EGL apps (like Chrome/Chromium) in Xmir (in DRI2 mode): Page contents never visible, all black, all white, or flickering

[Daniel van Vugt]

Chromium browser in Xmir (in DRI2 mode): Page contents never visible (all white) and/or all black windows

DRI2 mode is the default mode for Xmir on desktop and it fails in similar ways for both rootless and non-rootless Xmir. In chromium-browser, fully loaded pages often display as all white. Or you get the whole window being black.

In both cases for -rootless and non-rootless mode, using the software rendering fallback works around the problem:
   Xmir -sw

[Daniel van Vugt (vanvugt)]

These errors might be related:

$ chromium-browser
[8933:8933:1026/181138:ERROR:sync_control_vsync_provider.cc(60)] glXGetSyncValuesOML should not return TRUE with a media stream counter of 0.
[8933:8933:1026/181141:ERROR:sync_control_vsync_provider.cc(60)] glXGetSyncValuesOML should not return TRUE with a media stream counter of 0.
[8933:8933:1026/181152:ERROR:sync_control_vsync_provider.cc(60)] glXGetSyncValuesOML should not return TRUE with a media stream counter of 0.

[Daniel van Vugt (vanvugt)]

Fixed the above error messages yesterday but they are benign and not related to this bug.

I did however discover the same black flashing happens in the Unity 'system-settings' app when run through Xmir.

[Daniel van Vugt (vanvugt)]

Chromium seems to be very dependent on:
   https://www.opengl.org/registry/specs/OML/glx_sync_control.txt
which Xmir doesn't implement yet.

I'm working on a solution to this in Mir that will allow it to be implemented correctly in Xmir.

[Daniel van Vugt (vanvugt)]

I don't think the original description applies any more (since Chrome moved from GLX to EGL?)

What is still a problem is the black flickering in some GL apps, as can be seen in system-settings.

[kevin gunn (kgunn72)]

Fwiw, I was testing in the following manner
Zesty, fresh install unity8 deb based session, snap installed chrome (chrome-test)
Chrome launches fine but in terms of usability I saw massive flickering
with silo https://bileto.ubuntu.com/#/ticket/2383

Without that silo, there is still some out-of-order framerendering (for instance, a progress bar within a web page will take 2 steps fwd, 1 step back visually)
also, you can "feel" this when typing as letters will temporarily disappear just after typing.
Also, adding a tab causes chrome to crash

[Daniel van Vugt (vanvugt)]

Now that you mention it, that sounds like bug 1511278 which is probably related. Made progress on that last year with a proof of concept workaround. Essentially I think this is related to the fact that Xorg expects and requires single buffering (or at least back buffer preservation), but Mir supports neither of those yet.

[Daniel van Vugt (vanvugt)]

Fix/workaround for Chrome/Chromium committed at least:
https://git.launchpad.net/~xmir-team/xorg-server/+git/xmir/commit/?id=5ffed6c449b55ceebae193e22ecfc9377a87078c