Tooltips are special frames (see Frames) that are used to display helpful hints (a.k.a. “tips”) related to the current position of the mouse pointer. Emacs uses tooltips to display help strings about active portions of text (see Special Properties) and about various UI elements, such as menu items (see Extended Menu Items) and tool-bar buttons (see Tool Bar).
Tooltip Mode is a minor mode that enables display of tooltips. Turning off this mode causes the tooltips be displayed in the echo area. On text-mode (a.k.a. “TTY”) frames, tooltips are always displayed in the echo area.
When Emacs is built with GTK+ support, it by default displays tooltips
using GTK+ functions, and the appearance of the tooltips is then
controlled by GTK+ settings. GTK+ tooltips can be disabled by
changing the value of the variable x-gtk-use-system-tooltips to
nil. The rest of this subsection describes how to control
non-GTK+ tooltips, which are presented by Emacs itself.
Since tooltips are special frames, they have their frame parameters (see Frame Parameters). Unlike other frames, the frame parameters for tooltips are stored in a special variable.
This customizable option holds the frame parameters used for
displaying tooltips. Any font and color parameters are ignored, and
the corresponding attributes of the
tooltip face are used
top parameters are included, they
are used as absolute frame-relative coordinates where the tooltip
should be shown. (Mouse-relative position of the tooltip can be
customized using the variables described in Tooltips in The GNU Emacs Manual.) Note that the
parameters, if present, override the values of mouse-relative offsets.
tooltip face determines the appearance of text shown in
tooltips. It should generally use a variable-pitch font of size that
is preferably smaller than the default frame font.
This abnormal hook is a list of functions to call when Emacs needs to
display a tooltip. Each function is called with a single argument
event which is a copy of the last mouse movement event. If a
function on this list actually displays the tooltip, it should return
nil, and then the rest of the functions will not be
called. The default value of this variable is a single function
If you write your own function to be put on the tooltip-functions list, you may need to know the buffer of the mouse event that triggered the tooltip display. The following function provides that information.
This function returns the buffer over which event occurred.
Call it with the argument of the function from
tooltip-functions to obtain the buffer whose text triggered the
tooltip. Note that the event might occur not over a buffer (e.g.,
over the tool bar), in which case this function will return
Other aspects of tooltip display are controlled by several customizable settings; see Tooltips in The GNU Emacs Manual.