Let (Offscreen)RenderingContext implement CanvasContext (#36712)

this allows us to simplify canvas element/offscreen impl to only call
CanvasContext implementations (no more match statements).

This will help with impl more offscreen canvas contextl.

Testing: WPT and rustc

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/script/canvas_context.rs

@@ -5,6 +5,7 @@
 //! Common interfaces for Canvas Contexts
 
 use euclid::default::Size2D;
+use script_bindings::root::Dom;
 use script_layout_interface::{HTMLCanvasData, HTMLCanvasDataSource};
 use snapshot::Snapshot;
 
@@ -12,6 +13,10 @@ use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanva
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::htmlcanvaselement::HTMLCanvasElement;
 use crate::dom::node::{Node, NodeDamage};
+use crate::dom::types::{
+    CanvasRenderingContext2D, GPUCanvasContext, OffscreenCanvas, OffscreenCanvasRenderingContext2D,
+    WebGL2RenderingContext, WebGLRenderingContext,
+};
 
 pub(crate) trait LayoutCanvasRenderingContextHelpers {
     fn canvas_data_source(self) -> HTMLCanvasDataSource;
@@ -85,3 +90,180 @@ impl CanvasHelpers for HTMLCanvasElementOrOffscreenCanvas {
         }
     }
 }
+
+/// Non rooted variant of [`crate::dom::bindings::codegen::Bindings::HTMLCanvasElementBinding::RenderingContext`]
+#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
+#[derive(Clone, JSTraceable, MallocSizeOf)]
+pub(crate) enum RenderingContext {
+    Placeholder(Dom<OffscreenCanvas>),
+    Context2d(Dom<CanvasRenderingContext2D>),
+    WebGL(Dom<WebGLRenderingContext>),
+    WebGL2(Dom<WebGL2RenderingContext>),
+    #[cfg(feature = "webgpu")]
+    WebGPU(Dom<GPUCanvasContext>),
+}
+
+impl CanvasContext for RenderingContext {
+    type ID = ();
+
+    fn context_id(&self) -> Self::ID {}
+
+    fn canvas(&self) -> HTMLCanvasElementOrOffscreenCanvas {
+        match self {
+            RenderingContext::Placeholder(context) => (*context.context().unwrap()).canvas(),
+            RenderingContext::Context2d(context) => context.canvas(),
+            RenderingContext::WebGL(context) => context.canvas(),
+            RenderingContext::WebGL2(context) => context.canvas(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.canvas(),
+        }
+    }
+
+    fn resize(&self) {
+        match self {
+            RenderingContext::Placeholder(context) => (*context.context().unwrap()).resize(),
+            RenderingContext::Context2d(context) => context.resize(),
+            RenderingContext::WebGL(context) => context.resize(),
+            RenderingContext::WebGL2(context) => context.resize(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.resize(),
+        }
+    }
+
+    fn get_image_data(&self) -> Option<Snapshot> {
+        match self {
+            RenderingContext::Placeholder(context) => {
+                (*context.context().unwrap()).get_image_data()
+            },
+            RenderingContext::Context2d(context) => context.get_image_data(),
+            RenderingContext::WebGL(context) => context.get_image_data(),
+            RenderingContext::WebGL2(context) => context.get_image_data(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.get_image_data(),
+        }
+    }
+
+    fn origin_is_clean(&self) -> bool {
+        match self {
+            RenderingContext::Placeholder(context) => {
+                (*context.context().unwrap()).origin_is_clean()
+            },
+            RenderingContext::Context2d(context) => context.origin_is_clean(),
+            RenderingContext::WebGL(context) => context.origin_is_clean(),
+            RenderingContext::WebGL2(context) => context.origin_is_clean(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.origin_is_clean(),
+        }
+    }
+
+    fn size(&self) -> Size2D<u64> {
+        match self {
+            RenderingContext::Placeholder(context) => (*context.context().unwrap()).size(),
+            RenderingContext::Context2d(context) => context.size(),
+            RenderingContext::WebGL(context) => context.size(),
+            RenderingContext::WebGL2(context) => context.size(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.size(),
+        }
+    }
+
+    fn mark_as_dirty(&self) {
