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

Ryosuke Niwa rniwa at webkit.org
Thu Mar 14 13:38:39 PDT 2013

On Thu, Mar 14, 2013 at 12:55 PM, Dean Jackson <dino at apple.com> wrote:

> On 15/03/2013, at 6:50 AM, Dana Jansens <danakj at chromium.org> wrote:
> On Thu, Mar 14, 2013 at 3:46 PM, Dean Jackson <dino at apple.com> 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.

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
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