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Re: [Public WebGL] option for suggesting "low power" mode at context creation



On Thu, Sep 27, 2012 at 2:48 PM, Chris Marrin <cmarrin@apple.com> wrote:
>
> On Sep 27, 2012, at 2:01 PM, Kenneth Russell <kbr@google.com> wrote:
>
>
> One other issue needing consideration. Let's assume that the
> "preferLowPowerToHighPerformance" flag is added to the
> WebGLContextAttributes dictionary, and that
> WebGLRenderingContext.getContextAttributes() returns the correct value
> for the flag. (In other words, if the flag is set to true during
> getContext, and the machine has two GPUs, and the implementation
> supports low-power mode, then getContextAttributes() will return true
> for the flag as well; otherwise, false.)
>
> On dual-GPU Mac OS machines, at least, it will then be possible to get
> WebGL to run on either the integrated or discrete GPU, and detect
> which one is being used in JavaScript.
>
> In order to keep implementations honest, it will be necessary to
> change the WebGL conformance suite to run all of the tests twice, once
> on the integrated GPU and once on the discrete GPU. Further, there are
> currently many more test failures on Mac OS when running the
> conformance suite on integrated GPUs than on discrete GPUs. This means
> adding a low-power flag now will delay the point at which the next
> snapshot of the WebGL conformance tests could be successfully passed.
> There had been some hope that a new snapshot could be taken soon,
> after triaging the existing test failures on top of tree.
>
> Dean, Chris, any thoughts on this issue?
>
>
> If we are to make it possible for authors to control which GPU is being used
> then we certainly need to have a conformance suite that tests both paths.
> But an implementation can pass the conformance suite immediately by simply
> ignoring the flag and always enabling the GPU that passes.

That's true but then it should ship in that configuration. If that
implementation intends to ship honoring the low-power GPU preference,
then it should pass the conformance suite while honoring that
preference. All I'm trying to say here is that more work will be
needed on Apple's Intel OpenGL driver (and the WebGL conformance
suite) in order to reasonably add this flag. Given that, are you still
in favor of adding it?

-Ken

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