[webkit-dev] New web-facing canvas feature: "opaque" attribute

Stephen White senorblanco at chromium.org
Thu Mar 14 10:53:33 PDT 2013

Hi Dirk,

There have been at least five options considered, with contributions from
Chromium, Adobe and Mozilla so far.  The moz-opaque idea was first floated
by Robert O'Callahan from Mozilla, and Ian Hickson offered to spec it if
another browser vendor wanted to implement it.  I took him up on that
offer, and have made my humble effort to massage it into a concrete
proposal in the linked message above.

After proposing it here, the alternative suggestion is to sync it up with
the WebGL syntax, and use a context creation object at getContext() time
rather than an attribute on the <canvas> element.  I have no strong
feelings about this either way, and I'm working on a patch to try out the
WebGL approach (I already have a WebKit patch which implements the
platform-independent parts of the opaque attribute approach).  However, if
we do go that way, I'd prefer not to make this proposal conditional on
changes to the WebGL spec, concerns which I've outlined over on what-wg.


On Wed, Mar 13, 2013 at 12:30 PM, Dirk Schulze <dschulze at adobe.com> wrote:

> This is a very long thread and I did not see any conclusions or agreement
> on this thread. Can you summarize the topic and the status on the
> acceptance level please?
> Greetings,
> Dirk
> On Mar 13, 2013, at 9:15 AM, Stephen White <senorblanco at chromium.org>
> wrote:
> > Hi WebKittens,
> >
> > I'm planning to implement the canvas "opaque" attribute, as proposed
> here:
> http://lists.w3.org/Archives/Public/public-whatwg-archive/2013Mar/0109.html
> .
> >
> > This is an attribute that causes the allocation of an opaque backing
> store for <canvas>, allowing optimizations at the time the canvas is
> composited into the page, such as disabling blending and culling obscured
> content.  It is based on the moz-opaque attribute currently shipping in
> Firefox.
> >
> > I'll be placing the feature behind the build-time flag
> >
> > Let me know if you have any comments or concerns.
> >
> > Stephen
> > _______________________________________________
> > webkit-dev mailing list
> > webkit-dev at lists.webkit.org
> > https://lists.webkit.org/mailman/listinfo/webkit-dev
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