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28.11 Buffers and Windows

This section describes low-level functions for examining and setting the contents of windows. See Switching Buffers, for higher-level functions for displaying a specific buffer in a window.

function window-buffer \&optional window​

This function returns the buffer that window is displaying. If window is omitted or nil it defaults to the selected window. If window is an internal window, this function returns nil.

function set-window-buffer window buffer-or-name \&optional keep-margins​

This function makes window display buffer-or-name. window should be a live window; if nil, it defaults to the selected window. buffer-or-name should be a buffer, or the name of an existing buffer. This function does not change which window is selected, nor does it directly change which buffer is current (see Current Buffer). Its return value is nil.

If window is strongly dedicated to a buffer and buffer-or-name does not specify that buffer, this function signals an error. See Dedicated Windows.

By default, this function resets window’s position, display margins, fringe widths, and scroll bar settings, based on the local variables in the specified buffer. However, if the optional argument keep-margins is non-nil, it leaves window’s display margins, fringes and scroll bar settings alone.

When writing an application, you should normally use display-buffer (see Choosing Window) or the higher-level functions described in Switching Buffers, instead of calling set-window-buffer directly.

This runs window-scroll-functions, followed by window-configuration-change-hook. See Window Hooks.

variable buffer-display-count​

This buffer-local variable records the number of times a buffer has been displayed in a window. It is incremented each time set-window-buffer is called for the buffer.

variable buffer-display-time​

This buffer-local variable records the time at which a buffer was last displayed in a window. The value is nil if the buffer has never been displayed. It is updated each time set-window-buffer is called for the buffer, with the value returned by current-time (see Time of Day).

function get-buffer-window \&optional buffer-or-name all-frames​

This function returns the first window displaying buffer-or-name in the cyclic ordering of windows, starting from the selected window (see Cyclic Window Ordering). If no such window exists, the return value is nil.

buffer-or-name should be a buffer or the name of a buffer; if omitted or nil, it defaults to the current buffer. The optional argument all-frames specifies which windows to consider:

  • t means consider windows on all existing frames.
  • visible means consider windows on all visible frames.
  • 0 means consider windows on all visible or iconified frames.
  • A frame means consider windows on that frame only.
  • Any other value means consider windows on the selected frame.

Note that these meanings differ slightly from those of the all-frames argument to next-window (see Cyclic Window Ordering). This function may be changed in a future version of Emacs to eliminate this discrepancy.

function get-buffer-window-list \&optional buffer-or-name minibuf all-frames​

This function returns a list of all windows currently displaying buffer-or-name. buffer-or-name should be a buffer or the name of an existing buffer. If omitted or nil, it defaults to the current buffer. If the currently selected window displays buffer-or-name, it will be the first in the list returned by this function.

The arguments minibuf and all-frames have the same meanings as in the function next-window (see Cyclic Window Ordering). Note that the all-frames argument does not behave exactly like in get-buffer-window.

command replace-buffer-in-windows \&optional buffer-or-name​

This command replaces buffer-or-name with some other buffer, in all windows displaying it. buffer-or-name should be a buffer, or the name of an existing buffer; if omitted or nil, it defaults to the current buffer.

The replacement buffer in each window is chosen via switch-to-prev-buffer (see Window History). Any dedicated window displaying buffer-or-name is deleted if possible (see Dedicated Windows). If such a window is the only window on its frame and there are other frames on the same terminal, the frame is deleted as well. If the dedicated window is the only window on the only frame on its terminal, the buffer is replaced anyway.