DRI2GetMSC: Do not send a bogus ust for when the drawable is not displayed

According to the opengl glx_sync_control spec, the Unadjusted System Time
(or UST) is a 64-bit monotonically increasing counter that is available
throughout the system:
http://www.opengl.org/registry/specs/OML/glx_sync_control.txt

Therefore, sending 0, even in this corner case, is out of spec. However,
we cannot just return FALSE here as that triggers a BadDrawable error to
be sent, and as is often the case mishandled, to the client. This results
in a certain compositor terminating, for example.

As an alternative we can use the monotonic system timestamp which in
theory should also be monotonic with the previous and subsequent vblank
times.

Based on a patch by Daniel Kurtz.

Reported-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

0 files changed, 0 insertions, 0 deletions