24.2 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).

C-Mouse-2

In the mode line or scroll bar of a window, split that window.

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. If you are not using scrollbars, a vertical line separates the two windows. You can customize its color with the face vertical-border. Windows that are not the full width of the screen have mode lines, but they are truncated. On terminals where Emacs does not support highlighting, truncated mode lines sometimes do not appear in inverse video.

You can split a window horizontally or vertically by clicking C-Mouse-2 in the mode line or the scroll bar. The line of splitting goes through the place where you click: if you click on the mode line, the new scroll bar goes above the spot; if you click in the scroll bar, the mode line of the split window is side by side with your click.

When a window occupies less than the full width of the frame, it may become too narrow for most of the text lines in its buffer. If most of its lines are continued (see Continuation Lines), the buffer may become difficult to read. Therefore, Emacs automatically truncates lines if the window width becomes narrower than 50 columns. This truncation occurs regardless of the value of the variable truncate-lines (see Line Truncation); it is instead controlled by the variable truncate-partial-width-windows. If the value of truncate-partial-width-windows is a positive integer (the default is 50), that specifies the minimum width for a partial-width window before automatic line truncation occurs; if the value is nil, automatic line truncation is disabled; and for any other non-nil value, Emacs truncates lines in every partial-width window regardless of its width.

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

If split-window-keep-point is non-nil, the default, both of the windows resulting from C-x 2 inherit the value of point from the window that was split. This means that scrolling is inevitable. If this variable is nil, then C-x 2 tries to avoid scrolling the text currently visible on the screen, by putting point in each window at a position already visible in the window. It also selects whichever window contains the screen line that the cursor was previously on. Some users prefer that mode on slow terminals.