[LayoutNG] Offset of proxy fragments after spanner

When we were adding new proxy fragments directly after a spanner,
we were computing the wrong offset for these new fragmentainers.
This change fixes this by looking at the offset of the spanner when
determining the offset of proxy fragments in this case.

Bug: 1079031
Change-Id: I34a6358f9bc1b1d630d72bb268f3ae79edcdff00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2422424
Commit-Queue: Alison Maher <almaher@microsoft.com>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809460}

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

@@ -1094,20 +1094,34 @@ void NGOutOfFlowLayoutPart::AddOOFResultsToFragmentainer(
   }
 
   if (is_new_fragment) {
-    // Calculate the column inline progression in order to calculate the inline
-    // offset of any newly added column fragments.
-    if (column_inline_progression_ == kIndefiniteSize) {
-      LayoutUnit available_size =
-          container_builder_->ChildAvailableSize().inline_size;
-      const ComputedStyle& style = container_builder_->Style();
-      LayoutUnit column_inline_size =
-          ResolveUsedColumnInlineSize(available_size, style);
-      column_inline_progression_ =
-          column_inline_size + ResolveUsedColumnGap(available_size, style);
+    LogicalOffset offset;
+    if (index != num_children - 1 && !container_builder_->Children()[index + 1]
+                                          .fragment->IsFragmentainerBox()) {
+      // If we are a new fragment and are separated from other columns by a
+      // spanner, compute the correct column offset to use.
+      const auto& spanner = container_builder_->Children()[index + 1];
+      DCHECK(spanner.fragment->IsColumnSpanAll());
+
+      offset = spanner.offset;
+      LogicalSize spanner_size = spanner.fragment->Size().ConvertToLogical(
+          container_builder_->Style().GetWritingMode());
+      // TODO(almaher): Include trailing spanner margin.
+      offset.block_offset += spanner_size.block_size;
+    } else {
+      // Calculate the column inline progression in order to calculate the
+      // inline offset of any newly added column fragments.
+      if (column_inline_progression_ == kIndefiniteSize) {
+        LayoutUnit available_size =
+            container_builder_->ChildAvailableSize().inline_size;
+        const ComputedStyle& style = container_builder_->Style();
+        LayoutUnit column_inline_size =
+            ResolveUsedColumnInlineSize(available_size, style);
+        column_inline_progression_ =
+            column_inline_size + ResolveUsedColumnGap(available_size, style);
+      }
+      offset = fragmentainer.offset;
+      offset.inline_offset += column_inline_progression_;
     }
-
-    LogicalOffset offset = fragmentainer.offset;
-    offset.inline_offset += column_inline_progression_;
     container_builder_->AddChild(algorithm.Layout()->PhysicalFragment(),
                                  offset);
   } else {

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

@@ -966,8 +966,6 @@ TEST_F(NGOutOfFlowLayoutPartTest,
 
   // TODO(1079031): With top set to 0px, the abspos should start in the first
   // column with an offset of (0,0).
-  // TODO(1079031): The offsets of the columns following the spanner are
-  // incorrect. (The first should start at (0,10)).
   String expectation = R"DUMP(.:: LayoutNG Physical Fragment Tree ::.
   offset:unplaced size:1000x40
     offset:0,0 size:1000x40
@@ -981,13 +979,13 @@ TEST_F(NGOutOfFlowLayoutPartTest,
       offset:0,10 size:1000x0
       offset:0,10 size:1000x0
       offset:0,10 size:1000x0
-      offset:1016,0 size:492x30
+      offset:0,10 size:492x30
         offset:0,0 size:5x30
-      offset:1524,0 size:492x30
+      offset:508,10 size:492x30
         offset:0,0 size:5x30
-      offset:2032,0 size:492x30
+      offset:1016,10 size:492x30
         offset:0,0 size:5x30
-      offset:2540,0 size:492x30
+      offset:1524,10 size:492x30
         offset:0,0 size:5x20
 )DUMP";
   EXPECT_EQ(expectation, dump);
@@ -1026,8 +1024,6 @@ TEST_F(NGOutOfFlowLayoutPartTest,
 
   // TODO(1079031): With top set to 25px, the abspos should start in the third
   // column with an offset of (0,5).
-  // TODO(1079031): The offsets of the columns following the spanner are
-  // incorrect. (The first should start at (0,10)).
   String expectation = R"DUMP(.:: LayoutNG Physical Fragment Tree ::.
   offset:unplaced size:1000x40
     offset:0,0 size:1000x40
@@ -1038,11 +1034,11 @@ TEST_F(NGOutOfFlowLayoutPartTest,
         offset:0,0 size:30x10
           offset:0,0 size:30x10
       offset:0,10 size:1000x0
-      offset:1016,0 size:492x30
+      offset:0,10 size:492x30
         offset:0,15 size:5x15
-      offset:1524,0 size:492x30
+      offset:508,10 size:492x30
         offset:0,0 size:5x30
-      offset:2032,0 size:492x30
+      offset:1016,10 size:492x30
         offset:0,0 size:5x5
 )DUMP";
   EXPECT_EQ(expectation, dump);
@@ -1088,12 +1084,12 @@ TEST_F(NGOutOfFlowLayoutPartTest,
       offset:0,0 size:1000x0
       offset:0,0 size:1000x0
       offset:0,0 size:1000x0
+      offset:0,0 size:492x1
+        offset:0,0 size:5x1
       offset:508,0 size:492x1
         offset:0,0 size:5x1
       offset:1016,0 size:492x1
         offset:0,0 size:5x1
-      offset:1524,0 size:492x1
-        offset:0,0 size:5x1
 )DUMP";
   EXPECT_EQ(expectation, dump);
 }
@@ -1136,14 +1132,14 @@ TEST_F(NGOutOfFlowLayoutPartTest, AbsposFragWithSpannerAndNewEmptyColumns) {
       offset:0,0 size:1000x0
       offset:0,0 size:1000x0
       offset:0,0 size:1000x0
+      offset:0,0 size:492x40
       offset:508,0 size:492x40
-      offset:1016,0 size:492x40
         offset:0,39 size:5x1
+      offset:1016,0 size:492x40
+        offset:0,0 size:5x40
       offset:1524,0 size:492x40
         offset:0,0 size:5x40
       offset:2032,0 size:492x40
-        offset:0,0 size:5x40
-      offset:2540,0 size:492x40
         offset:0,0 size:5x39
 )DUMP";
   EXPECT_EQ(expectation, dump);