1281909 - Should I be able to piggyback custom properties on OffscreenCanvas objects transferred to a Worker?

Status: RESOLVED INVALID

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

Description

[Jukka Jylänki]

Attachment: worker_attribute_test.html

With the pref gfx.offscreencanvas.enabled = true in Nightly, run the attached html page.

That will print the following in console:

in main thread: canvas.id: mycustomid
inside worker: canvas.id: undefined

Is this expected behavior that the id field dies, or should it be possible to pass custom properties as part of an OffscreenCanvas object when transferring it to a Worker?

Comment 1

[Sotaro Ikeda [:sotaro]]

:pchang, can you answer for forward the question?

Comment 2

[Peter Chang[:pchang]]

Morris, any idea for this?

Comment 3

[Morris Tseng [:mtseng] [:Morris] (Inactive)]

Currently in our implementation, we don't transfer custom properties since custom properties may not transferable.

Comment 4

[Justin Novosad (Chrome Team, Google)]

In the spec, the shallow serialization algorithms used for transferring platform objects don't serialize custom properties.  For each type of platform object that is transferable, the spec defines the necessary transfer algorithms. The "transfer steps" and transfer-receiving steps" for OffscreenCanvas are defined here: https://html.spec.whatwg.org/multipage/canvas.html#offscreencanvas Those steps do not transfer custom properties.

Comment 5

[Jukka Jylänki]

Thanks for confirming Justin, much appreciated!