- From: James Robinson <jamesr@google.com>
- Date: Wed, 11 Dec 2013 21:28:45 -0800
- To: Rik Cabanier <cabanier@gmail.com>
- Cc: www-svg <www-svg@w3.org>, www-style list <www-style@w3.org>, "public-fx@w3.org" <public-fx@w3.org>
- Message-ID: <CAD73md+SBv8J7jXcnxJMwVWUOcnVXw-rH+=sH5tvC8K0Ruv0Qw@mail.gmail.com>
Why are you trying to define how canvas works in a CSS spec? Canvas is defined as part of HTML, including how the compositing operations are applied. The text here is completely unhelpful. - James On Dec 11, 2013 7:16 PM, "Rik Cabanier" <cabanier@gmail.com> wrote: > > > > On Wed, Dec 11, 2013 at 6:57 PM, James Robinson <jamesr@google.com> wrote: > >> >> On Wed, Dec 11, 2013 at 6:44 PM, Rik Cabanier <cabanier@gmail.com> wrote: >> >>> >>> >>>> >>>> Canvas is defined in HTML. Having text here to define a behavior that >>>> canvas does not use is just confusing with no upside. >>>> >>> >>> No, canvas refers to the compositing spec for the 'globalComposite' >>> operator [1]: >>> >>> The globalCompositeOperation attribute sets the current composition >>> operator, which controls how shapes and images are drawn onto the scratch >>> bitmap<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#scratch-bitmap>, >>> once they have had globalAlpha<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-globalalpha> and >>> the current transformation matrix applied. The possible values are those >>> defined in the Compositing and Blending specification. [COMPOSITE]<http://www.whatwg.org/specs/web-apps/current-work/multipage/references.html#refsCOMPOSITE> >>> >>> >>> Do you think the canvas spec should be more clear that compositing is >>> defined in the "Compositing and Blending specification"? >>> >> >> The paragraph in question - "9.2.3. Clip to self behavior" - describes a >> behavior that is not used by canvas, or (from what you've said) by anything >> in the Compositing and Blending spec. What value does it have other than >> creating confusion, in that case? >> > > Section 5-10 define a generic model for blending and compositing. > The normative section defines a subsection of that model. Hopefully we can > implement the whole model over the coming years. > By defining it this way, it should be more clear to an implementor how > things are supposed to be work. > For example, the problems that you mentioned earlier: > > Firefox applied the compositing operation to the entire canvas, respecting > the current clip, and WebKit applied the compositing operation only to the > "bounds" of the draw. > > would not have happened if there had been a definition like you find in > the current spec: > http://dev.w3.org/fxtf/compositing-1/#groupcompositingcliptoself > > I don't really see a way to define how compositing works in canvas without > describing the clip-to-self behavior somehow... >
Received on Thursday, 12 December 2013 05:29:12 UTC