canvas2d: Implement .reset() (#31258)

* Implement Canvas2D reset

* Update WPT tests

* Apply suggestions from code review

---------

Co-authored-by: Martin Robinson <mrobinson@igalia.com>

components/canvas/canvas_data.rs

@@ -1054,7 +1054,8 @@ impl<'a> CanvasData<'a> {
         self.backend.set_global_composition(op, &mut self.state);
     }
 
-    pub fn recreate(&mut self, size: Size2D<u64>) {
+    pub fn recreate(&mut self, size: Option<Size2D<u64>>) {
+        let size = size.unwrap_or_else(|| self.drawtarget.get_size().to_u64());
         self.drawtarget = self
             .backend
             .create_drawtarget(Size2D::new(size.width, size.height));

components/script/canvas_state.rs

@@ -216,7 +216,14 @@ impl CanvasState {
     pub fn set_bitmap_dimensions(&self, size: Size2D<u64>) {
         self.reset_to_initial_state();
         self.ipc_renderer
-            .send(CanvasMsg::Recreate(size, self.get_canvas_id()))
+            .send(CanvasMsg::Recreate(Some(size), self.get_canvas_id()))
+            .unwrap();
+    }
+
+    pub fn reset(&self) {
+        self.reset_to_initial_state();
+        self.ipc_renderer
+            .send(CanvasMsg::Recreate(None, self.get_canvas_id()))
             .unwrap();
     }
 

components/script/dom/canvasrenderingcontext2d.rs

@@ -74,7 +74,7 @@ impl CanvasRenderingContext2D {
         self.canvas_state
             .get_ipc_renderer()
             .send(CanvasMsg::Recreate(
-                size.to_u64(),
+                Some(size.to_u64()),
                 self.canvas_state.get_canvas_id(),
             ))
             .unwrap();
@@ -181,6 +181,11 @@ impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
         self.canvas_state.restore()
     }
 
+    /// <https://html.spec.whatwg.org/multipage/#dom-context-2d-reset>
+    fn Reset(&self) {
+        self.canvas_state.reset()
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-scale
     fn Scale(&self, x: f64, y: f64) {
         self.canvas_state.scale(x, y)

components/script/dom/offscreencanvasrenderingcontext2d.rs

@@ -213,6 +213,11 @@ impl OffscreenCanvasRenderingContext2DMethods for OffscreenCanvasRenderingContex
         self.canvas_state.restore()
     }
 
+    /// <https://html.spec.whatwg.org/multipage/#dom-context-2d-reset>
+    fn Reset(&self) {
+        self.canvas_state.reset()
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-globalalpha
     fn GlobalAlpha(&self) -> f64 {
         self.canvas_state.global_alpha()

components/script/dom/paintrenderingcontext2d.rs

@@ -95,6 +95,11 @@ impl PaintRenderingContext2DMethods for PaintRenderingContext2D {
         self.context.Restore()
     }
 
+    /// <https://html.spec.whatwg.org/multipage/#dom-context-2d-reset>
+    fn Reset(&self) {
+        self.context.Reset()
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-scale
     fn Scale(&self, x: f64, y: f64) {
         self.context.Scale(x, y)

components/script/dom/webidls/CanvasRenderingContext2D.webidl

@@ -44,6 +44,7 @@ interface mixin CanvasState {
   // state
   undefined save(); // push state on state stack
   undefined restore(); // pop state stack and restore state
+  undefined reset();
 };
 
 interface mixin CanvasTransform {

components/shared/canvas/canvas.rs

@@ -28,7 +28,7 @@ pub enum CanvasMsg {
     Canvas2d(Canvas2dMsg, CanvasId),
     FromLayout(FromLayoutMsg, CanvasId),
     FromScript(FromScriptMsg, CanvasId),
-    Recreate(Size2D<u64>, CanvasId),
+    Recreate(Option<Size2D<u64>>, CanvasId),
     Close(CanvasId),
 }