[Xcb] Why is an explicit xcb_flush needed?

[Nicholas Allen]

Hi,

I'm just curious as to why adding xcb_flush prior to xcb_wait_for_event
fixes most of my deadlocking issues. I would have thought that XCB would
flush automatically if it needs a reply for synchronous usage.

To me it seems like a bug in XCB that I need to explicitly call
xcb_flush before xcb_wait_for_reply but maybe I just don't understand
the design of XCB well enough. Sorry if this is a silly question but I
would like to start understanding what's causing my problems in order to
fix it...

Cheers,

Nick