[layout] Fix -webkit-line-clamp with text-overflow: ellipsis

Previously we'd apply line truncation when either -webkit-line-clamp
was active, *or* if "text-overflow: ellipsis" was active.

This patch disables the "text-overflow: ellipsis" branch when we are
within a -webkit-line-clamp context.

Bug: 1134483
Change-Id: I5ceb40732bd512e5eb8dc59365e10c4fdd4cf15d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2447610
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816554}

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

@@ -326,8 +326,11 @@ void NGInlineLayoutAlgorithm::CreateLine(
     container_builder_.SetHangInlineSize(hang_width);
   }
 
-  // Truncate the line if 'text-overflow: ellipsis' is set, or for line-clamp.
+  // Truncate the line if:
+  //  - 'text-overflow: ellipsis' is set and we *aren't* a line-clamp context.
+  //  - If we've reached the line-clamp limit.
   if (UNLIKELY((line_info->HasOverflow() &&
+                !ConstraintSpace().IsLineClampContext() &&
                 node_.GetLayoutBlockFlow()->ShouldTruncateOverflowingText()) ||
                ConstraintSpace().LinesUntilClamp() == 1)) {
     NGLineTruncator truncator(*line_info);

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

@@ -199,9 +199,14 @@ NGBlockLayoutAlgorithm::NGBlockLayoutAlgorithm(
     const NGLayoutAlgorithmParams& params)
     : NGLayoutAlgorithm(params),
       previous_result_(params.previous_result),
+      fit_all_lines_(false),
       is_resuming_(IsResumingLayout(params.break_token)),
-      exclusion_space_(params.space.ExclusionSpace()),
+      abort_when_bfc_block_offset_updated_(false),
+      has_processed_first_child_(false),
+      ignore_line_clamp_(false),
+      is_line_clamp_context_(params.space.IsLineClampContext()),
       lines_until_clamp_(params.space.LinesUntilClamp()),
+      exclusion_space_(params.space.ExclusionSpace()),
       early_break_(params.early_break) {}
 
 // Define the destructor here, so that we can forward-declare more in the
@@ -496,6 +501,7 @@ inline scoped_refptr<const NGLayoutResult> NGBlockLayoutAlgorithm::Layout(
   }
 
   if (Style().IsDeprecatedWebkitBoxWithVerticalLineClamp()) {
+    is_line_clamp_context_ = true;
     if (!ignore_line_clamp_)
       lines_until_clamp_ = Style().LineClamp();
   } else if (Style().HasLineClamp()) {
@@ -2494,6 +2500,7 @@ NGConstraintSpace NGBlockLayoutAlgorithm::CreateConstraintSpaceForChild(
       builder.SetAdjoiningObjectTypes(
           container_builder_.AdjoiningObjectTypes());
     }
+    builder.SetIsLineClampContext(is_line_clamp_context_);
     builder.SetLinesUntilClamp(lines_until_clamp_);
   } else if (child_data.allow_discard_start_margin) {
     // If the child is being resumed after a break, margins inside the child may

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

@@ -372,10 +372,10 @@ class CORE_EXPORT NGBlockLayoutAlgorithm
   // break. In that case we'll break before first_overflowing_line_. In this
   // case there'll either be enough widows for the next fragment, or we have
   // determined that we're unable to fulfill the widows request.
-  bool fit_all_lines_ = false;
+  bool fit_all_lines_ : 1;
 
   // Set if we're resuming layout of a node that has already produced fragments.
-  bool is_resuming_;
+  bool is_resuming_ : 1;
 
   // Set when we're to abort if the BFC block offset gets resolved or updated.
   // Sometimes we walk past elements (i.e. floats) that depend on the BFC block
@@ -383,21 +383,24 @@ class CORE_EXPORT NGBlockLayoutAlgorithm
   // When this happens, and we finally manage to resolve (or update) the BFC
   // block offset at some subsequent element, we need to check if this flag is
   // set, and abort layout if it is.
-  bool abort_when_bfc_block_offset_updated_ = false;
+  bool abort_when_bfc_block_offset_updated_ : 1;
 
   // This will be set during block fragmentation once we've processed the first
   // in-flow child of a container. It is used to check if we're at a valid class
   // A or B breakpoint (between block-level siblings or line box siblings).
-  bool has_processed_first_child_ = false;
+  bool has_processed_first_child_ : 1;
 
-  NGExclusionSpace exclusion_space_;
+  // If true, ignore the line-clamp property as truncation wont be required.
+  bool ignore_line_clamp_ : 1;
+
+  // If this is within a -webkit-line-clamp context.
+  bool is_line_clamp_context_ : 1;
 
   // If set, this is the number of lines until a clamp. A value of 1 indicates
   // the current line should be clamped. This may go negative.
   base::Optional<int> lines_until_clamp_;
 
-  // If true, ignore the line-clamp property as truncation wont be required.
-  bool ignore_line_clamp_ = false;
+  NGExclusionSpace exclusion_space_;
 
   // If set, one of the lines was clamped and this is the intrinsic size at the
   // time of the clamp.

