Implement new Webrender PushTextShadow API

Also includes an incidental bugfix for the rendering order of text decorations.

This change depends on servo/webrender#1454 being merged and upstreamed to servo.

components/gfx/display_list/mod.rs

@@ -605,6 +605,8 @@ pub enum DisplayItem {
     RadialGradient(Box<RadialGradientDisplayItem>),
     Line(Box<LineDisplayItem>),
     BoxShadow(Box<BoxShadowDisplayItem>),
+    PushTextShadow(Box<PushTextShadowDisplayItem>),
+    PopTextShadow(Box<PopTextShadowDisplayItem>),
     Iframe(Box<IframeDisplayItem>),
     PushStackingContext(Box<PushStackingContextItem>),
     PopStackingContext(Box<PopStackingContextItem>),
@@ -895,9 +897,6 @@ pub struct TextDisplayItem {
 
     /// The orientation of the text: upright or sideways left/right.
     pub orientation: TextOrientation,
-
-    /// The blur radius for this text. If zero, this text is not blurred.
-    pub blur_radius: Au,
 }
 
 #[derive(Clone, Eq, PartialEq, HeapSizeOf, Deserialize, Serialize)]
@@ -1180,6 +1179,29 @@ pub struct BoxShadowDisplayItem {
     pub clip_mode: BoxShadowClipMode,
 }
 
+/// Defines a text shadow that affects all items until the paired PopTextShadow.
+#[derive(Clone, HeapSizeOf, Deserialize, Serialize)]
+pub struct PushTextShadowDisplayItem {
+    /// Fields common to all display items.
+    pub base: BaseDisplayItem,
+
+    /// The offset of this shadow from the text.
+    pub offset: Vector2D<Au>,
+
+    /// The color of this shadow.
+    pub color: ColorF,
+
+    /// The blur radius for this shadow.
+    pub blur_radius: Au,
+}
+
+/// Defines a text shadow that affects all items until the next PopTextShadow.
+#[derive(Clone, HeapSizeOf, Deserialize, Serialize)]
+pub struct PopTextShadowDisplayItem {
+    /// Fields common to all display items.
+    pub base: BaseDisplayItem,
+}
+
 /// Defines a stacking context.
 #[derive(Clone, HeapSizeOf, Deserialize, Serialize)]
 pub struct PushStackingContextItem {
@@ -1233,6 +1255,8 @@ impl DisplayItem {
             DisplayItem::RadialGradient(ref gradient) => &gradient.base,
             DisplayItem::Line(ref line) => &line.base,
             DisplayItem::BoxShadow(ref box_shadow) => &box_shadow.base,
+            DisplayItem::PushTextShadow(ref push_text_shadow) => &push_text_shadow.base,
+            DisplayItem::PopTextShadow(ref pop_text_shadow) => &pop_text_shadow.base,
             DisplayItem::Iframe(ref iframe) => &iframe.base,
             DisplayItem::PushStackingContext(ref stacking_context) => &stacking_context.base,
             DisplayItem::PopStackingContext(ref item) => &item.base,
@@ -1353,6 +1377,8 @@ impl fmt::Debug for DisplayItem {
                 DisplayItem::RadialGradient(_) => "RadialGradient".to_owned(),
                 DisplayItem::Line(_) => "Line".to_owned(),
                 DisplayItem::BoxShadow(_) => "BoxShadow".to_owned(),
+                DisplayItem::PushTextShadow(_) => "PushTextShadow".to_owned(),
+                DisplayItem::PopTextShadow(_) => "PopTextShadow".to_owned(),
                 DisplayItem::Iframe(_) => "Iframe".to_owned(),
                 DisplayItem::PushStackingContext(_) |
                 DisplayItem::PopStackingContext(_) |

