restoring a saved window configuration is the only way for a window no longer on the screen to come back to life. (*Note Deleting Windows::.) Each window has the following attributes: * containing frame * window height * window width * window edges with respect to the frame or screen * the buffer it displays * position within the buffer at the upper left of the window * amount of horizontal scrolling, in columns * point * the mark * how recently the window was selected Users create multiple windows so they can look at several buffers at once. Lisp libraries use multiple windows for a variety of reasons, but most often to display related information. In Rmail, for example, you can move through a summary buffer in one window while the other window shows messages one at a time as they are reached. The meaning of "window" in XEmacs is similar to what it means in the context of general-purpose window systems such as X, but not identical. The X Window System places X windows on the screen; XEmacs uses one or more X windows as frames, and subdivides them into Emacs windows. When you use XEmacs on a character-only terminal, XEmacs treats the whole terminal screen as one frame. Most window systems support arbitrarily located overlapping windows. In contrast, Emacs windows are "tiled"; they never overlap, and together they fill the whole screen or frame. Because of the way in which XEmacs creates new windows and resizes them, you can't create every conceivable tiling of windows on an Emacs frame. *Note Splitting Windows::, and *Note Size of Window::. *Note Display::, for information on how the contents of the window's buffer are displayed in the window. - Function: windowp object This function returns `t' if OBJECT is a window.  File: lispref.info, Node: Splitting Windows, Next: Deleting Windows, Prev: Basic Windows, Up: Windows Splitting Windows ================= The functions described here are the primitives used to split a window into two windows. Two higher level functions sometimes split a window, but not always: `pop-to-buffer' and `display-buffer' (*note Displaying Buffers::). The functions described here do not accept a buffer as an argument. The two "halves" of the split window initially display the same buffer previously visible in the window that was split. - Function: one-window-p &optional nomini which-frames which-devices This function returns non-`nil' if there is only one window. The argument NOMINI, if non-`nil', means don't count the minibuffer even if it is active; otherwise, the minibuffer window is included, if active, in the total number of windows which is compared against one. The remaining arguments controls which set of windows are counted, as with `next-window'. - Command: split-window &optional window size horizontal This function splits WINDOW into two windows. The original window WINDOW remains the selected window, but occupies only part of its former screen area. The rest is occupied by a newly created window which is returned as the value of this function. If HORIZONTAL is non-`nil', then WINDOW splits into two side by side windows. The original window WINDOW keeps the leftmost SIZE columns, and gives the rest of the columns to the new window. Otherwise, it splits into windows one above the other, and WINDOW keeps the upper SIZE lines and gives the rest of the lines to the new window. The original window is therefore the left-hand or upper of the two, and the new window is the right-hand or lower. If WINDOW is omitted or `nil', then the selected window is split. If SIZE is omitted or `nil', then WINDOW is divided evenly into two parts. (If there is an odd line, it is allocated to the new window.) When `split-window' is called interactively, all its arguments are `nil'. The following example starts with one window on a frame that is 50 lines high by 80 columns wide; then the window is split. (setq w (selected-window)) => # (window-edges) ; Edges in order: => (0 0 80 50) ; left-top-right-bottom ;; Returns window created (setq w2 (split-window w 15)) => # (window-edges w2) => (0 15 80 50) ; Bottom window; ; top is line 15 (window-edges w) => (0 0 80 15) ; Top window The frame looks like this: __________ | | line 0 | w | |__________| | | line 15 | w2 | |__________| line 50 column 0 column 80 Next, the top window is split horizontally: (setq w3 (split-window w 35 t)) => # (window-edges w3) => (35 0 80 15) ; Left edge at column 35 (window-edges w) => (0 0 35 15) ; Right edge at column 35 (window-edges w2) => (0 15 80 50) ; Bottom window unchanged Now, the screen looks like this: column 35 __________ | | | line 0 | w | w3 | |___|______| | | line 15 | w2 | |__________| line 50 column 0 column 80 Normally, Emacs indicates the border between two side-by-side windows with a scroll bar (*note Scroll Bars: X Frame Properties.) or `|' characters. The display table can specify alternative border characters; see *Note Display Tables::. - Command: split-window-vertically &optional size This function splits the selected window into two windows, one above the other, leaving the selected window with SIZE lines. This function is simply an interface to `split-window'. Here is the complete function definition for it: (defun split-window-vertically (&optional arg) "Split current window into two windows, one above the other." (interactive "P") (split-window nil (and arg (prefix-numeric-value arg)))) - Command: