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This is Info file elisp, produced by Makeinfo-1.63 from the input file
elisp.texi.
This version is the edition 2.4.2 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.
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: elisp, Node: Buffer File Name, Next: Buffer Modification, Prev: Buffer Names, Up: Buffers
Buffer File Name
================
The "buffer file name" is the name of the file that is visited in
that buffer. When a buffer is not visiting a file, its buffer file name
is `nil'. Most of the time, the buffer name is the same as the
nondirectory part of the buffer file name, but the buffer file name and
the buffer name are distinct and can be set independently. *Note
Visiting Files::.
- Function: buffer-file-name &optional BUFFER
This function returns the absolute file name of the file that
BUFFER is visiting. If BUFFER is not visiting any file,
`buffer-file-name' returns `nil'. If BUFFER is not supplied, it
defaults to the current buffer.
(buffer-file-name (other-buffer))
=> "/usr/user/lewis/manual/files.texi"
- Variable: buffer-file-name
This buffer-local variable contains the name of the file being
visited in the current buffer, or `nil' if it is not visiting a
file. It is a permanent local, unaffected by
`kill-local-variables'.
buffer-file-name
=> "/usr/user/lewis/manual/buffers.texi"
It is risky to change this variable's value without doing various
other things. See the definition of `set-visited-file-name' in
`files.el'; some of the things done there, such as changing the
buffer name, are not strictly necessary, but others are essential
to avoid confusing Emacs.
- Variable: buffer-file-truename
This buffer-local variable holds the truename of the file visited
in the current buffer, or `nil' if no file is visited. It is a
permanent local, unaffected by `kill-local-variables'. *Note
Truenames::.
- Variable: buffer-file-number
This buffer-local variable holds the file number and directory
device number of the file visited in the current buffer, or `nil'
if no file or a nonexistent file is visited. It is a permanent
local, unaffected by `kill-local-variables'. *Note Truenames::.
The value is normally a list of the form `(FILENUM DEVNUM)'. This
pair of numbers uniquely identifies the file among all files
accessible on the system. See the function `file-attributes', in
*Note File Attributes::, for more information about them.
- Function: get-file-buffer FILENAME
This function returns the buffer visiting file FILENAME. If there
is no such buffer, it returns `nil'. The argument FILENAME, which
must be a string, is expanded (*note File Name Expansion::.), then
compared against the visited file names of all live buffers.
(get-file-buffer "buffers.texi")
=> #<buffer buffers.texi>
In unusual circumstances, there can be more than one buffer
visiting the same file name. In such cases, this function returns
the first such buffer in the buffer list.
- Command: set-visited-file-name FILENAME
If FILENAME is a non-empty string, this function changes the name
of the file visited in current buffer to FILENAME. (If the buffer
had no visited file, this gives it one.) The *next time* the
buffer is saved it will go in the newly-specified file. This
command marks the buffer as modified, since it does not (as far as
Emacs knows) match the contents of FILENAME, even if it matched the
former visited file.
If FILENAME is `nil' or the empty string, that stands for "no
visited file". In this case, `set-visited-file-name' marks the
buffer as having no visited file.
When the function `set-visited-file-name' is called interactively,
it prompts for FILENAME in the minibuffer.
See also `clear-visited-file-modtime' and
`verify-visited-file-modtime' in *Note Buffer Modification::.
- Variable: list-buffers-directory
This buffer-local variable records a string to display in a buffer
listing in place of the visited file name, for buffers that don't
have a visited file name. Dired buffers use this variable.
File: elisp, Node: Buffer Modification, Next: Modification Time, Prev: Buffer File Name, Up: Buffers
Buffer Modification
===================
Emacs keeps a flag called the "modified flag" for each buffer, to
record whether you have changed the text of the buffer. This flag is
set to `t' whenever you alter the contents of the buffer, and cleared
to `nil' when you save it. Thus, the flag shows whether there are
unsaved changes. The flag value is normally shown in the mode line
(*note Mode Line Variables::.), and controls saving (*note Saving
Buffers::.) and auto-saving (*note Auto-Saving::.).
Some Lisp programs set the flag explicitly. For example, the
function `set-visited-file-name' sets the flag to `t', because the text
does not match the newly-visited file, even if it is unchanged from the
file formerly visited.
The functions that modify the contents of buffers are described in
*Note Text::.
- Function: buffer-modified-p &optional BUFFER
This function returns `t' if the buffer BUFFER has been modified
since it was last read in from a file or saved, or `nil'
otherwise. If BUFFER is not supplied, the current buffer is
tested.
- Function: set-buffer-modified-p FLAG
This function marks the current buffer as modified if FLAG is
non-`nil', or as unmodified if the flag is `nil'.
