[FlexNG] Fix abspos legacy flex sandwich

Previously, if a legacy abspos child of an NG flexbox had a legacy
containing block, it could be positioned incorrectly.

This CL copies the staticpos logic from legacy flex, with a few minor
simplifications.

There's little refactoring of legacy to share code. Legacy continues to
mostly rely on methods in LayoutFlexibleBox that the new code can't use.
I don't want to risk altering legacy's behavior here, especially
considering this might be merged to 84.

Bug: 845235, 1066859
Change-Id: Ic07ed9e3fe5febe72981b47b0bacbc2b33691c71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2222112Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: David Grogan <dgrogan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#778008}

third_party/blink/renderer/core/layout/layout_block.cc

@@ -901,12 +901,13 @@ void LayoutBlock::LayoutPositionedObject(LayoutBox* positioned_object,
 
   LayoutObject* parent = positioned_object->Parent();
   bool layout_changed = false;
-  // TODO(dgrogan): The NG flexbox implementation doesn't have an analogous
-  // method yet, so abspos children of NG flexboxes that have a legacy
-  // containing block will not be positioned correctly.
-  if (parent->IsFlexibleBox() &&
-      ToLayoutFlexibleBox(parent)->SetStaticPositionForPositionedLayout(
-          *positioned_object)) {
+  if ((parent->IsLayoutNGFlexibleBox() &&
+       !positioned_object->IsLayoutNGMixin() &&
+       LayoutFlexibleBox::SetStaticPositionForChildInFlexNGContainer(
+           *positioned_object, To<LayoutBlock>(parent))) ||
+      (parent->IsFlexibleBox() &&
+       ToLayoutFlexibleBox(parent)->SetStaticPositionForPositionedLayout(
+           *positioned_object))) {
     // The static position of an abspos child of a flexbox depends on its size
     // (for example, they can be centered). So we may have to reposition the
     // item after layout.

third_party/blink/renderer/core/layout/layout_flexible_box.cc

@@ -1268,31 +1268,112 @@ void LayoutFlexibleBox::SetOverrideMainAxisContentSizeForChild(FlexItem& item) {
   }
 }
 
+namespace {
+
+LayoutUnit MainAxisStaticPositionCommon(const LayoutBox& child,
+                                        LayoutBox* parent,
+                                        LayoutUnit available_space) {
+  LayoutUnit offset = FlexLayoutAlgorithm::InitialContentPositionOffset(
+      parent->StyleRef(), available_space,
+      FlexLayoutAlgorithm::ResolvedJustifyContent(parent->StyleRef()), 1);
+  if (parent->StyleRef().ResolvedIsRowReverseFlexDirection() ||
+      parent->StyleRef().ResolvedIsColumnReverseFlexDirection())
+    offset = available_space - offset;
+  return offset;
+}
+
+LayoutUnit StaticMainAxisPositionForNGPositionedChild(const LayoutBox& child,
+                                                      LayoutBox* parent) {
+  const LayoutUnit available_space =
+      FlexLayoutAlgorithm::IsHorizontalFlow(parent->StyleRef())
+          ? parent->ContentWidth() - child.Size().Width()
+          : parent->ContentHeight() - child.Size().Height();
+  return MainAxisStaticPositionCommon(child, parent, available_space);
+}
+
+LayoutUnit CrossAxisStaticPositionCommon(const LayoutBox& child,
+                                         LayoutBox* parent,
+                                         LayoutUnit available_space) {
+  return FlexItem::AlignmentOffset(
+      available_space,
+      FlexLayoutAlgorithm::AlignmentForChild(parent->StyleRef(),
+                                             child.StyleRef()),
+      LayoutUnit(), LayoutUnit(),
+      parent->StyleRef().FlexWrap() == EFlexWrap::kWrapReverse,
+      parent->StyleRef().IsDeprecatedWebkitBox());
+}
+
+LayoutUnit StaticCrossAxisPositionForNGPositionedChild(const LayoutBox& child,
+                                                       LayoutBox* parent) {
+  const LayoutUnit available_space =
+      FlexLayoutAlgorithm::IsHorizontalFlow(parent->StyleRef())
+          ? parent->ContentHeight() - child.Size().Height()
+          : parent->ContentWidth() - child.Size().Width();
+  return CrossAxisStaticPositionCommon(child, parent, available_space);
+}
+
+LayoutUnit StaticInlinePositionForNGPositionedChild(const LayoutBox& child,
+                                                    LayoutBlock* parent) {
+  const LayoutUnit start_offset = parent->StartOffsetForContent();
+  if (parent->StyleRef().IsDeprecatedWebkitBox())
+    return start_offset;
+  return start_offset +
+         (parent->StyleRef().ResolvedIsColumnFlexDirection()
+              ? StaticCrossAxisPositionForNGPositionedChild(child, parent)
+              : StaticMainAxisPositionForNGPositionedChild(child, parent));
+}
+
+LayoutUnit StaticBlockPositionForNGPositionedChild(const LayoutBox& child,
+                                                   LayoutBlock* parent) {
+  return parent->BorderAndPaddingBefore() +
+         (parent->StyleRef().ResolvedIsColumnFlexDirection()
+              ? StaticMainAxisPositionForNGPositionedChild(child, parent)
+              : StaticCrossAxisPositionForNGPositionedChild(child, parent));
+}
+
+}  // namespace
+
+bool LayoutFlexibleBox::SetStaticPositionForChildInFlexNGContainer(
+    LayoutBox& child,
+    LayoutBlock* parent) {
+  const ComputedStyle& style = parent->StyleRef();
+  bool position_changed = false;
+  PaintLayer* child_layer = child.Layer();
+  if (child.StyleRef().HasStaticInlinePosition(
+          style.IsHorizontalWritingMode())) {
+    LayoutUnit inline_position =
+        StaticInlinePositionForNGPositionedChild(child, parent);
+    if (child_layer->StaticInlinePosition() != inline_position) {
+      child_layer->SetStaticInlinePosition(inline_position);
+      position_changed = true;
+    }
+  }
+  if (child.StyleRef().HasStaticBlockPosition(
+          style.IsHorizontalWritingMode())) {
+    LayoutUnit block_position =
+        StaticBlockPositionForNGPositionedChild(child, parent);
+    if (child_layer->StaticBlockPosition() != block_position) {
+      child_layer->SetStaticBlockPosition(block_position);
+      position_changed = true;
+    }
+  }
+  return position_changed;
+}
+
 LayoutUnit LayoutFlexibleBox::StaticMainAxisPositionForPositionedChild(
     const LayoutBox& child) {
   const LayoutUnit available_space =
       MainAxisContentExtent(ContentLogicalHeight()) -
       MainAxisExtentForChild(child);
 
