[LayoutNG] Allow negative-inline-size opportunity to fit zero-with lines

Following the CL:916262 that allowed zero-width layout opportunities,
this patch allows negative-width layout opportunities (e.g.,
120%-width floats.)

Zero-width lines (<br> only) can fit into such opportunities.

Bug: 636993
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I66cf214732a0618500f2422a285282deda4f7eb3
Reviewed-on: https://chromium-review.googlesource.com/870950
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551768}

third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-features=LayoutNG

@@ -1462,7 +1462,6 @@ crbug.com/591099 fast/text-autosizing/vertical-writing-mode.html [ Failure ]
 crbug.com/591099 fast/text-autosizing/wide-block.html [ Failure ]
 crbug.com/591099 fast/text-autosizing/wide-child.html [ Failure ]
 crbug.com/591099 fast/text-autosizing/wide-in-narrow-overflow-scroll.html [ Failure ]
-crbug.com/591099 fast/text/break-word-with-floats.html [ Failure ]
 crbug.com/591099 fast/text/complex-text-opacity.html [ Failure ]
 crbug.com/591099 fast/text/container-align-with-inlines.html [ Failure ]
 crbug.com/591099 fast/text/decorations-transformed.html [ Failure ]

third_party/blink/renderer/core/layout/ng/exclusions/ng_exclusion_space.cc

@@ -101,10 +101,18 @@ bool Intersects(const NGLayoutOpportunity& opportunity,
 bool Intersects(const NGExclusionSpace::NGShelf& shelf,
                 const NGBfcOffset& offset,
                 const LayoutUnit inline_size) {
-  return (shelf.line_right == LayoutUnit::Max() ||
-          shelf.line_right >= offset.line_offset) &&
-         (shelf.line_left == LayoutUnit::Min() ||
-          shelf.line_left <= offset.line_offset + inline_size);
+  if (shelf.line_right >= offset.line_offset &&
+      shelf.line_left <= offset.line_offset + inline_size)
+    return true;
+  // Negative available space creates a zero-width opportunity at the inline-end
+  // of the shelf. Consider such shelf intersects.
+  // TODO(kojii): This is correct to find layout opportunities for zero-width
+  // in-flow inline or block objects (e.g., <br>,) but not correct for
+  // zero-width floats.
+  if (UNLIKELY(shelf.line_left > offset.line_offset ||
+               shelf.line_right < offset.line_offset + inline_size))
+    return true;
+  return false;
 }
 
 // Creates a new layout opportunity. The given layout opportunity *must*
@@ -136,8 +144,11 @@ NGLayoutOpportunity CreateLayoutOpportunity(
   NGBfcOffset start_offset(std::max(shelf.line_left, offset.line_offset),
                            std::max(shelf.block_offset, offset.block_offset));
 
+  // Max with |start_offset.line_offset| in case the shelf has a negative
+  // inline-size.
   NGBfcOffset end_offset(
-      std::min(shelf.line_right, offset.line_offset + inline_size),
+      std::max(std::min(shelf.line_right, offset.line_offset + inline_size),
+               start_offset.line_offset),
       LayoutUnit::Max());
 
   return NGLayoutOpportunity(NGBfcRect(start_offset, end_offset));
@@ -333,6 +344,9 @@ void NGExclusionSpace::Add(scoped_refptr<const NGExclusion> exclusion) {
           }
         }
 
+        // Just in case the shelf has a negative inline-size.
+        shelf.line_right = std::max(shelf.line_left, shelf.line_right);
+
         // We can end up in a situation where a shelf is the same as the
         // previous one. For example:
         //
@@ -351,12 +365,7 @@ void NGExclusionSpace::Add(scoped_refptr<const NGExclusion> exclusion) {
         bool is_same_as_previous =
             (i > 0) && shelf.line_left == shelves_[i - 1].line_left &&
             shelf.line_right == shelves_[i - 1].line_right;
-
-        // The shelf also may now be non-existent. Note that zero inline size is
-        // allowed, since subsequent zero-size content may still fit there.
-        bool shelf_disappearing = shelf.line_right < shelf.line_left;
-
-        if (is_same_as_previous || shelf_disappearing) {
+        if (is_same_as_previous) {
           shelves_.EraseAt(i);
           removed_shelf = true;
         }

third_party/blink/renderer/core/layout/ng/exclusions/ng_exclusion_space_test.cc

@@ -97,16 +97,18 @@ TEST(NGExclusionSpaceTest, SingleExclusion) {
   TEST_OPPORTUNITY(opportunites[2], NGBfcOffset(LayoutUnit(10), LayoutUnit(90)),
                    NGBfcOffset(LayoutUnit(60), LayoutUnit::Max()));
 
-  // This will only produce two opportunities, as the RHS opportunity will be
-  // outside the search area.
+  // This will also produce three opportunities, as the RHS opportunity outside
+  // the search area creates a zero-width opportunity.
   opportunites = exclusion_space.AllLayoutOpportunities(
       /* offset */ {LayoutUnit(10), LayoutUnit(10)},
       /* available_size */ LayoutUnit(49));
 
-  EXPECT_EQ(2u, opportunites.size());
+  EXPECT_EQ(3u, opportunites.size());
   TEST_OPPORTUNITY(opportunites[0], NGBfcOffset(LayoutUnit(10), LayoutUnit(10)),
                    NGBfcOffset(LayoutUnit(59), LayoutUnit(20)));
-  TEST_OPPORTUNITY(opportunites[1], NGBfcOffset(LayoutUnit(10), LayoutUnit(90)),
+  TEST_OPPORTUNITY(opportunites[1], NGBfcOffset(LayoutUnit(60), LayoutUnit(10)),
+                   NGBfcOffset(LayoutUnit(60), LayoutUnit::Max()));
+  TEST_OPPORTUNITY(opportunites[2], NGBfcOffset(LayoutUnit(10), LayoutUnit(90)),
                    NGBfcOffset(LayoutUnit(59), LayoutUnit::Max()));
 }
 
