[LayoutNG] Introduce NGLineLayoutOpportunity.

There should be no behaviour change in this patch. This introduces the
"line layout opportunity concept" which has:
 - A line size.
 - A float line size.

Bug: 635619
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Ib8667a7c0909116da8e89cb2e20d9df66a2c401d
Reviewed-on: https://chromium-review.googlesource.com/1035617Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557614}

third_party/blink/renderer/core/layout/BUILD.gn

@@ -282,6 +282,8 @@ blink_core_sources("layout") {
     "multi_column_fragmentainer_group.h",
     "ng/exclusions/ng_exclusion_space.cc",
     "ng/exclusions/ng_exclusion_space.h",
+    "ng/exclusions/ng_layout_opportunity.h",
+    "ng/exclusions/ng_line_layout_opportunity.h",
     "ng/geometry/ng_bfc_offset.cc",
     "ng/geometry/ng_bfc_offset.h",
     "ng/geometry/ng_bfc_rect.cc",
@@ -290,7 +292,6 @@ blink_core_sources("layout") {
     "ng/geometry/ng_border_edges.h",
     "ng/geometry/ng_box_strut.cc",
     "ng/geometry/ng_box_strut.h",
-    "ng/geometry/ng_edge.h",
     "ng/geometry/ng_logical_offset.cc",
     "ng/geometry/ng_logical_offset.h",
     "ng/geometry/ng_logical_rect.cc",

third_party/blink/renderer/core/layout/ng/exclusions/ng_layout_opportunity.h

@@ -10,6 +10,11 @@
 
 namespace blink {
 
+// This struct represents an 2D-area where a NGFragment can fit within the
+// exclusion space. A layout opportunity is produced by the exclusion space by
+// calling FindLayoutOpportunity, or AllLayoutOpportunities.
+//
+// Its coordinates are relative to the BFC.
 struct CORE_EXPORT NGLayoutOpportunity {
   NGLayoutOpportunity()
       : rect(NGBfcOffset(LayoutUnit::Min(), LayoutUnit::Min()),

third_party/blink/renderer/core/layout/ng/exclusions/ng_line_layout_opportunity.h

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_EXCLUSIONS_NG_LINE_LAYOUT_OPPORTUNITY_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_EXCLUSIONS_NG_LINE_LAYOUT_OPPORTUNITY_H_
+
+#include "third_party/blink/renderer/core/core_export.h"
+#include "third_party/blink/renderer/platform/layout_unit.h"
+#include "third_party/blink/renderer/platform/wtf/allocator.h"
+
+namespace blink {
+
+// This struct represents a 1D-area where a line can fit. It is only used for
+// representing the inline size.
+struct CORE_EXPORT NGLineLayoutOpportunity {
+  STACK_ALLOCATED();
+
+  NGLineLayoutOpportunity() {}
+  NGLineLayoutOpportunity(LayoutUnit inline_size)
+      : line_right_offset(inline_size), float_line_right_offset(inline_size) {}
+  NGLineLayoutOpportunity(LayoutUnit line_left_offset,
+                          LayoutUnit line_right_offset,
+                          LayoutUnit float_line_left_offset,
+                          LayoutUnit float_line_right_offset,
+                          LayoutUnit bfc_block_offset,
+                          LayoutUnit line_block_size)
+      : line_left_offset(line_left_offset),
+        line_right_offset(line_right_offset),
+        float_line_left_offset(float_line_left_offset),
+        float_line_right_offset(float_line_right_offset),
+        bfc_block_offset(bfc_block_offset),
+        line_block_size(line_block_size) {}
+
+  // The available inline-size of the line, taking shapes into account. Both
+  // offsets are relative to the BFC coordinate system.
+  LayoutUnit line_left_offset;
+  LayoutUnit line_right_offset;
+
+  // The available inline-size of the line *for floats*. This is the same size
+  // as the layout opportunity which generated this object. Both offsets are
+  // relative to the BFC coordinate system.
+  LayoutUnit float_line_left_offset;
+  LayoutUnit float_line_right_offset;
+
+  LayoutUnit bfc_block_offset;
+
+  // The block-size this line layout opportunity was created with. Should
+  // *only* be used for re-querying for a new line layout opportunity with the
+  // same block-size.
+  LayoutUnit line_block_size;
+
+  LayoutUnit AvailableInlineSize() const {
+    DCHECK_GE(line_right_offset, line_left_offset);
+    return line_right_offset - line_left_offset;
+  }
+
+  LayoutUnit AvailableFloatInlineSize() const {
+    DCHECK_GE(float_line_right_offset, float_line_left_offset);
+    return float_line_right_offset - float_line_left_offset;
+  }
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_NG_EXCLUSIONS_NG_LINE_LAYOUT_OPPORTUNITY_H_

