[LayoutNG] Fix RTL text-align with trailing spaces

This patch fixes RTL 'text-align: start|right|center' not to
shift the line by the amount of trailing spaces.

Bug: 636993
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I99165bae187f7e76f183da20ce7a1909b10d1fc5
Reviewed-on: https://chromium-review.googlesource.com/1061273
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559161}

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

@@ -1318,7 +1318,6 @@ crbug.com/591099 fast/text/hide-atomic-inlines-after-ellipsis.html [ Failure ]
 crbug.com/591099 fast/text/international/bidi-linebreak-002.html [ Failure ]
 crbug.com/591099 fast/text/international/bidi-linebreak-003.html [ Failure ]
 crbug.com/714962 fast/text/international/hindi-whitespace.html [ Failure ]
-crbug.com/591099 fast/text/international/rtl-white-space-pre-wrap.html [ Failure ]
 crbug.com/796943 fast/text/international/shape-across-elements-simple.html [ Pass ]
 crbug.com/591099 fast/text/international/text-combine-image-test.html [ Failure ]
 crbug.com/591099 fast/text/large-text-composed-char.html [ Pass Timeout ]

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

@@ -43,8 +43,12 @@ struct NGLineAlign {
   NGLineAlign(const NGLineInfo&);
   NGLineAlign() = delete;
 
+  // The space to align or justify. This includes trailing spaces if exists.
   LayoutUnit space;
+
+  // The end offset with trailing spaces excluded.
   unsigned end_offset;
+  LayoutUnit trailing_spaces_width;
 };
 
 NGLineAlign::NGLineAlign(const NGLineInfo& line_info) {
@@ -56,14 +60,16 @@ NGLineAlign::NGLineAlign(const NGLineInfo& line_info) {
     const NGInlineItemResult& item_result = *it;
     if (!item_result.has_only_trailing_spaces) {
       end_offset = item_result.end_offset;
+      space += trailing_spaces_width;
       return;
     }
-    space += item_result.inline_size;
+    trailing_spaces_width += item_result.inline_size;
   }
 
   // An empty line, or only trailing spaces.
   DCHECK_EQ(space, line_info.AvailableWidth() - line_info.TextIndent());
   end_offset = line_info.StartOffset();
+  space += trailing_spaces_width;
 }
 
 }  // namespace
@@ -516,8 +522,9 @@ LayoutUnit NGInlineLayoutAlgorithm::OffsetForTextAlign(
   // Justification is applied in earlier phase, see PlaceItems().
   DCHECK_NE(text_align, ETextAlign::kJustify);
 
+  NGLineAlign align(line_info);
   return LineOffsetForTextAlign(text_align, line_info.BaseDirection(),
-                                NGLineAlign(line_info).space);
+                                align.space, align.trailing_spaces_width);
 }
 
 LayoutUnit NGInlineLayoutAlgorithm::ComputeContentSize(

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

@@ -242,7 +242,7 @@ NGLogicalOffset NGBlockLayoutAlgorithm::CalculateLogicalOffset(
   if (child.IsInline()) {
     LayoutUnit offset =
         LineOffsetForTextAlign(Style().GetTextAlign(), Style().Direction(),
-                               child_available_size_.inline_size);
+                               child_available_size_.inline_size, LayoutUnit());
     if (IsRtl(Style().Direction()))
       offset = child_available_size_.inline_size - offset;
     inline_offset += offset;
@@ -1272,7 +1272,7 @@ NGBfcOffset NGBlockLayoutAlgorithm::PositionEmptyChildWithParentBfc(
   if (child.IsInline()) {
     child_bfc_offset.line_offset +=
         LineOffsetForTextAlign(Style().GetTextAlign(), Style().Direction(),
-                               child_available_size_.inline_size);
+                               child_available_size_.inline_size, LayoutUnit());
   }
 
   AdjustToClearance(child_space.ClearanceOffset(), &child_bfc_offset);

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

@@ -634,7 +634,8 @@ void ApplyAutoMargins(const ComputedStyle& style,
 
 LayoutUnit LineOffsetForTextAlign(ETextAlign text_align,
                                   TextDirection direction,
-                                  LayoutUnit space_left) {
+                                  LayoutUnit space_left,
+                                  LayoutUnit trailing_spaces_width) {
   bool is_ltr = IsLtr(direction);
   if (text_align == ETextAlign::kStart || text_align == ETextAlign::kJustify)
     text_align = is_ltr ? ETextAlign::kLeft : ETextAlign::kRight;
@@ -653,19 +654,25 @@ LayoutUnit LineOffsetForTextAlign(ETextAlign text_align,
     }
     case ETextAlign::kRight:
     case ETextAlign::kWebkitRight: {
+      // In RTL, trailing spaces appear on the left of the line.
+      if (UNLIKELY(!is_ltr))
+        return space_left - trailing_spaces_width;
       // Wide lines spill out of the block based off direction.
       // So even if text-align is right, if direction is LTR, wide lines
       // should overflow out of the right side of the block.
-      if (space_left > LayoutUnit() || !is_ltr)
+      if (space_left > LayoutUnit())
         return space_left;
       return LayoutUnit();
     }
     case ETextAlign::kCenter:
     case ETextAlign::kWebkitCenter: {
-      if (is_ltr || space_left > LayoutUnit())
+      if (is_ltr)
         return (space_left / 2).ClampNegativeToZero();
+      // In RTL, trailing spaces appear on the left of the line.
+      if (space_left > LayoutUnit())
+        return (space_left / 2).ClampNegativeToZero() - trailing_spaces_width;
       // In RTL, wide lines should spill out to the left, same as kRight.
-      return space_left;
+      return space_left - trailing_spaces_width;
     }
     default:
       NOTREACHED();

third_party/blink/renderer/core/layout/ng/ng_length_utils.h

@@ -159,7 +159,8 @@ CORE_EXPORT void ApplyAutoMargins(const ComputedStyle& child_style,
 // text-align, direction and amount of unused space.
 CORE_EXPORT LayoutUnit LineOffsetForTextAlign(ETextAlign,
                                               TextDirection,
-                                              LayoutUnit space_left);
+                                              LayoutUnit space_left,
+                                              LayoutUnit trailing_spaces_width);
 
 CORE_EXPORT LayoutUnit ConstrainByMinMax(LayoutUnit length,
                                          base::Optional<LayoutUnit> min,