[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 #34 from W. James MacLean <wjmaclean at chromium.org>  2011-01-18 14:18:07 PST ---
(In reply to comment #33)
> Created an attachment (id=79326)
 --> (https://bugs.webkit.org/attachment.cgi?id=79326&action=review) [details]
> Patch

OK, this patch is an attempt to recover after the confusion of the last patch, where I suspect I was quite testing what I thought I was testing ...

Comments:

1) I have added a function called clearFramebuffer() to LayerRendererChromium and called it from initializeSharedObjects() to clear the display. Without this, a large number of tests fail on a Skia assertion

SkASSERT(r < a)

suggesting the alpha channel is unhappy. Placing it in initializeSharedObjects() means it gets cleared only once.

Question: is there any reason we should also do clearFramebuffer(m_offscreenFramebufferId)?

2) I have proposed a fix for setScissorRect() for the use case useRenderSurface(0) ... let me know if using thew contentRect from m_defaultRenderSurface seems correct. It seems to display OK for all cases I've tried.

3) Similarly, I've had to test for renderSurface == 0 in useRenderSurface and default to setting the drawViewPortRect according to m_defaultRenderSurface when renderSurface is 0.

4) A small number of test cases seem to have slight changes in pixel intensities --- imperceptible to my eye --- that seem to again be related to alpha channel values. One in particular, compositing/iframes/composited-iframe-alignment.html, tests fine if I delete the line clearFramebuffer(0) from initializeSharedObjects(), but this of course messes up a bunch of other tests (see (1)).

I would like to proceed with the patch despite these tests (can we temporarily mark them as expected-fail for offscreen compositing, or rebaseline for the offscreen case?). I will continue to try and hunt down the cause, but I think this will be easier once offscreen-compositing is part of the test suite (to prevent any other regressions).

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