- From: Robert O'Callahan <robert@ocallahan.org>
- Date: Fri, 30 Jul 2010 15:48:37 +1200
On Thu, Jul 29, 2010 at 10:09 AM, Oliver Hunt <oliver at apple.com> wrote: > This is the way the webkit canvas implementation has always worked, firefox > implemented this incorrectly, and the spec was based off of that > implementation. > I don't think "the spec was based off of that implementation" is true, since Firefox never matched the spec (certain operators such as "copy" were treated as source-bounded, because cairo does it that way, just like CG) until I fixed that relatively recently. Additionally the webkit behaviour is more powerful than the spec behaviour > as the spec behaviour can be emulated trivially on top of the webkit model, > but vice versa is much harder and much more expensive. > They're both pretty easy to emulate in terms of the other. But I agree that emulating an unbounded operator in terms of the source-bounded operator has a higher performance penalty, since the easy implementation is to use a temporary surface, where as to emulate source-bounded using unbounded you just do some extra clipping. As it happens, I'm expecting to see a proposal on public-canvas-api sometime soon that makes all composition source-bounded and has acceptable text defining the shape affected by the composition operation. It's tricky though, especially regarding shadows. But since I agree source-boundedness is more intuitive for authors, I'm open to changing Firefox to support it. Rob -- "Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true." [Acts 17:11] -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.whatwg.org/pipermail/whatwg-whatwg.org/attachments/20100730/5e4f38a3/attachment-0001.htm>
Received on Thursday, 29 July 2010 20:48:37 UTC