AGL_SWAP_LIMIT is slightly different than AGL_SWAP_INTERVAL (I
believe I have even mixed them up in the past).
The former turns on and off blocking on swaps when you get more than
2 frames ahead of the renderer. So if you draw at 100 fps and the
renderer can only renderer at 50 fps you will quickly hit the swap
limit. It is normally on and if you turn it off your app will be
allowed to get an "unlimited" amount of frames ahead. The reason
"unlimited is in quotes is that you will likely quickly run up
against some other system limitation, like amount of pending command
buffers available, so while the swap limit is no longer in place you
are not really allowed to get an unlimited amount of frames ahead.
Additionally, I contend that very few apps actually want to turn off
swap limit as you really do not want to be that out of sync with your
rendering (which likely is the user feedback). There are exceptions
but for most apps they will want to leave this on.
The actually enum you will likely want to use is the latter...
AGL_SWAP_INTERVAL
This is documented at <http://developer.apple.com/documentation/
GraphicsImaging/Reference/AGL_OpenGL/index.html> and should enable
and disable vbl syncing for your swaps.
I believe that AGL_SWAP_INTERVAL is defined for all Mac OS versions
of OpenGL.
Geoff Stahl
3D Software Engineer
Apple
On May 28, 2005, at 2:20 PM, Ivan Milles wrote:
An issue that doesn't make much problem for me, but has had me
wracking my head for quite some time now is the token AGL_SWAP_LIMIT.
In my current project, I have to call aglEnable (AGL_SWAP_LIMIT) to
make my context synch to the VBL. However, there is no Apple
documentation on the token, and it is not present in the older
headers? When I build a CFM version of my app, the token is
reported as an unknown identifier. Additionally, the Apple sample
code does not enable this token.
What do I make of this?
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