Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 60ced441fb04e7d2479607b827d2d2edaf1b27d8
https://github.com/WebKit/WebKit/commit/60ced441fb04e7d2479607b827d2d2edaf1b27d8
Author: Megan Gardner <[email protected]>
Date: 2026-09-22 (Tue, 22 Sep 2026)
Changed paths:
M Source/WebCore/editing/TextIterator.cpp
M
Tools/TestWebKitAPI/Tests/WebKit/WKWebView/mac/AttributedSubstringForProposedRange.mm
Log Message:
-----------
WebContent hangs for seconds resolving a character range on pages with tens
of thousands of sibling elements.
https://bugs.webkit.org/show_bug.cgi?id=324873
rdar://188117121
Reviewed by Pascoe.
resolveCharacterRange() called TextIterator::range() on every iteration, but
only
reads the result for the two runs that bound the requested range.
That's expensive because range() resolves m_positionOffsetBaseNode through
Node::computeNodeIndex(), which counts previous siblings. Runs emitted
by
emitCharacter() carry a base node -- a <br> gets one from handleNonTextNode() --
so resolving the Nth such run costs N and the loop goes quadratic. Runs from
emitText() clear the base node, which is why text-only documents never hit this.
So resolve it lazily: skip ahead when neither bound is in the current run.
That's
safe because range()'s normalization is idempotent and nothing else observes it;
handleTextRun() reads m_positionEndOffset directly, but only where the base node
is already null, and position() hands it to the caller.
Test:
Tools/TestWebKitAPI/Tests/WebKit/WKWebView/mac/AttributedSubstringForProposedRange.mm
* Source/WebCore/editing/TextIterator.cpp:
(WebCore::resolveCharacterRange):
*
Tools/TestWebKitAPI/Tests/WebKit/WKWebView/mac/AttributedSubstringForProposedRange.mm:
(markupWithSiblingLineBreaks):
(fastestFarRangeResolution):
(TEST(AttributedSubstringForProposedRange,
FarRangeResolutionScalesWithLineBreakCount)):
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