- From: L. David Baron <dbaron@dbaron.org>
- Date: Wed, 6 Mar 2013 16:32:50 -0800
- To: Rik Cabanier <cabanier@gmail.com>
- Cc: robert@ocallahan.org, public-fx@w3.org
On Wednesday 2013-03-06 16:13 -0800, Rik Cabanier wrote: > On Wed, Mar 6, 2013 at 3:19 PM, L. David Baron <dbaron@dbaron.org> wrote: > > Background images themselves are atomic, but you still need to > > specify what they're blended with. And since they don't create a > > stacking context, they sit in the middle of the very-complicated > > rules for painting stuff within a stacking context. > > > > yes, but your spec describes that order (except it doesn't handle multiple > backgrounds yet) so that should not be a big deal. It wouldn't be a big deal if the backgrounds were composited only against each other. But https://dvcs.w3.org/hg/FXTF/raw-file/fac7acff8efc/compositing/index.html#background-blend-mode says: # Each background image will blend with the element's background # and the background images at a lower z-index. I interpret "the element's background" as "the things behind the element", which also matches your explanation in: http://lists.w3.org/Archives/Public/public-fx/2013JanMar/0084.html where you wrote: # The background that is available for the # blend operation at that time is everything up to an ancestor that created a # stacking context. In this case you'd need to describe the grouping fully as I wrote here in http://dbaron.org/log/20130306-compositing-blending : # In order to specify blending an compositing throughout CSS in a # way that will be interoperable across browsers, the grouping in # CSS must be specified as clearly and with as much precision as # the ordering is. This means that everything in Appendix E of CSS # 2.1, plus all the additions to it from newer CSS modules that # have not been fully tracked, needs to specify not only the # ordering of the drawing operations but also their grouping. rather than describing only the parts I outlined in my post as I continued to say in: # If non-default compositing and blending is limited strictly to # elements that create stacking contexts, as I have proposed # (which means removing background-composite and # background-blend-mode), then the specification problem becomes # substantially easier, in that we at least only need to specify # and interoperably implement the grouping of those of the drawing # operations that involve elements creating stacking contexts, # which means, I think, that the grouping would only need to be # specified between: # # 1. Together, items (1) through (2) in the top level of Appendix E # 2. Each item in item (3) in the top level of Appendix E # 3. Together, items (4) through (7) in the top level of Appendix E # 4. Each item in item (8) in the top level of Appendix E # 5. Each item in item (9) in the top level of Appendix E # 6. Together, (10) in the top level of Appendix E which is what would be necessary if the background-* properties were dropped, or if they applied only to blending with other background layers and not the backdrop of the element (which would be relatively easy, but I suspect not very useful). -David -- 𝄞 L. David Baron http://dbaron.org/ 𝄂 𝄢 Mozilla http://www.mozilla.org/ 𝄂
Received on Thursday, 7 March 2013 00:33:18 UTC