Bug 49224 – [Chromium] Text jitter during 2D CSS transform

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Mihai Parparita]

Created attachment 73307 [details]
Test case

With Chrome 9.0.572.0 on Snow Leopard, the attached test case (which triggers a 2D rotation on hover) exhibits text jitter during the transition. WebKit nightlies do not.

I showed this to James, he wasn't sure if WebKit/Mac also uses the compositor but is better about text rendering, or if they're not ending up on their compositor code path in the first place.

[Nico Weber]

I bet this is a dupe of http://crbug.com/61647 . Looks like we just don't tell the context that it's ok to do subpixel aa.

[Mihai Parparita]

This may be related to http://crbug.com/57645, which was recently fixed. Is that change in the current dev channel? The last comments claims that it is, but http://nettuts.s3.amazonaws.com/771_sticky/step5.html still has (similar) flicker during transitions.

[Nico Weber]

http://crbug.com/57645 is fixed, the fix is on the dev channel, and it's unrelated. See comment 1.

[Nico Weber]

Created attachment 73426 [details]
Patch

[Nico Weber]

The patch also fixes http://code.google.com/p/chromium/issues/detail?id=61647 and http://code.google.com/p/chromium/issues/detail?id=60587

[Kenneth Russell]

Comment on attachment 73426 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=73426&action=review

> WebCore/platform/graphics/chromium/ContentLayerChromium.cpp:-88
> -#if PLATFORM(SKIA)
>          "  gl_FragColor = vec4(texColor.z, texColor.y, texColor.x, texColor.w) * alpha; \n"
> -#elif PLATFORM(CG)
> -        "  gl_FragColor = vec4(texColor.x, texColor.y, texColor.z, texColor.w) * alpha; \n"
> -#else
> -#error "Need to implement for your platform."
> -#endif

Could you also update the comment at the top of this block (not in this review)?

[Nico Weber]

Created attachment 73429 [details]
Patch

[Kenneth Russell]

Comment on attachment 73429 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=73429&action=review

Looks fine. One minor typo in comment; can fix upon commit.

> WebCore/platform/graphics/chromium/ContentLayerChromium.cpp:71
> +    // Color is in uses BGRA order.

Typo: "in uses BGRA" -> "in BGRA"

[Nico Weber]

Created attachment 73432 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 73432 [details]
Patch

Clearing flags on attachment: 73432

Committed r71717: <http://trac.webkit.org/changeset/71717>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.