components/layout/display_list_builder.rs

@@ -25,10 +25,10 @@ use gfx::display_list::{BLUR_INFLATION_FACTOR, BaseDisplayItem, BorderDetails, B
 use gfx::display_list::{BorderRadii, BoxShadowClipMode, BoxShadowDisplayItem, ClippingRegion};
 use gfx::display_list::{DisplayItem, DisplayItemMetadata, DisplayList, DisplayListSection};
 use gfx::display_list::{GradientDisplayItem, IframeDisplayItem, ImageBorder, ImageDisplayItem};
-use gfx::display_list::{LineDisplayItem, NormalBorder, OpaqueNode, RadialGradientDisplayItem};
-use gfx::display_list::{ScrollRoot, ScrollRootType, SolidColorDisplayItem, StackingContext};
-use gfx::display_list::{StackingContextType, TextDisplayItem, TextOrientation, WebGLDisplayItem};
-use gfx::display_list::WebRenderImageInfo;
+use gfx::display_list::{LineDisplayItem, NormalBorder, OpaqueNode, PushTextShadowDisplayItem};
+use gfx::display_list::{PopTextShadowDisplayItem, RadialGradientDisplayItem, ScrollRoot};
+use gfx::display_list::{ScrollRootType, SolidColorDisplayItem, StackingContext, StackingContextType};
+use gfx::display_list::{TextDisplayItem, TextOrientation, WebGLDisplayItem, WebRenderImageInfo};
 use gfx_traits::{combine_id_with_fragment_type, FragmentType, StackingContextId};
 use inline::{FIRST_FRAGMENT_OF_ELEMENT, InlineFlow, LAST_FRAGMENT_OF_ELEMENT};
 use ipc_channel::ipc;
@@ -526,16 +526,15 @@ pub trait FragmentDisplayListBuilding {
                                             state: &mut DisplayListBuildState,
                                             text_fragment: &ScannedTextFragmentInfo,
                                             stacking_relative_content_box: &Rect<Au>,
-                                            text_shadow: Option<&SimpleShadow>,
+                                            text_shadows: &[SimpleShadow],
                                             clip: &Rect<Au>);
 
     /// Creates the display item for a text decoration: underline, overline, or line-through.
     fn build_display_list_for_text_decoration(&self,
                                               state: &mut DisplayListBuildState,
                                               color: &RGBA,
                                               stacking_relative_box: &LogicalRect<Au>,
-                                              clip: &Rect<Au>,
-                                              blur: Au);
+                                              clip: &Rect<Au>);
 
     /// A helper method that `build_display_list` calls to create per-fragment-type display items.
     fn build_fragment_type_specific_display_items(&mut self,
@@ -1867,24 +1866,11 @@ impl FragmentDisplayListBuilding for Fragment {
                 ..
             }) |
             SpecificFragmentInfo::ScannedText(box ref text_fragment) => {
-                // Create items for shadows.
-                //
-                // NB: According to CSS-BACKGROUNDS, text shadows render in *reverse* order (front
-                // to back).
-
-                for text_shadow in self.style.get_inheritedtext().text_shadow.0.iter().rev() {
-                    self.build_display_list_for_text_fragment(state,
-                                                              &*text_fragment,
-                                                              &stacking_relative_content_box,
-                                                              Some(text_shadow),
-                                                              clip);
-                }
-
                 // Create the main text display item.
                 self.build_display_list_for_text_fragment(state,
                                                           &*text_fragment,
                                                           &stacking_relative_content_box,
-                                                          None,
+                                                          &self.style.get_inheritedtext().text_shadow.0,
                                                           clip);
 
