servo: Merge #15905 - Add gradient border support (from mephisto41:add-border-gradient); r=emilio

webrender add gradient border support in https://github.com/servo/webrender/pull/953. This pr add support in servo.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

<!-- Either: -->
- [X] These changes do not require tests because it should be covered by wpt

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

Source-Repo: https://github.com/servo/servo
Source-Revision: fd8127b23b177886217eb1f21963e6c02528647a

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 9f3188db40cd1d21acb98f2b7f6927961c8e71ad

servo/components/gfx/display_list/mod.rs

@@ -886,10 +886,7 @@ pub struct IframeDisplayItem {
 
 /// Paints a gradient.
 #[derive(Clone, Deserialize, HeapSizeOf, Serialize)]
-pub struct GradientDisplayItem {
-    /// Fields common to all display items.
-    pub base: BaseDisplayItem,
-
+pub struct Gradient {
     /// The start point of the gradient (computed during display list construction).
     pub start_point: Point2D<Au>,
 
@@ -900,6 +897,15 @@ pub struct GradientDisplayItem {
     pub stops: Vec<GradientStop>,
 }
 
+#[derive(Clone, Deserialize, HeapSizeOf, Serialize)]
+pub struct GradientDisplayItem {
+    /// Fields common to all display item.
+    pub base: BaseDisplayItem,
+
+    /// Contains all gradient data. Included start, end point and color stops.
+    pub gradient: Gradient,
+}
+
 /// A normal border, supporting CSS border styles.
 #[derive(Clone, HeapSizeOf, Deserialize, Serialize)]
 pub struct NormalBorder {
@@ -939,11 +945,22 @@ pub struct ImageBorder {
     pub repeat_vertical: webrender_traits::RepeatMode,
 }
 
+/// A border that is made of linear gradient
+#[derive(Clone, HeapSizeOf, Deserialize, Serialize)]
+pub struct GradientBorder {
+    /// The gradient info that this border uses, border-image-source.
+    pub gradient: Gradient,
+
+    /// Outsets for the border, as per border-image-outset.
+    pub outset: SideOffsets2D<f32>,
+}
+
 /// Specifies the type of border
 #[derive(Clone, HeapSizeOf, Deserialize, Serialize)]
 pub enum BorderDetails {
     Normal(NormalBorder),
     Image(ImageBorder),
+    Gradient(GradientBorder),
 }
 
 /// Paints a border.

servo/components/layout/display_list_builder.rs

@@ -20,6 +20,7 @@ use flow::{BaseFlow, Flow, IS_ABSOLUTELY_POSITIONED};
 use flow_ref::FlowRef;
 use fragment::{CoordinateSystem, Fragment, ImageFragmentInfo, ScannedTextFragmentInfo};
 use fragment::{SpecificFragmentInfo, TruncatedFragmentInfo};
+use gfx::display_list;
 use gfx::display_list::{BLUR_INFLATION_FACTOR, BaseDisplayItem, BorderDetails};
 use gfx::display_list::{BorderDisplayItem, ImageBorder, NormalBorder};
 use gfx::display_list::{BorderRadii, BoxShadowClipMode, BoxShadowDisplayItem, ClippingRegion};
@@ -350,6 +351,12 @@ pub trait FragmentDisplayListBuilding {
                                                image_url: &ServoUrl,
                                                background_index: usize);
 
+    fn convert_gradient(&self,
+                        absolute_bounds: &Rect<Au>,
+                        gradient: &Gradient,
+                        style: &ServoComputedValues)
+                        -> Option<display_list::Gradient>;
+
     /// Adds the display items necessary to paint the background linear gradient of this fragment
     /// to the appropriate section of the display list.
     fn build_display_list_for_background_gradient(&self,
@@ -831,20 +838,13 @@ impl FragmentDisplayListBuilding for Fragment {
         }
     }
 
-    fn build_display_list_for_background_gradient(&self,
-                                                  state: &mut DisplayListBuildState,
-                                                  display_list_section: DisplayListSection,
-                                                  absolute_bounds: &Rect<Au>,
-                                                  clip: &ClippingRegion,
-                                                  gradient: &Gradient,
-                                                  style: &ServoComputedValues) {
-        let mut clip = clip.clone();
-        clip.intersect_rect(absolute_bounds);
-
-
+    fn convert_gradient(&self,
+                        absolute_bounds: &Rect<Au>,
+                        gradient: &Gradient,
+                        style: &ServoComputedValues) -> Option<display_list::Gradient> {
         // FIXME: Repeating gradients aren't implemented yet.
         if gradient.repeating {
-          return;
+          return None;
         }
         let angle = if let GradientKind::Linear(angle_or_corner) = gradient.gradient_kind {
             match angle_or_corner {
@@ -869,7 +869,7 @@ impl FragmentDisplayListBuilding for Fragment {
             }
         } else {
             // FIXME: Radial gradients aren't implemented yet.
-            return;
+            return None;
         };
 
