Initial Steps OffScreenCanvas API

components/script/dom/offscreencanvasrenderingcontext2d.rs

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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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 crate::dom::bindings::codegen::Bindings::OffscreenCanvasRenderingContext2DBinding;
+use crate::dom::bindings::codegen::Bindings::OffscreenCanvasRenderingContext2DBinding::OffscreenCanvasRenderingContext2DMethods;
+use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
+use crate::dom::bindings::root::{Dom, DomRoot};
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::offscreencanvas::OffscreenCanvas;
+use dom_struct::dom_struct;
+use euclid::Size2D;
+
+#[dom_struct]
+pub struct OffscreenCanvasRenderingContext2D {
+    reflector_: Reflector,
+    canvas: Option<Dom<OffscreenCanvas>>,
+}
+
+impl OffscreenCanvasRenderingContext2D {
+    pub fn new_inherited(
+        _global: &GlobalScope,
+        canvas: Option<&OffscreenCanvas>,
+        _size: Size2D<u64>,
+    ) -> OffscreenCanvasRenderingContext2D {
+        OffscreenCanvasRenderingContext2D {
+            reflector_: Reflector::new(),
+            canvas: canvas.map(Dom::from_ref),
+        }
+    }
+
+    pub fn new(
+        _global: &GlobalScope,
+        canvas: &OffscreenCanvas,
+        _size: Size2D<u64>,
+    ) -> DomRoot<OffscreenCanvasRenderingContext2D> {
+        let boxed = Box::new(OffscreenCanvasRenderingContext2D::new_inherited(
+            _global,
+            Some(canvas),
+            _size,
+        ));
+        reflect_dom_object(
+            boxed,
+            _global,
+            OffscreenCanvasRenderingContext2DBinding::Wrap,
+        )
+    }
+}
+
+impl OffscreenCanvasRenderingContext2DMethods for OffscreenCanvasRenderingContext2D {
+    // https://html.spec.whatwg.org/multipage/offscreencontext2d-canvas
+    fn Canvas(&self) -> DomRoot<OffscreenCanvas> {
+        DomRoot::from_ref(self.canvas.as_ref().expect("No canvas."))
+    }
+}