+        match self {
+            RenderingContext::Placeholder(context) => (*context.context().unwrap()).mark_as_dirty(),
+            RenderingContext::Context2d(context) => context.mark_as_dirty(),
+            RenderingContext::WebGL(context) => context.mark_as_dirty(),
+            RenderingContext::WebGL2(context) => context.mark_as_dirty(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.mark_as_dirty(),
+        }
+    }
+
+    fn update_rendering(&self) {
+        match self {
+            RenderingContext::Placeholder(context) => {
+                (*context.context().unwrap()).update_rendering()
+            },
+            RenderingContext::Context2d(context) => context.update_rendering(),
+            RenderingContext::WebGL(context) => context.update_rendering(),
+            RenderingContext::WebGL2(context) => context.update_rendering(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.update_rendering(),
+        }
+    }
+
+    fn onscreen(&self) -> bool {
+        match self {
+            RenderingContext::Placeholder(context) => (*context.context().unwrap()).onscreen(),
+            RenderingContext::Context2d(context) => context.onscreen(),
+            RenderingContext::WebGL(context) => context.onscreen(),
+            RenderingContext::WebGL2(context) => context.onscreen(),
+            #[cfg(feature = "webgpu")]
+            RenderingContext::WebGPU(context) => context.onscreen(),
+        }
+    }
+}
+
+/// Non rooted variant of [`crate::dom::bindings::codegen::Bindings::OffscreenCanvasBinding::OffscreenRenderingContext`]
+#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
+#[derive(Clone, JSTraceable, MallocSizeOf)]
+pub(crate) enum OffscreenRenderingContext {
+    Context2d(Dom<OffscreenCanvasRenderingContext2D>),
+    //WebGL(Dom<WebGLRenderingContext>),
+    //WebGL2(Dom<WebGL2RenderingContext>),
+    //#[cfg(feature = "webgpu")]
+    //WebGPU(Dom<GPUCanvasContext>),
+}
+
+impl CanvasContext for OffscreenRenderingContext {
+    type ID = ();
+
+    fn context_id(&self) -> Self::ID {}
+
+    fn canvas(&self) -> HTMLCanvasElementOrOffscreenCanvas {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.canvas(),
+        }
+    }
+
+    fn resize(&self) {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.resize(),
+        }
+    }
+
+    fn get_image_data(&self) -> Option<Snapshot> {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.get_image_data(),
+        }
+    }
+
+    fn origin_is_clean(&self) -> bool {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.origin_is_clean(),
+        }
+    }
+
+    fn size(&self) -> Size2D<u64> {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.size(),
+        }
+    }
+
+    fn mark_as_dirty(&self) {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.mark_as_dirty(),
+        }
+    }
+
+    fn update_rendering(&self) {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.update_rendering(),
+        }
+    }
+
+    fn onscreen(&self) -> bool {
+        match self {
+            OffscreenRenderingContext::Context2d(context) => context.onscreen(),
+        }
+    }
+}

components/script/canvas_state.rs

@@ -36,6 +36,7 @@ use style_traits::{CssWriter, ParsingMode};
 use url::Url;
 use webrender_api::ImageKey;
 
+use crate::canvas_context::{OffscreenRenderingContext, RenderingContext};
 use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::{
     CanvasDirection, CanvasFillRule, CanvasImageSource, CanvasLineCap, CanvasLineJoin,
@@ -52,10 +53,10 @@ use crate::dom::canvaspattern::CanvasPattern;
 use crate::dom::dommatrix::DOMMatrix;
 use crate::dom::element::{Element, cors_setting_for_element};
 use crate::dom::globalscope::GlobalScope;
-use crate::dom::htmlcanvaselement::{CanvasContext, HTMLCanvasElement};
+use crate::dom::htmlcanvaselement::HTMLCanvasElement;
 use crate::dom::imagedata::ImageData;
 use crate::dom::node::{Node, NodeTraits};
-use crate::dom::offscreencanvas::{OffscreenCanvas, OffscreenCanvasContext};
+use crate::dom::offscreencanvas::OffscreenCanvas;
 use crate::dom::paintworkletglobalscope::PaintWorkletGlobalScope;
 use crate::dom::textmetrics::TextMetrics;
 use crate::script_runtime::CanGc;
@@ -522,7 +523,7 @@ impl CanvasState {
 