         // Get correct gradient line length, based on:
@@ -953,19 +953,39 @@ impl FragmentDisplayListBuilding for Fragment {
         let center = Point2D::new(absolute_bounds.origin.x + absolute_bounds.size.width / 2,
                                   absolute_bounds.origin.y + absolute_bounds.size.height / 2);
 
-        let base = state.create_base_display_item(absolute_bounds,
-                                                  &clip,
-                                                  self.node,
-                                                  style.get_cursor(Cursor::Default),
-                                                  display_list_section);
-        let gradient_display_item = DisplayItem::Gradient(box GradientDisplayItem {
-            base: base,
+        Some(display_list::Gradient {
             start_point: center - delta,
             end_point: center + delta,
             stops: stops,
-        });
+        })
+    }
 
-        state.add_display_item(gradient_display_item);
+    fn build_display_list_for_background_gradient(&self,
+                                                  state: &mut DisplayListBuildState,
+                                                  display_list_section: DisplayListSection,
+                                                  absolute_bounds: &Rect<Au>,
+                                                  clip: &ClippingRegion,
+                                                  gradient: &Gradient,
+                                                  style: &ServoComputedValues) {
+        let mut clip = clip.clone();
+        clip.intersect_rect(absolute_bounds);
+
+        let grad = self.convert_gradient(absolute_bounds, gradient, style);
+
+        if let Some(x) = grad {
+            let base = state.create_base_display_item(absolute_bounds,
+                                                      &clip,
+                                                      self.node,
+                                                      style.get_cursor(Cursor::Default),
+                                                      display_list_section);
+
+            let gradient_display_item = DisplayItem::Gradient(box GradientDisplayItem {
+                base: base,
+                gradient: x,
+            });
+
+            state.add_display_item(gradient_display_item);
+        }
     }
 
     fn build_display_list_for_box_shadow_if_applicable(&self,
@@ -1076,8 +1096,28 @@ impl FragmentDisplayListBuilding for Fragment {
                     }),
                 }));
             }
-            Some(computed::Image::Gradient(..)) => {
-                // TODO(gw): Handle border-image with gradient.
+            Some(computed::Image::Gradient(ref gradient)) => {
+                match gradient.gradient_kind {
+                    GradientKind::Linear(_) => {
+                        let grad = self.convert_gradient(&bounds, gradient, style);
+
+                        if let Some(x) = grad {
+                            state.add_display_item(DisplayItem::Border(box BorderDisplayItem {
+                                base: base,
+                                border_widths: border.to_physical(style.writing_mode),
+                                details: BorderDetails::Gradient(display_list::GradientBorder {
+                                    gradient: x,
+
+                                    // TODO(gw): Support border-image-outset
+                                    outset: SideOffsets2D::zero(),
+                                }),
+                            }));
+                        }
+                    }
+                    GradientKind::Radial(_, _) => {
+                        // TODO(gw): Handle border-image with radial gradient.
+                    }
+                }
             }
             Some(computed::Image::ImageRect(..)) => {
                 // TODO: Handle border-image with `-moz-image-rect`.

servo/components/layout/webrender_helpers.rs

@@ -351,20 +351,30 @@ impl WebRenderDisplayItemConverter for DisplayItem {
                             }
                         }
                     }
+                    BorderDetails::Gradient(ref gradient) => {
+                        webrender_traits::BorderDetails::Gradient(webrender_traits::GradientBorder {
+                            gradient: builder.create_gradient(
+                                          gradient.gradient.start_point.to_pointf(),
+                                          gradient.gradient.end_point.to_pointf(),
+                                          gradient.gradient.stops.clone(),
+                                          ExtendMode::Clamp),
+                            outset: gradient.outset,
+                        })
+                    }
                 };
 
                 builder.push_border(rect, clip, widths, details);
             }
             DisplayItem::Gradient(ref item) => {
                 let rect = item.base.bounds.to_rectf();
-                let start_point = item.start_point.to_pointf();
-                let end_point = item.end_point.to_pointf();
+                let start_point = item.gradient.start_point.to_pointf();
+                let end_point = item.gradient.end_point.to_pointf();
                 let clip = item.base.clip.to_clip_region(builder);
                 builder.push_gradient(rect,
                                       clip,
                                       start_point,
                                       end_point,
-                                      item.stops.clone(),
+                                      item.gradient.stops.clone(),
                                       ExtendMode::Clamp);
             }
             DisplayItem::Line(..) => {