The current returned value of XCBFlush is 0 on success, <= 0 otherwise. Maybe it would be better to have standard returned value (0 on failure, 1 on success)
This is already fixed in the current implementation -- I committed the change on Feb 23rd, 2006. The documentation needs to be updated, though: if you could do that, that'd be great.
Fixed on XcbApi wiki page.
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