         if let Some(context) = canvas.context() {
             match *context {
-                OffscreenCanvasContext::OffscreenContext2d(ref context) => {
+                OffscreenRenderingContext::Context2d(ref context) => {
                     context.send_canvas_2d_msg(Canvas2dMsg::DrawImageInOther(
                         self.get_canvas_id(),
                         image_size,
@@ -577,7 +578,7 @@ impl CanvasState {
 
         if let Some(context) = canvas.context() {
             match *context {
-                CanvasContext::Context2d(ref context) => {
+                RenderingContext::Context2d(ref context) => {
                     context.send_canvas_2d_msg(Canvas2dMsg::DrawImageInOther(
                         self.get_canvas_id(),
                         image_size,
@@ -586,12 +587,12 @@ impl CanvasState {
                         smoothing_enabled,
                     ));
                 },
-                CanvasContext::Placeholder(ref context) => {
+                RenderingContext::Placeholder(ref context) => {
                     let Some(context) = context.context() else {
                         return Err(Error::InvalidState);
                     };
                     match *context {
-                        OffscreenCanvasContext::OffscreenContext2d(ref context) => context
+                        OffscreenRenderingContext::Context2d(ref context) => context
                             .send_canvas_2d_msg(Canvas2dMsg::DrawImageInOther(
                                 self.get_canvas_id(),
                                 image_size,

components/script/dom/htmlcanvaselement.rs

@@ -27,14 +27,13 @@ use servo_media::streams::registry::MediaStreamId;
 use snapshot::Snapshot;
 use style::attr::AttrValue;
 
-use crate::canvas_context::CanvasContext as _;
 pub(crate) use crate::canvas_context::*;
 use crate::conversions::Convert;
 use crate::dom::attr::Attr;
 use crate::dom::bindings::callback::ExceptionHandling;
 use crate::dom::bindings::cell::{DomRefCell, Ref, ref_filter_map};
 use crate::dom::bindings::codegen::Bindings::HTMLCanvasElementBinding::{
-    BlobCallback, HTMLCanvasElementMethods, RenderingContext,
+    BlobCallback, HTMLCanvasElementMethods, RenderingContext as RootedRenderingContext,
 };
 use crate::dom::bindings::codegen::Bindings::MediaStreamBinding::MediaStreamMethods;
 use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLContextAttributes;
@@ -104,21 +103,10 @@ impl EncodedImageType {
     }
 }
 
-#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
-#[derive(Clone, JSTraceable, MallocSizeOf)]
-pub(crate) enum CanvasContext {
-    Placeholder(Dom<OffscreenCanvas>),
-    Context2d(Dom<CanvasRenderingContext2D>),
-    WebGL(Dom<WebGLRenderingContext>),
-    WebGL2(Dom<WebGL2RenderingContext>),
-    #[cfg(feature = "webgpu")]
-    WebGPU(Dom<GPUCanvasContext>),
-}
-
 #[dom_struct]
 pub(crate) struct HTMLCanvasElement {
     htmlelement: HTMLElement,
-    context: DomRefCell<Option<CanvasContext>>,
+    context: DomRefCell<Option<RenderingContext>>,
     // This id and hashmap are used to keep track of ongoing toBlob() calls.
     callback_id: Cell<u32>,
     #[ignore_malloc_size_of = "not implemented for webidl callbacks"]
@@ -159,14 +147,7 @@ impl HTMLCanvasElement {
 
     fn recreate_contexts_after_resize(&self) {
         if let Some(ref context) = *self.context.borrow() {
-            match *context {
+            context.resize()
-                CanvasContext::Context2d(ref context) => context.resize(),
-                CanvasContext::WebGL(ref context) => context.resize(),
-                CanvasContext::WebGL2(ref context) => context.resize(),
-                #[cfg(feature = "webgpu")]
-                CanvasContext::WebGPU(ref context) => context.resize(),
-                CanvasContext::Placeholder(ref context) => context.resize(self.get_size().cast()),
-            }
         }
     }
 
