28.4.3.3 Size Parameters

Frame parameters specify frame sizes in character units. On graphical displays, the default face determines the actual pixel sizes of these character units (see Face Attributes).

height

The height of the frame’s text area (see Frame Geometry), in characters.

width

The width of the frame’s text area (see Frame Geometry), in characters.

user-size

This does for the size parameters height and width what the user-position parameter (see user-position) does for the position parameters top and left.

fullscreen

This parameter specifies whether to maximize the frame’s width, height or both. Its value can be fullwidth, fullheight, fullboth, or maximized. A fullwidth frame is as wide as possible, a fullheight frame is as tall as possible, and a fullboth frame is both as wide and as tall as possible. A maximized frame is like a “fullboth” frame, except that it usually keeps its title bar and the buttons for resizing and closing the frame. Also, maximized frames typically avoid hiding any task bar or panels displayed on the desktop. A “fullboth” frame, on the other hand, usually omits the title bar and occupies the entire available screen space.

Full-height and full-width frames are more similar to maximized frames in this regard. However, these typically display an external border which might be absent with maximized frames. Hence the heights of maximized and full-height frames and the widths of maximized and full-width frames often differ by a few pixels.

With some window managers you may have to customize the variable frame-resize-pixelwise (see Size and Position) in order to make a frame truly appear maximized or full-screen. Moreover, some window managers might not support smooth transition between the various full-screen or maximization states. Customizing the variable x-frame-normalize-before-maximize can help to overcome that.

fullscreen-restore

This parameter specifies the desired fullscreen state of the frame after invoking the toggle-frame-fullscreen command (see Frame Commands in The GNU Emacs Manual) in the “fullboth” state. Normally this parameter is installed automatically by that command when toggling the state to fullboth. If, however, you start Emacs in the “fullboth” state, you have to specify the desired behavior in your initial file as, for example

(setq default-frame-alist
    '((fullscreen . fullboth) (fullscreen-restore . fullheight)))

This will give a new frame full height after typing in it F11 for the first time.