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

@@ -603,6 +603,9 @@ class CORE_EXPORT NGConstraintSpace final {
     return HasRareData() ? rare_data_->ClearanceOffset() : LayoutUnit::Min();
   }
 
+  // Return true if this is participating within a -webkit-line-clamp context.
+  bool IsLineClampContext() const { return bitfields_.is_line_clamp_context; }
+
   base::Optional<int> LinesUntilClamp() const {
     return HasRareData() ? rare_data_->LinesUntilClamp() : base::nullopt;
   }
@@ -1244,6 +1247,7 @@ class CORE_EXPORT NGConstraintSpace final {
           is_anonymous(false),
           is_new_formatting_context(false),
           is_orthogonal_writing_mode_root(false),
+          is_line_clamp_context(false),
           is_painted_atomically(false),
           use_first_line_style(false),
           ancestor_has_clearance_past_adjoining_floats(false),
@@ -1271,6 +1275,7 @@ class CORE_EXPORT NGConstraintSpace final {
              is_new_formatting_context == other.is_new_formatting_context &&
              is_orthogonal_writing_mode_root ==
                  other.is_orthogonal_writing_mode_root &&
+             is_line_clamp_context == other.is_line_clamp_context &&
              is_painted_atomically == other.is_painted_atomically &&
              use_first_line_style == other.use_first_line_style &&
              ancestor_has_clearance_past_adjoining_floats ==
@@ -1299,6 +1304,7 @@ class CORE_EXPORT NGConstraintSpace final {
     unsigned is_anonymous : 1;
     unsigned is_new_formatting_context : 1;
     unsigned is_orthogonal_writing_mode_root : 1;
+    unsigned is_line_clamp_context : 1;
 
     unsigned is_painted_atomically : 1;
     unsigned use_first_line_style : 1;

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

@@ -374,6 +374,11 @@ class CORE_EXPORT NGConstraintSpaceBuilder final {
                                                  section_index);
   }
 
+  void SetIsLineClampContext(bool is_line_clamp_context) {
+    DCHECK(!is_new_fc_);
+    space_.bitfields_.is_line_clamp_context = is_line_clamp_context;
+  }
+
   void SetLinesUntilClamp(const base::Optional<int>& clamp) {
 #if DCHECK_IS_ON()
     DCHECK(!is_lines_until_clamp_set_);

third_party/blink/web_tests/external/wpt/css/css-overflow/reference/webkit-line-clamp-036-ref.html

+<!DOCTYPE html>
+<meta charset="utf-8">
+<style>
+.clamp {
+  display: -webkit-box;
+  -webkit-box-orient: vertical;
+  width: 150px;
+  font: 16px / 32px monospace;
+  background-color: yellow;
+  padding: 4px;
+  overflow: hidden;
+}
+</style>
+<div class="clamp">
+  supercalifragilisticexpialidocious
+  supercalifragi…
+</div>

third_party/blink/web_tests/external/wpt/css/css-overflow/reference/webkit-line-clamp-037-ref.html

+<!DOCTYPE html>
+<meta charset="utf-8">
+<style>
+.clamp {
+  display: -webkit-box;
+  -webkit-box-orient: vertical;
+  width: 150px;
+  font: 16px / 32px monospace;
+  background-color: yellow;
+  padding: 4px;
+  overflow: hidden;
+}
+</style>
+<div class="clamp">
+  supercalifragilisticexpialidocious
+  supercalifragilisticexpialidocious
+</div>

third_party/blink/web_tests/external/wpt/css/css-overflow/webkit-line-clamp-036.html

+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://drafts.csswg.org/css-overflow-3/#webkit-line-clamp">
+<link rel="match" href="reference/webkit-line-clamp-036-ref.html">
+<meta name="assert" content="text-overflow: ellipsis shouldn't apply within a -webkit-line-clamp context.">
+<style>
+.clamp {
+  display: -webkit-box;
+  -webkit-box-orient: vertical;
+  -webkit-line-clamp: 2;
+  width: 150px;
+  font: 16px / 32px monospace;
+  background-color: yellow;
+  padding: 4px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+</style>
+<div class="clamp">
+  supercalifragilisticexpialidocious
+  supercalifragilisticexpialidocious
+  supercalifragilisticexpialidocious
+</div>

third_party/blink/web_tests/external/wpt/css/css-overflow/webkit-line-clamp-037.html

+<!DOCTYPE html>
+<meta charset="utf-8">
+<link rel="help" href="https://drafts.csswg.org/css-overflow-3/#webkit-line-clamp">
+<link rel="match" href="reference/webkit-line-clamp-037-ref.html">
+<meta name="assert" content="text-overflow: ellipsis shouldn't apply within a -webkit-line-clamp context.">
+<style>
+.clamp {
+  display: -webkit-box;
+  -webkit-box-orient: vertical;
+  -webkit-line-clamp: 2;
+  width: 150px;
+  font: 16px / 32px monospace;
+  background-color: yellow;
+  padding: 4px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+</style>
+<div class="clamp">
+  supercalifragilisticexpialidocious
+  supercalifragilisticexpialidocious
+</div>