split-window-horizontally &optional size This function splits the selected window into two windows side-by-side, leaving the selected window with SIZE columns. This function is simply an interface to `split-window'. Here is the complete definition for `split-window-horizontally' (except for part of the documentation string): (defun split-window-horizontally (&optional arg) "Split selected window into two windows, side by side..." (interactive "P") (split-window nil (and arg (prefix-numeric-value arg)) t))  File: lispref.info, 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 force This function removes WINDOW from the display. If WINDOW is omitted, then the selected window is deleted. If window is the only one on its frame, the frame is deleted as well. Normally, you cannot delete the last non-minibuffer-only frame (you must use `save-buffers-kill-emacs' or `kill-emacs'); an error is signaled instead. However, if optional second argument FORCE is non-`nil', you can delete the last frame. (This will automatically call `save-buffers-kill-emacs'.) This function returns `nil'. When `delete-window' is called interactively, the selected window is deleted. - Command: delete-other-windows &optional window This function makes WINDOW the only window on its frame, by deleting the other windows in that frame. If WINDOW is omitted or `nil', then the selected window is used by default. The result is `nil'. - Command: delete-windows-on buffer &optional which-frames which-devices This function deletes all windows showing BUFFER. If there are no windows showing BUFFER, it does nothing. `delete-windows-on' operates frame by frame. If a frame has several windows showing different buffers, then those showing BUFFER are removed, and the others expand to fill the space. 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 another buffer chosen with `other-buffer'. *Note The Buffer List::. The argument WHICH-FRAMES controls which frames to operate on: `nil' Delete all windows showing BUFFER in any frame. `t' Delete only windows showing BUFFER in the selected frame. `visible' Delete all windows showing BUFFER in any visible frame. `0' Delete all windows showing BUFFER in any visible frame. FRAME If it is a frame, delete all windows showing BUFFER in that frame. *Warning:* This is similar to, but not identical to, the meaning of the WHICH-FRAMES argument to `next-window'; the meanings of `nil' and `t' are reversed. The optional argument WHICH-DEVICES further clarifies on which devices to search for frames as specified by WHICH-FRAMES. This value is only meaningful if WHICH-FRAMES is not `t'. `nil' Consider all devices on the selected console. DEVICE Consider only the one device DEVICE. CONSOLE Consider all devices on CONSOLE. DEVICE-TYPE Consider all devices with device type DEVICE-TYPE. `window-system' Consider all devices on window system consoles. anything else Consider all devices without restriction. This function always returns `nil'.  File: lispref.info, 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 &optional device This function returns the selected window. This is the window in which the cursor appears and to which many commands apply. Each separate device can have its own selected window, which is remembered as focus changes from device to device. Optional argument DEVICE specifies which device to return the selected window for, and defaults to the selected device. - Function: select-window window &optional norecord 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. If optional argument NORECORD is non-`nil' then the global and per-frame buffer orderings are not modified, as by the function `record-buffer'. The return value is WINDOW. (setq w (next-window)) (select-window w) => # - Special Form: save-selected-window forms... This special form records the selected window, executes FORMS in sequence, then restores the earlier selected window. It does not save or restore anything about the sizes, arrangement or contents of windows; therefore, if the FORMS change them, the changes are permanent. The following functions choose one of the windows on the screen, offering various criteria for the choice. - Function: get-lru-window &optional which-frames which-devices 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. A minibuffer window is never a candidate. By default, only the windows in the selected frame are considered. The optional argument WHICH-FRAMES changes this behavior. Here are the possible values and their meanings: `nil' Consider all the windows in the selected windows's frame, plus the minibuffer used by that frame even if it lies in some other frame. `t' Consider all windows in all existing frames. `visible' Consider all windows in all visible frames. (To get useful results, you must ensure WINDOW is in a visible frame.) `0' Consider all windows in all visible or iconified frames. FRAME Consider all windows on frame FRAME. anything else Consider precisely the windows in the selected window's frame, and no others. The optional argument WHICH-DEVICES further clarifies on which devices to search for frames as specified by WHICH-FRAMES. This value is only meaningful if WHICH-FRAMES is non-`nil'. `nil' Consider all devices on the selected console. DEVICE Consider only the one device DEVICE. CONSOLE Consider all devices on CONSOLE. DEVICE-TYPE Consider all devices with device type DEVICE-TYPE. `window-system' Consider all devices on window system consoles. anything else Consider all devices without restriction. - Function: get-largest-window &optional which-frames which-devices This function returns the window with the largest area (height times width). If there are no side-by-side windows, then this is the window with the most lines. A minibuffer window is never a candidate. If there are two windows of the same size, then the function returns the window that is first in the cyclic ordering of windows (see following section), starting from the selected window. The remaining arguments control which set of windows are considered. See `next-window', above.  