Do not use buggy text_decorations_in_effect

components/layout_2020/display_list/mod.rs

@@ -17,6 +17,7 @@ use style::computed_values::text_decoration_style::T as ComputedTextDecorationSt
 use style::dom::OpaqueNode;
 use style::properties::ComputedValues;
 use style::values::computed::{BorderStyle, Length, LengthPercentage};
+use style::values::specified::text::TextDecorationLine;
 use style::values::specified::ui::CursorKind;
 use webrender_api::{self as wr, units};
 
@@ -128,14 +129,13 @@ impl Fragment {
         common.hit_info = hit_info(&fragment.parent_style, fragment.tag, Cursor::Text);
 
         let color = fragment.parent_style.clone_color();
-        let text_decorations = fragment
-            .parent_style
-            .get_inherited_text()
-            .text_decorations_in_effect;
         let font_metrics = &fragment.font_metrics;
 
         // Underline.
-        if text_decorations.underline {
+        if fragment
+            .text_decorations_in_effect
+            .contains(TextDecorationLine::UNDERLINE)
+        {
             let mut rect = rect;
             rect.origin.y = rect.origin.y + font_metrics.ascent - font_metrics.underline_offset;
             rect.size.height = font_metrics.underline_size;
@@ -143,7 +143,10 @@ impl Fragment {
         }
 
         // Overline.
-        if text_decorations.overline {
+        if fragment
+            .text_decorations_in_effect
+            .contains(TextDecorationLine::OVERLINE)
+        {
             let mut rect = rect;
             rect.size.height = font_metrics.underline_size;
             self.build_display_list_for_text_decoration(fragment, builder, &rect, color);
@@ -160,7 +163,10 @@ impl Fragment {
         );
 
         // Line-through.
-        if text_decorations.line_through {
+        if fragment
+            .text_decorations_in_effect
+            .contains(TextDecorationLine::LINE_THROUGH)
+        {
             let mut rect = rect;
             rect.origin.y = rect.origin.y + font_metrics.ascent - font_metrics.strikeout_offset;
             // XXX(ferjm) This does not work on MacOS #942

components/layout_2020/flow/inline.rs

@@ -26,6 +26,7 @@ use style::dom::OpaqueNode;
 use style::properties::ComputedValues;
 use style::values::computed::{Length, LengthPercentage, Percentage};
 use style::values::specified::text::TextAlignKeyword;
+use style::values::specified::text::TextDecorationLine;
 use style::Zero;
 use webrender_api::FontInstanceKey;
 
@@ -385,6 +386,18 @@ impl Lines {
             block: line_block_size,
         };
         self.next_line_block_position += size.block;
+
+        // From https://drafts.csswg.org/css-text-decor/#line-decoration
+        // "When specified on or propagated to an inline box,
+        // that box becomes a decorating box for that decoration,
+        // applying the decoration to all its fragments..."
+        let text_decoration_line = containing_block.style.clone_text_decoration_line();
+        if text_decoration_line != TextDecorationLine::NONE {
+            for fragment in &mut line_contents {
+                fragment.set_text_decorations_in_effect(text_decoration_line);
+            }
+        }
+
         self.fragments
             .push(Fragment::Anonymous(AnonymousFragment::new(
                 Rect { start_corner, size },
@@ -775,6 +788,7 @@ impl TextRun {
                     font_metrics,
                     font_key,
                     glyphs,
+                    text_decorations_in_effect: TextDecorationLine::NONE,
                 }));
             if runs.is_empty() {
                 break;

components/layout_2020/fragments.rs

@@ -19,6 +19,7 @@ use style::dom::OpaqueNode;
 use style::logical_geometry::WritingMode;
 use style::properties::ComputedValues;
 use style::values::computed::Length;
+use style::values::specified::text::TextDecorationLine;
 use style::Zero;
 use webrender_api::{FontInstanceKey, ImageKey};
 
@@ -121,6 +122,8 @@ pub(crate) struct TextFragment {
     #[serde(skip_serializing)]
     pub font_key: FontInstanceKey,
     pub glyphs: Vec<Arc<GlyphStore>>,
+    /// A flag that represents the _used_ value of the text-decoration property.
+    pub text_decorations_in_effect: TextDecorationLine,
 }
 
 #[derive(Serialize)]
@@ -192,6 +195,23 @@ impl AbsoluteOrFixedPositionedFragment {
     pub fn print(&self, tree: &mut PrintTree) {
         tree.add_item(format!("AbsoluteOrFixedPositionedFragment({:?})", self.0));
     }
+    
+    pub fn set_text_decorations_in_effect(&mut self, text_decorations: TextDecorationLine) {
+        match self {
+            Fragment::Text(fragment) => fragment.text_decorations_in_effect = text_decorations,
+            Fragment::Box(fragment) => {
+                for child in &mut fragment.children {
+                    child.set_text_decorations_in_effect(text_decorations);
+                }
+            },
+            Fragment::Anonymous(fragment) => {
+                for child in &mut fragment.children {
+                    child.set_text_decorations_in_effect(text_decorations);
+                }
+            },
+            _ => (),
+        }
+    }
 }
 
 impl AnonymousFragment {

components/style/values/specified/text.rs

@@ -217,7 +217,7 @@ impl ToComputedValue for TextOverflow {
 }
 
 bitflags! {
-    #[derive(MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[derive(MallocSizeOf, Serialize, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
     #[value_info(other_values = "none,underline,overline,line-through,blink")]
     #[repr(C)]
     /// Specified keyword values for the text-decoration-line property.