@@ -176,23 +157,14 @@ impl HTMLCanvasElement {
 
     pub(crate) fn origin_is_clean(&self) -> bool {
         match *self.context.borrow() {
-            Some(CanvasContext::Context2d(ref context)) => context.origin_is_clean(),
+            Some(ref context) => context.origin_is_clean(),
             _ => true,
         }
     }
 
     pub(crate) fn mark_as_dirty(&self) {
         if let Some(ref context) = *self.context.borrow() {
-            match *context {
+            context.mark_as_dirty()
-                CanvasContext::Context2d(ref context) => context.mark_as_dirty(),
-                CanvasContext::WebGL(ref context) => context.mark_as_dirty(),
-                CanvasContext::WebGL2(ref context) => context.mark_as_dirty(),
-                #[cfg(feature = "webgpu")]
-                CanvasContext::WebGPU(ref context) => context.mark_as_dirty(),
-                CanvasContext::Placeholder(ref _context) => {
-                    // TODO: Should this be marked as dirty?
-                },
-            }
         }
     }
 
@@ -222,12 +194,14 @@ impl LayoutHTMLCanvasElementHelpers for LayoutDom<'_, HTMLCanvasElement> {
     fn data(self) -> HTMLCanvasData {
         let source = unsafe {
             match self.unsafe_get().context.borrow_for_layout().as_ref() {
-                Some(CanvasContext::Context2d(context)) => context.to_layout().canvas_data_source(),
+                Some(RenderingContext::Context2d(context)) => {
-                Some(CanvasContext::WebGL(context)) => context.to_layout().canvas_data_source(),
+                    context.to_layout().canvas_data_source()
-                Some(CanvasContext::WebGL2(context)) => context.to_layout().canvas_data_source(),
+                },
+                Some(RenderingContext::WebGL(context)) => context.to_layout().canvas_data_source(),
+                Some(RenderingContext::WebGL2(context)) => context.to_layout().canvas_data_source(),
                 #[cfg(feature = "webgpu")]
-                Some(CanvasContext::WebGPU(context)) => context.to_layout().canvas_data_source(),
+                Some(RenderingContext::WebGPU(context)) => context.to_layout().canvas_data_source(),
-                Some(CanvasContext::Placeholder(_)) | None => HTMLCanvasDataSource::Empty,
+                Some(RenderingContext::Placeholder(_)) | None => HTMLCanvasDataSource::Empty,
             }
         };
 
@@ -246,14 +220,14 @@ impl LayoutHTMLCanvasElementHelpers for LayoutDom<'_, HTMLCanvasElement> {
 }
 
 impl HTMLCanvasElement {
-    pub(crate) fn context(&self) -> Option<Ref<CanvasContext>> {
+    pub(crate) fn context(&self) -> Option<Ref<RenderingContext>> {
         ref_filter_map(self.context.borrow(), |ctx| ctx.as_ref())
     }
 
     fn get_or_init_2d_context(&self, can_gc: CanGc) -> Option<DomRoot<CanvasRenderingContext2D>> {
         if let Some(ctx) = self.context() {
             return match *ctx {
-                CanvasContext::Context2d(ref ctx) => Some(DomRoot::from_ref(ctx)),
+                RenderingContext::Context2d(ref ctx) => Some(DomRoot::from_ref(ctx)),
                 _ => None,
             };
         }
@@ -261,7 +235,7 @@ impl HTMLCanvasElement {
         let window = self.owner_window();
         let size = self.get_size();
         let context = CanvasRenderingContext2D::new(window.as_global_scope(), self, size, can_gc);
-        *self.context.borrow_mut() = Some(CanvasContext::Context2d(Dom::from_ref(&*context)));
+        *self.context.borrow_mut() = Some(RenderingContext::Context2d(Dom::from_ref(&*context)));
         Some(context)
     }
 
