313721 2026-04-30 01:26:43 -0700 UseSkiaForComposition: compositing/update-compositing-rects-with-sharing-descendants.html fails 2026-05-04 03:11:02 -0700 1 1 1 Unclassified WebKit WebKitGTK WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED DoNotImportToRadar P2 Normal --- 1 fujii fujii bugs-noreply oldest_to_newest 2206144 0 fujii 2026-04-30 01:26:43 -0700 If UseSkiaForComposition is enabled, compositing/update-compositing-rects-with-sharing-descendants.html fails. 2206151 1 fujii 2026-04-30 01:45:33 -0700 Pull request: https://github.com/WebKit/WebKit/pull/63956 2206187 2 479387 fujii 2026-04-30 03:15:11 -0700 Created attachment 479387 test case 2206460 3 479407 fujii 2026-04-30 19:30:15 -0700 Created attachment 479407 test 2 2206497 4 479414 fujii 2026-04-30 23:18:35 -0700 Created attachment 479414 test 3 compositing/update-compositing-rects-with-sharing-descendants.html fails because the blue box isn't painted. However, with MiniBrowser, the blue box is painted. The difference between MiniBrowser and WebKitTestRunner is AsyncOverflowScrolling. By disabling AsyncOverflowScrolling, the artifact is reproducible with MiniBrowser. > ./Tools/Scripts/run-minibrowser --gtk --release --features=-AsyncOverflowScrolling ./LayoutTests/compositing/update-compositing-rects-with-sharing-descendants.html If AsyncOverflowScrolling is enabled, overflow:scroll div also gets a composited layer. And, the parent isolation:isolate layer and the child overflow:scroll layer overlaps. If overlap region is larger than non-overlap region, the non-overlap region is merged into the overlap region. https://github.com/WebKit/WebKit/blob/e3d5d9821fa8886c33382d72f35d0d201f24536f/Source/WebCore/platform/graphics/skia/SkiaCompositingLayer.cpp#L920-L925 This is the reason MiniBrowser paints the blue box. If I enlarge the blue box, MiniBrowser also doesn't paint the blue box. 2207137 5 ews-feeder 2026-05-04 03:10:59 -0700 Committed 312511@main (96de099fd31a): <https://commits.webkit.org/312511@main> Reviewed commits have been landed. Closing PR #63956 and removing active labels. 479387 2026-04-30 03:15:11 -0700 2026-04-30 03:15:11 -0700 test case isolate-layer.html text/html 4006 fujii PCFET0NUWVBFIEhUTUw+CjxzdHlsZT4KLnBsYWlkIHsKICAgYmFja2dyb3VuZDogbGluZWFyLWdy YWRpZW50KCNlNjY0NjUsICM5MTk4ZTUpOwp9Cjwvc3R5bGU+CjxodG1sIGNsYXNzPXBsYWlkPgoK ICA8cD4KICBZb3Ugc2hvdWxkIHNlZSBvbmx5IGJsdWUgYm94ZXMgb24gbGluZWFyIGdyYWRpZW50 IGJhY2tncm91bmQuCiAgPC9wPgoKPGRpdiBzdHlsZT0id2lkdGg6IDEyMHB4OyBoZWlnaHQ6IDEy MHB4OyBpc29sYXRpb246IGlzb2xhdGU7IGRpc3BsYXk6IGlubGluZS1ibG9jayI+CiAgPGRpdiBz dHlsZT0ibWl4LWJsZW5kLW1vZGU6IG5vcm1hbDsgd2lkdGg6IDEwMHB4OyBoZWlnaHQ6IDEwMHB4 OyBiYWNrZ3JvdW5kOiBibHVlOyB3aWxsLWNoYW5nZTogdHJhbnNmb3JtIj48L2Rpdj4KPC9kaXY+ Cgo8ZGl2IHN0eWxlPSJ3aWR0aDogMTIwcHg7IGhlaWdodDogMTIwcHg7IGlzb2xhdGlvbjogaXNv bGF0ZTsgZGlzcGxheTogaW5saW5lLWJsb2NrIj4KICA8ZGl2IHN0eWxlPSJtaXgtYmxlbmQtbW9k ZTogbXVsdGlwbHk7IHdpZHRoOiAxMDBweDsgaGVpZ2h0OiAxMDBweDsgYmFja2dyb3VuZDogYmx1 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