21.9 Special Events

Certain special events are handled at a very low level—as soon as they are read. The read-event function processes these events itself, and never returns them. Instead, it keeps waiting for the first event that is not special and returns that one.

Special events do not echo, they are never grouped into key sequences, and they never appear in the value of last-command-event or (this-command-keys). They do not discard a numeric argument, they cannot be unread with unread-command-events, they may not appear in a keyboard macro, and they are not recorded in a keyboard macro while you are defining one.

Special events do, however, appear in last-input-event immediately after they are read, and this is the way for the event’s definition to find the actual event.

The events types iconify-frame, make-frame-visible, delete-frame, drag-n-drop, language-change, and user signals like 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 special-event-map (see Controlling Active Maps).