mailbox-wait-for-event mailbox &key wait-reason wait-function process-other-messages-p no-hang-p stop-at-user-operation-p => event
The function
mailbox-wait-for-event
waits for an event in a mailbox in a "windowing friendly" way. It reads an event from the mailbox
mailbox
. If there is no event in the mailbox, it waits for an event (unless
no-hang-p
is true).
The value
event
is any object that was put in the mailbox, or
nil
if the mailbox is empty, possibly after waiting.
mailbox-wait-for-event
is the appropriate way to wait for an event in a mailbox in an application with a graphical user interface, because it interacts correctly with the windowing system. Most importantly, on Microsoft Windows, when
process-other-messages-p
is true it processes Windows messages while it is waiting. The default value of
process-other-messages-p
is
t
.
wait-function
is the wait function to be used, which is called with the mailbox
mailbox
as its argument. If
wait-function
is not supplied, a function that returns
t
when the mailbox is not empty is used is used internally.
wait-reason is used as the wait reason if it needs to wait. The default value of wait-reason is "Waiting for an event".
process-other-messages-p controls processing of other messages. On Microsoft Windows this means Windows messages. On other platforms it has no effect.
no-hang-p
controls whether
mailbox-wait-for-event
should really wait. If
no-hang-p
is true and there is no event, it returns immediately except on Microsoft Windows, where it may first process all Windows messages (depending on the value of
process-other-messages-p
). The default value of
no-hang-p
is
nil
.
stop-at-user-operation-p
on Microsoft Windows causes
mailbox-wait-for-event
to return if it received a user operation message (meaning keyboard or mouse input). It has no effect on other platforms. The default value of
stop-at-user-operation-p
is
nil
.
If
mailbox-wait-for-event
is called when not Lisp is not multiprocessing, it returns immediately. The return value is an event or
nil
.