[GEM-dev] graphics card switching in OS X and Gem

Max abonnements at revolwear.com
Tue Nov 20 16:00:49 CET 2012


Am 26.10.2012 um 11:13 schrieb zmoelnig at iem.at:
> Quoting Max <abonnements at revolwear.com>:
>> So i tried this for Pd and found that it is not affecting the graphics card switch until the moment you are loading Gem. So if you are patching with Gem loaded even without the window open the discreete card is used.
> 
> i think the logic behind automatically disabling the internal gfx-card is very simple: as soon as an application loads the libGL dylib, power-save mode is deactivated.
> if no application references libGL anymore, powersave mode is disabled.
> 
> now Gem is dynamically linked against libGL, which means that libGL is loaded as soon as Gem is loaded (opera is probably linked against libGL too, so as soon as you start opera, power-save mode is disabled).
> deferring the loading of libGL until Gem is used, might turn out to be quite tricky (note to myself: though it really might be possible, given that Gem uses glew to wrap around GL).

i've asked the programmer of gfxcardstatus, cody krieger, if that is how it works, and he replied:

> That's not quite right, but it's close.
> 
> It's not linking against any particular library or framework that's the issue - it's when you actually use anything OpenGL-related in practice. For example, as soon as you lay down a CALayer in a Cocoa application, the discrete GPU will power up in 10.7 and below (because CALayers are OpenGL-backed). In 10.8, this behavior changed a little, and just using CALayers (or anything from Core Animation) will no longer cause the discrete GPU to turn on, but direct use of OpenGL, among other things, will.
> 
> Hope that helps! :)
> 
> Cody


so IOhannes, it's not something what's particularly bugging me or what I find über important. It's a mere observation which I wanted to share.

max


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