@@ -273,7 +247,7 @@ impl HTMLCanvasElement {
     ) -> Option<DomRoot<WebGLRenderingContext>> {
         if let Some(ctx) = self.context() {
             return match *ctx {
-                CanvasContext::WebGL(ref ctx) => Some(DomRoot::from_ref(ctx)),
+                RenderingContext::WebGL(ref ctx) => Some(DomRoot::from_ref(ctx)),
                 _ => None,
             };
         }
@@ -289,7 +263,7 @@ impl HTMLCanvasElement {
             attrs,
             can_gc,
         )?;
-        *self.context.borrow_mut() = Some(CanvasContext::WebGL(Dom::from_ref(&*context)));
+        *self.context.borrow_mut() = Some(RenderingContext::WebGL(Dom::from_ref(&*context)));
         Some(context)
     }
 
@@ -305,7 +279,7 @@ impl HTMLCanvasElement {
         }
         if let Some(ctx) = self.context() {
             return match *ctx {
-                CanvasContext::WebGL2(ref ctx) => Some(DomRoot::from_ref(ctx)),
+                RenderingContext::WebGL2(ref ctx) => Some(DomRoot::from_ref(ctx)),
                 _ => None,
             };
         }
@@ -314,7 +288,7 @@ impl HTMLCanvasElement {
         let attrs = Self::get_gl_attributes(cx, options)?;
         let canvas = HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
         let context = WebGL2RenderingContext::new(&window, &canvas, size, attrs, can_gc)?;
-        *self.context.borrow_mut() = Some(CanvasContext::WebGL2(Dom::from_ref(&*context)));
+        *self.context.borrow_mut() = Some(RenderingContext::WebGL2(Dom::from_ref(&*context)));
         Some(context)
     }
 
@@ -327,7 +301,7 @@ impl HTMLCanvasElement {
     fn get_or_init_webgpu_context(&self, can_gc: CanGc) -> Option<DomRoot<GPUCanvasContext>> {
         if let Some(ctx) = self.context() {
             return match *ctx {
-                CanvasContext::WebGPU(ref ctx) => Some(DomRoot::from_ref(ctx)),
+                RenderingContext::WebGPU(ref ctx) => Some(DomRoot::from_ref(ctx)),
                 _ => None,
             };
         }
@@ -341,7 +315,8 @@ impl HTMLCanvasElement {
             .expect("Failed to get WebGPU channel")
             .map(|channel| {
                 let context = GPUCanvasContext::new(&global_scope, self, channel, can_gc);
-                *self.context.borrow_mut() = Some(CanvasContext::WebGPU(Dom::from_ref(&*context)));
+                *self.context.borrow_mut() =
+                    Some(RenderingContext::WebGPU(Dom::from_ref(&*context)));
                 context
             })
     }
@@ -349,8 +324,8 @@ impl HTMLCanvasElement {
     /// Gets the base WebGLRenderingContext for WebGL or WebGL 2, if exists.
     pub(crate) fn get_base_webgl_context(&self) -> Option<DomRoot<WebGLRenderingContext>> {
         match *self.context.borrow() {
-            Some(CanvasContext::WebGL(ref context)) => Some(DomRoot::from_ref(context)),
+            Some(RenderingContext::WebGL(ref context)) => Some(DomRoot::from_ref(context)),
-            Some(CanvasContext::WebGL2(ref context)) => Some(context.base_context()),
+            Some(RenderingContext::WebGL2(ref context)) => Some(context.base_context()),
             _ => None,
         }
     }
@@ -378,12 +353,7 @@ impl HTMLCanvasElement {
 
