Dragging a selection into a pseudo element results in incorrect selection of the host element.

megangardner · megangardner · commit 7bfe33497d6e · 2025-12-18T18:26:32.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=304434 rdar://142905243 Reviewed by Tim Nguyen. We do not support selection in pseudo elements. So when we drag a selection across a pseudo element, and we set the inner node for the hit test, if it is a pseudo element, we set the node to the host element instead. However, when we do this, we did nothing to set the localPoint in that element to something that made sense. In the following illustration, 'Pseudo' is a pseudo element, 'Element' is the host element that is a regular div otherwise. Pseudo Element ^ ^ | | When the cursor is at 'e' in Pseudo, and the element is reset, the cursor is then effectively at the second 'e' in Element. If you started your selection after the first 'E' and dragged backwards, once you reached the 'e' in Pseudo, you selection would be 'le', not just the first 'E' as you would expect. To avoid this issue, when setting the local point we check to see if the pseudo element identifier has been set, and if so, we zero out the point instead of using the offset that is not longer applicable. Progressed imported/w3c/web-platform-tests/css/css-pseudo/text-selection.html * Source/WebCore/rendering/HitTestResult.cpp: (WebCore::HitTestResult::setLocalPoint): * Source/WebCore/rendering/HitTestResult.h: (WebCore::HitTestResult::setLocalPoint): Deleted. * Source/WebCore/rendering/RenderObject.cpp: (WebCore::RenderObject::updateHitTestResult const): Canonical link: https://commits.webkit.org/304719@main
diff --git a/LayoutTests/imported/w3c/web-platform-tests/css/css-pseudo/text-selection-expected.txt b/LayoutTests/imported/w3c/web-platform-tests/css/css-pseudo/text-selection-expected.txt
@@ -2,8 +2,8 @@ helloworld
 helloworld
 helloworld
 
-FAIL Selection ending in ::before assert_equals: toString expected "hello" but got "o"
-FAIL Selection contained in ::before assert_equals: toString expected "" but got "llo"
+PASS Selection ending in ::before
+PASS Selection contained in ::before
 PASS Selection ending in ::marker
 PASS Selection contained in ::marker
 FAIL Selection ending in ::before-marker assert_equals: toString expected "hello" but got "o"
diff --git a/Source/WebCore/rendering/HitTestResult.cpp b/Source/WebCore/rendering/HitTestResult.cpp
@@ -206,6 +206,11 @@ LocalFrame* HitTestResult::innerNodeFrame() const
     return 0;
 }
 
+void HitTestResult::setLocalPoint(const LayoutPoint& p)
+{
+    m_localPoint = m_pseudoElementIdentifier ? LayoutPoint() : p;
+}
+
 std::optional<Style::PseudoElementIdentifier> HitTestResult::pseudoElementIdentifier() const
 {
     return m_pseudoElementIdentifier;
diff --git a/Source/WebCore/rendering/HitTestResult.h b/Source/WebCore/rendering/HitTestResult.h
@@ -99,7 +99,7 @@ class HitTestResult {
 
     // The hit-tested point in the coordinates of the inner node.
     const LayoutPoint& localPoint() const { return m_localPoint; }
-    void setLocalPoint(const LayoutPoint& p) { m_localPoint = p; }
+    void setLocalPoint(const LayoutPoint&);
 
     WEBCORE_EXPORT void setToNonUserAgentShadowAncestor();
 
diff --git a/Source/WebCore/rendering/RenderObject.cpp b/Source/WebCore/rendering/RenderObject.cpp
@@ -1887,8 +1887,8 @@ void RenderObject::updateHitTestResult(HitTestResult& result, const LayoutPoint&
         result.setInnerNode(node.get());
         if (!result.innerNonSharedNode())
             result.setInnerNonSharedNode(node.get());
-        result.setLocalPoint(point);
         result.setPseudoElementIdentifier(style().pseudoElementIdentifier());
+        result.setLocalPoint(point);
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -206,6 +206,11 @@ LocalFrame* HitTestResult::innerNodeFrame() const`
`206`	`206`	`return 0;`
`207`	`207`	`}`
`208`	`208`
	`209`	`+void HitTestResult::setLocalPoint(const LayoutPoint& p)`
	`210`	`+{`
	`211`	`+ m_localPoint = m_pseudoElementIdentifier ? LayoutPoint() : p;`
	`212`	`+}`
	`213`	`+`
`209`	`214`	`std::optional<Style::PseudoElementIdentifier> HitTestResult::pseudoElementIdentifier() const`
`210`	`215`	`{`
`211`	`216`	`return m_pseudoElementIdentifier;`
Original file line number	Diff line number	Diff line change
`@@ -1887,8 +1887,8 @@ void RenderObject::updateHitTestResult(HitTestResult& result, const LayoutPoint&`
`1887`	`1887`	`result.setInnerNode(node.get());`
`1888`	`1888`	`if (!result.innerNonSharedNode())`
`1889`	`1889`	`result.setInnerNonSharedNode(node.get());`
`1890`		`- result.setLocalPoint(point);`
`1891`	`1890`	`result.setPseudoElementIdentifier(style().pseudoElementIdentifier());`
	`1891`	`+ result.setLocalPoint(point);`
`1892`	`1892`	`}`
`1893`	`1893`	`}`
`1894`	`1894`