@@ -127,12 +129,14 @@ TEST(NGExclusionSpaceTest, TwoExclusions) {
           /* offset */ {LayoutUnit(), LayoutUnit()},
           /* available_size */ LayoutUnit(400));
 
-  EXPECT_EQ(3u, opportunites.size());
+  EXPECT_EQ(4u, opportunites.size());
   TEST_OPPORTUNITY(opportunites[0], NGBfcOffset(LayoutUnit(150), LayoutUnit()),
                    NGBfcOffset(LayoutUnit(400), LayoutUnit(75)));
-  TEST_OPPORTUNITY(opportunites[1], NGBfcOffset(LayoutUnit(), LayoutUnit(75)),
+  TEST_OPPORTUNITY(opportunites[1], NGBfcOffset(LayoutUnit(150), LayoutUnit()),
+                   NGBfcOffset(LayoutUnit(150), LayoutUnit::Max()));
+  TEST_OPPORTUNITY(opportunites[2], NGBfcOffset(LayoutUnit(), LayoutUnit(75)),
                    NGBfcOffset(LayoutUnit(100), LayoutUnit::Max()));
-  TEST_OPPORTUNITY(opportunites[2], NGBfcOffset(LayoutUnit(), LayoutUnit(150)),
+  TEST_OPPORTUNITY(opportunites[3], NGBfcOffset(LayoutUnit(), LayoutUnit(150)),
                    NGBfcOffset(LayoutUnit(400), LayoutUnit::Max()));
 }
 
@@ -286,5 +290,65 @@ TEST(NGExclusionSpaceTest, InsertBetweenShelves) {
                    NGBfcOffset(LayoutUnit(60), LayoutUnit::Max()));
 }
 
+TEST(NGExclusionSpaceTest, ZeroInlineSizeOpportunity) {
+  NGExclusionSpace exclusion_space;
+
+  exclusion_space.Add(NGExclusion::Create(
+      NGBfcRect(NGBfcOffset(LayoutUnit(), LayoutUnit()),
+                NGBfcOffset(LayoutUnit(100), LayoutUnit(10))),
+      EFloat::kLeft));
+
+  Vector<NGLayoutOpportunity> opportunites =
+      exclusion_space.AllLayoutOpportunities(
+          /* offset */ {LayoutUnit(), LayoutUnit()},
+          /* available_size */ LayoutUnit(100));
+
+  EXPECT_EQ(2u, opportunites.size());
+  TEST_OPPORTUNITY(opportunites[0], NGBfcOffset(LayoutUnit(100), LayoutUnit()),
+                   NGBfcOffset(LayoutUnit(100), LayoutUnit::Max()));
+  TEST_OPPORTUNITY(opportunites[1], NGBfcOffset(LayoutUnit(), LayoutUnit(10)),
+                   NGBfcOffset(LayoutUnit(100), LayoutUnit::Max()));
+}
+
+TEST(NGExclusionSpaceTest, NegativeInlineSizeOpportunityLeft) {
+  NGExclusionSpace exclusion_space;
+
+  exclusion_space.Add(NGExclusion::Create(
+      NGBfcRect(NGBfcOffset(LayoutUnit(), LayoutUnit()),
+                NGBfcOffset(LayoutUnit(120), LayoutUnit(10))),
+      EFloat::kLeft));
+
+  Vector<NGLayoutOpportunity> opportunites =
+      exclusion_space.AllLayoutOpportunities(
+          /* offset */ {LayoutUnit(), LayoutUnit()},
+          /* available_size */ LayoutUnit(100));
+
+  EXPECT_EQ(2u, opportunites.size());
+  TEST_OPPORTUNITY(opportunites[0], NGBfcOffset(LayoutUnit(120), LayoutUnit()),
+                   NGBfcOffset(LayoutUnit(120), LayoutUnit::Max()));
+  TEST_OPPORTUNITY(opportunites[1], NGBfcOffset(LayoutUnit(), LayoutUnit(10)),
+                   NGBfcOffset(LayoutUnit(100), LayoutUnit::Max()));
+}
+
+TEST(NGExclusionSpaceTest, NegativeInlineSizeOpportunityRight) {
+  NGExclusionSpace exclusion_space;
+
+  exclusion_space.Add(NGExclusion::Create(
+      NGBfcRect(NGBfcOffset(LayoutUnit(-20), LayoutUnit()),
+                NGBfcOffset(LayoutUnit(100), LayoutUnit(10))),
+      EFloat::kRight));
+
+  Vector<NGLayoutOpportunity> opportunites =
+      exclusion_space.AllLayoutOpportunities(
+          /* offset */ {LayoutUnit(), LayoutUnit()},
+          /* available_size */ LayoutUnit(100));
+
+  EXPECT_EQ(2u, opportunites.size());
+  TEST_OPPORTUNITY(opportunites[0], NGBfcOffset(LayoutUnit(), LayoutUnit()),
+                   NGBfcOffset(LayoutUnit(), LayoutUnit::Max()));
+  TEST_OPPORTUNITY(opportunites[1], NGBfcOffset(LayoutUnit(), LayoutUnit(10)),
+                   NGBfcOffset(LayoutUnit(100), LayoutUnit::Max()));
+}
+
 }  // namespace
 }  // namespace blink