W3C home > Mailing lists > Public > whatwg@whatwg.org > March 2013

Re: [whatwg] Enabling LCD Text and antialiasing in canvas

From: Mark Callow <callow.mark@artspark.co.jp>
Date: Thu, 14 Mar 2013 14:00:09 +0900
Message-ID: <51415959.3020600@artspark.co.jp>
To: Stephen White <senorblanco@chromium.org>
Cc: WHAT Working Group <whatwg@whatwg.org>, Rik Cabanier <cabanier@gmail.com>, Ian Hickson <ian@hixie.ch>, Robert O'Callahan <robert@ocallahan.org>
On 2013/03/13 2:03, Stephen White wrote:
> Description:
>
> The "opaque" attribute is a boolean attribute of the canvas element, whose
> presence indicates that the alpha values in the canvas backing store must
> be 1.0 at all times.  All canvas operations are modified to preserve this
> invariant.  If the "opaque" attribute is not present, or if parsing its
> value returns an error, then the default value (false) must be used instead.m
Could we align this with the existing WebGL canvas attribute instead of
having similar but opposite attributes on each. I.e. instead of "opaque"
have "alpha." When false the canvas is opaque (and it is not necessary
to store alpha values in the backing store). When true, the canvas is
potentially translucent. The default for "alpha" is true so that matches
the proposed default for opaque.

It will cause much less confusion if the same attribute serves the same
purpose on both types of canvas.

FYI, the description of the attribute in the WebGL spec is:

"If the value is true, the drawing buffer has an alpha channel for the
purposes of performing OpenGL destination alpha operations and
compositing with the page. If the value is false, no alpha buffer is
available. " 

Regards

    -Mark

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Received on Thursday, 14 March 2013 05:00:54 GMT

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