canvas: Use non rooted variant of HTMLCanvasElementOrOffscreenCanvas type (#38970)

Any RenderingContext/OffscreenRenderingContext type has readonly
"canvas" attribute
and associated native-code DOM context objects have reference to target
DOM canvas objects.
https://html.spec.whatwg.org/multipage/canvas.html#renderingcontext
https://html.spec.whatwg.org/multipage/canvas.html#offscreenrenderingcontext

And currently the reference to DOM canvas object is the rooting pointer
on the stack,
which leads to the circular reference problem.

The SpiderMonkey's (SM) garbage collector will not be able to free the
DOM canvas and context
objects (unreacheble from JS) because of the rooting pointer on stack
(see STACK_ROOTS).

And these objects will be stored until the associated script
runtime/thread will be terminated.

SM -> JS Roots -> DOM Canvas* (on heap) -> DOM Context (on heap)
SM -> Rust Roots -> Dom Canvas* (on stack) <- as "canvas" member field

Let's replace the rooting pointer to the traceble pointer (DomRoot ->
Dom)
in the "canvas" member field of DOM context object, which allows to
broke circular referencing problem.

Testing: No changes in existed tests

Signed-off-by: Andrei Volykhin <volykhin.andrei@huawei.com>
Co-authored-by: Andrei Volykhin <volykhin.andrei@huawei.com>

components/script/dom/canvas/2d/canvasrenderingcontext2d.rs

@@ -13,19 +13,23 @@ use servo_url::ServoUrl;
 use webrender_api::ImageKey;
 
 use super::canvas_state::CanvasState;
-use crate::canvas_context::{CanvasContext, CanvasHelpers, LayoutCanvasRenderingContextHelpers};
+use crate::canvas_context::{
+    CanvasContext, CanvasHelpers, HTMLCanvasElementOrOffscreenCanvas,
+    LayoutCanvasRenderingContextHelpers,
+};
 use crate::dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::{
     CanvasDirection, CanvasFillRule, CanvasImageSource, CanvasLineCap, CanvasLineJoin,
     CanvasRenderingContext2DMethods, CanvasTextAlign, CanvasTextBaseline,
 };
 use crate::dom::bindings::codegen::Bindings::DOMMatrixBinding::DOMMatrix2DInit;
 use crate::dom::bindings::codegen::UnionTypes::{
-    HTMLCanvasElementOrOffscreenCanvas, StringOrCanvasGradientOrCanvasPattern,
+    HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas,
+    StringOrCanvasGradientOrCanvasPattern,
 };
 use crate::dom::bindings::error::{ErrorResult, Fallible};
 use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::{DomGlobal, Reflector, reflect_dom_object};
-use crate::dom::bindings::root::{DomRoot, LayoutDom};
+use crate::dom::bindings::root::{Dom, DomRoot, LayoutDom};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::canvasgradient::CanvasGradient;
 use crate::dom::canvaspattern::CanvasPattern;
@@ -62,19 +66,18 @@ impl CanvasRenderingContext2D {
         })
     }
 
-    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     pub(crate) fn new(
         global: &GlobalScope,
         canvas: &HTMLCanvasElement,
         size: Size2D<u32>,
         can_gc: CanGc,
     ) -> Option<DomRoot<CanvasRenderingContext2D>> {
-        let boxed = Box::new(CanvasRenderingContext2D::new_inherited(
+        CanvasRenderingContext2D::new_inherited(
             global,
-            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(canvas)),
+            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(Dom::from_ref(canvas)),
             size,
-        )?);
-        Some(reflect_dom_object(boxed, global, can_gc))
+        )
+        .map(|context| reflect_dom_object(Box::new(context), global, can_gc))
     }
 
     // https://html.spec.whatwg.org/multipage/#reset-the-rendering-context-to-its-default-state
@@ -119,8 +122,8 @@ impl CanvasContext for CanvasRenderingContext2D {
         self.canvas_state.get_canvas_id()
     }
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
-        Some(self.canvas.clone())
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
+        Some(RootedHTMLCanvasElementOrOffscreenCanvas::from(&self.canvas))
     }
 
     fn update_rendering(&self, canvas_epoch: Epoch) -> bool {
@@ -178,7 +181,7 @@ impl CanvasRenderingContext2DMethods<crate::DomTypeHolder> for CanvasRenderingCo
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-canvas
     fn Canvas(&self) -> DomRoot<HTMLCanvasElement> {
         match &self.canvas {
-            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => canvas.clone(),
+            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => canvas.as_rooted(),
             _ => panic!("Should not be called from offscreen canvas"),
         }
     }

components/script/dom/canvas/2d/offscreencanvasrenderingcontext2d.rs

@@ -2,27 +2,30 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * 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;
-use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
 use canvas_traits::canvas::Canvas2dMsg;
 use dom_struct::dom_struct;
+use euclid::default::Size2D;
 use pixels::Snapshot;
 