File: lispref.info, Node: Cyclic Window Ordering, Next: Buffers and Windows, Prev: Selecting Windows, Up: Windows Cyclic Ordering of Windows ========================== When you use the command `C-x o' (`other-window') to select the next window, it moves through all the windows on the screen in a specific cyclic order. For any given configuration of windows, this order never varies. It is called the "cyclic ordering of windows". This ordering generally goes from top to bottom, and from left to right. But it may go down first or go right first, depending on the order in which the windows were split. If the first split was vertical (into windows one above each other), and then the subwindows were split horizontally, then the ordering is left to right in the top of the frame, and then left to right in the next lower part of the frame, and so on. If the first split was horizontal, the ordering is top to bottom in the left part, and so on. In general, within each set of siblings at any level in the window tree, the order is left to right, or top to bottom. - Function: next-window &optional window minibuf which-frames which-devices This function returns the window following WINDOW in the cyclic ordering of windows. This is the window that `C-x o' would select if typed when WINDOW is selected. If WINDOW is the only window visible, then this function returns WINDOW. If omitted, WINDOW defaults to the selected window. The value of the argument MINIBUF determines whether the minibuffer is included in the window order. Normally, when MINIBUF is `nil', the minibuffer is included if it is currently active; this is the behavior of `C-x o'. (The minibuffer window is active while the minibuffer is in use. *Note Minibuffers::.) If MINIBUF is `t', then the cyclic ordering includes the minibuffer window even if it is not active. If MINIBUF is neither `t' nor `nil', then the minibuffer window is not included even if it is active. By default, only the windows in the selected frame are considered. The optional argument WHICH-FRAMES changes this behavior. Here are the possible values and their meanings: `nil' Consider all the windows in WINDOW's frame, plus the minibuffer used by that frame even if it lies in some other frame. `t' Consider all windows in all existing frames. `visible' Consider all windows in all visible frames. (To get useful results, you must ensure WINDOW is in a visible frame.) `0' Consider all windows in all visible or iconified frames. FRAME Consider all windows on frame FRAME. anything else Consider precisely the windows in WINDOW's frame, and no others. The optional argument WHICH-DEVICES further clarifies on which devices to search for frames as specified by WHICH-FRAMES. This value is only meaningful if WHICH-FRAMES is non-`nil'. `nil' Consider all devices on the selected console. DEVICE Consider only the one device DEVICE. CONSOLE Consider all devices on CONSOLE. DEVICE-TYPE Consider all devices with device type DEVICE-TYPE. `window-system' Consider all devices on window system consoles. anything else Consider all devices without restriction. If you use consistent values for MINIBUF, WHICH-FRAMES, and WHICH-DEVICES, you can use `next-window' to iterate through the entire cycle of acceptable windows, eventually ending up back at the window you started with. `previous-window' traverses the same cycle, in the reverse order. This example assumes there are two windows, both displaying the buffer `windows.texi': (selected-window) => # (next-window (selected-window)) => # (next-window (next-window (selected-window))) => # - Function: previous-window &optional window minibuf which-frames which-devices This function returns the window preceding WINDOW in the cyclic ordering of windows. The other arguments specify which windows to include in the cycle, as in `next-window'. - Command: other-window count &optional which-frames which-devices This function selects the COUNTth following window in the cyclic order. If COUNT is negative, then it selects the -COUNTth preceding window. It returns `nil'. In an interactive call, COUNT is the numeric prefix argument. The other arguments specify which windows to include in the cycle, as in `next-window'. - Function: walk-windows function &optional minibuf which-frames which-devices This function cycles through all windows, calling `function' once for each window with the window as its sole argument. The other arguments specify which windows to cycle through, as in `next-window'.  