xcb: Remove useless flushes

Calling xcb_flush() right before QXcbConnection::sync() is pointless.
The flush sends all requests that were already queued to the server and
the call to sync() then just sends another request, flushes it and waits
for its reply. Having just sync() implicitly flush for us means less
overhead and has the same effect.

Another useless flush is in QXcbShmImage::put(). The only caller is
QXcbBackingStore::flush() and this calls put() in a loop. If we just
call xcb_flush() from flush(), then xcb can send more requests in a
single write() call again.

Finally, calling Q_XCB_NOOP() twice in a row without doing any
interaction with xcb in between doesn't help much, so remove one of the
two calls from QXcbShmImage::put()

Change-Id: Ia3d6945b8d961e2844fc3e31fdf8189c47b534d1
Signed-off-by: Uli Schlachter <psychon@znc.in>
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>

0 files changed, 0 insertions, 0 deletions