-  LayoutUnit offset = FlexLayoutAlgorithm::InitialContentPositionOffset(
-      StyleRef(), available_space,
-      FlexLayoutAlgorithm::ResolvedJustifyContent(StyleRef()), 1);
-  if (StyleRef().ResolvedIsRowReverseFlexDirection() ||
-      StyleRef().ResolvedIsColumnReverseFlexDirection())
-    offset = available_space - offset;
-  return offset;
+  return MainAxisStaticPositionCommon(child, this, available_space);
 }
 
 LayoutUnit LayoutFlexibleBox::StaticCrossAxisPositionForPositionedChild(
     const LayoutBox& child) {
   LayoutUnit available_space =
       CrossAxisContentExtent() - CrossAxisExtentForChild(child);
-  return FlexItem::AlignmentOffset(
-      available_space,
-      FlexLayoutAlgorithm::AlignmentForChild(StyleRef(), child.StyleRef()),
-      LayoutUnit(), LayoutUnit(),
-      StyleRef().FlexWrap() == EFlexWrap::kWrapReverse,
-      StyleRef().IsDeprecatedWebkitBox());
+  return CrossAxisStaticPositionCommon(child, this, available_space);
 }
 
 LayoutUnit LayoutFlexibleBox::StaticInlinePositionForPositionedChild(

third_party/blink/renderer/core/layout/layout_flexible_box.h

@@ -98,6 +98,8 @@ class CORE_EXPORT LayoutFlexibleBox : public LayoutBlock {
   // Returns true if the position changed. In that case, the child will have to
   // be laid out again.
   bool SetStaticPositionForPositionedLayout(LayoutBox& child);
+  static bool SetStaticPositionForChildInFlexNGContainer(LayoutBox& child,
+                                                         LayoutBlock* parent);
   LayoutUnit CrossAxisContentExtent() const;
 
  protected:

third_party/blink/web_tests/TestExpectations

@@ -1183,7 +1183,6 @@ virtual/layout_ng_fragment_traversal/external/wpt/css/CSS2/text/* [ Skip ]
 # Fail in NG flex, pass in legacy flex.
 crbug.com/845235 virtual/layout_ng_flex_box/external/wpt/css/css-flexbox/quirks-auto-block-size-with-percentage-item.html [ Pass Failure ]
 crbug.com/846557 [ Mac ] virtual/layout_ng_flex_box/css3/flexbox/button.html [ Failure ]
-crbug.com/1066859 external/wpt/css/css-flexbox/position-absolute-009.html [ Failure ]
 
 # Fail in both legacy flex and NG flex
 crbug.com/626703 virtual/layout_ng_flex_box/external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-align-self-baseline-horiz-008.xhtml [ Failure ]