[LayoutNG] Always perform fragment traversal if we can.

AppendSingleFragmentIgnoringPagination() is called when fragmentation gets disabled because of transforms. This needs to be fixed; see crbug.com/1058792 - in the meantime, let's at least traverse the fragment tree, to avoid DCHECK failures. Note that things aren't going to look or behave right if such nodes break into multiple fragments - neither with nor without this fix. Bug: 1146975 Change-Id: I7ded8d094185e69e39ce115b256661dee48f7e46 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2529099Reviewed-by: Koji Ishii <kojii@chromium.org> Reviewed-by: Chris Harrelson <chrishtr@chromium.org> Commit-Queue: Morten Stenshorne <mstensho@chromium.org> Cr-Commit-Position: refs/heads/master@{#826684}

[LayoutNG] Always perform fragment traversal if we can.
AppendSingleFragmentIgnoringPagination() is called when fragmentation gets disabled because of transforms. This needs to be fixed; see crbug.com/1058792 - in the meantime, let's at least traverse the fragment tree, to avoid DCHECK failures. Note that things aren't going to look or behave right if such nodes break into multiple fragments - neither with nor without this fix. Bug: 1146975 Change-Id: I7ded8d094185e69e39ce115b256661dee48f7e46 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2529099Reviewed-by: Koji Ishii <kojii@chromium.org> Reviewed-by: Chris Harrelson <chrishtr@chromium.org> Commit-Queue: Morten Stenshorne <mstensho@chromium.org> Cr-Commit-Position: refs/heads/master@{#826684}
938e32d0 · Morten Stenshorne · Commit Bot · 2b11db0a · 938e32d0 · 938e32d0
Commit 938e32d0 authored Nov 12, 2020 by Morten Stenshorne Committed by Commit Bot Nov 12, 2020
3 changed files
--- a/third_party/blink/renderer/core/paint/paint_layer.cc
+++ b/third_party/blink/renderer/core/paint/paint_layer.cc
@@ -1617,6 +1617,13 @@ void PaintLayer::AppendSingleFragmentIgnoringPagination(
                      offset_from_root);
  fragment.root_fragment_data = &root_layer->GetLayoutObject().FirstFragment();
  fragment.fragment_data = &GetLayoutObject().FirstFragment();
+  if (GetLayoutObject().CanTraversePhysicalFragments()) {
+    // Make sure that we actually traverse the fragment tree, by providing a
+    // physical fragment. Otherwise we'd fall back to LayoutObject traversal.
+    if (const auto* layout_box = GetLayoutBox())
+      fragment.physical_fragment = layout_box->GetPhysicalFragment(0);
+  }
  fragments.push_back(fragment);
 }

--- a/third_party/blink/web_tests/TestExpectations
+++ b/third_party/blink/web_tests/TestExpectations
@@ -995,6 +995,7 @@ virtual/layout_ng_block_frag/external/wpt/css/css-break/break-between-avoid-004.
 virtual/layout_ng_block_frag/external/wpt/css/css-break/fieldset-003.html [ Pass ]
 virtual/layout_ng_block_frag/external/wpt/css/css-break/fieldset-004.html [ Pass ]
 virtual/layout_ng_block_frag/external/wpt/css/css-break/forced-break-at-fragmentainer-start-000.html [ Pass ]
+virtual/layout_ng_block_frag/external/wpt/css/css-multicol/hit-test-transformed-child.html [ Pass ]
 virtual/layout_ng_block_frag/external/wpt/css/css-break/overflowed-block-with-no-room-after-000.html [ Pass ]
 virtual/layout_ng_block_frag/external/wpt/css/css-break/overflowed-block-with-no-room-after-001.html [ Pass ]
 virtual/layout_ng_block_frag/external/wpt/css/css-break/relpos-inline-hit-testing.html [ Pass ]
@@ -3216,6 +3217,7 @@ crbug.com/967329 external/wpt/css/css-multicol/columnfill-auto-max-height-002.ht
 crbug.com/829028 external/wpt/css/css-multicol/baseline-001.html [ Failure ]
 crbug.com/829028 external/wpt/css/css-multicol/baseline-007.html [ Failure ]
 crbug.com/829028 external/wpt/css/css-multicol/baseline-008.html [ Failure ]
+crbug.com/829028 external/wpt/css/css-multicol/hit-test-transformed-child.html [ Failure ]
 crbug.com/990240 external/wpt/css/css-multicol/multicol-breaking-000.html [ Failure ]
 crbug.com/990240 external/wpt/css/css-multicol/multicol-breaking-001.html [ Failure ]
 crbug.com/481431 external/wpt/css/css-multicol/multicol-breaking-004.html [ Failure ]

--- a/third_party/blink/web_tests/external/wpt/css/css-multicol/hit-test-transformed-child.html
+++ b/third_party/blink/web_tests/external/wpt/css/css-multicol/hit-test-transformed-child.html
+<!DOCTYPE html>
+<link rel="author" title="Morten Stenshorne" href="mailto:mstensho@chromium.org">
+<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1146975">
+<style>
+  body {
+      margin: 8px;
+  }
+</style>
+<div style="columns:2; column-fill:auto; height:100px;">
+  <div>
+    <div id="target" style="transform:translateX(100px) translateY(200px); width:50px; height:50px; background:blue;"></div>
+  </div>
+</div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+  test(()=> {
+      assert_equals(document.elementFromPoint(108, 208), target);
+      assert_equals(document.elementFromPoint(157, 208), target);
+      assert_equals(document.elementFromPoint(157, 257), target);
+  }, "inside");
+  test(()=> {
+      assert_not_equals(document.elementFromPoint(107, 208), target);
+      assert_not_equals(document.elementFromPoint(108, 207), target);
+      assert_not_equals(document.elementFromPoint(158, 257), target);
+      assert_not_equals(document.elementFromPoint(157, 258), target);
+      assert_not_equals(document.elementFromPoint(8, 8), target);
+  }, "outside");
+</script>