1289716 - Hold WebGLContext in WebGLExtensionLoseContext extension

Status: RESOLVED INVALID

(Core :: Graphics: CanvasWebGL, task, P3)

Description

[Jerry Shih[:jerry] (UTC+8) (inactive)]

Gecko doesn't detach the WebGLExtensionLoseContext extension when the context lost[1], so it might be possible that we use the WebGLExtensionLoseContext js object while the webglContext is gone.

I'm trying to hold one webglContext ref-count inside WebGLExtensionLoseContext to prevent that situation.

[1]
https://hg.mozilla.org/mozilla-central/annotate/ceb63dec9267e9bb62f5e5e1f4c9d32d3ac1fbac/dom/canvas/WebGLContext.cpp#l296

Comment 1

[Jerry Shih[:jerry] (UTC+8) (inactive)]

Attachment: hold WebGLContext in WebGLExtensionLoseContext extension. v1

Comment 2

[Jerry Shih[:jerry] (UTC+8) (inactive)]

Comment on attachment 8799623 [details] [diff] [review]
hold WebGLContext in WebGLExtensionLoseContext extension. v1

Review of attachment 8799623 [details] [diff] [review]:
-----------------------------------------------------------------

::: dom/canvas/WebGLExtensions.h
@@ +194,5 @@
> +    // "WEBGL_lose_context". The WebGLExtensionLoseContext js object might be
> +    // used while the WebGLContext is gone. Hold one webglContext ref-count here
> +    // to prevent this situation.
> +    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15.2
> +    RefPtr<WebGLContext> mWebGLContext;

If we have an WebGLExtensionLoseContext obj, the WebGLContext might be released after ~WebGLExtensionLoseContext.

WebGLContext doesn't have the WebGLExtensionLoseContext ref-count.
So, there is no reference cycle between these two object.

Comment 3

[Kelsey Gilbert [:jgilbert]]

Comment on attachment 8799623 [details] [diff] [review]
hold WebGLContext in WebGLExtensionLoseContext extension. v1

Review of attachment 8799623 [details] [diff] [review]:
-----------------------------------------------------------------

::: dom/canvas/WebGLExtensions.h
@@ +194,5 @@
> +    // "WEBGL_lose_context". The WebGLExtensionLoseContext js object might be
> +    // used while the WebGLContext is gone. Hold one webglContext ref-count here
> +    // to prevent this situation.
> +    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15.2
> +    RefPtr<WebGLContext> mWebGLContext;

WebGLContext::mExtensions holds a refcount to WebGLExtensionLoseContext.

Use a weak pointer in this case.

Comment 4

[Kelsey Gilbert [:jgilbert]]

We don't actually want a strong-ref there.