[Webkit-unassigned] [Bug 52311] [chromium] Add command-line flag to enable composite to offscreen texture.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=52311





--- Comment #41 from Vangelis Kokkevis <vangelis at chromium.org>  2011-01-19 13:53:26 PST ---
(In reply to comment #38)
> (In reply to comment #35)
> > (From update of attachment 79326 [details] [details])
> > View in context: https://bugs.webkit.org/attachment.cgi?id=79326&action=review
> > 
> > > Source/WebCore/platform/graphics/chromium/LayerRendererChromium.cpp:732
> > > +    IntRect contentRect(m_defaultRenderSurface->m_contentRect);
> > 
> > To avoid double assignment you could write this as:
> > IntRect contentRect = (m_currentRenderSurface ? m_currentRenderSurface->m_contentRect : m_defaultRenderSurface->m_contentRect)
> 
> Thanks ... I always seem to forget that assignment in a declaration invokes the copy-constructor.
> 
> (In reply to comment #36)
> 
> >I think there's a good opportunity now that you're getting the assert to  understand what's going wrong here.  Clearing the framebuffer at init time seems to mostly work but I'm curious why (and why it causes that one failure) and whether it's masking some other problem.  
> >
> >Have you tried calling:
> 
> >m_context->colorMask(true, true, true, true)
> 
> >in copyOffscreenTextureToDisplay() before drawing ?  The texture attached to the m_defaultRenderSurface should have a clear alpha channel.
> 
> This helps in that I can remove the code that clears the display in initializeSharedObjects(); I have updated to do this and remove clearFramebuffer() as it is not used now.
> 
> However, it doesn't clear up why we are getting those sporadic intensity changes. I suspect somehow the alpha channel is behind this, but I haven't figured out where/how this happens. I wondered if the call to clear() in drawLayers() might be somehow treating the texture differently from the display, although I can find no evidence for this.

Also, are the differences now limited to the color channels?  Is alpha always 1.0? 


> 
> The two interesting features are:
> 
> 1) The sporadic pixels are most often (but not always) associated with text, and

Does it look like it's around the edges of letters?  I wonder if it's somehow caused by subpixel AA in text...

> 
> 2) their frequency tends to increase as x increases.

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