Emacs provides miscellaneous functions for finding the height and width
of a window. The return value of many of these functions can be
specified either in units of pixels or in units of lines and columns.
On a graphical display, the latter actually correspond to the height and
width of a default character specified by the frame’s default font as
returned by frame-char-height and frame-char-width
(see Frame Font). Thus, if a window is displaying text with a
different font or size, the reported line height and column 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 number of lines comprising its body and its top and bottom decorations (see Basic Concepts of Emacs Windows).
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.
If a window’s pixel height is not an integral multiple of its frame’s default character height, the number of lines occupied by the window is rounded internally. This is done in a way such that, if the window is a parent window, the sum of the total heights of all its child windows internally equals the total height of their parent. This means that although two windows have the same pixel height, their internal total heights may differ by one line. This means also, that if window is vertically combined and has a next sibling, the topmost row of that sibling can be calculated as the sum of this window’s topmost row and total height (see Coordinates and Windows)
If the optional argument round is ceiling, this
function returns the smallest integer larger than window’s pixel
height divided by the character height of its frame; if it is
floor, it returns the largest integer smaller than said value;
with any other round it returns the internal value of
windows’s total height.
The total width of a window is the number of columns comprising its body and its left and right decorations (see Basic Concepts of Emacs Windows).
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.
If a window’s pixel width is not an integral multiple of its frame’s
character width, the number of columns occupied by the window is rounded
internally. This is done in a way such that, if the window is a parent
window, the sum of the total widths of all its children internally
equals the total width of their parent. This means that although two
windows have the same pixel width, their internal total widths may
differ by one column. This means also, that if this window is
horizontally combined and has a next sibling, the leftmost column of
that sibling can be calculated as the sum of this window’s leftmost
column and total width (see Coordinates and Windows). The optional
argument round behaves as it does for window-total-height.
This function returns either the total height in lines or the total
width in columns 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 optional
argument round behaves as it does for window-total-height.
The following two functions can be used to return the total size of a window in units of pixels.
This function returns the total height of window window in pixels. window must be a valid window and defaults to the selected one.
The return value includes the heights of window’s top and bottom decorations. If window is an internal window, its pixel height is the pixel height of the screen areas spanned by its children.
This function returns the width of window window in pixels. window must be a valid window and defaults to the selected one.
The return value includes the widths of window’s left and right decorations. If window is an internal window, its pixel width is the width of the screen areas spanned by its children.
The following functions can be used to determine whether a given window has any adjacent windows.
This function returns non-nil if window has no other window
above or below it in its frame. More precisely, this means that the
total height of window equals the total height of the root window
on that frame. The minibuffer window does not count in this regard. If
window is omitted or nil, it defaults to the selected
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 body, which does not include any of its top or bottom decorations (see Basic Concepts of Emacs Windows).
This function returns the height, in lines, of the body of window
window. If window is omitted or nil, it defaults to
the selected window; otherwise it must be a live window.
The optional argument pixelwise defines the units to use for the
height. If nil, return the body height of window in
characters, rounded down to the nearest integer, if necessary. This
means that if a line at the bottom of the text area is only partially
visible, that line is not counted. It also means that the height of a
window’s body can never exceed its total height as returned by
window-total-height.
If pixelwise is remap and the default face is remapped
(see Face Remapping), use the remapped face to determine the
character height. For any other non-nil value, return the
height in pixels.
The body width of a window is the width of its body and of the text area, which does not include any of its left or right decorations (see Basic Concepts of Emacs Windows).
Note that when one or both fringes are removed (by setting their width
to zero), the display engine reserves two character cells, one on each
side of the window, for displaying the continuation and truncation
glyphs, which leaves 2 columns less for text display. (The function
window-max-chars-per-line, described below, takes this
peculiarity into account.)
This function returns the width, in columns, of the body of window
window. If window is omitted or nil, it defaults to
the selected window; otherwise it must be a live window.
The optional argument pixelwise defines the units to use for the
width. If nil, return the body width of window in
characters, rounded down to the nearest integer, if necessary. This
means that if a column on the right of the text area is only partially
visible, that column is not counted. It also means that the width of
a window’s body can never exceed its total width as returned by
window-total-width.
If pixelwise is remap and the default face is remapped
(see Face Remapping), use the remapped face to determine the
character width. For any other non-nil value, return the width
in pixels.
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. In either case, the optional
argument pixelwise is passed to the function called.
The pixel heights of a window’s mode, tab and header line can be retrieved with the functions given below. Their return value is usually accurate unless the window has not been displayed before: In that case, the return value is based on an estimate of the font used for the window’s frame.
This function returns the height in pixels of window’s mode line. window must be a live window and defaults to the selected one. If window has no mode line, the return value is zero.
This function returns the height in pixels of window’s tab line. window must be a live window and defaults to the selected one. If window has no tab line, the return value is zero.
This function returns the height in pixels of window’s header line. window must be a live window and defaults to the selected one. If window has no header line, the return value is zero.
Functions for retrieving the height and/or width of window dividers (see Window Dividers), fringes (see Fringes), scroll bars (see Scroll Bars), and display margins (see Displaying in the Margins) are described in the corresponding sections.
If your Lisp program needs to make layout decisions, you will find the following function useful:
This function returns the number of characters displayed in the
specified face face in the specified window window (which
must be a live window). If face was remapped (see Face Remapping), the information is returned for the remapped face. If
omitted or nil, face defaults to the default face, and
window defaults to the selected window.
Unlike window-body-width, this function accounts for the actual
size of face’s font, instead of working in units of the canonical
character width of window’s frame (see Frame Font). It also
accounts for space used by the continuation glyph, if window lacks
one or both of its fringes.
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. They also obey the variable
window-size-fixed, with which a window can be fixed in
size (see Preserving Window Sizes).
This option specifies the minimum total height, in lines, of any window. Its value has to accommodate at least one text line and any top or bottom decorations.
This option specifies the minimum total width, in columns, of any window. Its value has to accommodate at least two text columns and any left or right decorations.
The following function tells how small a specific window can get taking
into account the sizes of its areas and the values of
window-min-height, window-min-width and
window-size-fixed (see Preserving Window Sizes).
This function returns the minimum size of window. window
must be a valid window and defaults to the selected one. The optional
argument horizontal non-nil means to return the minimum
number of columns of window; otherwise return the minimum number
of window’s lines.
The return value makes sure that all components of window remain
fully visible if window’s size were actually set to it. With
horizontal nil it includes any top or bottom decorations.
With horizontal non-nil it includes any left or right
decorations of window.
The optional argument ignore, if non-nil, means ignore
restrictions imposed by fixed size windows, window-min-height or
window-min-width settings. If ignore equals safe,
live windows may get as small as window-safe-min-height lines and
window-safe-min-width columns. If ignore is a window,
ignore restrictions for that window only. Any other non-nil
value means ignore all of the above restrictions for all windows.
The optional argument pixelwise non-nil means to return the
minimum size of window counted in pixels.