third_party/blink/renderer/core/layout/ng/geometry/ng_edge.h

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef NGEdge_h
-#define NGEdge_h
-
-#include "third_party/blink/renderer/core/core_export.h"
-#include "third_party/blink/renderer/platform/layout_unit.h"
-
-namespace blink {
-
-// Struct to represent a simple edge that has start and end.
-struct CORE_EXPORT NGEdge {
-  LayoutUnit start;
-  LayoutUnit end;
-};
-
-}  // namespace blink
-
-#endif  // NGEdge_h

third_party/blink/renderer/core/layout/ng/inline/ng_inline_layout_algorithm.cc

@@ -618,6 +618,11 @@ scoped_refptr<NGLayoutResult> NGInlineLayoutAlgorithm::Layout() {
     exclusion_space =
         std::make_unique<NGExclusionSpace>(*initial_exclusion_space);
 
+    NGLineLayoutOpportunity line_opportunity(
+        opportunity.rect.LineStartOffset(), opportunity.rect.LineEndOffset(),
+        opportunity.rect.LineStartOffset(), opportunity.rect.LineEndOffset(),
+        opportunity.rect.BlockStartOffset(), LayoutUnit());
+
     NGLineInfo line_info;
     NGLineBreaker line_breaker(
         Node(), NGLineBreakerMode::kContent, constraint_space_,
@@ -626,14 +631,14 @@ scoped_refptr<NGLayoutResult> NGInlineLayoutAlgorithm::Layout() {
 
     // TODO(ikilpatrick): Does this always succeed when we aren't an empty
     // inline?
-    if (!line_breaker.NextLine(opportunity, &line_info))
+    if (!line_breaker.NextLine(line_opportunity, &line_info))
       break;
 
     // If this fragment will be larger than the inline-size of the opportunity,
     // *and* the opportunity is smaller than the available inline-size, and the
     // container autowraps, continue to the next opportunity.
-    if (line_info.Width() > opportunity.rect.InlineSize() &&
-        opportunity.rect.InlineSize() !=
+    if (line_info.Width() > line_opportunity.AvailableInlineSize() &&
+        line_opportunity.AvailableInlineSize() !=
             ConstraintSpace().AvailableSize().inline_size &&
         Node().Style().AutoWrap())
       continue;

third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.cc

@@ -596,8 +596,7 @@ static LayoutUnit ComputeContentSize(NGInlineNode node,
   scoped_refptr<NGInlineBreakToken> break_token;
   NGLineInfo line_info;
   NGExclusionSpace empty_exclusion_space;
-  NGLayoutOpportunity opportunity(NGBfcRect(
-      NGBfcOffset(), NGBfcOffset(available_inline_size, LayoutUnit::Max())));
+  NGLineLayoutOpportunity line_opportunity(available_inline_size);
   LayoutUnit result;
   LayoutUnit previous_floats_inline_size =
       input.float_left_inline_size + input.float_right_inline_size;
@@ -608,7 +607,7 @@ static LayoutUnit ComputeContentSize(NGInlineNode node,
                                &unpositioned_floats,
                                nullptr /* container_builder */,
                                &empty_exclusion_space, 0u, break_token.get());
-    if (!line_breaker.NextLine(opportunity, &line_info))
+    if (!line_breaker.NextLine(line_opportunity, &line_info))
       break;
 
