[LayoutNG] Support column rules in fragment painting.

And enable fragment painting for multicol containers.

Rules are to be painted "just above the border of the multicol
container" [1]. At the same time, "the rules need to scroll along with
the columns" [1]. Hence, we'll paint it as the first item in the
foreground phase, so that we get scroll offsets applied.

[1] https://drafts.csswg.org/css-multicol/#column-gaps-and-rules

By enabling fragment painting for multicol containers, we break one
outline test. The fix is easy, but I'd rather deal with that in a
follow-up.

Bug: 829028
Change-Id: Ie5e4ac267967f185a588bfc36f1902a2b1659413
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1899784
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714376}

third_party/blink/renderer/core/layout/ng/layout_ng_block_flow_mixin.cc

@@ -205,6 +205,9 @@ bool LayoutNGBlockFlowMixin<
   if (PaintFragment())
     return false;
 
+  if (Base::StyleRef().HasColumnRule())
+    return false;
+
   return Base::PaintedOutputOfObjectHasNoEffectRegardlessOfSize();
 }
 
@@ -283,12 +286,6 @@ void LayoutNGBlockFlowMixin<Base>::Paint(const PaintInfo& paint_info) const {
     }
   }
 
-  // |NGBoxFragmentPainter| currently doesn't support column rules.
-  if (UNLIKELY(Base::MultiColumnFlowThread())) {
-    Base::Paint(paint_info);
-    return;
-  }
-
   if (const NGPaintFragment* paint_fragment = PaintFragment()) {
     NGBoxFragmentPainter(*paint_fragment).Paint(paint_info);
     return;

third_party/blink/renderer/core/layout/ng/ng_block_node.cc

@@ -841,6 +841,7 @@ void NGBlockNode::CopyFragmentDataToLayoutBox(
   }
 
   LayoutBlock* block = DynamicTo<LayoutBlock>(box_);
+  bool needs_full_invalidation = false;
   if (LIKELY(block && is_last_fragment)) {
     LayoutUnit intrinsic_block_size =
         layout_result.UnconstrainedIntrinsicBlockSize();
@@ -854,6 +855,11 @@ void NGBlockNode::CopyFragmentDataToLayoutBox(
     if (UNLIKELY(flow_thread)) {
       UpdateLegacyMultiColumnFlowThread(*this, flow_thread, constraint_space,
                                         physical_fragment);
+
+      // Issue full invalidation, in case the number of column rules have
+      // changed.
+      if (Style().HasColumnRule())
+        needs_full_invalidation = true;
     }
 
     BoxLayoutExtraInput input(*block);
@@ -867,7 +873,11 @@ void NGBlockNode::CopyFragmentDataToLayoutBox(
   }
 
   box_->UpdateAfterLayout();
-  box_->ClearNeedsLayout();
+
+  if (needs_full_invalidation)
+    box_->ClearNeedsLayoutWithFullPaintInvalidation();
+  else
+    box_->ClearNeedsLayout();
 
   // Overflow computation depends on this being set.
   if (LIKELY(block_flow))

third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.cc

@@ -383,6 +383,12 @@ void NGBoxFragmentPainter::PaintObject(
       (!physical_box_fragment.Children().empty() ||
        physical_box_fragment.HasItems()) &&
       !paint_info.DescendantPaintingBlocked()) {
+    if (RuntimeEnabledFeatures::LayoutNGFragmentPaintEnabled()) {
+      if (UNLIKELY(paint_phase == PaintPhase::kForeground &&
+                   box_fragment_.Style().HasColumnRule()))
+        PaintColumnRules(paint_info, paint_offset);
+    }
+
     if (paint_phase != PaintPhase::kFloat) {
       if (physical_box_fragment.ChildrenInline()) {
         DCHECK(paint_fragment_ || PhysicalFragment().HasItems());
@@ -844,6 +850,106 @@ void NGBoxFragmentPainter::PaintBoxDecorationBackgroundWithRect(
     paint_info.context.EndLayer();
 }
 
