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Re: [Public WebGL] Few questions/comments about context creation attributes



On Tue, May 25, 2010 at 06:59, Kenneth Russell <kbr@google.com> wrote:
> We discussed this at length earlier in the working group. The basic
> question is whether getContext("webgl") should ever return null if the
> hardware is capable of running WebGL. The earlier consensus was that
> it is easier to program to a "closest fit" context selection model
> than a "minimum requirements" model.

Good to know, nothing in the specification does imply this model
afaik, quite the opposite if you consider repeated usage of "at
least".
Does it means that for instance when "stencil:true" is passed but
stencil is not supported with the given canvas resolution on a given
hardware, WebGL will give back a context without stencil buffer since
it would be the closest fit it could find ? Could get funny results if
the application relies on it.
Or "closest fit" works only with regards to precision in each buffer ?
In this case, right now with the booleans attribute WebGL indeed
defines a minimum fit model ("at least").

That said I understand the intention and agree that the closest-fit
model sounds more web-ish :)
I think should add a bit about this in the spec so that
implementations (and implementations to-be) do not assume otherwise.

I think replacing some of the boolean context attributes with integers
as suggested would be the perfect opportunity to do that, what do you
think ?
It works beautifully with the "closest fit" model as well, allowing
WebGL to return the closest fit to what is requested/preferred by the
developer as soon as better support lands in implementations [1].
Also since we use a "closest fit" model adding minX/maxX for every
attribute later on does make even less sense imho (one would assume
that if the closest fit is below minimum or above maximum a context
cannot be created and null should be returned - breaking the whole
purpose of the closest-fit model).


Regards,


[1] : e.g {depth:24} does not return null not supported, just returns
the "closest-fit" 16-bit depth buffer if not supported, and returns a
24-bit on supporting implementations where it makes sense.
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