Gifs with high fps are lagging when screensaver is in background mode

[waitsnake]

Gifs with high fps are lagging when screensaver is in background mode

[Waitsnake]

I investigate the problem a bit further:

• when starting the "background mode" from Terminal window directly with "/System/Library/CoreServices/ScreenSaverEngine.app/Contents/MacOS/ScreenSaverEngine -window" there is no lagging at all -> lagging seams related to starting it from launchd as a daemon instead of a normal user program
• tried changing process priority handling with "nice" and "renice", but this do not change anything -> it is not an process priority problem
• I suspect something with the timing events of the ScreenSaverView that fires "animateOneFrame" method is odd when startet as daemon with launchd. Timing Events seams to collected over a period and then all fired together over a short time. I think I remember Craig Federighi presented this feature called "Timer Coalescing" years ago for 10.9 on a keynote and they use it to save energy. Seams they use it only for daemons (started by launchd I use it for the start of the background mode) and never for normal user programs (like starting it from Terminal as user).

[Waitsnake]

I investigate the "Timer Coalescing" trace a bit further:

• disabling "Timer Coalescing" systemwide by use of "sudo sysctl -w kern.timer.coalescing_enabled=0" -> This completely solve the issue and I see no more lags! -> Anyway, but doing this systemwide is not an option, since this will drain battery too much and also needs admin rights. -> But it shows that "Timer Coalescing" is really the problem here!
• I tired to disable "Timer Coalescing" only for the Screensaver by using launchd option "LegacyTimers" set to "true" -> unfortunately this makes no difference! According to older descriptions this option should have worked? -> Maybe Apple broke this option years ago?

[Waitsnake]

I investigate the "LegacyTimers" trace a bit further:

• looking for official description of launchd configuration with "man launchd.plist" shows, that "LegacyTimers" set to "true" only works when a second option "ProcessType" is set to "Interactive" -> This solve the issue and I see no more lags! And now we only did it for the screensaver and not system wide.

[Waitsnake]

Fix will come with next release.