+void NGBoxFragmentPainter::PaintColumnRules(
+    const PaintInfo& paint_info,
+    const PhysicalOffset& paint_offset) {
+  const ComputedStyle& style = box_fragment_.Style();
+  DCHECK(style.HasColumnRule());
+
+  // TODO(crbug.com/792437): Certain rule styles should be converted.
+  EBorderStyle rule_style = style.ColumnRuleStyle();
+
+  if (DrawingRecorder::UseCachedDrawingIfPossible(paint_info.context,
+                                                  GetDisplayItemClient(),
+                                                  DisplayItem::kColumnRules))
+    return;
+
+  DrawingRecorder recorder(paint_info.context, GetDisplayItemClient(),
+                           DisplayItem::kColumnRules);
+
+  const Color& rule_color =
+      LayoutObject::ResolveColor(style, GetCSSPropertyColumnRuleColor());
+  LayoutUnit rule_thickness(style.ColumnRuleWidth());
+  PhysicalRect previous_column;
+  bool past_first_column_in_row = false;
+  for (const NGLink& child : box_fragment_.Children()) {
+    if (!child->IsColumnBox()) {
+      // Column spanner. Continue in the next row, if there are 2 columns or
+      // more there.
+      past_first_column_in_row = false;
+      previous_column = PhysicalRect();
+      continue;
+    }
+
+    PhysicalRect current_column(child.offset, child->Size());
+    if (!past_first_column_in_row) {
+      // Rules are painted *between* columns. Need to see if we have a second
+      // one before painting anything.
+      past_first_column_in_row = true;
+      previous_column = current_column;
+      continue;
+    }
+
+    PhysicalRect rule;
+    BoxSide box_side;
+    if (previous_column.Y() == current_column.Y() ||
+        previous_column.Bottom() == current_column.Bottom()) {
+      // Horizontal writing-mode.
+      DCHECK(style.IsHorizontalWritingMode());
+      LayoutUnit center;
+      if (previous_column.X() < current_column.X()) {
+        // Left to right.
+        center = (previous_column.X() + current_column.Right()) / 2;
+        box_side = BoxSide::kLeft;
+      } else {
+        // Right to left.
+        center = (current_column.X() + previous_column.Right()) / 2;
+        box_side = BoxSide::kRight;
+      }
+      // The last column may be shorter than the previous ones, but otherwise
+      // they should be the same.
+      LayoutUnit rule_length = previous_column.Height();
+      DCHECK_GE(rule_length, current_column.Height());
+      rule.offset.top = previous_column.offset.top;
+      rule.size.height = rule_length;
+      rule.offset.left = center - rule_thickness / 2;
+      rule.size.width = rule_thickness;
+    } else {
+      // Vertical writing-mode.
+      LayoutUnit center;
+      if (previous_column.Y() < current_column.Y()) {
+        // Top to bottom.
+        center = (previous_column.Y() + current_column.Bottom()) / 2;
+        box_side = BoxSide::kTop;
+      } else {
+        // Bottom to top.
+        center = (current_column.Y() + previous_column.Bottom()) / 2;
+        box_side = BoxSide::kBottom;
+      }
+      // The last column may be shorter than the previous ones, but otherwise
+      // they should be the same.
+      LayoutUnit rule_length = previous_column.Width();
+      DCHECK_GE(rule_length, current_column.Width());
+      rule.offset.left = previous_column.offset.left;
+      rule.size.width = rule_length;
+      rule.offset.top = center - rule_thickness / 2;
+      rule.size.height = rule_thickness;
+    }
+
+    // TODO(crbug.com/792435): The spec actually kind of says that the rules
+    // should be as tall as the entire multicol container, not just as tall as
+    // the column fragments (this difference matters when block-size is
+    // specified and columns are balanced).
+
+    rule.Move(paint_offset);
+    ObjectPainter::DrawLineForBoxSide(paint_info.context, rule.X(), rule.Y(),
+                                      rule.Right(), rule.Bottom(), box_side,
+                                      rule_color, rule_style, 0, 0, true);
+
+    previous_column = current_column;
+  }
+}
+
 // TODO(kojii): This logic is kept in sync with BoxPainter. Not much efforts to
 // eliminate LayoutObject dependency were done yet.
 void NGBoxFragmentPainter::PaintBackground(