+use crate::canvas_context::{CanvasContext, HTMLCanvasElementOrOffscreenCanvas};
 use crate::dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::{
     CanvasDirection, CanvasFillRule, CanvasImageSource, CanvasLineCap, CanvasLineJoin,
-    CanvasTextAlign, CanvasTextBaseline,
+    CanvasRenderingContext2DMethods, CanvasTextAlign, CanvasTextBaseline,
 };
 use crate::dom::bindings::codegen::Bindings::DOMMatrixBinding::DOMMatrix2DInit;
 use crate::dom::bindings::codegen::Bindings::OffscreenCanvasRenderingContext2DBinding::OffscreenCanvasRenderingContext2DMethods;
-use crate::dom::bindings::codegen::UnionTypes::StringOrCanvasGradientOrCanvasPattern;
+use crate::dom::bindings::codegen::UnionTypes::{
+    HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas,
+    StringOrCanvasGradientOrCanvasPattern,
+};
 use crate::dom::bindings::error::{ErrorResult, Fallible};
 use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::reflect_dom_object;
-use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::canvasgradient::CanvasGradient;
 use crate::dom::canvaspattern::CanvasPattern;
+use crate::dom::canvasrenderingcontext2d::CanvasRenderingContext2D;
 use crate::dom::dommatrix::DOMMatrix;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::imagedata::ImageData;
@@ -31,8 +34,6 @@ use crate::dom::path2d::Path2D;
 use crate::dom::textmetrics::TextMetrics;
 use crate::script_runtime::CanGc;
 
-use super::canvasrenderingcontext2d::CanvasRenderingContext2D;
-
 #[dom_struct]
 pub(crate) struct OffscreenCanvasRenderingContext2D {
     context: CanvasRenderingContext2D,
@@ -42,28 +43,26 @@ impl OffscreenCanvasRenderingContext2D {
     #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     fn new_inherited(
         global: &GlobalScope,
-        canvas: &OffscreenCanvas,
+        canvas: HTMLCanvasElementOrOffscreenCanvas,
+        size: Size2D<u32>,
     ) -> Option<OffscreenCanvasRenderingContext2D> {
-        let size = canvas.get_size().cast();
         Some(OffscreenCanvasRenderingContext2D {
-            context: CanvasRenderingContext2D::new_inherited(
-                global,
-                HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(DomRoot::from_ref(canvas)),
-                size,
-            )?,
+            context: CanvasRenderingContext2D::new_inherited(global, canvas, size)?,
         })
     }
 
-    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     pub(crate) fn new(
         global: &GlobalScope,
         canvas: &OffscreenCanvas,
+        size: Size2D<u32>,
         can_gc: CanGc,
     ) -> Option<DomRoot<OffscreenCanvasRenderingContext2D>> {
-        let boxed = Box::new(OffscreenCanvasRenderingContext2D::new_inherited(
-            global, canvas,
-        )?);
-        Some(reflect_dom_object(boxed, global, can_gc))
+        OffscreenCanvasRenderingContext2D::new_inherited(
+            global,
+            HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(Dom::from_ref(canvas)),
+            size,
+        )
+        .map(|context| reflect_dom_object(Box::new(context), global, can_gc))
     }
 
     pub(crate) fn send_canvas_2d_msg(&self, msg: Canvas2dMsg) {
@@ -78,7 +77,7 @@ impl CanvasContext for OffscreenCanvasRenderingContext2D {
         self.context.context_id()
     }
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
         self.context.canvas()
     }
 
@@ -109,7 +108,7 @@ impl OffscreenCanvasRenderingContext2DMethods<crate::DomTypeHolder>
     // https://html.spec.whatwg.org/multipage/offscreencontext2d-canvas
     fn Canvas(&self) -> DomRoot<OffscreenCanvas> {
         match self.context.canvas() {
-            Some(HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas)) => canvas,
+            Some(RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas)) => canvas,
             _ => panic!("Should not be called from onscreen canvas"),
         }
     }

components/script/dom/canvas/canvas_context.rs

@@ -6,19 +6,17 @@
 
 use base::Epoch;
 use euclid::default::Size2D;
-use layout_api::HTMLCanvasData;
 use pixels::Snapshot;
 use script_bindings::root::{Dom, DomRoot};
 use webrender_api::ImageKey;
 
