[Webkit-unassigned] [Bug 227792] New: Canvas and OffscreenCanvas getContext should convert argument to object before trying to convert it to a dictionary

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=227792

            Bug ID: 227792
           Summary: Canvas and OffscreenCanvas getContext should convert
                    argument to object before trying to convert it to a
                    dictionary
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Canvas
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: clord at igalia.com
                CC: dino at apple.com
        Depends on: 225836
            Blocks: 225870

Since r277543, which introduced canvas settings handling, imported/w3c/web-platform-tests/html/canvas/offscreen/the-offscreen-canvas/2d.getcontext.extraargs.html and the worker equivalent have been failing. This is due to a TypeError when trying to convert the non-object arguments into a dictionary.

Reading the spec, both the section on getContext[1] and the section on context creation[2], it seems that arguments are expected to be converted to either an object or null before being converted to a settings dictionary. As we lack this step, there are more situations where we throw an exception when a compliant browser wouldn't.

[1] https://html.spec.whatwg.org/multipage/canvas.html#dom-offscreencanvas-getcontext
[2] https://html.spec.whatwg.org/multipage/canvas.html#offscreen-2d-context-creation-algorithm

Ms2ger is working on more tests for this in WPT, we should fix this bug and sync those tests here once they exist.


Referenced Bugs:

https://bugs.webkit.org/show_bug.cgi?id=225836
[Bug 225836] Move CanvasRenderingContext2DSettings down to CanvasRenderingContext2DBase so it can be used there (and to support OffscreenCanvas)
https://bugs.webkit.org/show_bug.cgi?id=225870
[Bug 225870] [GLIB] Several offscreen canvas tests are failing since r277543
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