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28.3 Window Sizes

The following schematic shows the structure of a live window: 

              _________________________________________
           ^ |______________ Header Line_______________|
           | |LS|LF|LM|                       |RM|RF|RS| ^
           | |  |  |  |                       |  |  |  | |
      Window |  |  |  |       Text Area       |  |  |  | Window
      Total  |  |  |  |     (Window Body)     |  |  |  | Body
      Height |  |  |  |                       |  |  |  | Height
           | |  |  |  |<- Window Body Width ->|  |  |  | |
           | |__|__|__|_______________________|__|__|__| v
           v |_______________ Mode Line _______________|
     
              <----------- Window Total Width -------->

At the center of the window is the text area, or body, where the buffer text is displayed. On each side of the text area is a series of vertical areas; from innermost to outermost, these are the left and right margins, denoted by LM and RM in the schematic (see Display Margins); the left and right fringes, denoted by LF and RF (see Fringes); and the left or right scroll bar, only one of which is present at any time, denoted by LS and RS (see Scroll Bars). At the top of the window is an optional header line (see Header Lines), and at the bottom of the window is the mode line (see Mode Line Format).

Emacs provides several functions for finding the height and width of a window. Except where noted, Emacs reports window heights and widths as integer numbers of lines and columns, respectively. On a graphical display, each “line” and “column” actually corresponds to the height and width of a “default” character specified by the frame's default font. Thus, if a window is displaying text with a different font or size, the reported height and width for that window may differ from the actual number of text lines or columns displayed within it.

The total height of a window is the distance between the top and bottom of the window, including the header line (if one exists) and the mode line. The total width of a window is the distance between the left and right edges of the mode line. Note that the height of a frame is not the same as the height of its windows, since a frame may also contain an echo area, menu bar, and tool bar (see Size and Position).

— Function: window-total-height &optional window

This function returns the total height, in lines, of the window window. If window is omitted or nil, it defaults to the selected window. If window is an internal window, the return value is the total height occupied by its descendant windows.

— Function: window-total-width &optional window

This function returns the total width, in columns, of the window window. If window is omitted or nil, it defaults to the selected window. If window is internal, the return value is the total width occupied by its descendant windows.

— Function: window-total-size &optional window horizontal

This function returns either the total height or width of the window window. If horizontal is omitted or nil, this is equivalent to calling window-total-height for window; otherwise it is equivalent to calling window-total-width for window.

The following functions can be used to determine whether a given window has any adjacent windows.

— Function: window-full-height-p &optional window

This function returns non-nil if window has no other window above or below it in its frame, i.e., its total height equals the total height of the root window on that frame. If window is omitted or nil, it defaults to the selected window.

— Function: window-full-width-p &optional window

This function returns non-nil if window has no other window to the left or right in its frame, i.e., its total width equals that of the root window on that frame. If window is omitted or nil, it defaults to the selected window.

The body height of a window is the height of its text area, which does not include the mode or header line. Similarly, the body width is the width of the text area, which does not include the scroll bar, fringes, or margins.

— Function: window-body-height &optional window

This function returns the body height, in lines, of the window window. If window is omitted or nil, it defaults to the selected window; otherwise it must be a live window.

If there is a partially-visible line at the bottom of the text area, that counts as a whole line; to exclude such a partially-visible line, use window-text-height, below.

— Function: window-body-width &optional window

This function returns the body width, in columns, of the window window. If window is omitted or nil, it defaults to the selected window; otherwise it must be a live window.

— Function: window-body-size &optional window horizontal

This function returns the body height or body width of window. If horizontal is omitted or nil, it is equivalent to calling window-body-height for window; otherwise it is equivalent to calling window-body-width.

— Function: window-text-height &optional window

This function is like window-body-height, except that any partially-visible line at the bottom of the text area is not counted.

For compatibility with previous versions of Emacs, window-height is an alias for window-total-height, and window-width is an alias for window-body-width. These aliases are considered obsolete and will be removed in the future.

Commands that change the size of windows (see Resizing Windows), or split them (see Splitting Windows), obey the variables window-min-height and window-min-width, which specify the smallest allowable window height and width. See Deleting and Rearranging Windows. They also obey the variable window-size-fixed, with which a window can be fixed in size:

— Variable: window-size-fixed

If this buffer-local variable is non-nil, the size of any window displaying the buffer cannot normally be changed. Deleting a window or changing the frame's size may still change its size, if there is no choice.

If the value is height, then only the window's height is fixed; if the value is width, then only the window's width is fixed. Any other non-nil value fixes both the width and the height.

— Function: window-size-fixed-p &optional window horizontal

This function returns a non-nil value if window's height is fixed. If window is omitted or nil, it defaults to the selected window. If the optional argument horizontal is non-nil, the return value is non-nil if window's width is fixed.

A nil return value does not necessarily mean that window can be resized in the desired direction. To determine that, use the function window-resizable. See Resizing Windows.

See Coordinates and Windows, for more functions that report the positions of various parts of a window relative to the frame, from which you can calculate its size. In particular, you can use the functions window-pixel-edges and window-inside-pixel-edges to find the size in pixels, for graphical displays.