-use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
+use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
 use crate::dom::bindings::inheritance::Castable;
-use crate::dom::html::htmlcanvaselement::HTMLCanvasElement;
 use crate::dom::node::{Node, NodeDamage};
 #[cfg(feature = "webgpu")]
 use crate::dom::types::GPUCanvasContext;
 use crate::dom::types::{
-    CanvasRenderingContext2D, ImageBitmapRenderingContext, OffscreenCanvas,
+    CanvasRenderingContext2D, HTMLCanvasElement, ImageBitmapRenderingContext, OffscreenCanvas,
     OffscreenCanvasRenderingContext2D, WebGL2RenderingContext, WebGLRenderingContext,
 };
 
@@ -27,8 +25,45 @@ pub(crate) trait LayoutCanvasRenderingContextHelpers {
     fn canvas_data_source(self) -> Option<ImageKey>;
 }
 
-pub(crate) trait LayoutHTMLCanvasElementHelpers {
-    fn data(self) -> HTMLCanvasData;
+/// Non rooted variant of [`crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas`]
+#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
+#[derive(Clone, JSTraceable, MallocSizeOf)]
+pub(crate) enum HTMLCanvasElementOrOffscreenCanvas {
+    HTMLCanvasElement(Dom<HTMLCanvasElement>),
+    OffscreenCanvas(Dom<OffscreenCanvas>),
+}
+
+impl From<&RootedHTMLCanvasElementOrOffscreenCanvas> for HTMLCanvasElementOrOffscreenCanvas {
+    /// Returns a traced version suitable for use as member of other DOM objects.
+    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
+    fn from(
+        value: &RootedHTMLCanvasElementOrOffscreenCanvas,
+    ) -> HTMLCanvasElementOrOffscreenCanvas {
+        match value {
+            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
+                HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas.as_traced())
+            },
+            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => {
+                HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas.as_traced())
+            },
+        }
+    }
+}
+
+impl From<&HTMLCanvasElementOrOffscreenCanvas> for RootedHTMLCanvasElementOrOffscreenCanvas {
+    /// Returns a rooted version suitable for use on the stack.
+    fn from(
+        value: &HTMLCanvasElementOrOffscreenCanvas,
+    ) -> RootedHTMLCanvasElementOrOffscreenCanvas {
+        match value {
+            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
+                RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas.as_rooted())
+            },
+            HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => {
+                RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas.as_rooted())
+            },
+        }
+    }
 }
 
 pub(crate) trait CanvasContext {
@@ -36,7 +71,7 @@ pub(crate) trait CanvasContext {
 
     fn context_id(&self) -> Self::ID;
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas>;
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas>;
 
     fn resize(&self);
 
@@ -61,7 +96,8 @@ pub(crate) trait CanvasContext {
     }
 
     fn mark_as_dirty(&self) {
-        if let Some(HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas)) = &self.canvas()
+        if let Some(RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas)) =
+            self.canvas()
         {
             canvas.upcast::<Node>().dirty(NodeDamage::Other);
         }
@@ -82,12 +118,12 @@ pub(crate) trait CanvasContext {
         };
 
         match canvas {
-            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(ref canvas) => {
+            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
                 canvas.upcast::<Node>().is_connected()
             },
             // FIXME(34628): Offscreen canvases should be considered offscreen if a placeholder is set.
             // <https://www.w3.org/TR/webgpu/#abstract-opdef-updating-the-rendering-of-a-webgpu-canvas>
-            HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(_) => false,
+            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(_) => false,
         }
     }
 }
@@ -109,12 +145,36 @@ impl CanvasHelpers for HTMLCanvasElementOrOffscreenCanvas {
 
     fn canvas(&self) -> Option<DomRoot<HTMLCanvasElement>> {
         match self {
-            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => Some(canvas.clone()),
+            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
+                Some(canvas.as_rooted())
+            },
             HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => canvas.placeholder(),
         }
     }
 }
 