     pub(crate) fn get_image_data(&self) -> Option<Snapshot> {
         match self.context.borrow().as_ref() {
-            Some(CanvasContext::Context2d(context)) => context.get_image_data(),
+            Some(context) => context.get_image_data(),
-            Some(CanvasContext::WebGL(context)) => context.get_image_data(),
-            Some(CanvasContext::WebGL2(context)) => context.get_image_data(),
-            #[cfg(feature = "webgpu")]
-            Some(CanvasContext::WebGPU(context)) => context.get_image_data(),
-            Some(CanvasContext::Placeholder(context)) => context.get_image_data(),
             None => {
                 let size = self.get_size();
                 if size.width == 0 || size.height == 0 {
@@ -466,7 +436,7 @@ impl HTMLCanvasElementMethods<crate::DomTypeHolder> for HTMLCanvasElement {
     // is set to placeholder, the user agent must throw an "InvalidStateError" DOMException and leave the
     // attribute's value unchanged.
     fn SetWidth(&self, value: u32, can_gc: CanGc) -> Fallible<()> {
-        if let Some(CanvasContext::Placeholder(_)) = *self.context.borrow() {
+        if let Some(RenderingContext::Placeholder(_)) = *self.context.borrow() {
             return Err(Error::InvalidState);
         }
 
@@ -485,7 +455,7 @@ impl HTMLCanvasElementMethods<crate::DomTypeHolder> for HTMLCanvasElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-canvas-height
     fn SetHeight(&self, value: u32, can_gc: CanGc) -> Fallible<()> {
-        if let Some(CanvasContext::Placeholder(_)) = *self.context.borrow() {
+        if let Some(RenderingContext::Placeholder(_)) = *self.context.borrow() {
             return Err(Error::InvalidState);
         }
 
@@ -506,26 +476,26 @@ impl HTMLCanvasElementMethods<crate::DomTypeHolder> for HTMLCanvasElement {
         id: DOMString,
         options: HandleValue,
         can_gc: CanGc,
-    ) -> Fallible<Option<RenderingContext>> {
+    ) -> Fallible<Option<RootedRenderingContext>> {
         // Always throw an InvalidState exception when the canvas is in Placeholder mode (See table in the spec).
-        if let Some(CanvasContext::Placeholder(_)) = *self.context.borrow() {
+        if let Some(RenderingContext::Placeholder(_)) = *self.context.borrow() {
             return Err(Error::InvalidState);
         }
 
         Ok(match &*id {
             "2d" => self
                 .get_or_init_2d_context(can_gc)
-                .map(RenderingContext::CanvasRenderingContext2D),
+                .map(RootedRenderingContext::CanvasRenderingContext2D),
             "webgl" | "experimental-webgl" => self
                 .get_or_init_webgl_context(cx, options, can_gc)
-                .map(RenderingContext::WebGLRenderingContext),
+                .map(RootedRenderingContext::WebGLRenderingContext),
             "webgl2" | "experimental-webgl2" => self
                 .get_or_init_webgl2_context(cx, options, can_gc)
-                .map(RenderingContext::WebGL2RenderingContext),
+                .map(RootedRenderingContext::WebGL2RenderingContext),
             #[cfg(feature = "webgpu")]
             "webgpu" => self
                 .get_or_init_webgpu_context(can_gc)
-                .map(RenderingContext::GPUCanvasContext),
+                .map(RootedRenderingContext::GPUCanvasContext),
             _ => None,
         })
     }
@@ -672,7 +642,8 @@ impl HTMLCanvasElementMethods<crate::DomTypeHolder> for HTMLCanvasElement {
             can_gc,
         );
         // Step 4. Set this canvas element's context mode to placeholder.
-        *self.context.borrow_mut() = Some(CanvasContext::Placeholder(offscreen_canvas.as_traced()));
+        *self.context.borrow_mut() =
+            Some(RenderingContext::Placeholder(offscreen_canvas.as_traced()));
 
         // Step 5. Return offscreenCanvas.
         Ok(offscreen_canvas)

components/script/dom/offscreencanvas.rs

@@ -9,9 +9,10 @@ use euclid::default::Size2D;
 use js::rust::{HandleObject, HandleValue};
 use snapshot::Snapshot;
 
