Re-use the TextMetrics data structure in the Layout 2020 fragment tree (#30823)

This data structure has all of the metrics needed to render a font and
is in `Au`. We'll need more of these metrics for implementing
`vertical-align` and its use doesn't increase the size of the Fragment
tree (as the BoxFragment is still larger). In addition, this will be
helpful when switching layout to `Au`.

components/layout_2020/display_list/mod.rs

@@ -281,7 +281,7 @@ impl Fragment {
             .to_physical(fragment.parent_style.writing_mode, containing_block)
             .translate(containing_block.origin.to_vector());
         let mut baseline_origin = rect.origin.clone();
-        baseline_origin.y += fragment.font_metrics.ascent;
+        baseline_origin.y += Length::from(fragment.font_metrics.ascent);
         let glyphs = glyphs(&fragment.glyphs, baseline_origin);
         if glyphs.is_empty() {
             return;
@@ -306,10 +306,6 @@ impl Fragment {
         let color = fragment.parent_style.clone_color();
         let font_metrics = &fragment.font_metrics;
         let dppx = builder.context.style_context.device_pixel_ratio().get();
-        let round_to_nearest_device_pixel = |value: Length| -> Length {
-            // Round to the nearest integer device pixel, ensuring at least one device pixel.
-            Length::new((value.px() * dppx).round().max(1.0) / dppx)
-        };
 
         // Underline.
         if fragment
@@ -317,8 +313,9 @@ impl Fragment {
             .contains(TextDecorationLine::UNDERLINE)
         {
             let mut rect = rect;
-            rect.origin.y = rect.origin.y + font_metrics.ascent - font_metrics.underline_offset;
+            rect.origin.y =
-            rect.size.height = round_to_nearest_device_pixel(font_metrics.underline_size);
+                rect.origin.y + Length::from(font_metrics.ascent - font_metrics.underline_offset);
+            rect.size.height = Length::new(font_metrics.underline_size.to_nearest_pixel(dppx));
             self.build_display_list_for_text_decoration(fragment, builder, &rect, &color);
         }
 
@@ -328,7 +325,7 @@ impl Fragment {
             .contains(TextDecorationLine::OVERLINE)
         {
             let mut rect = rect;
-            rect.size.height = round_to_nearest_device_pixel(font_metrics.underline_size);
+            rect.size.height = Length::new(font_metrics.underline_size.to_nearest_pixel(dppx));
             self.build_display_list_for_text_decoration(fragment, builder, &rect, &color);
         }
 
@@ -349,9 +346,10 @@ impl Fragment {
             .contains(TextDecorationLine::LINE_THROUGH)
         {
             let mut rect = rect;
-            rect.origin.y = rect.origin.y + font_metrics.ascent - font_metrics.strikeout_offset;
+            rect.origin.y =
+                rect.origin.y + Length::from(font_metrics.ascent - font_metrics.strikeout_offset);
             // XXX(ferjm) This does not work on MacOS #942
-            rect.size.height = round_to_nearest_device_pixel(font_metrics.strikeout_size);
+            rect.size.height = Length::new(font_metrics.strikeout_size.to_nearest_pixel(dppx));
             self.build_display_list_for_text_decoration(fragment, builder, &rect, &color);
         }
     }

components/layout_2020/flow/inline.rs

@@ -8,6 +8,7 @@ use std::vec::IntoIter;
 
 use app_units::Au;
 use atomic_refcell::AtomicRef;
+use gfx::font::FontMetrics;
 use gfx::text::glyph::GlyphStore;
 use gfx::text::text_run::GlyphRun;
 use log::warn;
@@ -32,7 +33,7 @@ use crate::flow::FlowLayout;
 use crate::formatting_contexts::IndependentFormattingContext;
 use crate::fragment_tree::{
     AnonymousFragment, BaseFragmentInfo, BoxFragment, CollapsedBlockMargins, CollapsedMargin,
-    FontMetrics, Fragment, HoistedSharedFragment, TextFragment,
+    Fragment, HoistedSharedFragment, TextFragment,
 };
 use crate::geom::{LogicalRect, LogicalVec2};
 use crate::positioned::{
@@ -893,7 +894,7 @@ impl<'a, 'b> InlineFormattingContextState<'a, 'b> {
         glyph_store: std::sync::Arc<GlyphStore>,
         base_fragment_info: BaseFragmentInfo,
         parent_style: &Arc<ComputedValues>,
-        font_metrics: FontMetrics,
+        font_metrics: &FontMetrics,
         font_key: FontInstanceKey,
     ) {
         let inline_advance = Length::from(glyph_store.total_advance());
@@ -926,7 +927,7 @@ impl<'a, 'b> InlineFormattingContextState<'a, 'b> {
                 text: vec![glyph_store],
                 base_fragment_info: base_fragment_info.into(),
                 parent_style: parent_style.clone(),
-                font_metrics,
+                font_metrics: font_metrics.clone(),
                 font_key,
                 text_decoration_line: self.current_inline_container_state().text_decoration_line,
             }),
@@ -1644,7 +1645,7 @@ impl TextRun {
             );
 
