Update fill and stroke style only when required

So far fill and stroke style updates have been sent to the canvas paint
thread by `SetFillStyle()` and `SetStrokeStyle()`. This resulted in
fill/stroke style updates not being considered by the canvas paint
thread between the latest call of `SetFillStyle()`/`SetStrokeStyle()` and
the drawing operation (e.g. fill or stroke).

This issue is solved by making `SetFillStyle()` and `SetStrokeStyle()`
update the local canvas state and propagating the state to the canvas
paint thread right before any drawing operation that requires it.

components/script/canvas_state.rs

@@ -654,6 +654,7 @@ impl CanvasState {
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-fillrect
     pub fn fill_rect(&self, x: f64, y: f64, width: f64, height: f64) {
         if let Some(rect) = self.create_drawable_rect(x, y, width, height) {
+            self.update_fill_style();
             self.send_canvas_2d_msg(Canvas2dMsg::FillRect(rect));
         }
     }
@@ -668,6 +669,7 @@ impl CanvasState {
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-strokerect
     pub fn stroke_rect(&self, x: f64, y: f64, width: f64, height: f64) {
         if let Some(rect) = self.create_drawable_rect(x, y, width, height) {
+            self.update_stroke_style();
             self.send_canvas_2d_msg(Canvas2dMsg::StrokeRect(rect));
         }
     }
@@ -756,31 +758,31 @@ impl CanvasState {
             StringOrCanvasGradientOrCanvasPattern::String(string) => {
                 if let Ok(rgba) = self.parse_color(canvas, &string) {
                     self.state.borrow_mut().stroke_style = CanvasFillOrStrokeStyle::Color(rgba);
-                    self.send_canvas_2d_msg(Canvas2dMsg::SetStrokeStyle(FillOrStrokeStyle::Color(
-                        rgba,
-                    )));
                 }
             },
             StringOrCanvasGradientOrCanvasPattern::CanvasGradient(gradient) => {
                 self.state.borrow_mut().stroke_style =
                     CanvasFillOrStrokeStyle::Gradient(Dom::from_ref(&*gradient));
-                self.send_canvas_2d_msg(Canvas2dMsg::SetStrokeStyle(
-                    gradient.to_fill_or_stroke_style(),
-                ));
             },
             StringOrCanvasGradientOrCanvasPattern::CanvasPattern(pattern) => {
                 self.state.borrow_mut().stroke_style =
                     CanvasFillOrStrokeStyle::Pattern(Dom::from_ref(&*pattern));
-                self.send_canvas_2d_msg(Canvas2dMsg::SetStrokeStyle(
-                    pattern.to_fill_or_stroke_style(),
-                ));
                 if !pattern.origin_is_clean() {
                     self.set_origin_unclean();
                 }
             },
         }
     }
 
+    fn update_stroke_style(&self) {
+        let style = match &self.state.borrow().stroke_style {
+            CanvasFillOrStrokeStyle::Color(rgba) => FillOrStrokeStyle::Color(*rgba),
+            CanvasFillOrStrokeStyle::Gradient(gradient) => gradient.to_fill_or_stroke_style(),
+            CanvasFillOrStrokeStyle::Pattern(pattern) => pattern.to_fill_or_stroke_style(),
+        };
+        self.send_canvas_2d_msg(Canvas2dMsg::SetStrokeStyle(style));
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-strokestyle
     pub fn fill_style(&self) -> StringOrCanvasGradientOrCanvasPattern {
         match self.state.borrow().fill_style {
@@ -808,31 +810,31 @@ impl CanvasState {
             StringOrCanvasGradientOrCanvasPattern::String(string) => {
                 if let Ok(rgba) = self.parse_color(canvas, &string) {
                     self.state.borrow_mut().fill_style = CanvasFillOrStrokeStyle::Color(rgba);
-                    self.send_canvas_2d_msg(Canvas2dMsg::SetFillStyle(FillOrStrokeStyle::Color(
-                        rgba,
-                    )))
                 }
             },
             StringOrCanvasGradientOrCanvasPattern::CanvasGradient(gradient) => {
                 self.state.borrow_mut().fill_style =
                     CanvasFillOrStrokeStyle::Gradient(Dom::from_ref(&*gradient));
-                self.send_canvas_2d_msg(Canvas2dMsg::SetFillStyle(
-                    gradient.to_fill_or_stroke_style(),
-                ));
             },
             StringOrCanvasGradientOrCanvasPattern::CanvasPattern(pattern) => {
                 self.state.borrow_mut().fill_style =
                     CanvasFillOrStrokeStyle::Pattern(Dom::from_ref(&*pattern));
-                self.send_canvas_2d_msg(Canvas2dMsg::SetFillStyle(
-                    pattern.to_fill_or_stroke_style(),
-                ));
                 if !pattern.origin_is_clean() {
                     self.set_origin_unclean();
                 }
             },
         }
     }
 
+    fn update_fill_style(&self) {
+        let style = match &self.state.borrow().fill_style {
+            CanvasFillOrStrokeStyle::Color(rgba) => FillOrStrokeStyle::Color(*rgba),
+            CanvasFillOrStrokeStyle::Gradient(gradient) => gradient.to_fill_or_stroke_style(),
+            CanvasFillOrStrokeStyle::Pattern(pattern) => pattern.to_fill_or_stroke_style(),
+        };
+        self.send_canvas_2d_msg(Canvas2dMsg::SetFillStyle(style));
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-createlineargradient
     pub fn create_linear_gradient(
         &self,
@@ -995,6 +997,7 @@ impl CanvasState {
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-filltext
     pub fn fill_text(&self, text: DOMString, x: f64, y: f64, max_width: Option<f64>) {
         let parsed_text: String = text.into();
+        self.update_fill_style();
         self.send_canvas_2d_msg(Canvas2dMsg::FillText(parsed_text, x, y, max_width));
     }
 
@@ -1302,11 +1305,13 @@ impl CanvasState {
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-fill
     pub fn fill(&self, _fill_rule: CanvasFillRule) {
         // TODO: Process fill rule
+        self.update_fill_style();
         self.send_canvas_2d_msg(Canvas2dMsg::Fill);
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-stroke
     pub fn stroke(&self) {
+        self.update_stroke_style();
         self.send_canvas_2d_msg(Canvas2dMsg::Stroke);
     }