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:
> http://appletoolbox.com/2010/05/macbook-pro-mid-2010-graphics-switching-which-apps-trigger-how-to-monitor/
> http://www.cocoabuilder.com/archive/cocoa/293116-i5-i7-auto-graphics-switching.html
> http://support.apple.com/kb/HT3207
>
> 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
discre...

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
<http://www.chronosnet.com/>

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