19.11 Minibuffer Windows

These functions access and select minibuffer windows, test whether they are active and control how they get resized.

Function: active-minibuffer-window

This function returns the currently active minibuffer window, or nil if there is none.

Function: minibuffer-window &optional frame

This function returns the minibuffer window used for frame frame. If frame is nil, that stands for the current frame. Note that the minibuffer window used by a frame need not be part of that frame—a frame that has no minibuffer of its own necessarily uses some other frame’s minibuffer window.

Function: set-minibuffer-window window

This function specifies window as the minibuffer window to use. This affects where the minibuffer is displayed if you put text in it without invoking the usual minibuffer commands. It has no effect on the usual minibuffer input functions because they all start by choosing the minibuffer window according to the current frame.

Function: window-minibuffer-p &optional window

This function returns non-nil if window is a minibuffer window. window defaults to the selected window.

It is not correct to determine whether a given window is a minibuffer by comparing it with the result of (minibuffer-window), because there can be more than one minibuffer window if there is more than one frame.

Function: minibuffer-window-active-p window

This function returns non-nil if window is the currently active minibuffer window.

The following two options control whether minibuffer windows are resized automatically and how large they can get in the process.

User Option: resize-mini-windows

This option specifies whether minibuffer windows are resized automatically. The default value is grow-only, which means that a minibuffer window by default expands automatically to accommodate the text it displays and shrinks back to one line as soon as the minibuffer gets empty. If the value is t, Emacs will always try to fit the height of a minibuffer window to the text it displays (with a minimum of one line). If the value is nil, a minibuffer window never changes size automatically. In that case the window resizing commands (see Resizing Windows) can be used to adjust its height.

User Option: max-mini-window-height

This option provides a maximum height for resizing minibuffer windows automatically. A floating-point number specifies a fraction of the frame’s height; an integer specifies the maximum number of lines. The default value is 0.25.