This chapter describes most of the functions and variables related to Emacs windows. See section Emacs Display, for information on how text is displayed in 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 any 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). See section The 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. (See section Deleting Windows.)
Each window has the following attributes:
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, not all conceivable tilings of windows on an Emacs frame are actually possible. See section Splitting Windows, and section The Size of a Window.
See section Emacs Display, for information on how the contents of the window's buffer are displayed in the window.
t if object is a window.
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 (see section Displaying Buffers in Windows).
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.
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 (see section Window Frame Parameters) or `|' characters. The display table can specify alternative border characters; see section Display Tables.
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, ..." (interactive "P") (split-window nil (and arg (prefix-numeric-value arg))))
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))
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:
niltvisibleA 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 (see section 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.
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.
nil. 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.
nil, then the selected window is used by default.
The return value is nil.
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. See section
The Buffer List.
The argument frame controls which frames to operate
on. This function does not use it in quite the same way as the
other functions which scan all windows; specifically, the values
t and nil have the opposite of their
meanings in other functions. Here are the full details:
nil, operate on all frames.
t, operate on the selected frame.
visible, operate on all visible
frames.
This function always returns nil.
When a window is selected, the buffer in the window becomes the current buffer, and the cursor will appear in it.
The return value is window.
(setq w (next-window))
(select-window w)
=> #<window 65 on windows.texi>
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 saves only 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.
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.
nil, consider windows on the selected
frame.
t, consider windows on all frames.
visible, consider windows on all visible
frames.
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 to
consider. See get-lru-window, above.
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.
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. See section 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:
niltvisibleThis 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>
next-window.
nil. In an interactive call, count is the numeric prefix argument.
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.
This section describes low-level functions to examine windows or to display buffers in windows in a precisely controlled fashion. See the following section 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.
nil. This is the fundamental
primitive for changing which buffer is displayed in a window, and
all ways of doing that call this function.
(set-window-buffer (selected-window) "foo")
=> nil
(window-buffer)
=> #<buffer windows.texi>
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. See section
Cyclic Ordering of Windows. The argument all-frames controls which windows to consider.
nil, consider windows on the selected
frame.
t, consider windows on all frames.
visible, consider windows on all visible
frames.
The two optional arguments work like the optional arguments of
next-window (see section Cyclic Ordering of Windows); 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.
nil, consider windows on the selected
frame.
t, consider windows on all frames.
visible, consider windows on all visible
frames.
set-window-buffer is called, it
sets this variable to (current-time) in the specified
buffer (see section Time of Day).
When a buffer is first created, buffer-display-time
starts out with the value nil.
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. See the preceding section
for low-level functions that give you more precise control. All of
these functions work by calling set-window-buffer.
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 would be gratuitous and surprise the
user. Instead, use set-buffer and
save-current-buffer (see section The Current Buffer), which designate
buffers as current for programmed access without affecting the
display of buffers in windows.
set-buffer, which makes
buffer-or-name the current buffer but does not display
it in the selected window. See section The 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. See section How Emacs Chooses a Major Mode.
Normally the specified buffer is put at the front of the buffer
list (both the selected frame's buffer list and the
frame-independent buffer list). This affects the operation of
other-buffer. However, if norecord is
non-nil, this is not done. See section 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.
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.
This function updates the buffer list just like
switch-to-buffer unless norecord is
non-nil.
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
section Choosing a Window for
Display.
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. See section Choosing a Window for Display.
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. See section How Emacs Chooses a Major Mode.
This function updates the buffer list just like
switch-to-buffer unless norecord is
non-nil.
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.
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.
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.
If the argument frame is non-nil, it
specifies which frames to check when deciding whether the buffer is
already displayed. If the buffer is already displayed in some
window on one of these frames, display-buffer simply
returns that window. Here are the possible values of
frame:
nil, consider windows on the selected
frame.
t, consider windows on all frames.
visible, consider windows on all visible
frames.
Precisely how display-buffer finds or creates a
window depends on the variables described below.
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.
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.
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.
See section Frames, for more information.
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.
display-buffer makes a new frame. See section Frame Parameters, for more information
about frame parameters.
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.)
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.
The default value of this variable is
special-display-popup-frame.
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.
special-display-popup-frame to use when
it creates a frame.
display-buffer handles
the buffer by switching to it in the selected window.
display-buffer handles the
buffer by switching to it in the selected window.
