[CSS Regions] Elements with overflow:auto are not painted inside regions when following a float

[Radu Stavila]

Created attachment 228502 [details]
Test-case

Elements with overflow:auto are not painted inside regions when following a float. See attached test-case. The blue div should be painted next to the float but it doesn't appear at all.

[Radu Stavila]

Further findings:
1. Adding margin-left to the overflow:auto element causes it to appear. However, hit-testing inside it is not working.
2. Setting scrollbar preferences to always show causes the element to appear. The float before it now has a strange disabled scrollbar. The same as above, hit-testing is not working in the overflow:auto element.

[Radu Stavila]

Created attachment 230822 [details]
Patch

[Radu Stavila]

Added patch for the painting of the overflow:auto elements.

Additional issues:
- invalid scrollbar appears in some situations: https://bugs.webkit.org/show_bug.cgi?id=132562
- hit-testing does not work properly on the overflow:auto element: https://bugs.webkit.org/show_bug.cgi?id=132563

[Dave Hyatt]

Comment on attachment 230822 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=230822&action=review

r-

> Source/WebCore/rendering/RenderLayer.cpp:5657
> +            // Boxes inside flow threads don't have their logical left computed to avoid
> +            // floats. Instead, that information is kept in their RenderBoxRegionInfo structure.
> +            // As such, the layer bounds must be enlarged to encompass their background rect
> +            // to ensure intersecting them won't result in an empty rect, which would eventually
> +            // cause paint rejection.
> +            if (flowThread) {
> +                if (flowThread->style().isHorizontalWritingMode())
> +                    layerBounds.shiftMaxXEdgeTo(std::max(layerBounds.maxX(), backgroundRect.rect().maxX()));
> +                else
> +                    layerBounds.shiftMaxYEdgeTo(std::max(layerBounds.maxY(), backgroundRect.rect().maxY()));
> +            }

Don't run this code for columns, so change to if (flowThread && flowThread->isNamedRenderFlowThread())

[Radu Stavila]

Created attachment 230830 [details]
Patch implementing reviewer feedback

[Radu Stavila]

Created attachment 230831 [details]
Patch implementing reviewer feedback

[Dave Hyatt]

Comment on attachment 230831 [details]
Patch implementing reviewer feedback

r=me

[WebKit Commit Bot]

Comment on attachment 230831 [details]
Patch implementing reviewer feedback

Clearing flags on attachment: 230831

Committed r168288: <http://trac.webkit.org/changeset/168288>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.