third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.h

@@ -79,6 +79,7 @@ class NGBoxFragmentPainter : public BoxPainterBase {
   void PaintBoxDecorationBackgroundWithRect(const PaintInfo&,
                                             const PhysicalRect&,
                                             const DisplayItemClient&);
+  void PaintColumnRules(const PaintInfo&, const PhysicalOffset& paint_offset);
   bool BackgroundIsKnownToBeOpaque(const PaintInfo&);
 
   void PaintInternal(const PaintInfo&);

third_party/blink/renderer/core/style/computed_style.h

@@ -1261,6 +1261,12 @@ class ComputedStyle : public ComputedStyleBase,
            !ColumnRuleColorInternal().Alpha();
   }
   bool ColumnRuleEquivalent(const ComputedStyle& other_style) const;
+  bool HasColumnRule() const {
+    if (LIKELY(!SpecifiesColumns()))
+      return false;
+    return ColumnRuleWidth() && !ColumnRuleIsTransparent() &&
+           BorderStyleIsVisible(ColumnRuleStyle());
+  }
 
   // Flex utility functions.
   bool ResolvedIsColumnFlexDirection() const {

third_party/blink/web_tests/TestExpectations

@@ -1024,7 +1024,6 @@ crbug.com/988015 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/mult
 crbug.com/988015 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/multicol-span-all-dynamic-add-003.html [ Failure ]
 crbug.com/994172 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/multicol-span-all-dynamic-add-007.html [ Failure Crash ]
 crbug.com/924142 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/multicol-span-all-dynamic-add-010.html [ Crash Pass ]
-crbug.com/988015 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/multicol-span-all-dynamic-add-013.html [ Failure ]
 crbug.com/874051 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/multicol-span-all-fieldset-001.html [ Failure ]
 crbug.com/874051 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/multicol-span-all-fieldset-002.html [ Failure ]
 crbug.com/874051 virtual/layout_ng_block_frag/external/wpt/css/css-multicol/multicol-span-all-fieldset-003.html [ Failure ]
@@ -1141,6 +1140,7 @@ crbug.com/954171 virtual/layout_ng_block_frag/fast/multicol/float-with-margin-mo
 crbug.com/954171 virtual/layout_ng_block_frag/fast/multicol/float-with-margin-moved-by-child-line-and-unbreakable.html [ Failure Crash ]
 crbug.com/954171 virtual/layout_ng_block_frag/fast/multicol/float-with-margin-moved-by-child-line.html [ Failure Crash ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/float-with-margin-moved-unbreakable.html [ Failure ]
+crbug.com/829028 virtual/layout_ng_block_frag/fast/multicol/focus-outline.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/forced-break-after-block-with-spanner.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/forced-break-after-empty-block-after-spanner.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/forced-break-after-last-block-before-spanner.html [ Failure ]
@@ -1208,7 +1208,6 @@ crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/positioned-split.htm
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/positive-leading.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/pushed-line-affected-by-float.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/relayout-and-push-float.html [ Failure ]
-crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/rule-in-nested-with-too-tall-line.html [ Failure ]
 crbug.com/714962 virtual/layout_ng_block_frag/fast/multicol/scale-transform-text.html [ Failure ]
 crbug.com/874506 virtual/layout_ng_block_frag/fast/multicol/scrollable-basic.html [ Failure ]
 crbug.com/591099 virtual/layout_ng_block_frag/fast/multicol/scrolling-overflow.html [ Failure ]