+impl CanvasHelpers for RootedHTMLCanvasElementOrOffscreenCanvas {
+    fn size(&self) -> Size2D<u32> {
+        match self {
+            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
+                canvas.get_size().cast()
+            },
+            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => canvas.get_size(),
+        }
+    }
+
+    fn canvas(&self) -> Option<DomRoot<HTMLCanvasElement>> {
+        match self {
+            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
+                Some(canvas.clone())
+            },
+            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => {
+                canvas.placeholder()
+            },
+        }
+    }
+}
+
 /// 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)]
@@ -133,7 +193,7 @@ impl CanvasContext for RenderingContext {
 
     fn context_id(&self) -> Self::ID {}
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
         match self {
             RenderingContext::Placeholder(offscreen_canvas) => offscreen_canvas.context()?.canvas(),
             RenderingContext::Context2d(context) => context.canvas(),
@@ -297,7 +357,7 @@ impl CanvasContext for OffscreenRenderingContext {
 
     fn context_id(&self) -> Self::ID {}
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
         match self {
             OffscreenRenderingContext::Context2d(context) => context.canvas(),
             OffscreenRenderingContext::BitmapRenderer(context) => context.canvas(),

components/script/dom/canvas/imagebitmaprenderingcontext.rs

@@ -9,11 +9,14 @@ use euclid::default::Size2D;
 use pixels::Snapshot;
 use webrender_api::ImageKey;
 
-use crate::canvas_context::{CanvasContext, CanvasHelpers, LayoutCanvasRenderingContextHelpers};
+use crate::canvas_context::{
+    CanvasContext, CanvasHelpers, HTMLCanvasElementOrOffscreenCanvas,
+    LayoutCanvasRenderingContextHelpers,
+};
 use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::bindings::codegen::Bindings::ImageBitmapBinding::ImageBitmapMethods;
 use crate::dom::bindings::codegen::Bindings::ImageBitmapRenderingContextBinding::ImageBitmapRenderingContextMethods;
-use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
+use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::reflector::{Reflector, reflect_dom_object};
 use crate::dom::bindings::root::{DomRoot, LayoutDom};
@@ -37,6 +40,7 @@ pub(crate) struct ImageBitmapRenderingContext {
 
 impl ImageBitmapRenderingContext {
     /// <https://html.spec.whatwg.org/multipage/#imagebitmaprenderingcontext-creation-algorithm>
+    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     fn new_inherited(canvas: HTMLCanvasElementOrOffscreenCanvas) -> ImageBitmapRenderingContext {
         ImageBitmapRenderingContext {
             reflector_: Reflector::new(),
@@ -48,11 +52,13 @@ impl ImageBitmapRenderingContext {
 
     pub(crate) fn new(
         global: &GlobalScope,
-        canvas: HTMLCanvasElementOrOffscreenCanvas,
+        canvas: &RootedHTMLCanvasElementOrOffscreenCanvas,
         can_gc: CanGc,
     ) -> DomRoot<ImageBitmapRenderingContext> {
         reflect_dom_object(
-            Box::new(ImageBitmapRenderingContext::new_inherited(canvas)),
+            Box::new(ImageBitmapRenderingContext::new_inherited(
+                HTMLCanvasElementOrOffscreenCanvas::from(canvas),
+            )),
             global,
             can_gc,
         )
@@ -99,8 +105,8 @@ impl CanvasContext for ImageBitmapRenderingContext {
 
     fn context_id(&self) -> Self::ID {}
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
-        Some(self.canvas.clone())
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
+        Some(RootedHTMLCanvasElementOrOffscreenCanvas::from(&self.canvas))
     }
 
     /// <https://html.spec.whatwg.org/multipage/#the-canvas-element:concept-canvas-bitmaprenderer>
@@ -158,8 +164,8 @@ impl CanvasContext for ImageBitmapRenderingContext {
 
 impl ImageBitmapRenderingContextMethods<crate::DomTypeHolder> for ImageBitmapRenderingContext {
     /// <https://html.spec.whatwg.org/multipage/#dom-imagebitmaprenderingcontext-canvas>
-    fn Canvas(&self) -> HTMLCanvasElementOrOffscreenCanvas {
-        self.canvas.clone()
+    fn Canvas(&self) -> RootedHTMLCanvasElementOrOffscreenCanvas {
+        RootedHTMLCanvasElementOrOffscreenCanvas::from(&self.canvas)
     }
 
     /// <https://html.spec.whatwg.org/multipage/#dom-imagebitmaprenderingcontext-transferfromimagebitmap>