File: lispref.info, Node: Buffers and Windows, Next: Displaying Buffers, Prev: Cyclic Window Ordering, Up: Windows Buffers and Windows =================== This section describes low-level functions to examine windows or to display buffers in windows in a precisely controlled fashion. *Note Displaying Buffers::, for related functions that find a window to use and specify a buffer for it. The functions described there are easier to use than these, but they employ heuristics in choosing or creating a window; use these functions when you need complete control. - Function: set-window-buffer window buffer-or-name &optional norecord This function makes WINDOW display BUFFER-OR-NAME as its contents. BUFFER-OR-NAME can be a buffer or a buffer name. With non-`nil' optional argument NORECORD, do not modify the global or per-frame buffer ordering. This function returns `nil'. (set-window-buffer (selected-window) "foo") => nil - Function: window-buffer &optional window This function returns the buffer that WINDOW is displaying. If WINDOW is omitted, this function returns the buffer for the selected window. (window-buffer) => # - Function: get-buffer-window buffer-or-name &optional which-frames which-devices 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 remaining arguments control which windows to consider. They have the same meaning as for `next-window'.  File: lispref.info, Node: Displaying Buffers, Next: Choosing Window, Prev: Buffers and Windows, Up: Windows Displaying Buffers in Windows ============================= In this section we describe convenient functions that choose a window automatically and use it to display a specified buffer. These functions can also split an existing window in certain circumstances. We also describe variables that parameterize the heuristics used for choosing a window. *Note Buffers and Windows::, for low-level functions that give you more precise control. Do not use the functions in this section in order to make a buffer current so that a Lisp program can access or modify it; they are too drastic for that purpose, since they change the display of buffers in windows, which is gratuitous and will surprise the user. Instead, use `set-buffer' (*note Current Buffer::) and `save-excursion' (*note Excursions::), which designate buffers as current for programmed access without affecting the display of buffers in windows. - Command: switch-to-buffer buffer-or-name &optional norecord This function makes BUFFER-OR-NAME the current buffer, and also displays the buffer in the selected window. This means that a human can see the buffer and subsequent keyboard commands will apply to it. Contrast this with `set-buffer', which makes BUFFER-OR-NAME the current buffer but does not display it in the selected window. *Note Current Buffer::. If BUFFER-OR-NAME does not identify an existing buffer, then a new buffer by that name is created. The major mode for the new buffer is set according to the variable `default-major-mode'. *Note Auto Major Mode::. Normally the specified buffer is put at the front of the buffer list. This affects the operation of `other-buffer'. However, if NORECORD is non-`nil', this is not done. *Note The Buffer List::. The `switch-to-buffer' function is often used interactively, as the binding of `C-x b'. It is also used frequently in programs. It always returns `nil'. - Command: switch-to-buffer-other-window buffer-or-name This function makes BUFFER-OR-NAME the current buffer and displays it in a window not currently selected. It then selects that window. The handling of the buffer is the same as in `switch-to-buffer'. The currently selected window is absolutely never used to do the job. If it is the only window, then it is split to make a distinct window for this purpose. If the selected window is already displaying the buffer, then it continues to do so, but another window is nonetheless found to display it in as well. - Function: pop-to-buffer buffer-or-name &optional other-window on-frame This function makes BUFFER-OR-NAME the current buffer and switches to it in some window, preferably not the window previously selected. The "popped-to" window becomes the selected window within its frame. If the variable `pop-up-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::. If ON-FRAME is non-`nil', it is the frame to pop to this buffer on. An example use of this function is found at the end of *Note Filter Functions::. - Command: replace-buffer-in-windows buffer &optional which-frames which-devices 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. The optional arguments WHICH-FRAMES and WHICH-DEVICES have the same meaning as with `delete-windows-on'. This function returns `nil'.  File: lispref.info, Node: Choosing Window, Next: Window Point, Prev: Displaying Buffers, Up: Windows Choosing a Window for Display ============================= This section describes the basic facility that chooses a window to display a buffer in--`display-buffer'. All the higher-level functions and commands use this subroutine. Here we describe how to use `display-buffer' and how to customize it. - Command: display-buffer buffer-or-name &optional not-this-window override-frame 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. BUFFER-OR-NAME can be a buffer or the name of one. 