     break_token = line_breaker.CreateBreakToken(line_info, nullptr);

third_party/blink/renderer/core/layout/ng/inline/ng_line_breaker.cc

@@ -153,8 +153,9 @@ void NGLineBreaker::ComputeBaseDirection(const NGLineInfo& line_info) {
 }
 
 // Initialize internal states for the next line.
-void NGLineBreaker::PrepareNextLine(const NGLayoutOpportunity& opportunity,
-                                    NGLineInfo* line_info) {
+void NGLineBreaker::PrepareNextLine(
+    const NGLineLayoutOpportunity& line_opportunity,
+    NGLineInfo* line_info) {
   NGInlineItemResults* item_results = &line_info->Results();
   item_results->clear();
   line_info->SetStartOffset(offset_);
@@ -177,17 +178,12 @@ void NGLineBreaker::PrepareNextLine(const NGLayoutOpportunity& opportunity,
   // regardless of 'text-indent'.
   line_.position = line_info->TextIndent();
 
-  line_.opportunity = opportunity;
-  line_.line_left_bfc_offset = opportunity.rect.LineStartOffset();
-  line_.line_right_bfc_offset = opportunity.rect.LineEndOffset();
-  bfc_block_offset_ = opportunity.rect.BlockStartOffset();
+  line_.line_opportunity = line_opportunity;
 }
 
-bool NGLineBreaker::NextLine(const NGLayoutOpportunity& opportunity,
+bool NGLineBreaker::NextLine(const NGLineLayoutOpportunity& line_opportunity,
                              NGLineInfo* line_info) {
-  bfc_block_offset_ = constraint_space_.BfcOffset().block_offset;
-
-  PrepareNextLine(opportunity, line_info);
+  PrepareNextLine(line_opportunity, line_info);
   BreakLine(line_info);
 
   if (line_info->Results().IsEmpty())
@@ -294,14 +290,14 @@ void NGLineBreaker::UpdatePosition(const NGInlineItemResults& results) {
 }
 
 void NGLineBreaker::ComputeLineLocation(NGLineInfo* line_info) const {
-  LayoutUnit bfc_line_offset = line_.line_left_bfc_offset;
+  LayoutUnit bfc_line_offset = line_.line_opportunity.line_left_offset;
   LayoutUnit available_width = line_.AvailableWidth();
 
   // Negative margins can make the position negative, but the inline size is
   // always positive or 0.
-  line_info->SetLineBfcOffset({bfc_line_offset, bfc_block_offset_},
-                              available_width,
-                              line_.position.ClampNegativeToZero());
+  line_info->SetLineBfcOffset(
+      {bfc_line_offset, line_.line_opportunity.bfc_block_offset},
+      available_width, line_.position.ClampNegativeToZero());
 }
 
 NGLineBreaker::LineBreakState NGLineBreaker::HandleText(
@@ -397,7 +393,7 @@ void NGLineBreaker::BreakText(NGInlineItemResult* item_result,
   //   * If offset == item.EndOffset(): the break opportunity at the end fits,
   //     or the first break opportunity is beyond the end.
   //     There may be room for more characters.
-  // * If width > available_width: The first break opporunity does not fit.
+  // * If width > available_width: The first break opportunity does not fit.
   //   offset is the first break opportunity, either inside, at the end, or
   //   beyond the end.
   if (item_result->end_offset < item.EndOffset()) {
@@ -643,8 +639,6 @@ void NGLineBreaker::HandleAtomicInline(const NGInlineItem& item,
 // We have this check if there are already UnpositionedFloats as we aren't
 // allowed to position a float "above" another float which has come before us
 // in the document.
-//
-// TODO(glebl): Add the support of clearance for inline floats.
 void NGLineBreaker::HandleFloat(const NGInlineItem& item,
                                 NGLineInfo* line_info,
                                 NGInlineItemResult* item_result) {
@@ -691,6 +685,8 @@ void NGLineBreaker::HandleFloat(const NGInlineItem& item,
        margins.InlineSum())
           .ClampNegativeToZero();
 