components/script/dom/canvas/offscreencanvas.rs

@@ -20,7 +20,7 @@ use crate::dom::bindings::codegen::Bindings::OffscreenCanvasBinding::{
     ImageEncodeOptions, OffscreenCanvasMethods,
     OffscreenRenderingContext as RootedOffscreenRenderingContext,
 };
-use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
+use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::refcounted::{Trusted, TrustedPromise};
 use crate::dom::bindings::reflector::{DomGlobal, reflect_dom_object_with_proto};
@@ -135,7 +135,8 @@ impl OffscreenCanvas {
                 _ => None,
             };
         }
-        let context = OffscreenCanvasRenderingContext2D::new(&self.global(), self, can_gc)?;
+        let context =
+            OffscreenCanvasRenderingContext2D::new(&self.global(), self, self.get_size(), can_gc)?;
         *self.context.borrow_mut() = Some(OffscreenRenderingContext::Context2d(Dom::from_ref(
             &*context,
         )));
@@ -159,11 +160,10 @@ impl OffscreenCanvas {
         // Step 1. Let context be the result of running the
         // ImageBitmapRenderingContext creation algorithm given this and
         // options.
-        let context = ImageBitmapRenderingContext::new(
-            &self.global(),
-            HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(DomRoot::from_ref(self)),
-            can_gc,
-        );
+        let canvas =
+            RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(DomRoot::from_ref(self));
+
+        let context = ImageBitmapRenderingContext::new(&self.global(), &canvas, can_gc);
 
         // Step 2. Set this's context mode to bitmaprenderer.
         *self.context.borrow_mut() = Some(OffscreenRenderingContext::BitmapRenderer(

components/script/dom/gpucanvascontext.rs

@@ -2,15 +2,14 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use base::Epoch;
 use dom_struct::dom_struct;
 use webrender_api::ImageKey;
 
+use crate::canvas_context::LayoutCanvasRenderingContextHelpers;
 use crate::dom::bindings::codegen::Bindings::GPUCanvasContextBinding::GPUCanvasContextMethods;
-use crate::dom::bindings::codegen::UnionTypes;
+use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
 use crate::dom::bindings::reflector::Reflector;
 use crate::dom::bindings::root::LayoutDom;
-use crate::dom::html::htmlcanvaselement::LayoutCanvasRenderingContextHelpers;
 
 #[dom_struct]
 pub(crate) struct GPUCanvasContext {
@@ -26,7 +25,7 @@ impl GPUCanvasContext {
 
 impl GPUCanvasContextMethods<crate::DomTypeHolder> for GPUCanvasContext {
     /// <https://gpuweb.github.io/gpuweb/#dom-gpucanvascontext-canvas>
-    fn Canvas(&self) -> UnionTypes::HTMLCanvasElementOrOffscreenCanvas {
+    fn Canvas(&self) -> RootedHTMLCanvasElementOrOffscreenCanvas {
         unimplemented!()
     }
 }

components/script/dom/html/htmlcanvaselement.rs

@@ -24,7 +24,7 @@ use servo_media::streams::MediaStreamType;
 use servo_media::streams::registry::MediaStreamId;
 use style::attr::AttrValue;
 
-pub(crate) use crate::canvas_context::*;
+use crate::canvas_context::{CanvasContext, LayoutCanvasRenderingContextHelpers, RenderingContext};
 use crate::conversions::Convert;
 use crate::dom::attr::Attr;
 use crate::dom::bindings::callback::ExceptionHandling;
@@ -34,7 +34,7 @@ use crate::dom::bindings::codegen::Bindings::HTMLCanvasElementBinding::{
 };
 use crate::dom::bindings::codegen::Bindings::MediaStreamBinding::MediaStreamMethods;
 use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLContextAttributes;
-use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
+use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
 use crate::dom::bindings::conversions::ConversionResult;
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::inheritance::Castable;
@@ -156,6 +156,10 @@ impl HTMLCanvasElement {
     }
 }
 
+pub(crate) trait LayoutHTMLCanvasElementHelpers {
+    fn data(self) -> HTMLCanvasData;
+}
+
 impl LayoutHTMLCanvasElementHelpers for LayoutDom<'_, HTMLCanvasElement> {
     #[allow(unsafe_code)]
     fn data(self) -> HTMLCanvasData {
@@ -227,11 +231,10 @@ impl HTMLCanvasElement {
         // Step 1. Let context be the result of running the
         // ImageBitmapRenderingContext creation algorithm given this and
         // options.
-        let context = ImageBitmapRenderingContext::new(
-            &self.owner_global(),
-            HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self)),
-            can_gc,
-        );
+        let canvas =
+            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
+
+        let context = ImageBitmapRenderingContext::new(&self.owner_global(), &canvas, can_gc);
 