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 will
not try to use that window to display any other buffer.
t if window is marked as dedicated;
otherwise nil.
nil, and nondedicated otherwise.
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.
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.
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.
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.
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 section Motion by Text Lines.
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 completes without
being preempted.
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
nil.
If update is non-nil,
window-end always returns an up-to-date value for
where the window ends. If the saved value is valid,
window-end returns that; otherwise it computes the
correct value by scanning the buffer text.
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 ;; theset-window-startexpression. ---------- 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 ;; theset-window-startexpression. ---------- 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.
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. See
section Horizontal 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. See section The
Current Buffer.
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.
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.
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. See section Minibuffer Miscellany.
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".
nil, it tells scroll-other-window
which buffer to scroll.
scroll-conservatively. The difference is
that it if its value is n, that permits scrolling only
by precisely n lines, not a smaller number. This feature
does not work with scroll-margin. The default value is
zero.
nil, the scroll functions move point so that the
vertical position of the cursor is unchanged, when that is
possible.
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.
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)
Because we read English from left to right in the "inner loop",
and from top to bottom in the "outer loop", horizontal scrolling is
not like vertical scrolling. Vertical scrolling involves selection
of a contiguous portion of text to display, but 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.
window-hscroll
(below).
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.
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
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)))))
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:
frame-height on that frame
(since the last line is always reserved for the minibuffer). If window is nil, the function uses the
selected window.
(window-height)
=> 23
(split-window-vertically)
=> #<window 4 on windows.texi>
(window-height)
=> 11
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
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)(4), 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
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.
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.
(defun enlarge-window-horizontally (columns) (enlarge-window columns t))
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.
(defun shrink-window-horizontally (columns) (shrink-window columns t))
window-min-height lines. However, the command does nothing if the window is already too small to display the whole text of the buffer, or if part of the contents are currently scrolled off screen, or if the window is not the full width of its frame, or if the window is the only window in its frame.
The following two variables constrain the window-size-changing functions to a minimum height and width.
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.
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.
This section describes how to relate screen coordinates to windows.
window-at returns
nil. If you omit frame, the selected frame is used.
The argument coordinates is a cons cell of the 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 returned by 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)mode-linevertical-splitnilThe function coordinates-in-window-p does not
require a frame as argument because it always uses the frame that
window is on.
A window configuration records the entire layout of one 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. See section Frame Configurations.
window-min-height, window-min-width and
minibuffer-scroll-window. An exception is made for
point in the current buffer, whose value is not saved.
current-window-configuration. This configuration is
restored in the frame from which configuration was made,
whether that frame is selected or not. This always counts as a
window size change and triggers execution of the
window-size-change-functions (see section Hooks for Window Scrolling and
Changes), because set-window-configuration doesn't
know how to tell whether the new configuration actually differs
from the old one. If the frame which configuration was saved from is
dead, all this function does is restore the three variables
window-min-height, window-min-width and
minibuffer-scroll-window.
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)))
save-excursion also, if you wish
to preserve that. Don't use this construct when save-selected-window
is all you need.
Exit from save-window-excursion always triggers
execution of the window-size-change-functions. (It
doesn't know how to tell whether the restored configuration
actually differs from the one in effect at the end of the
forms.)
The return value is the value of the final form in forms. For example:
(split-window)
=> #<window 25 on control.texi>
(setq w (selected-window))
=> #<window 19 on control.texi>
(save-window-excursion
(delete-other-windows w)
(switch-to-buffer "foo")
'do-something)
=> do-something
;; The screen is now split again.
t if object is a window configuration.
t even if those aspects
differ. The function equal can also compare two window
configurations; it regards configurations as unequal if they differ
in any respect, even a saved point or mark.
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.
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 in the implementation of Lazy Lock mode; see section
`Font Lock Support Modes' in The GNU Emacs Manual.
Displaying a different buffer in the window also runs these functions.
These functions must be careful in using window-end
(see section The Window Start
Position); if you need an up-to-date value, you must use the
update argument to ensure you get it.
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
(see section 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 (see section Selecting Windows) is what you need
here.
set-window-redisplay-end-trigger. The functions are
called with two arguments: the window, and the end trigger
position. Storing nil for the end trigger position
turns off the feature, and the trigger value is automatically reset
to nil just after the hook is run.