Another effect of calling this function is to cause unconditional
redisplay of the mode line for the current buffer. In fact, the
function `force-mode-line-update' works by doing this:
(set-buffer-modified-p (buffer-modified-p))
- Command: not-modified
This command marks the current buffer as unmodified, and not
needing to be saved. With prefix arg, it marks the buffer as
modified, so that it will be saved at the next suitable occasion.
Don't use this function in programs, since it prints a message in
the echo area; use `set-buffer-modified-p' (above) instead.
- Function: buffer-modified-tick &optional BUFFER
This function returns BUFFER's modification-count. This is a
counter that increments every time the buffer is modified. If
BUFFER is `nil' (or omitted), the current buffer is used.
File: elisp, Node: Modification Time, Next: Read Only Buffers, Prev: Buffer Modification, Up: Buffers
Comparison of Modification Time
===============================
Suppose that you visit a file and make changes in its buffer, and
meanwhile the file itself is changed on disk. At this point, saving the
buffer would overwrite the changes in the file. Occasionally this may
be what you want, but usually it would lose valuable information. Emacs
therefore checks the file's modification time using the functions
described below before saving the file.
- Function: verify-visited-file-modtime BUFFER
This function compares what BUFFER has recorded for the
modification time of its visited file against the actual
modification time of the file as recorded by the operating system.
The two should be the same unless some other process has written
the file since Emacs visited or saved it.
The function returns `t' if the last actual modification time and
Emacs's recorded modification time are the same, `nil' otherwise.
- Function: clear-visited-file-modtime
This function clears out the record of the last modification time
of the file being visited by the current buffer. As a result, the
next attempt to save this buffer will not complain of a
discrepancy in file modification times.
This function is called in `set-visited-file-name' and other
exceptional places where the usual test to avoid overwriting a
changed file should not be done.
- Function: visited-file-modtime
This function returns the buffer's recorded last file modification
time, as a list of the form `(HIGH . LOW)'. (This is the same
format that `file-attributes' uses to return time values; see
*Note File Attributes::.)
- Function: set-visited-file-modtime &optional TIME
This function updates the buffer's record of the last modification
time of the visited file, to the value specified by TIME if TIME
is not `nil', and otherwise to the last modification time of the
visited file.
If TIME is not `nil', it should have the form `(HIGH . LOW)' or
`(HIGH LOW)', in either case containing two integers, each of
which holds 16 bits of the time.
This function is useful if the buffer was not read from the file
normally, or if the file itself has been changed for some known
benign reason.
- Function: ask-user-about-supersession-threat FILENAME
This function is used to ask a user how to proceed after an
attempt to modify an obsolete buffer visiting file FILENAME. An
"obsolete buffer" is an unmodified buffer for which the associated
file on disk is newer than the last save-time of the buffer. This
means some other program has probably altered the file.
Depending on the user's answer, the function may return normally,
in which case the modification of the buffer proceeds, or it may
signal a `file-supersession' error with data `(FILENAME)', in which
case the proposed buffer modification is not allowed.
This function is called automatically by Emacs on the proper
occasions. It exists so you can customize Emacs by redefining it.
See the file `userlock.el' for the standard definition.
See also the file locking mechanism in *Note File Locks::.
File: elisp, Node: Read Only Buffers, Next: The Buffer List, Prev: Modification Time, Up: Buffers
Read-Only Buffers
=================
If a buffer is "read-only", then you cannot change its contents,
although you may change your view of the contents by scrolling and
narrowing.
Read-only buffers are used in two kinds of situations:
* A buffer visiting a write-protected file is normally read-only.
Here, the purpose is to show the user that editing the buffer with
the aim of saving it in the file may be futile or undesirable.
The user who wants to change the buffer text despite this can do
so after clearing the read-only flag with `C-x C-q'.
* Modes such as Dired and Rmail make buffers read-only when altering
the contents with the usual editing commands is probably a mistake.
The special commands of these modes bind `buffer-read-only' to
`nil' (with `let') or bind `inhibit-read-only' to `t' around the
places where they change the text.
- Variable: buffer-read-only
This buffer-local variable specifies whether the buffer is
read-only. The buffer is read-only if this variable is non-`nil'.
- Variable: inhibit-read-only
If this variable is non-`nil', then read-only buffers and read-only
characters may be modified. Read-only characters in a buffer are
those that have non-`nil' `read-only' properties (either text
properties or overlay properties). *Note Special Properties::,
for more information about text properties. *Note Overlays::, for
more information about overlays and their properties.
