Missing initialization of force_legacy_layout.

AttachContext.force_legacy_layout was not initialized for slot elements when attaching for assigned flat tree children. We did not fall back to legacy layout for children of a slot styled as a multicol container. Bug: 1127874 Change-Id: I092ce2bb6f1af6a0af67c47d692f8f41284eedb4 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410487 Commit-Queue: Rune Lillesveen <[email protected]> Reviewed-by: Morten Stenshorne <[email protected]> Cr-Commit-Position: refs/heads/master@{#807405} GitOrigin-RevId: 006d6e80175126c646f089ee68c791bc7d24e1dc
mjfroman · Sep 16, 2020 · c3f9f43 · c3f9f43
1 parent ffc10a6
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diff --git a/blink/renderer/core/html/html_slot_element.cc b/blink/renderer/core/html/html_slot_element.cc
@@ -339,6 +339,8 @@ void HTMLSlotElement::AttachLayoutTree(AttachContext& context) {
   if (SupportsAssignment()) {
     LayoutObject* layout_object = GetLayoutObject();
     AttachContext children_context(context);
+    if (ShouldForceLegacyLayout())
+      children_context.force_legacy_layout = true;
     const ComputedStyle* style = GetComputedStyle();
     if (layout_object || !style || style->IsEnsuredInDisplayNone()) {
       children_context.previous_in_flow = nullptr;

diff --git a/blink/renderer/core/layout/force_legacy_layout_test.cc b/blink/renderer/core/layout/force_legacy_layout_test.cc
@@ -109,4 +109,30 @@ TEST_F(ForceLegacyLayoutTest, ForceLegacyBfcRecalcAncestorStyle) {
   EXPECT_EQ(UsesNGLayout(*child), EditingNGEnabled());
 }
 
+TEST_F(ForceLegacyLayoutTest, ForceLegacyMulticolSlot) {
+  if (!RuntimeEnabledFeatures::LayoutNGEnabled())
+    return;
+  if (RuntimeEnabledFeatures::LayoutNGBlockFragmentationEnabled())
+    return;
+
+  SetBodyInnerHTML(R"HTML(
+    <div id="host">
+      <p id="slotted"></p>
+    </div>
+  )HTML");
+
+  Element* host = GetDocument().getElementById("host");
+  ShadowRoot& shadow_root =
+      host->AttachShadowRootInternal(ShadowRootType::kOpen);
+  shadow_root.setInnerHTML(R"HTML(
+    <style>
+      slot { columns: 2; display: block }
+    </style>
+    <slot></slot>
+  )HTML");
+
+  UpdateAllLifecyclePhasesForTest();
+  EXPECT_FALSE(UsesNGLayout(*GetDocument().getElementById("slotted")));
+}
+
 }  // namespace blink