[cssom-view] colorDepth/pixelDepth, match implementations or theoretical purity?

In https://www.w3.org/Bugs/Public/show_bug.cgi?id=17522 we have a 
situation where all implementations and the spec agree on one thing, but 
that thing is wrong according to the industry standard terms. It is 
obvious that Glenn and I have different ideas about what the spec should 
say. In HTML, the policy in situations like these have almost always 
been to just match the implementations.

There can be reasonable exceptions where we would want to not match 
implementations despite interoperability, like if a security problem is 
identified or if a different definition would be vastly superior *and* 
the feature is not widely used in the Web such that changing it does not 
cause compat problems.

In the case of colorDepth and pixelDepth, the proposed change does not 
address any security problem. It would start to expose the number of 
bits in the alpha channel (also see 

The attributes can be used for fingerprinting. The proposed change does 
not change that, in fact it probably increases the fingerprinting. If we 
want to remove this fingerprinting vector, the attributes can be made to 
return a static value, probably 24. It seems at least some current 
implementations do not return a static value.

I'd like to hear from other people what they think. Do implementers want 
to change these to match the industry terms? Or remove the 
fingerprinting vector? Or leave as is?

Simon Pieters
Opera Software

Received on Tuesday, 18 June 2013 10:23:59 UTC