                 if opts::get().show_debug_fragment_borders {
@@ -2066,22 +2052,20 @@ impl FragmentDisplayListBuilding for Fragment {
                                             state: &mut DisplayListBuildState,
                                             text_fragment: &ScannedTextFragmentInfo,
                                             stacking_relative_content_box: &Rect<Au>,
-                                            text_shadow: Option<&SimpleShadow>,
+                                            text_shadows: &[SimpleShadow],
                                             clip: &Rect<Au>) {
+
+        // NB: The order for painting text components (CSS Text Decoration Module Level 3) is:
+        // shadows, underline, overline, text, text-emphasis, and then line-through.
+
         // TODO(emilio): Allow changing more properties by ::selection
-        let text_color = if let Some(shadow) = text_shadow {
-            // If we're painting a shadow, paint the text the same color as the shadow.
-            self.style().resolve_color(shadow.color)
-        } else if text_fragment.selected() {
-            // Otherwise, paint the text with the color as described in its styling.
+        // Paint the text with the color as described in its styling.
+        let text_color = if text_fragment.selected() {
             self.selected_style().get_color().color
         } else {
             self.style().get_color().color
         };
-        let offset = text_shadow.map_or(Vector2D::zero(), |s| {
-            Vector2D::new(s.horizontal, s.vertical)
-        });
-        let shadow_blur_radius = text_shadow.map(|s| s.blur).unwrap_or(Au(0));
+
 
         // Determine the orientation and cursor to use.
         let (orientation, cursor) = if self.style.writing_mode.is_vertical() {
@@ -2097,28 +2081,32 @@ impl FragmentDisplayListBuilding for Fragment {
         // FIXME(pcwalton): Get the real container size.
         let container_size = Size2D::zero();
         let metrics = &text_fragment.run.font_metrics;
-        let stacking_relative_content_box = stacking_relative_content_box.translate(&offset);
         let baseline_origin = stacking_relative_content_box.origin +
             LogicalPoint::new(self.style.writing_mode,
                               Au(0),
                               metrics.ascent).to_physical(self.style.writing_mode,
                                                           container_size).to_vector();
 
-        // Create the text display item.
+        // Base item for all text/shadows
         let base = state.create_base_display_item(&stacking_relative_content_box,
                                                   LocalClip::from(clip.to_rectf()),
                                                   self.node,
                                                   self.style().get_cursor(cursor),
                                                   DisplayListSection::Content);
-        state.add_display_item(DisplayItem::Text(box TextDisplayItem {
-            base: base,
-            text_run: text_fragment.run.clone(),
-            range: text_fragment.range,
-            text_color: text_color.to_gfx_color(),
-            orientation: orientation,
-            baseline_origin: baseline_origin,
-            blur_radius: shadow_blur_radius,
-        }));
+
+        // NB: According to CSS-BACKGROUNDS, text shadows render in *reverse* order (front
+        // to back).
+
+        // Shadows
+        for shadow in text_shadows.iter().rev() {
+            state.add_display_item(DisplayItem::PushTextShadow(box PushTextShadowDisplayItem {
+                base: base.clone(),
+                blur_radius: shadow.blur,
+                offset: Vector2D::new(shadow.horizontal, shadow.vertical),
+                color: self.style().resolve_color(shadow.color).to_gfx_color(),
+            }));
+        }
+
 
         // Create display items for text decorations.
         let mut text_decorations = self.style()
@@ -2131,8 +2119,10 @@ impl FragmentDisplayListBuilding for Fragment {
 
         let stacking_relative_content_box =
             LogicalRect::from_physical(self.style.writing_mode,
-                                       stacking_relative_content_box,
+                                       *stacking_relative_content_box,
                                        container_size);
+
+        // Underline
         if let Some(ref underline_color) = text_decorations.underline {
             let mut stacking_relative_box = stacking_relative_content_box;
             stacking_relative_box.start.b = stacking_relative_content_box.start.b +
@@ -2141,20 +2131,35 @@ impl FragmentDisplayListBuilding for Fragment {
             self.build_display_list_for_text_decoration(state,
                                                         underline_color,
                                                         &stacking_relative_box,
-                                                        clip,
-                                                        shadow_blur_radius);
+                                                        clip);
         }
 
+        // Overline
         if let Some(ref overline_color) = text_decorations.overline {
             let mut stacking_relative_box = stacking_relative_content_box;
             stacking_relative_box.size.block = metrics.underline_size;
             self.build_display_list_for_text_decoration(state,
                                                         overline_color,
                                                         &stacking_relative_box,
-                                                        clip,
-                                                        shadow_blur_radius);
+                                                        clip);
         }
 
