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

Vladimir Vukicevic vladimir at mozilla.com
Fri Mar 15 21:11:27 PDT 2013

On 3/15/2013 6:23 PM, Kenneth Russell wrote:
>     Is there a nontrivial amount of content depending on it? That
>     would be more relevant precedent than merely being in the code base.
> How would one determine that? Searching for "getcontext webgl alpha 
> false" returns many web pages on the topic, but doesn't seem to find 
> JavaScript source code.
> For one high-profile example, Angry Birds HD for the browser uses this 
> flag; it uncovered a bug in the Mac OS X OpenGL driver on AMD GPUs.

Setting alpha: false is generally recommended for some extra performance 
with WebGL.  There was some discussion even about whether it should be 
the default, but we ended up going with alpha: true for compat with 
canvas 2d and for least surprise when mixing it with web content ("Why 
doesn't my CSS background show up on WebGL canvas elements?").  So I'd 
imagine there's a lot of content out there that sets alpha: false.

      - Vlad

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