Events can be sent at any time, not necessarily when the client is ready to recieve an event. Therefore they must be stored temporarily from that they are read from the network until the client is ready to handle them. Read but unhandled events are stored on an event queue in the Display object. There are two functions to access this queue:
Return the next event in the event queue. If the event queue is empty, block until an event is read from the network, and return that one.
Return the number of events which can be returned without blocking.
A trivial event loop would simply loop infinitely, waiting for an event and then handling it. It could look like this:
while 1: event = disp.next_event() handle_event(event)
However, most applications need more control, e.g. to simultaneously
handle a network connection or at regular intervals schedule timeouts.
select is often used for this.
can be used with
select, since they have the required
fileno() method. When
select indicates that a
Display object is ready for reading, that means that the server
has sent some data to the client. That alone doesn't guarantee that an
entire event has arrived, so one must first use
to make sure that
next_event() will return without blocking. A
simple event loop which waits for events or a one-second timeout looks
while 1: # Wait for display to send something, or a timeout of one second readable, w, e = select.select([disp], , , 1) # if no files are ready to be read, it's an timeout if not readable: handle_timeout() # if display is readable, handle as many events as have been recieved elif disp in readable: i = disp.pending_events() while i > 0: event = disp.next_event() handle_event(event) i = i - 1 # loop around to wait for more things to happen
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