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. If OVERRIDE-FRAME is non-`nil', display on that frame instead of the current frame (or the dedicated frame). `display-buffer' returns the window chosen to display BUFFER-OR-NAME. Precisely how `display-buffer' finds or creates a window depends on the variables described below. A window can be marked as "dedicated" to a particular buffer. Then XEmacs will not automatically change which buffer appears in the window, such as `display-buffer' might normally do. - Function: window-dedicated-p window This function returns WINDOW's dedicated object, usually `t' or `nil'. - Function: set-window-buffer-dedicated window buffer This function makes WINDOW display BUFFER and be dedicated to that buffer. Then XEmacs will not automatically change which buffer appears in WINDOW. If BUFFER is `nil', this function makes WINDOW not be dedicated (but doesn't change which buffer appears in it currently). - User Option: pop-up-windows This variable controls whether `display-buffer' makes new windows. If it is non-`nil' and there is only one window, then that window is split. If it is `nil', then `display-buffer' does not split the single window, but uses it whole. - User Option: split-height-threshold This variable determines when `display-buffer' may split a window, if there are multiple windows. `display-buffer' always splits the largest window if it has at least this many lines. If the largest window is not this tall, it is split only if it is the sole window and `pop-up-windows' is non-`nil'. - User Option: pop-up-frames This variable controls whether `display-buffer' makes new frames. If it is non-`nil', `display-buffer' looks for an existing window already displaying the desired buffer, on any visible frame. If it finds one, it returns that window. Otherwise it makes a new frame. The variables `pop-up-windows' and `split-height-threshold' do not matter if `pop-up-frames' is non-`nil'. If `pop-up-frames' is `nil', then `display-buffer' either splits a window or reuses one. *Note Frames::, for more information. - Variable: pop-up-frame-function This variable specifies how to make a new frame if `pop-up-frames' is non-`nil'. Its value should be a function of no arguments. When `display-buffer' makes a new frame, it does so by calling that function, which should return a frame. The default value of the variable is a function that creates a frame using properties from `pop-up-frame-plist'. - Variable: pop-up-frame-plist This variable holds a plist specifying frame properties used when `display-buffer' makes a new frame. *Note Frame Properties::, for more information about frame properties. - 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 a plist, specifying frame properties, 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-plist This variable holds frame properties for `special-display-popup-frame' to use when it creates a frame. - Variable: same-window-buffer-names A list of buffer names for buffers that should be displayed in the selected window. If the buffer's name is in this list, `display-buffer' handles the buffer by switching to it in the selected window. - Variable: same-window-regexps A list of regular expressions that specify buffers that should be displayed in the selected window. If the buffer's name matches any of the regular expressions in this list, `display-buffer' handles the buffer by switching to it in the selected window. - Variable: display-buffer-function This variable is the most flexible way to customize the behavior of `display-buffer'. If it is non-`nil', it should be a function that `display-buffer' calls to do the work. The function should accept two arguments, the same two arguments that `display-buffer' received. It should choose or create a window, display the specified buffer, and then return the window. This hook takes precedence over all the other options and hooks described above. A window can be marked as "dedicated" to its buffer. Then `display-buffer' does not try to use that window. - Function: window-dedicated-p window This function returns `t' if WINDOW is marked as dedicated; otherwise `nil'. - Function: set-window-dedicated-p window flag This function marks WINDOW as dedicated if FLAG is non-`nil', and nondedicated otherwise.  File: lispref.info, Node: Window Point, Next: Window Start, Prev: Choosing Window, Up: Windows Windows and Point ================= Each window has its own value of point, independent of the value of point in other windows displaying the same buffer. This makes it useful to have multiple windows showing one buffer. * The window point is established when a window is first created; it is initialized from the buffer's point, or from the window point of another window opened on the buffer if such a window exists. * Selecting a window sets the value of point in its buffer to the window's value of point. Conversely, deselecting a window sets the window's value of point from that of the buffer. Thus, when you switch between windows that display a given buffer, the point value for the selected window is in effect in the buffer, while the point values for the other windows are stored in those windows. * As long as the selected window displays the current buffer, the window's point and the buffer's point always move together; they remain equal. * *Note Positions::, for more details on buffer positions. As far as the user is concerned, point is where the cursor is, and when the user switches to another buffer, the cursor jumps to the position of point in that buffer. - Function: window-point &optional window This function returns the current position of point in WINDOW. For a non-selected 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 the value of 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.