On May 15, 2005, at 8:39 PM, Steve Christensen wrote:
A posting to the Carbon list on Friday (5/13) mentioned a change to
the HIToolbox that can cause a slowdown (on purpose) if you try to
draw faster than the video card's frame rate. This may be related
to what you're seeing.
This is the document they refer to (and please note the constant
disclaimers for the performance-zapping "feature"):
If beam synchronization is disabled using Quartz Debug, everything
works properly again. I confirmed this with MacFOH, and all windows
maintain 75 fps regardless if they're occluded and being composited.
According to the above doc, only apps linked against 10.4 will use
the "automatic" beam sync. It is definitely a bug in CGS: all apps
are being force-synchronized (regardless of executable link), and
unfortunately this feature SUCKS to begin with. Anything forcibly
imposed on developers further restricts our ability to provide high-
performance without making constant workarounds for these
"conveniences". If the API were nicely rolled into CG, NSScreen,
etc, then it would be more useful. If this behavior was in fact only
enabled by the link version of the executable, I'm in luck, because I
can build just the executable with Panther, and everything else with
Tiger if necessary, hopefully avoiding this sync issue.
On a good note, using Quartz Debug to turn off beam synchronization
globally actually makes Tiger seem fast, like Panther. I'm never
turning it back on... ;)
--
Shaun Wexler
MacFOH http://www.macfoh.com
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