         // Step 2. Set this's context mode to bitmaprenderer.
         *self.context_mode.borrow_mut() =
@@ -254,9 +257,10 @@ impl HTMLCanvasElement {
             };
         }
         let window = self.owner_window();
+        let canvas =
+            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
         let size = self.get_size();
         let attrs = Self::get_gl_attributes(cx, options)?;
-        let canvas = HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
         let context = WebGLRenderingContext::new(
             &window,
             &canvas,
@@ -286,9 +290,10 @@ impl HTMLCanvasElement {
             };
         }
         let window = self.owner_window();
+        let canvas =
+            RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(self));
         let size = self.get_size();
         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_mode.borrow_mut() = Some(RenderingContext::WebGL2(Dom::from_ref(&*context)));
         Some(context)

components/script/dom/webgl/webgl2renderingcontext.rs

@@ -29,7 +29,7 @@ use url::Host;
 use webrender_api::ImageKey;
 
 use super::validations::types::TexImageTarget;
-use crate::canvas_context::CanvasContext;
+use crate::canvas_context::{CanvasContext, LayoutCanvasRenderingContextHelpers};
 use crate::dom::bindings::codegen::Bindings::WebGL2RenderingContextBinding::{
     WebGL2RenderingContextConstants as constants, WebGL2RenderingContextMethods,
 };
@@ -38,15 +38,14 @@ use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::{
 };
 use crate::dom::bindings::codegen::UnionTypes::{
     ArrayBufferViewOrArrayBuffer, Float32ArrayOrUnrestrictedFloatSequence,
-    HTMLCanvasElementOrOffscreenCanvas, Int32ArrayOrLongSequence,
-    Uint32ArrayOrUnsignedLongSequence,
+    HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas,
+    Int32ArrayOrLongSequence, Uint32ArrayOrUnsignedLongSequence,
 };
 use crate::dom::bindings::error::{ErrorResult, Fallible};
 use crate::dom::bindings::reflector::{DomGlobal, Reflector, reflect_dom_object};
 use crate::dom::bindings::root::{Dom, DomRoot, LayoutDom, MutNullableDom, ToLayout};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::globalscope::GlobalScope;
-use crate::dom::html::htmlcanvaselement::LayoutCanvasRenderingContextHelpers;
 #[cfg(feature = "webxr")]
 use crate::dom::promise::Promise;
 use crate::dom::webgl::validations::WebGLValidator;
@@ -133,7 +132,7 @@ struct ReadPixelsSizes {
 impl WebGL2RenderingContext {
     fn new_inherited(
         window: &Window,
-        canvas: &HTMLCanvasElementOrOffscreenCanvas,
+        canvas: &RootedHTMLCanvasElementOrOffscreenCanvas,
         size: Size2D<u32>,
         attrs: GLContextAttributes,
         can_gc: CanGc,
@@ -179,10 +178,9 @@ impl WebGL2RenderingContext {
         })
     }
 
-    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     pub(crate) fn new(
         window: &Window,
-        canvas: &HTMLCanvasElementOrOffscreenCanvas,
+        canvas: &RootedHTMLCanvasElementOrOffscreenCanvas,
         size: Size2D<u32>,
         attrs: GLContextAttributes,
         can_gc: CanGc,
@@ -973,8 +971,8 @@ impl CanvasContext for WebGL2RenderingContext {
         self.base.context_id()
     }
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
-        self.base.canvas().clone()
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
+        self.base.canvas()
     }
 
     fn resize(&self) {
@@ -1000,7 +998,7 @@ impl CanvasContext for WebGL2RenderingContext {
 
 impl WebGL2RenderingContextMethods<crate::DomTypeHolder> for WebGL2RenderingContext {
     /// <https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.1>
-    fn Canvas(&self) -> HTMLCanvasElementOrOffscreenCanvas {
+    fn Canvas(&self) -> RootedHTMLCanvasElementOrOffscreenCanvas {
         self.base.Canvas()
     }
 

components/script/dom/webgl/webglrenderingcontext.rs

@@ -35,7 +35,9 @@ use serde::{Deserialize, Serialize};
 use servo_config::pref;
 use webrender_api::ImageKey;
 
-use crate::canvas_context::CanvasContext;
+use crate::canvas_context::{
+    CanvasContext, HTMLCanvasElementOrOffscreenCanvas, LayoutCanvasRenderingContextHelpers,
+};
 use crate::dom::bindings::cell::{DomRefCell, Ref, RefMut};
 use crate::dom::bindings::codegen::Bindings::ANGLEInstancedArraysBinding::ANGLEInstancedArraysConstants;
 use crate::dom::bindings::codegen::Bindings::EXTBlendMinmaxBinding::EXTBlendMinmaxConstants;
@@ -47,7 +49,8 @@ use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::{
 };
 use crate::dom::bindings::codegen::UnionTypes::{
     ArrayBufferViewOrArrayBuffer, Float32ArrayOrUnrestrictedFloatSequence,
-    HTMLCanvasElementOrOffscreenCanvas, Int32ArrayOrLongSequence,
+    HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas,
+    Int32ArrayOrLongSequence,
 };
 use crate::dom::bindings::conversions::DerivedFrom;
 use crate::dom::bindings::error::{Error, ErrorResult, Fallible};
@@ -56,7 +59,6 @@ use crate::dom::bindings::reflector::{DomGlobal, DomObject, Reflector, reflect_d
 use crate::dom::bindings::root::{DomOnceCell, DomRoot, LayoutDom, MutNullableDom};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::event::{Event, EventBubbles, EventCancelable};
-use crate::dom::html::htmlcanvaselement::LayoutCanvasRenderingContextHelpers;
 use crate::dom::node::{Node, NodeDamage, NodeTraits};
 #[cfg(feature = "webxr")]
 use crate::dom::promise::Promise;
@@ -216,9 +218,10 @@ pub(crate) struct WebGLRenderingContext {
 }
 
