26.19 Tooltips
Tooltips are small windows that display text information at the
current mouse position. They activate when there is a pause in mouse
movement. There are two types of tooltip: help tooltips and GUD
tooltips.
Help tooltips typically display over text—including the mode
line—but may be also available for many other parts of the Emacs
frame such as the tool bar and menu items.
You can toggle help tooltips (Tooltip mode) with the command
M-x tooltip-mode. When Tooltip mode is disabled, the help text
is displayed in the echo area instead.
GUD tooltips show values of variables. They are useful when
you are debugging a program. See Debugger Operation.
The variables tooltip-delay
specifies how long Emacs should
wait before displaying a tooltip. For additional customization
options for displaying tooltips, use M-x customize-group
<RET> tooltip <RET>. See X Resources, for information on
customizing the windows that display tooltips.