If `inhibit-read-only' is `t', all `read-only' character
properties have no effect. If `inhibit-read-only' is a list, then
`read-only' character properties have no effect if they are members
of the list (comparison is done with `eq').
- Command: toggle-read-only
This command changes whether the current buffer is read-only. It
is intended for interactive use; don't use it in programs. At any
given point in a program, you should know whether you want the
read-only flag on or off; so you can set `buffer-read-only'
explicitly to the proper value, `t' or `nil'.
- Function: barf-if-buffer-read-only
This function signals a `buffer-read-only' error if the current
buffer is read-only. *Note Interactive Call::, for another way to
signal an error if the current buffer is read-only.
File: elisp, Node: The Buffer List, Next: Creating Buffers, Prev: Read Only Buffers, Up: Buffers
The Buffer List
===============
The "buffer list" is a list of all live buffers. Creating a buffer
adds it to this list, and killing a buffer deletes it. The order of
the buffers in the list is based primarily on how recently each buffer
has been displayed in the selected window. Buffers move to the front
of the list when they are selected and to the end when they are buried.
Several functions, notably `other-buffer', use this ordering. A
buffer list displayed for the user also follows this order.
- Function: buffer-list
This function returns a list of all buffers, including those whose
names begin with a space. The elements are actual buffers, not
their names.
(buffer-list)
=> (#<buffer buffers.texi>
#<buffer *Minibuf-1*> #<buffer buffer.c>
#<buffer *Help*> #<buffer TAGS>)
;; Note that the name of the minibuffer
;; begins with a space!
(mapcar (function buffer-name) (buffer-list))
=> ("buffers.texi" " *Minibuf-1*"
"buffer.c" "*Help*" "TAGS")
The list that `buffer-list' returns is constructed specifically by
`buffer-list'; it is not an internal Emacs data structure, and
modifying it has no effect on the order of buffers. If you want to
change the order of buffers in the list, here is an easy way:
(defun reorder-buffer-list (new-list)
(while new-list
(bury-buffer (car new-list))
(setq new-list (cdr new-list))))
With this method, you can specify any order for the list, but there
is no danger of losing a buffer or adding something that is not a valid
live buffer.
- Function: other-buffer &optional BUFFER VISIBLE-OK
This function returns the first buffer in the buffer list other
than BUFFER. Usually this is the buffer most recently shown in
the selected window, aside from BUFFER. Buffers whose names start
with a space are not considered.
If BUFFER is not supplied (or if it is not a buffer), then
`other-buffer' returns the first buffer on the buffer list that is
not visible in any window in a visible frame.
If the selected frame has a non-`nil' `buffer-predicate'
parameter, then `other-buffer' uses that predicate to decide which
buffers to consider. It calls the predicate once for each buffer,
and if the value is `nil', that buffer is ignored. *Note X Frame
Parameters::.
If VISIBLE-OK is `nil', `other-buffer' avoids returning a buffer
visible in any window on any visible frame, except as a last
resort. If VISIBLE-OK is non-`nil', then it does not matter
whether a buffer is displayed somewhere or not.
If no suitable buffer exists, the buffer `*scratch*' is returned
(and created, if necessary).
- Command: bury-buffer &optional BUFFER-OR-NAME
This function puts BUFFER-OR-NAME at the end of the buffer list
without changing the order of any of the other buffers on the list.
This buffer therefore becomes the least desirable candidate for
`other-buffer' to return.
If BUFFER-OR-NAME is `nil' or omitted, this means to bury the
current buffer. In addition, if the buffer is displayed in the
selected window, this switches to some other buffer (obtained using
`other-buffer') in the selected window. But if the buffer is
displayed in some other window, it remains displayed there.
If you wish to replace a buffer in all the windows that display
it, use `replace-buffer-in-windows'. *Note Buffers and Windows::.
File: elisp, 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")
=> #<buffer 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 `<N>' 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")
=> #<buffer bar>
(generate-new-buffer "bar")
=> #<buffer bar<2>>
(generate-new-buffer "bar")
=> #<buffer bar<3>>
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: elisp, Node: Killing Buffers, Next: Indirect Buffers, Prev: Creating Buffers, Up: Buffers
Killing Buffers
===============
"Killing a buffer" makes its name unknown to Emacs 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, Emacs
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'. You can use this
feature to test whether a buffer has been killed:
(defun buffer-killed-p (buffer)
"Return t if BUFFER is killed."
(not (buffer-name buffer)))
- Command: kill-buffer BUFFER-OR-NAME
This function kills the buffer BUFFER-OR-NAME, freeing all its
memory for other uses or to be returned to the operating system.
It returns `nil'.
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: elisp, 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.
