GNU Emacs Lisp Reference Manual

25.13: The Size of a Window

An Emacs window is rectangular, and its size information consists of the height (the number of lines) and the width (the number of character positions in each line). The mode line is included in the height. But the width does not count the scroll bar or the column of `|' characters that separates side-by-side windows.

The following three functions return size information about a window:

Function: window-height &optional window

This function returns the number of lines in window, including its mode line. If window fills its entire frame, this is one less than the value of frame-height on that frame (since the last line is always reserved for the minibuffer).

If window is nil, the function uses the selected window.

(window-height)
     => 23
(split-window-vertically)
     => #
(window-height)
     => 11

Function: window-width &optional window

This function returns the number of columns in window. If window fills its entire frame, this is the same as the value of frame-width on that frame. The width does not include the window's scroll bar or the column of `|' characters that separates side-by-side windows.

If window is nil, the function uses the selected window.

(window-width)
     => 80

Function: window-edges &optional window

This function returns a list of the edge coordinates of window. If window is nil, the selected window is used.

The order of the list is (left top right bottom), all elements relative to 0, 0 at the top left corner of the frame. The element right of the value is one more than the rightmost column used by window, and bottom is one more than the bottommost row used by window and its mode-line.

When you have side-by-side windows, the right edge value for a window with a neighbor on the right includes the width of the separator between the window and that neighbor. This separator may be a column of `|' characters or it may be a scroll bar. Since the width of the window does not include this separator, the width does not equal the difference between the right and left edges in this case.

Here is the result obtained on a typical 24-line terminal with just one window:

(window-edges (selected-window))
     => (0 0 80 23)

The bottom edge is at line 23 because the last line is the echo area.

If window is at the upper left corner of its frame, right and bottom are the same as the values returned by (window-width) and (window-height) respectively, and top and bottom are zero. For example, the edges of the following window are `0 0 5 8'. Assuming that the frame has more than 8 columns, the last column of the window (column 7) holds a border rather than text. The last row (row 4) holds the mode line, shown here with `xxxxxxxxx'.

           0    
           _______
        0 |       | 
          |       |   
          |       | 
          |       | 
          xxxxxxxxx  4

                  7  

When there are side-by-side windows, any window not at the right edge of its frame has a separator in its last column or columns. The separator counts as one or two columns in the width of the window. A window never includes a separator on its left, since that belongs to the window to the left.

In the following example, let's suppose that the frame is 7 columns wide. Then the edges of the left window are `0 0 4 3' and the edges of the right window are `4 0 7 3'.

           ___ ___
          |   |   |    
          |   |   |    
          xxxxxxxxx 

           0  34  7