             Ok(BreakAndShapeResult {
-                font_metrics: (&font.metrics).into(),
+                font_metrics: font.metrics.clone(),
                 font_key: font.font_key,
                 runs,
                 break_at_start,
@@ -1729,7 +1730,7 @@ impl TextRun {
                 run.glyph_store,
                 self.base_fragment_info,
                 &self.parent_style,
-                font_metrics,
+                &font_metrics,
                 font_key,
             );
         }
@@ -1930,7 +1931,7 @@ struct TextRunLineItem {
 fn line_height(parent_style: &ComputedValues, font_metrics: &FontMetrics) -> Length {
     let font_size = parent_style.get_font().font_size.computed_size();
     match parent_style.get_inherited_text().line_height {
-        LineHeight::Normal => font_metrics.line_gap,
+        LineHeight::Normal => Length::from(font_metrics.line_gap),
         LineHeight::Number(number) => font_size * number.0,
         LineHeight::Length(length) => length.0,
     }
@@ -1946,8 +1947,8 @@ fn line_gap_from_style(layout_context: &LayoutContext, style: &ComputedValues) -
                 return Length::zero();
             },
         };
-        let font_metrics: FontMetrics = (&font.borrow().metrics).into();
+        let font = font.borrow();
-        font_metrics.line_gap
+        Length::from(font.metrics.line_gap)
     })
 }
 
@@ -1961,8 +1962,8 @@ fn line_height_from_style(layout_context: &LayoutContext, style: &ComputedValues
                 return Length::zero();
             },
         };
-        let font_metrics: FontMetrics = (&font.borrow().metrics).into();
+        let font = font.borrow();
-        line_height(style, &font_metrics)
+        line_height(style, &font.metrics)
     })
 }
 

components/layout_2020/fragment_tree/fragment.rs

@@ -4,7 +4,7 @@
 
 use std::sync::Arc;
 
-use gfx::font::FontMetrics as GfxFontMetrics;
+use gfx::font::FontMetrics;
 use gfx::text::glyph::GlyphStore;
 use gfx_traits::print_tree::PrintTree;
 use msg::constellation_msg::{BrowsingContextId, PipelineId};
@@ -75,29 +75,6 @@ pub(crate) struct AnonymousFragment {
     pub scrollable_overflow: PhysicalRect<Length>,
 }
 
-#[derive(Clone, Copy, Serialize)]
-pub(crate) struct FontMetrics {
-    pub ascent: Length,
-    pub line_gap: Length,
-    pub underline_offset: Length,
-    pub underline_size: Length,
-    pub strikeout_offset: Length,
-    pub strikeout_size: Length,
-}
-
-impl From<&GfxFontMetrics> for FontMetrics {
-    fn from(metrics: &GfxFontMetrics) -> FontMetrics {
-        FontMetrics {
-            ascent: metrics.ascent.into(),
-            line_gap: metrics.line_gap.into(),
-            underline_offset: metrics.underline_offset.into(),
-            underline_size: metrics.underline_size.into(),
-            strikeout_offset: metrics.strikeout_offset.into(),
-            strikeout_size: metrics.strikeout_size.into(),
-        }
-    }
-}
-
 #[derive(Serialize)]
 pub(crate) struct TextFragment {
     pub base: BaseFragment,

tests/wpt/meta/css/css-text-decor/text-decoration-thickness-from-zero-sized-font.html.ini

@@ -1,2 +0,0 @@
-[text-decoration-thickness-from-zero-sized-font.html]
-  expected: FAIL