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Introduce a variant of xcb_poll_for_event for examining event queue. 

In some circumstances using xcb_poll_for_event is suboptimal because
it checks the connection for new events. This may lead to a lot of
failed nonblocking read system calls.

Signed-off-by: Rami Ylimäki <rami.ylimaki@vincit.fi>
Signed-off-by: Jamey Sharp <jamey@minilop.net>
This commit is contained in:
Rami Ylimäki 2011-03-22 14:33:23 +02:00 committed by Jamey Sharp
parent b64cd0df88
commit 527df3c84b
2 changed files with 28 additions and 2 deletions
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16
src/xcb.h
View File

@ -271,6 +271,22 @@ xcb_generic_event_t *xcb_wait_for_event(xcb_connection_t *c);
*/
xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c);
/**
* @brief Returns the next event without reading from the connection.
* @param c: The connection to the X server.
* @return The next already queued event from the server.
*
* This is a version of xcb_poll_for_event that only examines the
* event queue for new events. The function doesn't try to read new
* events from the connection if no queued events are found.
*
* This function is useful for callers that know in advance that all
* interesting events have already been read from the connection. For
* example, callers might use xcb_wait_for_reply and be interested
* only of events that preceded a specific reply.
*/
xcb_generic_event_t *xcb_poll_for_queued_event(xcb_connection_t *c);
/**
* @brief Returns the next event or error that precedes the given request.
* @param c: The connection to the X server.

14
src/xcb_in.c
View File

@ -535,7 +535,7 @@ xcb_generic_event_t *xcb_wait_for_event(xcb_connection_t *c)
return ret;
}
xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)
static xcb_generic_event_t *poll_for_next_event(xcb_connection_t *c, int queued)
{
xcb_generic_event_t *ret = 0;
if(!c->has_error)
@ -543,13 +543,23 @@ xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)
pthread_mutex_lock(&c->iolock);
/* FIXME: follow X meets Z architecture changes. */
ret = get_event(c);
if(!ret && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
if(!ret && !queued && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
ret = get_event(c);
pthread_mutex_unlock(&c->iolock);
}
return ret;
}
xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)
{
return poll_for_next_event(c, 0);
}
xcb_generic_event_t *xcb_poll_for_queued_event(xcb_connection_t *c)
{
return poll_for_next_event(c, 1);
}
static xcb_generic_event_t *get_event_until(xcb_connection_t *c, uint64_t request)
{
if(c->in.events && XCB_SEQUENCE_COMPARE(c->in.events->sequence, <=, request))