IntersectionObserver root rect with padding is incorrect if there's overflow clipping.

johannesodland · Ahmad Saleem · commit 30ee8b0124be · 2025-12-11T08:05:24.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=263316 Reviewed by Simon Fraser. Switch from using contentBoxRect to paddingBoxRect according to discussion in w3c/IntersectionObserver#504 * LayoutTests/imported/w3c/web-platform-tests/intersection-observer/padding-clip-expected.txt: * Source/WebCore/page/IntersectionObserver.cpp: (WebCore::IntersectionObserver::computeIntersectionState const): Canonical link: https://commits.webkit.org/304296@main
diff --git a/LayoutTests/imported/w3c/web-platform-tests/intersection-observer/padding-clip-expected.txt b/LayoutTests/imported/w3c/web-platform-tests/intersection-observer/padding-clip-expected.txt
@@ -1,3 +1,3 @@
 
-FAIL Scrollport is used rather than content rect to compute intersection ratio assert_equals: Should be completely visible. expected 1 but got 0.6399999856948853
+PASS Scrollport is used rather than content rect to compute intersection ratio
 
diff --git a/Source/WebCore/page/IntersectionObserver.cpp b/Source/WebCore/page/IntersectionObserver.cpp
@@ -442,7 +442,7 @@ auto IntersectionObserver::computeIntersectionState(const IntersectionObserverRe
             if (root() == &target.document())
                 intersectionState.rootBounds = layoutViewportRectForIntersection();
             else if (rootRenderer->hasNonVisibleOverflow())
-                intersectionState.rootBounds = rootRenderer->contentBoxRect();
+                intersectionState.rootBounds = rootRenderer->paddingBoxRect();
             else
                 intersectionState.rootBounds = { FloatPoint(), rootRenderer->size() };
 

Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,3 @@`
`1`	`1`
`2`		`-FAIL Scrollport is used rather than content rect to compute intersection ratio assert_equals: Should be completely visible. expected 1 but got 0.6399999856948853`
	`2`	`+PASS Scrollport is used rather than content rect to compute intersection ratio`
`3`	`3`