Bug 96586 – Borders for rounded rects should be rendered with antialias on

• Component: Layout and Rendering
• Status: RESOLVED CONFIGURATION CHANGED

[KyungTae Kim]

On RenderBoxModelObject::clipBorderSidePolygon, borders for RenderBox rendered as 4 convex polygons.
When the convex polygons are clipped, antialias is set by  the border matches its adjacent sides or not.

But for rounded rects, the borders should be rendered with antialias on,
because the rounded edge can be aliased,
and  mismatch between border and contents can happen because the rounded rects contents always rendered with antialias on.

[Alexey Proskuryakov]

Do you have a test case where this is causing issues?

[KyungTae Kim]

Created attachment 164064 [details]
Patch

[KyungTae Kim]

I found the bug on mobile browser.
When zoomed out to very small zoom ratio,
the contents and the border was mismatched because the border was drawn as AA off and the contents was drawn as AA on.
But I couldn't find or make a suitable layouttest test case because on PC browsers, 
zoom is done by relayouting.
In this case, what kind of test case is needed?

[WebKit Review Bot]

Comment on attachment 164064 [details]
Patch

Attachment 164064 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/13849475

New failing tests:
fast/borders/border-radius-groove-03.html
fast/borders/border-radius-groove-01.html
fast/borders/borderRadiusDotted02.html
fast/borders/borderRadiusDashed04.html
fast/backgrounds/background-leakage.html
fast/borders/border-radius-wide-border-04.html
fast/borders/borderRadiusDashed02.html
fast/borders/borderRadiusDashed01.html
fast/borders/borderRadiusAllStylesAllCorners.html
fast/borders/borderRadiusDashed03.html
fast/borders/border-radius-wide-border-02.html
fast/borders/borderRadiusDotted03.html
fast/borders/borderRadiusDotted05.html
fast/borders/borderRadiusArcs01.html
fast/borders/borderRadiusDouble05.html
fast/borders/border-radius-wide-border-03.html
fast/borders/borderRadiusDotted06.html
fast/borders/border-radius-inset-outset.html
fast/borders/borderRadiusDouble07.html
fast/borders/borderRadiusDouble06.html
fast/borders/border-styles-split.html
fast/box-shadow/inset.html
fast/borders/borderRadiusDouble04.html
fast/borders/borderRadiusDouble02.html
fast/borders/borderRadiusDashed05.html
fast/backgrounds/background-leakage-transforms.html
fast/borders/borderRadiusDotted04.html
fast/borders/borderRadiusDouble01.html
fast/borders/borderRadiusDouble03.html
fast/borders/border-radius-groove-02.html

[Eric Seidel (no email)]

Could you post a demonstration page?  We have tools to see the individual pixels, but your'e correct, we don't have layout-less pinch-zoom in the browser on the desktop.  A demonstration page would help as we could view it on mobile if necessary too.

[KyungTae Kim]

Created attachment 164342 [details]
test page that the border is not displayed because of the mismatch of AA settings of border and fillcolor

[KyungTae Kim]

Created attachment 164345 [details]
screenshot of the testpage

[Andreas Kling]

Comment on attachment 164064 [details]
Patch

Clearing review flag on patches from before 2014. If this patch is still relevant, please reset the r? flag.

[Simon Fraser (smfr)]

I don't think this bug occurs any more.