auto merge of #4891 : mmatyas/servo/canvas_gradient, r=jdm

Based on [ebalint](https://github.com/ebalint)'s original patch, this commit implements the linear and radial gradients for the canvas. The PR also includes test cases.
Depends on #4623 and servo/rust-azure#136.

5 files changed, 101 insertions, 5 deletions

diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index 505307dd7bf..9e7b7012190 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -34,6 +34,7 @@ use dom::bindings::refcounted::Trusted;
 use dom::bindings::utils::{Reflectable, Reflector, WindowProxyHandler};
 use script_task::ScriptChan;
 
+use canvas::canvas_paint_task::{CanvasGradientStop, LinearGradientStyle, RadialGradientStyle};
 use cssparser::RGBA;
 use encoding::types::EncodingRef;
 use geom::matrix2d::Matrix2D;
@@ -233,6 +234,7 @@ no_jsmanaged_fields!(LengthOrPercentageOrAuto);
 no_jsmanaged_fields!(RGBA);
 no_jsmanaged_fields!(Matrix2D<T>);
 no_jsmanaged_fields!(StorageType);
+no_jsmanaged_fields!(CanvasGradientStop, LinearGradientStyle, RadialGradientStyle);
 
 impl JSTraceable for Box<ScriptChan+Send> {
     #[inline]
diff --git a/components/script/dom/canvasgradient.rs b/components/script/dom/canvasgradient.rs
index def78ca7f33..c1e61a12c26 100644
--- a/components/script/dom/canvasgradient.rs
+++ b/components/script/dom/canvasgradient.rs
@@ -2,10 +2,80 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::bindings::utils::Reflector;
+use cssparser::RGBA;
+use canvas::canvas_paint_task::{CanvasGradientStop, FillOrStrokeStyle, LinearGradientStyle, RadialGradientStyle};
+use dom::bindings::cell::DOMRefCell;
+use dom::bindings::codegen::Bindings::CanvasGradientBinding;
+use dom::bindings::codegen::Bindings::CanvasGradientBinding::CanvasGradientMethods;
+use dom::bindings::global::GlobalRef;
+use dom::bindings::js::{JSRef, Temporary};
+use dom::bindings::utils::{Reflector, reflect_dom_object};
+use dom::canvasrenderingcontext2d::parse_color;
 
 #[dom_struct]
 pub struct CanvasGradient {
     reflector_: Reflector,
+    style: CanvasGradientStyle,
+    stops: DOMRefCell<Vec<CanvasGradientStop>>,
 }
 
+#[jstraceable]
+pub enum CanvasGradientStyle {
+    Linear(LinearGradientStyle),
+    Radial(RadialGradientStyle),
+}
+
+impl CanvasGradient {
+    fn new_inherited(style: CanvasGradientStyle) -> CanvasGradient {
+        CanvasGradient {
+            reflector_: Reflector::new(),
+            style: style,
+            stops: DOMRefCell::new(Vec::new()),
+        }
+    }
+
+    pub fn new(global: GlobalRef, style: CanvasGradientStyle) -> Temporary<CanvasGradient> {
+        reflect_dom_object(box CanvasGradient::new_inherited(style),
+                           global, CanvasGradientBinding::Wrap)
+    }
+}
+
+impl<'a> CanvasGradientMethods for JSRef<'a, CanvasGradient> {
+    fn AddColorStop(self, offset: f32, color: String) {
+        let default_black = RGBA {
+            red: 0.0,
+            green: 0.0,
+            blue: 0.0,
+            alpha: 1.0,
+        };
+
+        self.stops.borrow_mut().push(CanvasGradientStop {
+            offset: offset as f64,
+            color: parse_color(color.as_slice()).unwrap_or(default_black),
+        });
+    }
+}
+
+pub trait ToFillOrStrokeStyle {
+    fn to_fill_or_stroke_style(&self) -> FillOrStrokeStyle;
+}
+
+impl<'a> ToFillOrStrokeStyle for JSRef<'a, CanvasGradient> {
+    fn to_fill_or_stroke_style(&self) -> FillOrStrokeStyle {
+        let gradient_stops = self.stops.borrow().clone();
+        match self.style {
+            CanvasGradientStyle::Linear(ref gradient) =>  {
+                FillOrStrokeStyle::LinearGradient(
+                    LinearGradientStyle::new(gradient.x0, gradient.y0,
+                                             gradient.x1, gradient.y1,
+                                             gradient_stops))
+            },
+            CanvasGradientStyle::Radial(ref gradient) => {
+                FillOrStrokeStyle::RadialGradient(
+                    RadialGradientStyle::new(gradient.x0, gradient.y0, gradient.r0,
+                                             gradient.x1, gradient.y1, gradient.r1,
+                                             gradient_stops))
+            }
+        }
+    }
+}
diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index d481aca911f..a029b3d3c54 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -7,11 +7,12 @@ use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasRen
 use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasWindingRule;
 use dom::bindings::codegen::Bindings::ImageDataBinding::ImageDataMethods;
 use dom::bindings::codegen::UnionTypes::StringOrCanvasGradientOrCanvasPattern;
-use dom::bindings::error::Error::IndexSize;
+use dom::bindings::error::Error::{IndexSize, TypeError};
 use dom::bindings::error::Fallible;
 use dom::bindings::global::{GlobalRef, GlobalField};
 use dom::bindings::js::{JS, JSRef, LayoutJS, Temporary};
 use dom::bindings::utils::{Reflector, reflect_dom_object};
+use dom::canvasgradient::{CanvasGradient, CanvasGradientStyle, ToFillOrStrokeStyle};
 use dom::htmlcanvaselement::{HTMLCanvasElement, HTMLCanvasElementHelpers};
 use dom::imagedata::{ImageData, ImageDataHelpers};
 
