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LibWeb: Fix O(n^2) traversal in hit testing

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We already walk the entire paint tree within each stacking context in
the main hit testing function (StackingContext::hit_test()), so there's
no need for each individual paintable to walk its own children again.

By not doing that, we remove a source of O(n^2) traversal which made hit
testing on deeply nested web pages unbearably slow.
This commit is contained in:
Andreas Kling 2022-03-21 12:12:50 +01:00
parent f7cfd47b48
commit 996f3228a2
2 changed files with 8 additions and 18 deletions
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11
Userland/Libraries/LibWeb/Painting/PaintableBox.cpp
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@ -535,16 +535,9 @@ Optional<HitTestResult> PaintableBox::hit_test(Gfx::FloatPoint const& position,
return stacking_context()->hit_test(position, type);
}
Optional<HitTestResult> result;
if (absolute_border_box_rect().contains(position.x(), position.y()))
result = HitTestResult { *this };
for_each_child_in_paint_order([&](auto& child) {
if (child.paintable()) {
if (auto child_result = child.paintable()->hit_test(position, type); child_result.has_value())
result = move(child_result);
}
});
return result;
return HitTestResult { *this };
return {};
}
Optional<HitTestResult> PaintableWithLines::hit_test(const Gfx::FloatPoint& position, HitTestType type) const