[webkit-qt] WebGL on Qt5-Beta1

Ganesh S ganesh.sathyanarayanan at gmail.com
Tue Nov 6 02:15:30 PST 2012


I am running Qt5-Beta1 on mips platform using eglfs plugin.

I am trying to run a simple WebGL example such as

However, in the section where am supposed to see an animated triangle, I
see a static image with strange symbols (such "&", mouse cursors etc). The
image isn't random - always the same image appears.

I do not use the webkit that comes with the Qt source archive, although I
tried that, and the issue occurred in that too. I use a particular version
of webkit from the mainline stream (webkit.org). I have also tried the very
latest git-clone of qt5, and its webkit, and that has the issue too.

Note that when I build the same webkit source-base as above with a Qt 4.8
installation (QWS mode with eglnullws), WebGL works fine, and am able to
see the animated triangle. Other WebGL demos also seem to run okay.

So one would think the issue does not lie in webkit, but I tried to debug
the issue to see the call stack and noticed the below.

For normal update of the WebView:
QGLContext::makeCurrent() ==> QOpenGLContext::makeCurrent()
==> QEGLPlatformContext::makeCurrent() ==> eglMakeCurrent()
This is followed by calls to eglSwapBuffers() in a similar call hierarchy
and then doneCurrent()

For the EglFSWindow that is opened to render the WebGL, I was able to
observe such a call hierarchy only for makeCurrent(). There were no
following calls to swapBuffers().
==> QOpenGLContext::makeCurrent() ==> QEGLPlatformContext::makeCurrent()
==> eglMakeCurrent()

The call to the ultimate eglMakeCurrent() does indeed return true. I
grepped for swapBuffers() within webkit, but could not find one for the Qt

I am not exactly sure how to proceed, as calls to
m_platformContext->swapBuffers() manually leads to hangs and/or crashes.
If you have faced a similar issue, or have any suggestions for me to go
fwd, please let me know

Thank you for your time

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