@@ -23,7 +24,9 @@ use geom::rect::Rect;
 use geom::size::Size2D;
 
 use canvas::canvas_paint_task::{CanvasMsg, CanvasPaintTask, FillOrStrokeStyle};
+use canvas::canvas_paint_task::{LinearGradientStyle, RadialGradientStyle};
 
+use std::borrow::ToOwned;
 use std::cell::Cell;
 use std::num::{Float, ToPrimitive};
 use std::sync::mpsc::{channel, Sender};
@@ -215,6 +218,9 @@ impl<'a> CanvasRenderingContext2DMethods for JSRef<'a, CanvasRenderingContext2D>
                     _ => {}
                 }
             }
+            StringOrCanvasGradientOrCanvasPattern::eCanvasGradient(gradient) => {
+                self.renderer.send(CanvasMsg::SetFillStyle(gradient.root().r().to_fill_or_stroke_style())).unwrap();
+            }
             _ => {}
         }
     }
@@ -264,6 +270,22 @@ impl<'a> CanvasRenderingContext2DMethods for JSRef<'a, CanvasRenderingContext2D>
         let canvas_size = self.canvas.root().r().get_size();
         self.renderer.send(CanvasMsg::PutImageData(data, image_data_rect, dirty_rect, canvas_size)).unwrap()
     }
+
+    fn CreateLinearGradient(self, x0: f64, y0: f64, x1: f64, y1: f64) -> Fallible<Temporary<CanvasGradient>> {
+        if [x0, y0, x1, y1].iter().any(|x| x.is_nan() || x.is_infinite()) {
+            return Err(TypeError("One of the arguments of createLinearGradient() is not a finite floating-point value.".to_owned()));
+        }
+        Ok(CanvasGradient::new(self.global.root().r(),
+                               CanvasGradientStyle::Linear(LinearGradientStyle::new(x0, y0, x1, y1, Vec::new()))))
+    }
+
+    fn CreateRadialGradient(self, x0: f64, y0: f64, r0: f64, x1: f64, y1: f64, r1: f64) -> Fallible<Temporary<CanvasGradient>> {
+        if [x0, y0, r0, x1, y1, r1].iter().any(|x| x.is_nan() || x.is_infinite()) {
+            return Err(TypeError("One of the arguments of createRadialGradient() is not a finite floating-point value.".to_owned()));
+        }
+        Ok(CanvasGradient::new(self.global.root().r(),
+                               CanvasGradientStyle::Radial(RadialGradientStyle::new(x0, y0, r0, x1, y1, r1, Vec::new()))))
+    }
 }
 
 #[unsafe_destructor]
diff --git a/components/script/dom/webidls/CanvasGradient.webidl b/components/script/dom/webidls/CanvasGradient.webidl
index 1dc1ac4c1f0..fbeab843987 100644
--- a/components/script/dom/webidls/CanvasGradient.webidl
+++ b/components/script/dom/webidls/CanvasGradient.webidl
@@ -6,7 +6,7 @@
 interface CanvasGradient {
   // opaque object
   // addColorStop should take a double
-  //void addColorStop(float offset, DOMString color);
+  void addColorStop(float offset, DOMString color);
 };
 
 
diff --git a/components/script/dom/webidls/CanvasRenderingContext2D.webidl b/components/script/dom/webidls/CanvasRenderingContext2D.webidl
index f9a4c7b68f8..e0861f02cbd 100644
--- a/components/script/dom/webidls/CanvasRenderingContext2D.webidl
+++ b/components/script/dom/webidls/CanvasRenderingContext2D.webidl
@@ -52,8 +52,10 @@ interface CanvasRenderingContext2D {
   // colours and styles (see also the CanvasDrawingStyles interface)
            attribute (DOMString or CanvasGradient or CanvasPattern) strokeStyle; // (default black)
            attribute (DOMString or CanvasGradient or CanvasPattern) fillStyle; // (default black)
-  //CanvasGradient createLinearGradient(double x0, double y0, double x1, double y1);
-  //CanvasGradient createRadialGradient(double x0, double y0, double r0, double x1, double y1, double r1);
+  [Throws]
+  CanvasGradient createLinearGradient(double x0, double y0, double x1, double y1);
+  [Throws]
+  CanvasGradient createRadialGradient(double x0, double y0, double r0, double x1, double y1, double r1);
   //CanvasPattern createPattern(CanvasImageSource image, [TreatNullAs=EmptyString] DOMString repetition);
 
   // shadows