These two lines are responsible for [1]: https://searchfox.org/mozilla-central/rev/0e8b28fb355afd2fcc69d34e8ed66bbabf59a59a/layout/generic/nsIFrame.cpp#2569-2570
Bug 1710978 Comment 6 Edit History
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These two lines are responsible for most of the hit test items on the page[1]. [1]: https://searchfox.org/mozilla-central/rev/0e8b28fb355afd2fcc69d34e8ed66bbabf59a59a/layout/generic/nsIFrame.cpp#2569-2570
These two lines are responsible for 1688 out of the 1763 hit test items on the page[1]. [1]: https://searchfox.org/mozilla-central/rev/0e8b28fb355afd2fcc69d34e8ed66bbabf59a59a/layout/generic/nsIFrame.cpp#2569-2570
These[1] two lines are responsible for 1688 out of the 1763 (96%) `nsDisplayCompositorHitTestInfo` items on the page. Without these additional hit test items, the amount of `ClipChain(ClipChainItem)` in WRDL goes down from 886 to 609. This is not linear because both `ClipManager` and `HitTestInfoManager` can sometimes reuse their results (for example in the case of sibling items). [1]: https://searchfox.org/mozilla-central/rev/0e8b28fb355afd2fcc69d34e8ed66bbabf59a59a/layout/generic/nsIFrame.cpp#2569-2570