+  LayoutUnit bfc_block_offset = line_.line_opportunity.bfc_block_offset;
+
   // The float should be positioned after the current line if:
   //  - It can't fit.
   //  - It will be moved down due to block-start edge alignment.
@@ -700,9 +696,9 @@ void NGLineBreaker::HandleFloat(const NGInlineItem& item,
   //    the line breaker has run).
   bool float_after_line =
       !line_.CanFit(inline_margin_size) ||
-      exclusion_space_->LastFloatBlockStart() > bfc_block_offset_ ||
+      exclusion_space_->LastFloatBlockStart() > bfc_block_offset ||
       exclusion_space_->ClearanceOffset(float_style.Clear()) >
-          bfc_block_offset_ ||
+          bfc_block_offset ||
       mode_ != NGLineBreakerMode::kContent;
 
   // Check if we already have a pending float. That's because a float cannot be
@@ -711,30 +707,26 @@ void NGLineBreaker::HandleFloat(const NGInlineItem& item,
     AddUnpositionedFloat(unpositioned_floats_, container_builder_,
                          std::move(unpositioned_float));
   } else {
-    LayoutUnit origin_block_offset = bfc_block_offset_;
-
     NGPositionedFloat positioned_float = PositionFloat(
-        origin_block_offset, constraint_space_.BfcOffset().block_offset,
+        bfc_block_offset, constraint_space_.BfcOffset().block_offset,
         unpositioned_float.get(), constraint_space_, exclusion_space_);
     positioned_floats_->push_back(positioned_float);
 
     DCHECK_EQ(positioned_float.bfc_offset.block_offset,
-              bfc_block_offset_ + margins.block_start);
+              bfc_block_offset + margins.block_start);
 
     if (float_style.Floating() == EFloat::kLeft) {
-      line_.line_left_bfc_offset = std::max(
-          line_.line_left_bfc_offset,
+      line_.line_opportunity.line_left_offset = std::max(
+          line_.line_opportunity.line_left_offset,
           positioned_float.bfc_offset.line_offset + inline_margin_size -
               margins.LineLeft(TextDirection::kLtr));
     } else {
-      line_.line_right_bfc_offset =
-          std::min(line_.line_right_bfc_offset,
+      line_.line_opportunity.line_right_offset =
+          std::min(line_.line_opportunity.line_right_offset,
                    positioned_float.bfc_offset.line_offset -
                        margins.LineLeft(TextDirection::kLtr));
     }
 
-    DCHECK_GE(line_.line_left_bfc_offset, LayoutUnit());
-    DCHECK_GE(line_.line_right_bfc_offset, LayoutUnit());
     DCHECK_GE(line_.AvailableWidth(), LayoutUnit());
   }
 }
@@ -930,7 +922,7 @@ NGLineBreaker::LineBreakState NGLineBreaker::HandleOverflow(
   }
 
   // Let this line overflow.
-  // If there was a break opporunity, the overflow should stop there.
+  // If there was a break opportunity, the overflow should stop there.
   if (break_before) {
     Rewind(line_info, break_before);
     return LineBreakState::kTrailing;

third_party/blink/renderer/core/layout/ng/inline/ng_line_breaker.h

@@ -6,7 +6,7 @@
 #define NGLineBreaker_h
 
 #include "third_party/blink/renderer/core/core_export.h"
-#include "third_party/blink/renderer/core/layout/ng/exclusions/ng_layout_opportunity.h"
+#include "third_party/blink/renderer/core/layout/ng/exclusions/ng_line_layout_opportunity.h"
 #include "third_party/blink/renderer/core/layout/ng/inline/ng_inline_item_result.h"
 #include "third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.h"
 #include "third_party/blink/renderer/platform/fonts/shaping/harf_buzz_shaper.h"
@@ -47,7 +47,7 @@ class CORE_EXPORT NGLineBreaker {
 
