On 15/03/2013, at 7:55 AM, Gregg Tavares <[email protected]> wrote: > > > > On Thu, Mar 14, 2013 at 1:38 PM, Ryosuke Niwa <[email protected]> wrote: > On Thu, Mar 14, 2013 at 12:55 PM, Dean Jackson <[email protected]> wrote: > > On 15/03/2013, at 6:50 AM, Dana Jansens <[email protected]> wrote: > >> On Thu, Mar 14, 2013 at 3:46 PM, Dean Jackson <[email protected]> wrote: >> I'm not sure I like this proposal. Why is canvas special? Why doesn't <img> >> get an opaque attribute (or flag)? Why not every element? >> >> There is ongoing work to infer opaqueness in every other kind of element >> when possible. See for example https://bugs.webkit.org/show_bug.cgi?id=70634 > > Yes, I'd prefer to infer it rather than specify it. For example, I could > infer that a canvas is opaque if it has a non-transparent CSS > background-color. > > The content of the canvas has to be blended with the background color so that > doesn't help optimization. If there's a background color you first have to do > a full blend of the contents of the canvas with the background color. Where > as if the canvas has no alpha then that step can be avoided.
We're probably getting a bit off the general topic here, but why don't you consider the background color as a fillRect(0, 0, width, height) on the empty canvas? As has been said, this doesn't change the behaviour of the painting/blending operations in the canvas itself, just how it is composited into the document. I guess we should take this conversation to the HTML list. Dean > > > > I like this approach. It means that developers don't have to explicitly use > this feature to get the performance benefits. > > In fact, this is the preferred performance optimization approach on the Web. > We don't provide explicit APIs to optimize performance. We make sensible APIs > which allows us to implement more optimizations on common cases behind the > scene. > > - R. Niwa > > > _______________________________________________ > webkit-dev mailing list > [email protected] > https://lists.webkit.org/mailman/listinfo/webkit-dev > >
_______________________________________________ webkit-dev mailing list [email protected] https://lists.webkit.org/mailman/listinfo/webkit-dev
