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Re: [Public WebGL] WebGLContextAttributes



On Jan 6, 2010, at 4:30 PM, Kenneth Russell wrote:

> On Wed, Jan 6, 2010 at 5:19 AM, Chris Marrin <cmarrin@apple.com> wrote:
>> 
>> On Jan 5, 2010, at 4:17 PM, Kenneth Russell wrote:
>> 
>> ,,,As Philip pointed out we also need to remove the NameSetter,
>> 
>> NameGetter and NameDeleter extended attributes. In other words, rather
>> 
>> than trying to specify it as a dictionary, we need to state which
>> 
>> attributes the DOM code will look up via callbacks. This is the IDL
>> 
>> which will give us the desired result:
>> 
>>    [Callback] interface WebGLContextAttributes {
>> 
>>        attribute boolean alpha;
>> 
>>        attribute boolean depth;
>> 
>>        attribute boolean stencil;
>> 
>>        attribute boolean antialias;
>> 
>>        attribute boolean premultipliedAlpha;
>> 
>>    };
>> 
>> 
>> Are there any objections to my updating the specification for
>> 
>> WebGLContextAttributes?
>> 
>> 
>> None from me. In fact, I would appreciate it!
>> 
>> Sections 5.1 and 5.1.1 have been updated. Feedback welcome.
>> 
>> Looking at the changes, it strikes me  that this is not as flexible as the
>> original design. Originally I had envisioned allowing any data type to be
>> passed in the attributes. This would allow in the future to, for instance,
>> pass the desired number of bits for the depth buffer, or a string describing
>> the antialias mode. I wonder if it would be reasonable to change the
>> attribute types to 'any' and state that in this release any value passed is
>> interpreted as a boolean, using normal ECMAScript conversion rules.
> 
> I've updated the IDL and surrounding docs to take this suggestion into
> account. I have some doubts as to whether this scheme will be
> future-proof, though. If we change the semantics of the "depth"
> attribute in the future to indicate the minimum number of depth bits,
> then anyone who had explicitly put "true" for that attribute's value
> in their code might start getting a depth buffer of minimum 1 bit. It
> might be better to be explicit about the types and assume that we will
> add new attributes to cover things like number of alpha or depth bits.


This is why I have minimums for things like depth (16 bits). We should go over all the values, but hopefully we can make the definitions tight enough so that a boolean value today will maintain the same meaning in the future.

-----
~Chris
cmarrin@apple.com




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