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. This includes the text properties as well as
the characters themselves.
But in all other respects, the indirect buffer and its base buffer
are completely separate. They have different names, different values of
point, different narrowing, different markers and overlays (though
inserting or deleting text in either buffer relocates the markers and
overlays for both), different major modes, and different local
variables.
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 effectively kills the indirect buffer in that it cannot
ever again be the current buffer.
- 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.
- Function: buffer-base-buffer 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.
File: elisp, 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.
* Scrolling Hooks:: Hooks that run when you scroll a window.
* Horizontal Scrolling:: Moving text sideways on the window.
* Size of Window:: Accessing the size of a window.
* Resizing Windows:: Changing the size of a window.
* Coordinates and Windows:: Converting coordinates to windows.
* Window Configurations:: Saving and restoring the state of the screen.
File: elisp, Node: Basic Windows, Next: Splitting Windows, Up: Windows
Basic Concepts of Emacs Windows
===============================
A "window" in Emacs is the physical area of the screen in which a
buffer is displayed. The term is also used to refer to a Lisp object
that represents that screen area in Emacs Lisp. It should be clear
from the context which is meant.
Emacs groups windows into frames. A frame represents an area of
screen available for Emacs to use. Each frame always contains at least
one window, but you can subdivide it vertically or horizontally into
multiple nonoverlapping Emacs windows.
In each frame, at any time, one and only one window is designated as
"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 screen or frame
* 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 Emacs is similar to what it means in the
context of general-purpose window systems such as X, but not identical.
The X Window System places X windows on the screen; Emacs uses one or
more X windows as frames, and subdivides them into Emacs windows. When
you use Emacs on a character-only terminal, Emacs treats the whole
terminal screen as one frame.
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 Emacs 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: elisp, 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.
- 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 screen that is 50
lines high by 80 columns wide; then the window is split.
(setq w (selected-window))
=> #<window 8 on windows.texi>
(window-edges) ; Edges in order:
=> (0 0 80 50) ; left--top--right--bottom
;; Returns window created
(setq w2 (split-window w 15))
=> #<window 28 on windows.texi>
(window-edges w2)
=> (0 15 80 50) ; Bottom window;
; top is line 15
(window-edges w)
=> (0 0 80 15) ; Top window
The screen 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 32 on windows.texi>
(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 Parameters.)
or `|' characters. The display table can specify alternative
border characters; see *Note Display Tables::.
- Command: split-window-vertically 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-windows'. Here is
the complete function definition for it:
(defun split-window-vertically (&optional arg)
"Split current window into two windows, ..."
(interactive "P")
(split-window nil (and arg (prefix-numeric-value arg))))
- Command: split-window-horizontally 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-windows'. 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))
- Function: one-window-p &optional NO-MINI ALL-FRAMES
This function returns non-`nil' if there is only one window. The
argument NO-MINI, 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 argument ALL-FRAMES specifies which frames to consider. Here
are the possible values and their meanings:
`nil'
Count the windows in the selected frame, plus the minibuffer
used by that frame even if it lies in some other frame.
`t'
Count all windows in all existing frames.
`visible'
Count all windows in all visible frames.
0
Count all windows in all visible or iconified frames.
anything else
Count precisely the windows in the selected frame, and no
others.
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 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 FRAME
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 FRAME controls which frames to operate on:
* If it is `nil', operate on the selected frame.
* If it is `t', operate on all frames.
* If it is `visible', operate on all visible frames.
* 0 If it is 0, operate on all visible or iconified frames.
* If it is a frame, operate on that 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>
- Macro: save-selected-window FORMS...
This macro records the selected window, executes FORMS in
sequence, then restores the earlier selected window.
This macro does not save or restore anything about the sizes,
arrangement or contents of windows; therefore, if the FORMS change
them, the change persists.
Each frame, at any time, has a window selected within the frame.
This macro only saves *the* selected window; it does not save
anything about other frames. If the FORMS select some other frame
and alter the window selected within it, the change persists.
The following functions choose one of the windows on the screen,
offering various criteria for the choice.
- Function: get-lru-window &optional FRAME
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.
The argument FRAME controls which windows are considered.
* If it is `nil', consider windows on the selected frame.
* If it is `t', consider windows on all frames.
* If it is `visible', consider windows on all visible frames.
* If it is 0, consider windows on all visible or iconified
frames.
* If it is a frame, consider windows on that frame.
- Function: get-largest-window &optional FRAME
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 argument FRAME controls which set of windows are considered.
See `get-lru-window', above.
