[Webkit-unassigned] [Bug 73645] Philip canvas tests fail with non unity device scale factor

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=73645





--- Comment #2 from Matthew Delaney <mdelaney at apple.com>  2012-02-22 10:27:05 PST ---
You're correct, just about every one of our canvas layout tests (including philip's) wasn't written with this behavior in mind. By this behavior, I mean specifically the decision to automatically scale up the backing store and then give all those bits via getImageData and friends. On the same note, this behavior breaks a lot of webpages that use get/putImageData and toDataURL without accounting for the increased backing store.

Even if the way the tests sample the canvas took this behavior into account, there would still be additional side effects from this behavior that our layout tests don't account for such as rounding differences due to the increased scale.

A large number of tests currently pass largely due to the fact that the pixels that they're actually checking happen to have the same values (e.g. a whole section of the canvas is green, so sampling the device pixel at x or 2x will likely hit green in both cases).

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