Multiple Windows
****************

Emacs can split a frame into two or many windows.  Multiple windows can display parts of different buffers, or different parts of one buffer.  Multiple frames always imply multiple windows, because each window belongs to one and only one frame.

Concepts of Emacs Windows
=========================

When multiple windows are being displayed, each window has an Emacs buffer designated for display in it.  The same buffer may appear in more than one window; if it does, any changes in its text are displayed in all the windows where it appears.  But the windows showing the same buffer can show different parts of it, because each window has its own value of point.

At any time, one of the windows is the selected window; the buffer this window is displaying is the current buffer.  The terminal's cursor shows the location of point in this window.  Each other window has a location of point as well, but since the terminal has only one cursor there is no way to show where those locations are.  When you make multiple frames, each frame has a cursor which appears in the frame's selected window.

Commands to move point affect the value of point for the selected Emacs window only.  They do not change the value of point in any other Emacs window, even one showing the same buffer.  The same is true for commands such as C-x b to change the selected buffer in the selected window; they do not affect other windows at all.  However, there are other commands such as C-x 4 b that select a different window and switch buffers in it.  Also, all commands that display information in a window, including (for example) C-h f (describe-function) and C-x C-b (list-buffers), work by switching buffers in a nonselected window without affecting the selected window.

When multiple windows show the same buffer, they can have different regions, because they can have different values of point.  This means that in Transient Mark mode, each window highlights a different part of the buffer.  The part that is highlighted in the selected window is the region that editing commands use.

Each window has its own mode line, which displays the buffer name, modification status and major and minor modes of the buffer that is displayed in the window.  See Mode Line, for full details on the mode line.

Splitting Windows
=================

C-x 2
     Split the selected window into two windows, one above the other (split-window-vertically).

C-x 3
     Split the selected window into two windows positioned side by side (split-window-horizontally).

The command C-x 2 (split-window-vertically) breaks the selected window into two windows, one above the other.  Both windows start out displaying the same buffer, with the same value of point.  By default the two windows each get half the height of the window that was split; a numeric argument specifies how many lines to give to the top window.

C-x 3 (split-window-horizontally) breaks the selected window into two side-by-side windows.  A numeric argument specifies how many columns to give the one on the left.  A line of vertical bars separates the two windows.  Windows that are not the full width of the screen have mode lines, but they are truncated; also, they do not always appear in inverse video, because the Emacs display routines have not been taught how to display a region of inverse video that is only part of a line on the screen.

When a window is less than the full width, text lines too long to fit are frequent.  Continuing all those lines might be confusing.  The variable truncate-partial-width-windows can be set non-nil to force truncation in all windows less than the full width of the screen, independent of the buffer being displayed and its value for truncate-lines.  See Continuation Lines.

Horizontal scrolling is often used in side-by-side windows. See Display.

If split-window-keep-point is non-nil, C-x 2 tries to avoid shifting any text on the screen by putting point in whichever window happens to contain the screen line the cursor is already on.  The default is that split-window-keep-point is non-nil on slow terminals.

Using Other Windows
===================

C-x o
     Select another window (other-window).  That is o, not zero.

C-M-v
     Scroll the next window (scroll-other-window).

M-x compare-windows
     Find next place where the text in the selected window does not match the text in the next window.

To select a different window, use C-x o (other-window). That is an o, for `other', not a zero.  When there are more than two windows, this command moves through all the windows in a cyclic order, generally top to bottom and left to right.  After the rightmost and bottommost window, it goes back to the one at the upper left corner.  A numeric argument means to move several steps in the cyclic order of windows.  A negative argument moves around the cycle in the opposite order. When the minibuffer is active, the minibuffer is the last window in the cycle; you can switch from the minibuffer window to one of the other windows, and later switch back and finish supplying the minibuffer argument that is requested.  See Minibuffer Edit.

The usual scrolling commands (see Display) apply to the selected window only, but there is one command to scroll the next window. C-M-v (scroll-other-window) scrolls the window that C-x o would select.  It takes arguments, positive and negative, like C-v.  (In the minibuffer, C-M-v scrolls the window that contains the minibuffer help display, if any, rather than the next window in the standard cyclic order.)

The command M-x compare-windows lets you compare two files or buffers visible in two windows, by moving through them to the next mismatch.  See Comparing Files.

Displaying in Another Window
============================

C-x 4 is a prefix key for commands that select another window (splitting the window if there is only one) and select a buffer in that window.  Different C-x 4 commands have different ways of finding the buffer to select.

C-x 4 b BUFNAME RET
     Select buffer BUFNAME in another window.  This runs switch-to-buffer-other-window.

C-x 4 C-o BUFNAME RET
     Display buffer BUFNAME in another window, but don't select that buffer or that window.  This runs display-buffer.

C-x 4 f FILENAME RET
     Visit file FILENAME and select its buffer in another window.  This runs find-file-other-window.  See Visiting.

C-x 4 d DIRECTORY RET
     Select a Dired buffer for directory DIRECTORY in another window. This runs dired-other-window.  See Dired.

C-x 4 m
     Start composing a mail message in another window.  This runs mail-other-window; its same-window analogue is C-x m (see Sending Mail).

C-x 4 .
     Find a tag in the current tag table in another window.  This runs find-tag-other-window, the multiple-window variant of M-. (see Tags).

C-x 4 r FILENAME RET
     Visit file FILENAME read-only, and select its buffer in another window.  This runs find-file-read-only-other-window. See Visiting.

Deleting and Rearranging Windows
================================

C-x 0
     Get rid of the selected window (delete-window).  That is a zero.

C-x 1
     Get rid of all windows except the selected one (delete-other-windows).

C-x ^
     Make selected window taller (enlarge-window).

C-x }
     Make selected window wider (enlarge-window-horizontally).

To delete a window, type C-x 0 (delete-window).  (That is a zero.)  The space occupied by the deleted window is given to an adjacent window (but not the minibuffer window, even if that is active at the time).  Once a window is deleted, its attributes are forgotten; only restoring a window configuration can bring it back.  Deleting the window has no effect on the buffer it used to display; the buffer continues to exist, and you can select it in any window with C-x b.

C-x 1 (delete-other-windows) is more powerful than C-x 0; it deletes all the windows except the selected one (and the minibuffer); the selected window expands to use the whole frame except for the echo area.

To readjust the division of space among vertically adjacent windows, use C-x ^ (enlarge-window).  It makes the currently selected window get one line bigger, or as many lines as is specified with a numeric argument.  With a negative argument, it makes the selected window smaller.  C-x } (enlarge-window-horizontally) makes the selected window wider by the specified number of columns.  The extra screen space given to a window comes from one of its neighbors, if that is possible.  If this makes any window too small, it is deleted and its space is given to an adjacent window.  The minimum size is specified by the variables window-min-height and window-min-width.