 impl WebGLRenderingContext {
+    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     pub(crate) fn new_inherited(
         window: &Window,
-        canvas: &HTMLCanvasElementOrOffscreenCanvas,
+        canvas: HTMLCanvasElementOrOffscreenCanvas,
         webgl_version: WebGLVersion,
         size: Size2D<u32>,
         attrs: GLContextAttributes,
@@ -248,7 +251,7 @@ impl WebGLRenderingContext {
                 webgl_version,
                 glsl_version: ctx_data.glsl_version,
                 limits: ctx_data.limits,
-                canvas: canvas.clone(),
+                canvas,
                 last_error: Cell::new(None),
                 texture_packing_alignment: Cell::new(4),
                 texture_unpacking_settings: Cell::new(TextureUnpacking::CONVERT_COLORSPACE),
@@ -285,13 +288,19 @@ impl WebGLRenderingContext {
     #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     pub(crate) fn new(
         window: &Window,
-        canvas: &HTMLCanvasElementOrOffscreenCanvas,
+        canvas: &RootedHTMLCanvasElementOrOffscreenCanvas,
         webgl_version: WebGLVersion,
         size: Size2D<u32>,
         attrs: GLContextAttributes,
         can_gc: CanGc,
     ) -> Option<DomRoot<WebGLRenderingContext>> {
-        match WebGLRenderingContext::new_inherited(window, canvas, webgl_version, size, attrs) {
+        match WebGLRenderingContext::new_inherited(
+            window,
+            HTMLCanvasElementOrOffscreenCanvas::from(canvas),
+            webgl_version,
+            size,
+            attrs,
+        ) {
             Ok(ctx) => Some(reflect_dom_object(Box::new(ctx), window, can_gc)),
             Err(msg) => {
                 error!("Couldn't create WebGLRenderingContext: {}", msg);
@@ -304,10 +313,10 @@ impl WebGLRenderingContext {
                     can_gc,
                 );
                 match canvas {
-                    HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
+                    RootedHTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => {
                         event.upcast::<Event>().fire(canvas.upcast(), can_gc);
                     },
-                    HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => {
+                    RootedHTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => {
                         event.upcast::<Event>().fire(canvas.upcast(), can_gc);
                     },
                 }
@@ -1930,8 +1939,8 @@ impl CanvasContext for WebGLRenderingContext {
         self.webgl_sender.context_id()
     }
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
-        Some(self.canvas.clone())
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
+        Some(RootedHTMLCanvasElementOrOffscreenCanvas::from(&self.canvas))
     }
 
     fn resize(&self) {
@@ -2075,8 +2084,8 @@ impl Drop for WebGLRenderingContext {
 
 impl WebGLRenderingContextMethods<crate::DomTypeHolder> for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.1
-    fn Canvas(&self) -> HTMLCanvasElementOrOffscreenCanvas {
-        self.canvas.clone()
+    fn Canvas(&self) -> RootedHTMLCanvasElementOrOffscreenCanvas {
+        RootedHTMLCanvasElementOrOffscreenCanvas::from(&self.canvas)
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.11

components/script/dom/webgpu/gpucanvascontext.rs

@@ -20,7 +20,10 @@ use wgpu_core::id;
 
