[webkit-qt] [QtWebKit] Issues with WebGL on top of DirectFBGL

david.corvoysier at orange.com david.corvoysier at orange.com
Fri Oct 21 02:52:50 PDT 2011

> - have you considered using a QGLPixelBuffer instead of a QGLWidget
for WebGL ? If yes why did you choose the latter ?
>I think QGLWidget was a bit more straightforward - you just share the
context with the parent and use an FBO. For most use cases this does not
cause drawing issues.

Actually, we are still using the WebGL FBO, but the context is created
by a QGLPixelBuffer and not a QGLWidget: it requires only a small change
at initialization, and we don't need to allocate another eglsurface
(which was what we couldn't do on our target).

>It's probably possible to implement this with a pixel buffer as well -
though how would that work in a cross process environment? 
>Right now my thoughts for WebKit2 are to either use EGL images (with
Mesa for desktop) or streamline GL commands to the UI process.

Since as I said we still use a FBO, there is no difference in
implementation with the QGLWidget approach.
That said, I haven't looked much into WebKit2, but my understanding is
that the rendering and composition (UI) processes are separated. I
assume that layers are prepared in the rendering processes, and at some
point you pass an 'image' and a geometric transformation to the
composition process (very much like in the texture mapper). The main
question is how you make your intermediate rendering available to the
composition process: you can use shared memory if you have a system
buffer, but if your rendering has been done by the gpu, you may want to
avoid the soft copy: this can be achieved more easily on the desktop
(Mesa/DRI) than on embedded targets, where you will probably have to
rely on proprietary mechanisms. The other option is as you said to
streamline GL commands to the UI process. This is probably a bit more
complicated (but chrome has an implementation for that already if I
remember well how their own gpu process works), and you gain the ability
to further isolate the rendering processes: imagine for instance that
you want to restrict the gpu access to the UI process only for security

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