Bug 134950 – Subpixel rendering: Adjust cliprect with devicePixelFractionFromRenderer() before painting.

• Status: RESOLVED
• Resolution: FIXED
• Component: Layout and Rendering

[zalan]

It breaks painting when the compositing layer has tiled layering.
 
This is a workaround until bug 134947 gets fixed.

[zalan]

<rdar://problem/17617994>

[zalan]

Created attachment 234963 [details]
Patch

[zalan]

Created attachment 234964 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 234964 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=234964&action=review

> Source/WebCore/ChangeLog:9
> +        When the compositing layer has tiled layering, offsetting the cliprect with the subpixel accumulation

"has tiled layering" -> "is tiled".

> Source/WebCore/ChangeLog:10
> +        leaves a line of one device pixel gap on the non-leftmost tiles. It's because leftmost tiles get

leaves single device-pixel gap

> Source/WebCore/rendering/RenderLayer.cpp:1697
> +        // FIXME: Moving the cliprect by subPixelAccumulation requires to get IntRect enclosing removed from clipping/dirtyPaintRect.

"requires removal of the enclosingIntRect code from..."

> Source/WebCore/rendering/RenderLayer.cpp:3596
> +        if (!paintingInfo.subPixelAccumulation.isEmpty())
> +            adjustedClipRect.expand(paintingInfo.subPixelAccumulation);

I'm not sure I agree with this expanding here. You're fixing a bug specific to tiled layers with a change that affects clipping in all composited layers, and may actually result in incorrect clipping.

[zalan]

Created attachment 235030 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 235030 [details]
Patch

Clearing flags on attachment: 235030

Committed r171165: <http://trac.webkit.org/changeset/171165>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.