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Bug 1751789 - Better handle the case where the deferred transform item's ASR is a descendant of the current item's ASR. r=tnikkel

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Depends on D136828

Differential Revision: https://phabricator.services.mozilla.com/D136829
This commit is contained in:
Botond Ballo
2022-01-27 01:08:21 +00:00
parent e1c61ea7dd
commit 8ca5317636
1 changed files with 13 additions and 1 deletions
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14
gfx/layers/wr/WebRenderCommandBuilder.cpp
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@@ -1852,7 +1852,19 @@ void WebRenderCommandBuilder::CreateWebRenderCommandsFromDisplayList(
mAsrStack.empty() ? nullptr : mAsrStack.back();
newLayerData->ComputeDeferredTransformInfo(aSc, item);
mAsrStack.push_back(asr);
const ActiveScrolledRoot* stopAtAsrForDescendants = asr;
// While unusual and probably indicative of a poorly behaved display
// list, it's possible to have a deferred transform item which we
// will emit as its own layer on the way out of the recursion, whose
// ASR (let's call it T) is a *descendant* of the current item's ASR.
// In such cases, make sure our descendants have stopAtAsr=T, otherwise
// ASRs in the range [T, asr) may be emitted in duplicate, leading to
// cylic scroll metadata annotations.
if (newLayerData->mTransformShouldGetOwnLayer) {
stopAtAsrForDescendants = ActiveScrolledRoot::PickDescendant(
asr, newLayerData->mDeferredItem->GetActiveScrolledRoot());
}
mAsrStack.push_back(stopAtAsrForDescendants);
}
}