Bug 236800 – drop-shadow filter doesn't work correctly in tiled backing layer

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Fujii Hironori]

drop-shadow filter doesn't work correctly in tiled backing layer

[Fujii Hironori]

Created attachment 452412 [details]
test case (for low DPI display)

[Fujii Hironori]

Created attachment 452415 [details]
[screenshot] STP 140

[Fujii Hironori]

Created attachment 452416 [details]
[screenshot] GTK port

[Simon Fraser (smfr)]

There are a number of existing bugs about drop-shadow repaints. This is probably a dup.

[Fujii Hironori]

This is not a drop-shadow repainting issue. If the element is painted in another tile, the drop-shadow can't be drawn.

[Fujii Hironori]

Created attachment 452430 [details]
test case 2

This issue doesn't need tiled backed layer.
If the element is placed outside of the view, its drop-shadow isn't painted.

[Radar WebKit Bug Importer]

<rdar://problem/89382612>

[Fujii Hironori]

Created attachment 453816 [details]
WIP patch

[Fujii Hironori]

Created attachment 453934 [details]
WIP patch

[Fujii Hironori]

Created attachment 453937 [details]
WIP patch

[Fujii Hironori]

https://github.com/web-platform-tests/wpt/pull/33080

[Simon Fraser (smfr)]

I think I may end up fixing this via bug 207586

[Simon Fraser (smfr)]

I tested, and the patch in 207586 fixes the testcase.

[Fujii Hironori]

(In reply to Simon Fraser (smfr) from comment #13)
> I tested, and the patch in 207586 fixes the testcase.

Unfortunately, your patch (attachment#454007 [details]) doesn't fix this test https://github.com/web-platform-tests/wpt/pull/33080

[Simon Fraser (smfr)]

Seems like we need both fixes.

[Simon Fraser (smfr)]

Comment on attachment 453937 [details]
WIP patch

View in context: https://bugs.webkit.org/attachment.cgi?id=453937&action=review

> Source/WebCore/rendering/RenderLayerFilters.cpp:149
> +        LayoutBoxExtent flippedOutsets { outsets.bottom(), outsets.left(), outsets.top(), outsets.right() };

Why the flipping?

[Fujii Hironori]

Comment on attachment 453937 [details]
WIP patch

View in context: https://bugs.webkit.org/attachment.cgi?id=453937&action=review

>> Source/WebCore/rendering/RenderLayerFilters.cpp:149
>> +        LayoutBoxExtent flippedOutsets { outsets.bottom(), outsets.left(), outsets.top(), outsets.right() };
> 
> Why the flipping?

If the drop-shadow is cast to the right direction, dirtyRect needs to be extended to left direction to calculate targetBoundingBox.

[Fujii Hironori]

Created attachment 454557 [details]
Patch

[EWS Watchlist]

This patch modifies the imported WPT tests. Please ensure that any changes on the tests (not coming from a WPT import) are exported to WPT. Please see https://trac.webkit.org/wiki/WPTExportProcess

[Fujii Hironori]

Created attachment 454620 [details]
Patch for landing

[Alexey Proskuryakov]

Comment on attachment 454620 [details]
Patch for landing

View in context: https://bugs.webkit.org/attachment.cgi?id=454620&action=review

> LayoutTests/platform/ios-wk2/TestExpectations:2223
> +webkit.org/b/237849 imported/w3c/web-platform-tests/css/filter-effects/filters-drop-shadow-003.html [ ImageOnlyFailure ]

Why is it OK to land with this? Seems like a a big problem for this change to not have a test that starts to pass on iOS.

[Fujii Hironori]

Comment on attachment 454620 [details]
Patch for landing

View in context: https://bugs.webkit.org/attachment.cgi?id=454620&action=review

>> LayoutTests/platform/ios-wk2/TestExpectations:2223
>> +webkit.org/b/237849 imported/w3c/web-platform-tests/css/filter-effects/filters-drop-shadow-003.html [ ImageOnlyFailure ]
> 
> Why is it OK to land with this? Seems like a a big problem for this change to not have a test that starts to pass on iOS.

I don’t think it’s a big problem. iOS has one more problem. This isn’t sufficient for it.

[Alexey Proskuryakov]

I'm not saying that you need to fix all bugs that impact web-platform-tests/css/filter-effects/filters-drop-shadow-003.html in this patch. What I am saying is that I see it as a problem to land a fix that doesn't make any tests go from failing to passing on iOS.

[Fujii Hironori]

Created attachment 455989 [details]
Patch for landing

[Fujii Hironori]

Created attachment 455990 [details]
drop-shadow-in-tiled-backing.html

[EWS]

Committed r292059 (248994@main): <https://commits.webkit.org/248994@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 455989 [details].