Bug 64584 – Avoid rounded rect corner-drawing overhead if no corners are visible

• Status: RESOLVED
• Resolution: FIXED
• Component: WebCore Misc.

[Ian Henderson]

We fall into a slow path when drawing a border for an element with nonzero border-radius.  If the rounded corners are outside the clip rect, however, we can set their radius to zero without visual effect.

[Ian Henderson]

Created attachment 100939 [details]
proposed patch

[Ian Henderson]

<rdar://problem/9326550>

[Simon Fraser (smfr)]

Comment on attachment 100939 [details]
proposed patch

View in context: https://bugs.webkit.org/attachment.cgi?id=100939&action=review

Let's see one more version. I'd also like to see an interactive testcase attached to the bug (maybe a roundrect inside a scrollable overflow region) so that behavior can be checked manually.

> Source/WebCore/ChangeLog:8
> +        No new tests, behavior is unaffected.

Well, behavior is affected, but not in a way that should affect visible rendering.

> Source/WebCore/rendering/RenderBoxModelObject.cpp:1425
> +    // If one of the corners falls outside the clip region, pretend it has no radius.

The comment should mention that this is done for performance reasons.

> Source/WebCore/rendering/RenderBoxModelObject.cpp:1450
> +        outerBorder.setRadii(adjustedOuterRadii);

You could avoid setting this if you didn't change any corners. I think you should also skip this entire block if rect is entirely inside the clip.

[Ian Henderson]

Created attachment 101007 [details]
test case

Here's a test case—normal, dotted, and dashed borders with positive border-radius in overflow: scroll divs.

[Ian Henderson]

Created attachment 101011 [details]
updated patch

Addressed Simon's comments and moved the corner-adjusting code into a separate static function.

[Simon Fraser (smfr)]

Comment on attachment 101011 [details]
updated patch

Nice.

[WebKit Review Bot]

Comment on attachment 101011 [details]
updated patch

Clearing flags on attachment: 101011

Committed r91090: <http://trac.webkit.org/changeset/91090>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.