Subject: Re: Automatic graphics switching...

On Mar 29, 2011, at 3:16 PM, Jason Harris wrote:

> Hi All,
> Some users are complaining that my application (MacHg) is causing their
> MacBooks to switch from using the integrated Intel (lower power) card to the
> NVIDIA (higher power) graphics card.
> Eg some related articles I dug up:
> However, my application do...

esn't appear on the surface to make heavy use of

> graphics. (It does make heavy use of GCD though). Is there a general cause
> for this switching of the graphics card?.

There are a few of them I know about:
1. Your application starts CoreAnimation by calling -setWantsLayer: on a view
with a layer, or adding a layer in IB
2. Your application initializes an NSOpenGLView using a pixel format that works
best using the discrete GPU
3. Your application initializes a QTCaptureView, QTMovieView, or QCView
4. The user plugged in an external display (external displays must use the

te GPU)

There might be more, but those are the ones I know about.

> How can I find out when such a switch occurs in my code and for what reasons?

If you have a dual-GPU Mac, then try breaking on IOServiceOpen and look at the
stack trace when it breaks. If you don't, then you can't.

Nick Zitzmann


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