+use crate::canvas_context::{CanvasContext, OffscreenRenderingContext};
 use crate::dom::bindings::cell::{DomRefCell, Ref, ref_filter_map};
 use crate::dom::bindings::codegen::Bindings::OffscreenCanvasBinding::{
-    OffscreenCanvasMethods, OffscreenRenderingContext,
+    OffscreenCanvasMethods, OffscreenRenderingContext as RootedOffscreenRenderingContext,
 };
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::reflector::{DomGlobal, reflect_dom_object_with_proto};
@@ -23,20 +24,12 @@ use crate::dom::htmlcanvaselement::HTMLCanvasElement;
 use crate::dom::offscreencanvasrenderingcontext2d::OffscreenCanvasRenderingContext2D;
 use crate::script_runtime::{CanGc, JSContext};
 
-#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
-#[derive(Clone, JSTraceable, MallocSizeOf)]
-pub(crate) enum OffscreenCanvasContext {
-    OffscreenContext2d(Dom<OffscreenCanvasRenderingContext2D>),
-    //WebGL(Dom<WebGLRenderingContext>),
-    //WebGL2(Dom<WebGL2RenderingContext>),
-}
-
 #[dom_struct]
 pub(crate) struct OffscreenCanvas {
     eventtarget: EventTarget,
     width: Cell<u64>,
     height: Cell<u64>,
-    context: DomRefCell<Option<OffscreenCanvasContext>>,
+    context: DomRefCell<Option<OffscreenRenderingContext>>,
     placeholder: Option<Dom<HTMLCanvasElement>>,
 }
 
@@ -77,20 +70,18 @@ impl OffscreenCanvas {
 
     pub(crate) fn origin_is_clean(&self) -> bool {
         match *self.context.borrow() {
-            Some(OffscreenCanvasContext::OffscreenContext2d(ref context)) => {
+            Some(ref context) => context.origin_is_clean(),
-                context.origin_is_clean()
-            },
             _ => true,
         }
     }
 
-    pub(crate) fn context(&self) -> Option<Ref<OffscreenCanvasContext>> {
+    pub(crate) fn context(&self) -> Option<Ref<OffscreenRenderingContext>> {
         ref_filter_map(self.context.borrow(), |ctx| ctx.as_ref())
     }
 
     pub(crate) fn get_image_data(&self) -> Option<Snapshot> {
         match self.context.borrow().as_ref() {
-            Some(OffscreenCanvasContext::OffscreenContext2d(context)) => context.get_image_data(),
+            Some(context) => context.get_image_data(),
             None => {
                 let size = self.get_size();
                 if size.width == 0 || size.height == 0 {
@@ -108,13 +99,13 @@ impl OffscreenCanvas {
     ) -> Option<DomRoot<OffscreenCanvasRenderingContext2D>> {
         if let Some(ctx) = self.context() {
             return match *ctx {
-                OffscreenCanvasContext::OffscreenContext2d(ref ctx) => Some(DomRoot::from_ref(ctx)),
+                OffscreenRenderingContext::Context2d(ref ctx) => Some(DomRoot::from_ref(ctx)),
             };
         }
         let context = OffscreenCanvasRenderingContext2D::new(&self.global(), self, can_gc);
-        *self.context.borrow_mut() = Some(OffscreenCanvasContext::OffscreenContext2d(
+        *self.context.borrow_mut() = Some(OffscreenRenderingContext::Context2d(Dom::from_ref(
-            Dom::from_ref(&*context),
+            &*context,
-        ));
+        )));
         Some(context)
     }
 
@@ -125,19 +116,6 @@ impl OffscreenCanvas {
     pub(crate) fn placeholder(&self) -> Option<&HTMLCanvasElement> {
         self.placeholder.as_deref()
     }
-
-    pub(crate) fn resize(&self, size: Size2D<u64>) {
-        self.width.set(size.width);
-        self.height.set(size.height);
-
-        if let Some(canvas_context) = self.context() {
-            match &*canvas_context {
-                OffscreenCanvasContext::OffscreenContext2d(rendering_context) => {
-                    rendering_context.set_canvas_bitmap_dimensions(self.get_size());
-                },
-            }
-        }
-    }
 }
 
