- From: Oliver Hunt <oliver@apple.com>
- Date: Fri, 16 Oct 2009 21:37:11 -0700
On Oct 16, 2009, at 8:10 PM, Robert O'Callahan wrote: > On Sat, Oct 17, 2009 at 4:01 AM, Philip Taylor <excors+whatwg at gmail.com > > wrote: > Yes, mostly. http://philip.html5.org/tests/canvas/suite/tests/index.2d.composite.uncovered.html > has relevant tests, matching what I believed the spec said - on > Windows, Opera 10 passes them all, Firefox 3.5 passes all except > 'copy' (https://bugzilla.mozilla.org/show_bug.cgi?id=366283), Safari 4 > and Chrome 3 fail them all. > > (Looking at the spec quickly now, I don't see anything that actually > states this explicitly - the only reference to infinite transparent > black bitmaps is when drawing shadows. But > http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#drawing-model > is phrased in terms of rendering shapes onto an image, then > compositing the image within the clipping region, so I believe it is > meant to work as I said (and definitely not by compositing only within > the extent of the shape drawn onto the image).) > > Yes, I think that's pretty clear as written. > > I think there is a reasonable argument that the spec should be > changed so that compositing happens only within the shape. (In cairo > terminology, all operators should be bounded.) Perhaps that's what > Safari and Chrome developers want. This is the behaviour of the original canvas implementation (and it makes a degree of sense -- it is possible to fake composition implying an infinite 0-alpha surrounding when the default composite operator does not do this, but vice versa is not possible). That said I suspect we are unable to do anything this anymore :-/ > Rob --Oliver -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.whatwg.org/pipermail/whatwg-whatwg.org/attachments/20091016/454417c9/attachment.htm>
Received on Friday, 16 October 2009 21:37:11 UTC