On Thu, Sep 22, 2011 at 10:27 AM, Christopher Wright < christopher_wri...@apple.com> wrote:
> > Is the part that I've put in bold true for all execution modes? Why is it > that this improves performance if when the patch doesn't contain OpenGL > code? Related to the last question (basically, the inverse), what happens if > one forgets to do this that would cause bad performance? > > I haven't looked at the document fully (so I could be missing some > context), but I don't think that statement's true generally. > Cool, then my gut impression is correct. I still find the line a little bit curious, but I'm guessing this is something you would have seen had it created a negative impact on performance when not expected to. > > By itself, CGLMacro.h just defines a bunch of entry point expansions for gl > functions. It also pulls in some other GL headers, but unless you're using > actual GL functionality I don't think it would matter much. > > If you forget to include the file and you try to use GL you'll end up doing > non-direct dispatched gl calls (you'll operate on the current context, which > isn't necessarily the context QC wants you to use), so you'll probably just > get bad results (or ok results if you're lucky - don't depend on being lucky > though, just do the right thing). Sure, I've made this mistake before in that scenario and have seen the bad performance results, but I'd always assumed that if it wasn't directly using OpenGL that it was more correct not to import that. Though I'd read that line in the documentation before, I'd entirely glossed over it, I guess because it doesn't seem to be expected. > direct dispatch calls will save you a bit of time, but I'd be more > concerned about correctness before performance. > > > Correctness being, don't import it if you're not using it? I guess it bears testing both ways, and I'm definitely not asking for a definitive answer, but a general guideline (which it seems like you just described!). Thanks for your thoughts on this one.
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