Bug 93344 – CanvasRenderingContext2D::createPattern() should return null, if non-decodable image argument

• Status: RESOLVED
• Resolution: CONFIGURATION CHANGED
• Component: Canvas

[Jussi Kukkonen (jku)]

Spec says: "If the image argument is an HTMLImageElement object that is not fully decodable ... then the implementation must return null." This does not currently happen so these tests fail:
  canvas/philip/tests/2d.pattern.image.broken.html = TEXT
  canvas/philip/tests/2d.pattern.image.incomplete.empty.html = TEXT
  canvas/philip/tests/2d.pattern.image.incomplete.omitted.html = TEXT


HTMLImageElement does not seem to have "decodability" as a property and things are slightly complicated by the img.complete property being slightly illogical for this: currently images with empty, missing or non-existing source are "complete" (and IIRC this is according to current spec). So possibly these cases would have to be tested in CanvasRenderingContext2D. I'll take a closer look, advice is welcome also.

[Jussi Kukkonen (jku)]

to improve searchability: above comment relates to CanvasRenderingContext2D::createPattern()

[Jussi Kukkonen (jku)]

After some testing:

2d.pattern.image.incomplete.omitted:
works after checking image->src().isValid()) before creating pattern

2d.pattern.image.broken:
needs knowledge of whether image really is decodable

2d.pattern.image.incomplete.empty:
the image url used in createPattern() ends up as the _page_ url because HTMLIMageElement does document().completeURL(). This would still work with knowledge of whether image really is decodable

[Brent Fulgham]

It looks like this was done as part of Bug 180718.