File: elisp, Node: Cyclic Window Ordering, Next: Buffers and Windows, Prev: Selecting Windows, Up: Windows
Cyclic Ordering of Windows
==========================
When you use the command `C-x o' (`other-window') to select the next
window, it moves through all the windows on the screen in a specific
cyclic order. For any given configuration of windows, this order never
varies. It is called the "cyclic ordering of windows".
This ordering generally goes from top to bottom, and from left to
right. But it may go down first or go right first, depending on the
order in which the windows were split.
If the first split was vertical (into windows one above each other),
and then the subwindows were split horizontally, then the ordering is
left to right in the top of the frame, and then left to right in the
next lower part of the frame, and so on. If the first split was
horizontal, the ordering is top to bottom in the left part, and so on.
In general, within each set of siblings at any level in the window tree,
the order is left to right, or top to bottom.
- Function: next-window &optional WINDOW MINIBUF ALL-FRAMES
This function returns the window following WINDOW in the cyclic
ordering of windows. This is the window that `C-x o' would select
if typed when WINDOW is selected. If WINDOW is the only window
visible, then this function returns WINDOW. If omitted, WINDOW
defaults to the selected window.
The value of the argument MINIBUF determines whether the
minibuffer is included in the window order. Normally, when
MINIBUF is `nil', the minibuffer is included if it is currently
active; this is the behavior of `C-x o'. (The minibuffer window
is active while the minibuffer is in use. *Note Minibuffers::.)
If MINIBUF is `t', then the cyclic ordering includes the
minibuffer window even if it is not active.
If MINIBUF is neither `t' nor `nil', then the minibuffer window is
not included even if it is active.
The argument ALL-FRAMES specifies which frames to consider. Here
are the possible values and their meanings:
`nil'
Consider all the windows in WINDOW's frame, plus the
minibuffer used by that frame even if it lies in some other
frame.
`t'
Consider all windows in all existing frames.
`visible'
Consider all windows in all visible frames. (To get useful
results, you must ensure WINDOW is in a visible frame.)
0
Consider all windows in all visible or iconified frames.
anything else
Consider precisely the windows in WINDOW's frame, and no
others.
This example assumes there are two windows, both displaying the
buffer `windows.texi':
(selected-window)
=> #<window 56 on windows.texi>
(next-window (selected-window))
=> #<window 52 on windows.texi>
(next-window (next-window (selected-window)))
=> #<window 56 on windows.texi>
- Function: previous-window &optional WINDOW MINIBUF ALL-FRAMES
This function returns the window preceding WINDOW in the cyclic
ordering of windows. The other arguments specify which windows to
include in the cycle, as in `next-window'.
- Command: other-window COUNT
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.
- Function: walk-windows PROC &optional MINIBUF ALL-FRAMES
This function cycles through all windows, calling `proc' once for
each window with the window as its sole argument.
The optional arguments MINIBUF and ALL-FRAMES specify the set of
windows to include in the scan. See `next-window', above, for
details.
File: 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
display buffers in windows in a precisely controlled fashion. *Note
Displaying Buffers::, for related functions that find a window to use
and specify a buffer for it. The functions described there are easier
to use than these, but they employ heuristics in choosing or creating a
window; use these functions when you need complete control.
- Function: set-window-buffer WINDOW BUFFER-OR-NAME
This function makes WINDOW display BUFFER-OR-NAME as its contents.
It returns `nil'.
(set-window-buffer (selected-window) "foo")
=> nil
- Function: window-buffer &optional WINDOW
This function returns the buffer that WINDOW is displaying. If
WINDOW is omitted, this function returns the buffer for the
selected window.
(window-buffer)
=> #<buffer windows.texi>
- Function: get-buffer-window BUFFER-OR-NAME &optional 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 windows to consider.
* If it is `nil', consider windows on the selected frame.
* If it is `t', consider windows on all frames.
* If it is `visible', consider windows on all visible frames.
* If it is 0, consider windows on all visible or iconified
frames.
* If it is a frame, consider windows on that frame.
- Function: get-buffer-window-list BUFFER-OR-NAME &optional MINIBUF
ALL-FRAMES
This function returns a list of all the windows currently
displaying BUFFER-OR-NAME.
The two optional arguments work like the optional arguments of
`next-window' (*note Cyclic Window Ordering::.); they are *not*
like the single optional argument of `get-buffer-window'. Perhaps
we should change `get-buffer-window' in the future to make it
compatible with the other functions.
The argument ALL-FRAMES controls which windows to consider.
* If it is `nil', consider windows on the selected frame.
* If it is `t', consider windows on all frames.
* If it is `visible', consider windows on all visible frames.
* If it is 0, consider windows on all visible or iconified
frames.
* If it is a frame, consider windows on that frame.