parameters are used to display the help-echo text are described in
@ref{Text help-echo}.
-@cindex @code{signal usr1} event
-@cindex @code{signal usr2} event
+@cindex @code{sigusr1} event
+@cindex @code{sigusr2} event
@cindex user signals
-@item signal usr1
-@itemx signal usr2
-These event sequences are generated when the Emacs process receives
+@item sigusr1
+@itemx sigusr2
+These events are generated when the Emacs process receives
the signals @code{SIGUSR1} and @code{SIGUSR2}. They contain no
additional data because signals do not carry additional information.
+
+To catch a user signal, bind the corresponding event to an interactive
+command in the @code{special-event-map} (@pxref{Active Keymaps}).
+The command is called with no arguments, and the specific signal event is
+available in @code{last-input-event}. For example:
+
+@example
+(defun sigusr-handler ()
+ (interactive)
+ (message "Caught signal %S" last-input-event))
+
+(define-key special-event-map [sigusr1] 'sigusr-handler)
+@end example
+
+To test the signal handler, you can make Emacs send a signal to itself:
+
+@example
+(signal-process (emacs-pid) 'sigusr1)
+@end example
@end table
If one of these events arrives in the middle of a key sequence---that
after they are read, and this is the way for the event's definition to
find the actual event.
-The events types @code{iconify-frame}, @code{make-frame-visible} and
-@code{delete-frame} are normally handled in this way. The keymap which
+The events types @code{iconify-frame}, @code{make-frame-visible},
+@code{delete-frame}, @code{drag-n-drop}, and user signals like
+@code{sigusr1} are normally handled in this way. The keymap which
defines how to handle special events---and which events are special---is
in the variable @code{special-event-map} (@pxref{Active Keymaps}).