layout: Port border-image support for legacy layout (#32874)

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/layout_2020/display_list/gradient.rs

@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use euclid::Size2D;
 use style::color::mix::ColorInterpolationMethod;
 use style::properties::ComputedValues;
 use style::values::computed::image::{EndingShape, Gradient, LineDirection};
@@ -11,15 +12,25 @@ use style::values::computed::{
 use style::values::generics::image::{
     Circle, ColorStop, Ellipse, GradientFlags, GradientItem, ShapeExtent,
 };
-use webrender_api::{self as wr, units};
+use webrender_api::units::LayoutPixel;
+use webrender_api::{
+    self as wr, units, ConicGradient as WebRenderConicGradient,
+    Gradient as WebRenderLinearGradient, RadialGradient as WebRenderRadialGradient,
+};
 use wr::ColorF;
 
+pub(super) enum WebRenderGradient {
+    Linear(WebRenderLinearGradient),
+    Radial(WebRenderRadialGradient),
+    Conic(WebRenderConicGradient),
+}
+
 pub(super) fn build(
     style: &ComputedValues,
     gradient: &Gradient,
-    layer: &super::background::BackgroundLayer,
+    size: Size2D<f32, LayoutPixel>,
     builder: &mut super::DisplayListBuilder,
-) {
+) -> WebRenderGradient {
     match gradient {
         Gradient::Linear {
             ref items,
@@ -33,7 +44,7 @@ pub(super) fn build(
             direction,
             color_interpolation_method,
             *flags,
-            layer,
+            size,
             builder,
         ),
         Gradient::Radial {
@@ -50,7 +61,7 @@ pub(super) fn build(
             position,
             color_interpolation_method,
             *flags,
-            layer,
+            size,
             builder,
         ),
         Gradient::Conic {
@@ -66,7 +77,7 @@ pub(super) fn build(
             *color_interpolation_method,
             items,
             *flags,
-            layer,
+            size,
             builder,
         ),
     }
@@ -79,13 +90,12 @@ pub(super) fn build_linear(
     line_direction: &LineDirection,
     _color_interpolation_method: &ColorInterpolationMethod,
     flags: GradientFlags,
-    layer: &super::background::BackgroundLayer,
+    gradient_box: Size2D<f32, LayoutPixel>,
     builder: &mut super::DisplayListBuilder,
-) {
+) -> WebRenderGradient {
     use style::values::specified::position::HorizontalPositionKeyword::*;
     use style::values::specified::position::VerticalPositionKeyword::*;
     use units::LayoutVector2D as Vec2;
-    let gradient_box = layer.tile_size;
 
     // A vector of length 1.0 in the direction of the gradient line
     let direction = match line_direction {
@@ -168,16 +178,12 @@ pub(super) fn build_linear(
     } else {
         wr::ExtendMode::Clamp
     };
-    let linear_gradient = builder
-        .wr()
-        .create_gradient(start_point, end_point, stops, extend_mode);
-    builder.wr().push_gradient(
-        &layer.common,
-        layer.bounds,
-        linear_gradient,
-        layer.tile_size,
-        layer.tile_spacing,
-    )
+    WebRenderGradient::Linear(builder.wr().create_gradient(
+        start_point,
+        end_point,
+        stops,
+        extend_mode,
+    ))
 }
 
 /// <https://drafts.csswg.org/css-images-3/#radial-gradients>
@@ -189,10 +195,9 @@ pub(super) fn build_radial(
     center: &Position,
     _color_interpolation_method: &ColorInterpolationMethod,
     flags: GradientFlags,
-    layer: &super::background::BackgroundLayer,
+    gradient_box: Size2D<f32, LayoutPixel>,
     builder: &mut super::DisplayListBuilder,
-) {
-    let gradient_box = layer.tile_size;
+) -> WebRenderGradient {
     let center = units::LayoutPoint::new(
         center
             .horizontal
@@ -277,16 +282,12 @@ pub(super) fn build_radial(
     } else {
         wr::ExtendMode::Clamp
     };
-    let radial_gradient = builder
-        .wr()
-        .create_radial_gradient(center, radii, stops, extend_mode);
-    builder.wr().push_radial_gradient(
-        &layer.common,
-        layer.bounds,
-        radial_gradient,
-        layer.tile_size,
-        layer.tile_spacing,
-    )
+    WebRenderGradient::Radial(builder.wr().create_radial_gradient(
+        center,
+        radii,
+        stops,
+        extend_mode,
+    ))
 }
 
 /// <https://drafts.csswg.org/css-images-4/#conic-gradients>
@@ -298,10 +299,9 @@ fn build_conic(
     _color_interpolation_method: ColorInterpolationMethod,
     items: &[GradientItem<Color, AngleOrPercentage>],
     flags: GradientFlags,
-    layer: &super::background::BackgroundLayer,
+    gradient_box: Size2D<f32, LayoutPixel>,
     builder: &mut super::DisplayListBuilder<'_>,
-) {
-    let gradient_box = layer.tile_size;
+) -> WebRenderGradient {
     let center = units::LayoutPoint::new(
         center
             .horizontal
@@ -319,17 +319,12 @@ fn build_conic(
     } else {
         wr::ExtendMode::Clamp
     };
-    let conic_gradient =
-        builder
-            .wr()
-            .create_conic_gradient(center, angle.radians(), stops, extend_mode);
-    builder.wr().push_conic_gradient(
-        &layer.common,
-        layer.bounds,
-        conic_gradient,
-        layer.tile_size,
-        layer.tile_spacing,
-    )
+    WebRenderGradient::Conic(builder.wr().create_conic_gradient(
+        center,
+        angle.radians(),
+        stops,
+        extend_mode,
+    ))
 }
 
 fn conic_gradient_items_to_color_stops(