[whatwg] CanvasRenderingContext2D::createPattern and partially loaded images

Eric Seidel eric at webkit.org
Fri Aug 8 17:04:47 PDT 2008


If the image argument is an HTMLImageElement object whose complete
attribute is false, then the implementation must raise an


On Fri, Aug 8, 2008 at 5:03 PM, Eric Seidel <eric at webkit.org> wrote:
> http://www.whatwg.org/specs/web-apps/current-work/#createpattern
> Notes that:
> The first argument gives the image to use as the pattern (either an
> HTMLImageElement or an HTMLCanvasElement). Modifying this image after
> calling the createPattern() method must not affect the pattern.
> What does this mean for images which are not yet fully loaded from the
> network?  Safari's current behavior is that the pattern will draw the
> image with as much data as we know about that network resource *at the
> time the pattern is drawn*.  Instead of at the time the pattern is
> created (as the spec seems to imply).  Meaning if you're a web author,
> and you don't bother to listen for Image load events, if your user is
> on a slow network, each time you draw your pattern, you'll have
> slightly more of the image until it completes.
> I can disable this feature of Safari (make it so that
> "createPattern()" creates a copy of the image, in whatever loaded
> state it may be), or we can change the spec to say that incremental
> loading images do not count as "modifying the image after calling
> createPattern()".
> Thoughts?
> -eric

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