   // Compute the next line break point and produces NGInlineItemResults for
   // the line.
-  bool NextLine(const NGLayoutOpportunity&, NGLineInfo*);
+  bool NextLine(const NGLineLayoutOpportunity& line_opportunity, NGLineInfo*);
 
   // Create an NGInlineBreakToken for the last line returned by NextLine().
   scoped_refptr<NGInlineBreakToken> CreateBreakToken(
@@ -71,11 +71,7 @@ class CORE_EXPORT NGLineBreaker {
     // that computes position in visual order, this position in logical order.
     LayoutUnit position;
 
-    // The current opportunity.
-    NGLayoutOpportunity opportunity;
-
-    LayoutUnit line_left_bfc_offset;
-    LayoutUnit line_right_bfc_offset;
+    NGLineLayoutOpportunity line_opportunity;
 
     // True if this line is the "first formatted line".
     // https://www.w3.org/TR/CSS22/selector.html#first-formatted-line
@@ -95,8 +91,7 @@ class CORE_EXPORT NGLineBreaker {
     bool is_after_forced_break = false;
 
     LayoutUnit AvailableWidth() const {
-      DCHECK_GE(line_right_bfc_offset, line_left_bfc_offset);
-      return line_right_bfc_offset - line_left_bfc_offset;
+      return line_opportunity.AvailableInlineSize();
     }
     bool CanFit() const { return position <= AvailableWidth(); }
     bool CanFit(LayoutUnit extra) const {
@@ -116,7 +111,7 @@ class CORE_EXPORT NGLineBreaker {
 
   void BreakLine(NGLineInfo*);
 
-  void PrepareNextLine(const NGLayoutOpportunity&, NGLineInfo*);
+  void PrepareNextLine(const NGLineLayoutOpportunity&, NGLineInfo*);
 
   void UpdatePosition(const NGInlineItemResults&);
   void ComputeLineLocation(NGLineInfo*) const;
@@ -187,8 +182,6 @@ class CORE_EXPORT NGLineBreaker {
   HarfBuzzShaper shaper_;
   ShapeResultSpacing<String> spacing_;
   bool previous_line_had_forced_break_ = false;
-  LayoutUnit bfc_line_offset_;
-  LayoutUnit bfc_block_offset_;
   const Hyphenation* hyphenation_ = nullptr;
 
   // Keep track of handled float items. See HandleFloat().

third_party/blink/renderer/core/layout/ng/inline/ng_line_breaker_test.cc

@@ -46,16 +46,14 @@ class NGLineBreakerTest : public NGBaseLayoutAlgorithmTest {
 
     Vector<NGInlineItemResults> lines;
     NGExclusionSpace exclusion_space;
-    NGLayoutOpportunity opportunity;
-    opportunity.rect =
-        NGBfcRect(NGBfcOffset(), {available_width, LayoutUnit::Max()});
+    NGLineLayoutOpportunity line_opportunity(available_width);
     NGLineInfo line_info;
     while (!break_token || !break_token->IsFinished()) {
       NGLineBreaker line_breaker(node, NGLineBreakerMode::kContent, *space,
                                  &positioned_floats, &unpositioned_floats,
                                  /* container_builder */ nullptr,
                                  &exclusion_space, 0u, break_token.get());
-      if (!line_breaker.NextLine(opportunity, &line_info))
+      if (!line_breaker.NextLine(line_opportunity, &line_info))
         break;
 
       break_token = line_breaker.CreateBreakToken(line_info, nullptr);