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

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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>
This commit is contained in:
Andrei Volykhin 2025-09-03 22:24:48 +03:00 • committed by GitHub
parent 2c7866eb24
commit 8a62984c2f
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GPG key ID: B5690EEEBB952194
11 changed files with 191 additions and 116 deletions
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23
components/script/dom/html/htmlcanvaselement.rs
View file

@ -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)