[Webkit-unassigned] [Bug 51928] [chromium] Enable reuse of RenderSurface for drawing.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=51928


Vincent Scheib <scheib at chromium.org> changed:

           What    |Removed                     |Added
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                 CC|                            |enne at google.com




--- Comment #11 from Vincent Scheib <scheib at chromium.org>  2011-01-07 10:08:32 PST ---
(In reply to comment #10)
> (In reply to comment #8)
> > This change seems to violate the comment above it:
> > 
> >     // Mask out writes to alpha channel: subpixel antialiasing via Skia results in invalid
> >     // zero alpha values on text glyphs. The root layer is always opaque.
> >     m_context->colorMask(true, true, true, false);
> > 
> > Either this change is wrong, or the comment is wrong.  Vangelis, what do you think?
> 
> I've moved the comment along with the change to the color mask, but I do not know about the origin of the comment.
> 
> I'm happy to prepare a test-patch people could apply to ToT to see for themselves the difference between leaving the alpha mask on and off, if that would help. As mentioned earlier, so far it's just the one test case I know of that triggers it.


The comment originated with a change I made to remove zero values from the alpha channel. Writing to the alpha channel is momentarily disabled:
http://trac.webkit.org/changeset/69266
+    // Mask out writes to alpha channel: ClearType via Skia results in invalid
+    // zero alpha values on text glyphs. The root layer is always opaque.
+    GLC(m_context, m_context->colorMask(true, true, true, false));
     TransformationMatrix layerMatrix;
     layerMatrix.translate3d( ... );
     LayerChromium::drawTexturedQuad( ... );
+    GLC(m_context, m_context->colorMask(true, true, true, true));

A trivial change, then this change that modified logic and comment:
http://trac.webkit.org/changeset/74568
The color mask is modified to only ever be set to false for alpha.

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