tree 030f8448a22c0763abfc608d3aa59e39bbd01b90
parent f928d8282c6ed30f215bd3c3b93ebf7a176853ea
author Morten Stenshorne <mstensho@chromium.org> 1645432555 -0800
committer Blink WPT Bot <blink-w3c-test-autoroller@chromium.org> 1645433308 -0800

Pre-paint: Update first-for-node state at fragmentainers.

A nested multicol container may have a padding so tall that there won't
be room for any columns until we get to the next outer column. An
out-of-flow positioned descendant that is *not* contained by the
innermost multicol container needs to be visited exactly once. We missed
the OOF, because is_parent_first_for_node in PrePaintTreeWalk::
WalkLayoutObjectChildren() was wrong. It was set by the inner multicol
container, but the first fragment of the inner multicol container is one
without columns (just padding there), and OOFs are only discovered when
walking inside columns.

  Box (block-flow-root block-flow)      #outer
    Box (column block-flow)
      Box (block-flow-root block-flow)  #inner
    Box (column block-flow)
      Box (block-flow-root block-flow)  #inner
        Box (column block-flow)

Therefore, update is_parent_first_for_node for each column as well.

WalkFragmentationContextRootChildren() already did quite a few things to
the PrePaintTreeWalkContext object passed, which we'd have to reset when
entering non-fragmentainer children (such as column spanners). This
would be one more thing to reset. Instead of this mess, establish a new
PrePaintTreeWalkContext for each column. (It also looks like we had
forgotten to reset fragmentation_nesting_level when entering spanners.)
This also allows us to add some constness to the PrePaintTreeWalkContext
argument.

Bug: 1295998
Change-Id: I8c471936be9c05a6475a4c135bfa7490ac7b09a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3468548
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/main@{#973450}