+        // Text
+        state.add_display_item(DisplayItem::Text(box TextDisplayItem {
+            base: base.clone(),
+            text_run: text_fragment.run.clone(),
+            range: text_fragment.range,
+            text_color: text_color.to_gfx_color(),
+            orientation: orientation,
+            baseline_origin: baseline_origin,
+        }));
+
+
+        // TODO(#17715): emit text-emphasis marks here.
+        // (just push another TextDisplayItem?)
+
+
+        // Line-Through
         if let Some(ref line_through_color) = text_decorations.line_through {
             let mut stacking_relative_box = stacking_relative_content_box;
             stacking_relative_box.start.b = stacking_relative_box.start.b + metrics.ascent -
@@ -2163,40 +2168,36 @@ impl FragmentDisplayListBuilding for Fragment {
             self.build_display_list_for_text_decoration(state,
                                                         line_through_color,
                                                         &stacking_relative_box,
-                                                        clip,
-                                                        shadow_blur_radius);
+                                                        clip);
+        }
+
+        // Pair all the PushTextShadows
+        for _ in text_shadows {
+            state.add_display_item(DisplayItem::PopTextShadow(box PopTextShadowDisplayItem {
+                base: base.clone(),
+            }));
         }
     }
 
     fn build_display_list_for_text_decoration(&self,
                                               state: &mut DisplayListBuildState,
                                               color: &RGBA,
                                               stacking_relative_box: &LogicalRect<Au>,
-                                              clip: &Rect<Au>,
-                                              blur_radius: Au) {
-        // Perhaps surprisingly, text decorations are box shadows. This is because they may need
-        // to have blur in the case of `text-shadow`, and this doesn't hurt performance because box
-        // shadows are optimized into essentially solid colors if there is no need for the blur.
-        //
+                                              clip: &Rect<Au>) {
         // FIXME(pcwalton, #2795): Get the real container size.
         let container_size = Size2D::zero();
         let stacking_relative_box = stacking_relative_box.to_physical(self.style.writing_mode,
                                                                       container_size);
         let base = state.create_base_display_item(
-            &shadow_bounds(&stacking_relative_box, blur_radius, Au(0)),
+            &stacking_relative_box,
             LocalClip::from(clip.to_rectf()),
             self.node,
             self.style.get_cursor(Cursor::Default),
             DisplayListSection::Content);
-        state.add_display_item(DisplayItem::BoxShadow(box BoxShadowDisplayItem {
+
+        state.add_display_item(DisplayItem::SolidColor(box SolidColorDisplayItem {
             base: base,
-            box_bounds: stacking_relative_box,
             color: color.to_gfx_color(),
-            offset: Vector2D::zero(),
-            blur_radius: blur_radius,
-            spread_radius: Au(0),
-            border_radius: Au(0),
-            clip_mode: BoxShadowClipMode::None,
         }));
     }
 

components/layout/webrender_helpers.rs

@@ -289,7 +289,6 @@ impl WebRenderDisplayItemConverter for DisplayItem {
                                       item.text_run.font_key,
                                       item.text_color,
                                       item.text_run.actual_pt_size,
-                                      item.blur_radius.to_f32_px(),
                                       None);
                 }
             }
@@ -449,6 +448,19 @@ impl WebRenderDisplayItemConverter for DisplayItem {
                                         item.border_radius.to_f32_px(),
                                         item.clip_mode.to_clip_mode());
             }
+            DisplayItem::PushTextShadow(ref item) => {
+                let rect = item.base.bounds.to_rectf();
+                builder.push_text_shadow(rect,
+                                         Some(item.base.local_clip),
+                                         webrender_api::TextShadow {
+                                             blur_radius: item.blur_radius.to_f32_px(),
+                                             offset: item.offset.to_vectorf(),
+                                             color: item.color,
+                                         });
+            }
+            DisplayItem::PopTextShadow(_) => {
+                builder.pop_text_shadow();
+            }
             DisplayItem::Iframe(ref item) => {
                 let rect = item.base.bounds.to_rectf();
                 let pipeline_id = item.iframe.to_webrender();