 impl OffscreenCanvasMethods<crate::DomTypeHolder> for OffscreenCanvas {
@@ -160,11 +138,11 @@ impl OffscreenCanvasMethods<crate::DomTypeHolder> for OffscreenCanvas {
         id: DOMString,
         _options: HandleValue,
         can_gc: CanGc,
-    ) -> Fallible<Option<OffscreenRenderingContext>> {
+    ) -> Fallible<Option<RootedOffscreenRenderingContext>> {
         match &*id {
             "2d" => Ok(self
                 .get_or_init_2d_context(can_gc)
-                .map(OffscreenRenderingContext::OffscreenCanvasRenderingContext2D)),
+                .map(RootedOffscreenRenderingContext::OffscreenCanvasRenderingContext2D)),
             /*"webgl" | "experimental-webgl" => self
                 .get_or_init_webgl_context(cx, options)
                 .map(OffscreenRenderingContext::WebGLRenderingContext),
@@ -187,11 +165,7 @@ impl OffscreenCanvasMethods<crate::DomTypeHolder> for OffscreenCanvas {
         self.width.set(value);
 
         if let Some(canvas_context) = self.context() {
-            match &*canvas_context {
+            canvas_context.resize();
-                OffscreenCanvasContext::OffscreenContext2d(rendering_context) => {
-                    rendering_context.set_canvas_bitmap_dimensions(self.get_size());
-                },
-            }
         }
 
         if let Some(canvas) = &self.placeholder {
@@ -209,11 +183,7 @@ impl OffscreenCanvasMethods<crate::DomTypeHolder> for OffscreenCanvas {
         self.height.set(value);
 
         if let Some(canvas_context) = self.context() {
-            match &*canvas_context {
+            canvas_context.resize();
-                OffscreenCanvasContext::OffscreenContext2d(rendering_context) => {
-                    rendering_context.set_canvas_bitmap_dimensions(self.get_size());
-                },
-            }
         }
 
         if let Some(canvas) = &self.placeholder {

components/script/dom/offscreencanvasrenderingcontext2d.rs

@@ -3,11 +3,10 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::dom::bindings::codegen::GenericBindings::CanvasRenderingContext2DBinding::CanvasRenderingContext2D_Binding::CanvasRenderingContext2DMethods;
-use crate::canvas_context::CanvasContext as _;
+use crate::canvas_context::CanvasContext;
 use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
 use canvas_traits::canvas::Canvas2dMsg;
 use dom_struct::dom_struct;
-use euclid::default::Size2D;
 use snapshot::Snapshot;
 
 use crate::dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::{
@@ -64,21 +63,33 @@ impl OffscreenCanvasRenderingContext2D {
         reflect_dom_object(boxed, global, can_gc)
     }
 
-    pub(crate) fn set_canvas_bitmap_dimensions(&self, size: Size2D<u64>) {
-        self.context.set_canvas_bitmap_dimensions(size.cast());
-    }
-
     pub(crate) fn send_canvas_2d_msg(&self, msg: Canvas2dMsg) {
         self.context.send_canvas_2d_msg(msg)
     }
+}
 
-    pub(crate) fn origin_is_clean(&self) -> bool {
+impl CanvasContext for OffscreenCanvasRenderingContext2D {
-        self.context.origin_is_clean()
+    type ID = <CanvasRenderingContext2D as CanvasContext>::ID;
+
+    fn context_id(&self) -> Self::ID {
+        self.context.context_id()
     }
 
-    pub(crate) fn get_image_data(&self) -> Option<Snapshot> {
+    fn canvas(&self) -> HTMLCanvasElementOrOffscreenCanvas {
+        self.context.canvas()
+    }
+
+    fn resize(&self) {
+        self.context.resize()
+    }
+
+    fn get_image_data(&self) -> Option<Snapshot> {
         self.context.get_image_data()
     }
+
+    fn origin_is_clean(&self) -> bool {
+        self.context.origin_is_clean()
+    }
 }
 
 impl OffscreenCanvasRenderingContext2DMethods<crate::DomTypeHolder>