 use super::gpuconvert::convert_texture_descriptor;
 use super::gputexture::GPUTexture;
-use crate::canvas_context::{CanvasContext, CanvasHelpers};
+use crate::canvas_context::{
+    CanvasContext, CanvasHelpers, HTMLCanvasElementOrOffscreenCanvas,
+    LayoutCanvasRenderingContextHelpers,
+};
 use crate::conversions::Convert;
 use crate::dom::bindings::codegen::Bindings::GPUCanvasContextBinding::GPUCanvasContextMethods;
 use crate::dom::bindings::codegen::Bindings::WebGPUBinding::GPUTexture_Binding::GPUTextureMethods;
@@ -29,15 +32,15 @@ use crate::dom::bindings::codegen::Bindings::WebGPUBinding::{
     GPUObjectDescriptorBase, GPUTextureDescriptor, GPUTextureDimension, GPUTextureFormat,
     GPUTextureUsageConstants,
 };
-use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
+use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas as RootedHTMLCanvasElementOrOffscreenCanvas;
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::reflector::{DomGlobal, Reflector, reflect_dom_object};
-use crate::dom::bindings::root::{DomRoot, LayoutDom, MutNullableDom};
+use crate::dom::bindings::root::{Dom, DomRoot, LayoutDom, MutNullableDom};
 use crate::dom::bindings::str::USVString;
 use crate::dom::bindings::weakref::WeakRef;
 use crate::dom::document::WebGPUContextsMap;
 use crate::dom::globalscope::GlobalScope;
-use crate::dom::html::htmlcanvaselement::{HTMLCanvasElement, LayoutCanvasRenderingContextHelpers};
+use crate::dom::html::htmlcanvaselement::HTMLCanvasElement;
 use crate::dom::node::NodeTraits;
 use crate::script_runtime::CanGc;
 
@@ -91,6 +94,7 @@ pub(crate) struct GPUCanvasContext {
 }
 
 impl GPUCanvasContext {
+    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
     fn new_inherited(
         global: &GlobalScope,
         canvas: HTMLCanvasElementOrOffscreenCanvas,
@@ -139,7 +143,7 @@ impl GPUCanvasContext {
         let this = reflect_dom_object(
             Box::new(GPUCanvasContext::new_inherited(
                 global,
-                HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(DomRoot::from_ref(canvas)),
+                HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(Dom::from_ref(canvas)),
                 channel,
                 document.webgpu_contexts(),
             )),
@@ -328,8 +332,8 @@ impl CanvasContext for GPUCanvasContext {
         })
     }
 
-    fn canvas(&self) -> Option<HTMLCanvasElementOrOffscreenCanvas> {
-        Some(self.canvas.clone())
+    fn canvas(&self) -> Option<RootedHTMLCanvasElementOrOffscreenCanvas> {
+        Some(RootedHTMLCanvasElementOrOffscreenCanvas::from(&self.canvas))
     }
 }
 
@@ -341,8 +345,8 @@ impl LayoutCanvasRenderingContextHelpers for LayoutDom<'_, GPUCanvasContext> {
 
 impl GPUCanvasContextMethods<crate::DomTypeHolder> for GPUCanvasContext {
     /// <https://gpuweb.github.io/gpuweb/#dom-gpucanvascontext-canvas>
-    fn Canvas(&self) -> HTMLCanvasElementOrOffscreenCanvas {
-        self.canvas.clone()
+    fn Canvas(&self) -> RootedHTMLCanvasElementOrOffscreenCanvas {
+        RootedHTMLCanvasElementOrOffscreenCanvas::from(&self.canvas)
     }
 
     /// <https://gpuweb.github.io/gpuweb/#dom-gpucanvascontext-configure>

components/script/dom/webxr/xrwebgllayer.rs

@@ -10,14 +10,13 @@ use euclid::{Rect, Size2D};
 use js::rust::HandleObject;
 use webxr_api::{ContextId as WebXRContextId, LayerId, LayerInit, Viewport};
 
-use crate::canvas_context::CanvasContext as _;
+use crate::canvas_context::CanvasContext;
 use crate::conversions::Convert;
 use crate::dom::bindings::codegen::Bindings::WebGL2RenderingContextBinding::WebGL2RenderingContextConstants as constants;
 use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextMethods;
 use crate::dom::bindings::codegen::Bindings::XRWebGLLayerBinding::{
     XRWebGLLayerInit, XRWebGLLayerMethods, XRWebGLRenderingContext,
 };
-use crate::dom::bindings::codegen::UnionTypes::HTMLCanvasElementOrOffscreenCanvas;
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::num::Finite;
@@ -125,14 +124,7 @@ impl XRWebGLLayer {
                 size.1.try_into().unwrap_or(0),
             )
         } else {
-            let size = match self.context().Canvas() {
-                HTMLCanvasElementOrOffscreenCanvas::HTMLCanvasElement(canvas) => canvas.get_size(),
-                HTMLCanvasElementOrOffscreenCanvas::OffscreenCanvas(canvas) => {
-                    let size = canvas.get_size();
-                    Size2D::new(size.width, size.height)
-                },
-            };
-            Size2D::from_untyped(size)
+            Size2D::from_untyped(self.context().size())
         }
     }