globalAlpha will still work but will always composite with an opaque backdrop (which is black by default)
On Wed, Mar 13, 2013 at 3:25 PM, Elliott Sprehn <[email protected]>wrote: > alpha:false is super confusing to me. It makes it sound as though all > draw*() operations that use an alpha channel will fail... does globalAlpha > still work? > > It's sad that WebGL picked such a generic name that isn't about all > "alpha" related things. > > > On Wed, Mar 13, 2013 at 2:59 PM, Rik Cabanier <[email protected]> wrote: > >> The main reason for this feature is to enhance performance of canvas >> operations. >> Are we certain that this will always be the case? For instance, is google >> going to make certain that the cairo and core graphics backends don't slow >> down? >> >> Rik >> >> >> On Wed, Mar 13, 2013 at 1:21 PM, Brandon Jones <[email protected]>wrote: >> >>> I think "opaque" vs. "alpha: false" is a matter of opinion. The >>> functionality doesn't change, regardless of what you call it. >>> >>> I agree with Gregg that this really should be implemented to reflect the >>> functionality that WebGL already has. Wether 2D or 3D, there's a lot of >>> common ground between the various canvas contexts and it doesn't make much >>> sense to reinvent the wheel when one context type has already implemented >>> the functionality. >>> >>> --Brandon >>> >>> >>> On Wed, Mar 13, 2013 at 1:02 PM, Maciej Stachowiak <[email protected]>wrote: >>> >>>> >>>> An attribute on the canvas element would presumably be equally >>>> applicable to all contexts. Is there a reason that it's better to have >>>> opaqueness specified at context creation time instead of on the canvas? >>>> Also, I think "opaque" is easier to understand than "alpha: false". >>>> >>>> - Maciej >>>> >>>> On Mar 13, 2013, at 9:57 AM, Gregg Tavares <[email protected]> wrote: >>>> >>>> It would be nice if this was the same as WebGL instead of different. >>>> Especially because 2d canvas and WebGL need to inter-operate in the near >>>> future. >>>> >>>> In WebGL to create a canvas with no alpha (an opaque canvas) you do this >>>> >>>> gl = canvas.getContext("experimental-webgl", { alpha: false }); >>>> >>>> Why can't 2D canvas be this >>>> >>>> ctx = canvas.getContext("2d", {alpha: false}); >>>> >>>> As for why this is important to be the same see the proposal for Canvas >>>> in Workers here (http://wiki.whatwg.org/wiki/CanvasInWorkers) >>>> >>>> In that proposal the "backingstore" of a canvas can be moved to/from a >>>> worker. That solution may or many not be the final solution but it points >>>> out that whatever solution is chosen we need the solution to work for both >>>> canvas 2d and WebGL and as such needs a common way to create backing stores >>>> with no alpha. >>>> >>>> >>>> >>>> On Wed, Mar 13, 2013 at 9:30 AM, Dirk Schulze <[email protected]> >>>> 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 <[email protected]> >>>>> 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 >>>>> ENABLE(OPAQUE_CANVAS). >>>>> > >>>>> > Let me know if you have any comments or concerns. >>>>> > >>>>> > Stephen >>>>> > _______________________________________________ >>>>> > 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 >>>>> >>>> >>>> _______________________________________________ >>>> 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 >>>> >>>> >>> >>> _______________________________________________ >>> 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 >> >> >
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