[Xcb] xcb_present_notify_msc

Ravi Agnihotri ravi5208 at gmail.com
Tue Apr 26 13:03:34 UTC 2016


Hope you can help my understanding.

Firstly, when calling xcb_present_notify_msc() what is the meaning of the

That if I wish to determine the current MSC value would I sent this to 0?

xcb_present_notify_msc(c, win, 0, 0, 0, 0);

By way of some background. Application rendering to offscreen double
buffers that are consumed by a compositor using triple buffering. When the
app renders to the offscreen buffers it needs to be aware of when the
buffers are consumed and hence able to be reused.

What I don't understand is, when does the CRTC MSC value get updated, that
is, should this happen on a vsync boundary only when a flip happens trigger
in this case by the compositor. My assumption is that this is what should
happen so that you can just add 1 to the returned MSC value and use this
for the target_msc when you really do have something. This should therefore
tie the applications back buffers that are rendered to the appropriate
compositor render.

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