[whatwg] isPointInPath v. set of pixels in canvas hit regions

Charles Pritchard chuck at jumis.com
Thu Jul 5 13:32:38 PDT 2012

On Jul 5, 2012, at 1:05 PM, Edward O'Connor <eoconnor at apple.com> wrote:

> Hi,
> As things currently stand in the spec, implementations basically need to
> keep N+1 bitmaps per canvas, where N is the number of hit regions. I
> doubt any implementors would be enthusiastic to implement hit regions
> like this. From a WebKit perspective, we'd much prefer keeping a Path
> for each hit region, and then simply using isPointInPath for hit
> testing. This also implies that the current piggybacking of "Clear
> regions that cover the pixels" in clearRect() could go away. Yay! :)

I couldn't agree more.

The hit testing code from SVG in WebKit could easily be reused by the Canvas implementation.

I believe the rationale for bitmap backing was based on an assumption that it would be easier for authors. I've consistently argued against this assumption.


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