29.3.4 Frame Size And Position

You can read or change the size and position of a frame using the frame parameters left, top, height, and width. Whatever geometry parameters you don't specify are chosen by the window manager in its usual fashion.

Here are some special features for working with sizes and positions. (For the precise meaning of "selected frame" used by these functions, see 29.9 Input Focus.)

Function: set-frame-position frame left top

This function sets the position of the top left corner of frame to left and top. These arguments are measured in pixels, and normally count from the top left corner of the screen.

Negative parameter values position the bottom edge of the window up from the bottom edge of the screen, or the right window edge to the left of the right edge of the screen. It would probably be better if the values were always counted from the left and top, so that negative arguments would position the frame partly off the top or left edge of the screen, but it seems inadvisable to change that now.

Function: frame-height &optional frame

Function: frame-width &optional frame

These functions return the height and width of frame, measured in lines and columns. If you don't supply frame, they use the selected frame.

Function: screen-height

Function: screen-width

These functions are old aliases for frame-height and frame-width. When you are using a non-window terminal, the size of the frame is normally the same as the size of the terminal screen.

Function: frame-pixel-height &optional frame

Function: frame-pixel-width &optional frame

These functions return the height and width of frame, measured in pixels. If you don't supply frame, they use the selected frame.

Function: frame-char-height &optional frame

Function: frame-char-width &optional frame

These functions return the height and width of a character in frame, measured in pixels. The values depend on the choice of font. If you don't supply frame, these functions use the selected frame.

Function: set-frame-size frame cols rows

This function sets the size of frame, measured in characters; cols and rows specify the new width and height.

To set the size based on values measured in pixels, use frame-char-height and frame-char-width to convert them to units of characters.

Function: set-frame-height frame lines &optional pretend

This function resizes frame to a height of lines lines. The sizes of existing windows in frame are altered proportionally to fit.

If pretend is non-nil, then Emacs displays lines lines of output in frame, but does not change its value for the actual height of the frame. This is only useful for a terminal frame. Using a smaller height than the terminal actually implements may be useful to reproduce behavior observed on a smaller screen, or if the terminal malfunctions when using its whole screen. Setting the frame height "for real" does not always work, because knowing the correct actual size may be necessary for correct cursor positioning on a terminal frame.

Function: set-frame-width frame width &optional pretend

This function sets the width of frame, measured in characters. The argument pretend has the same meaning as in set-frame-height.

The older functions set-screen-height and set-screen-width were used to specify the height and width of the screen, in Emacs versions that did not support multiple frames. They are semi-obsolete, but still work; they apply to the selected frame.

Function: x-parse-geometry geom

The function x-parse-geometry converts a standard X window geometry string to an alist that you can use as part of the argument to make-frame.

The alist describes which parameters were specified in geom, and gives the values specified for them. Each element looks like (parameter . value). The possible parameter values are left, top, width, and height.

For the size parameters, the value must be an integer. The position parameter names left and top are not totally accurate, because some values indicate the position of the right or bottom edges instead. These are the value possibilities for the position parameters:

an integer

A positive integer relates the left edge or top edge of the window to the left or top edge of the screen. A negative integer relates the right or bottom edge of the window to the right or bottom edge of the screen.

(+ position)

This specifies the position of the left or top edge of the window relative to the left or top edge of the screen. The integer position may be positive or negative; a negative value specifies a position outside the screen.

(- position)

This specifies the position of the right or bottom edge of the window relative to the right or bottom edge of the screen. The integer position may be positive or negative; a negative value specifies a position outside the screen.

Here is an example:

(x-parse-geometry "35x70+0-0") => ((height . 70) (width . 35) (top - 0) (left . 0))