How precise is the timing clock in tcl? When using the after command, an interesting thing happens when you start using small values, you don't necessarily get the callback until later. This can cause problems if you are doing animation, like I am right now.
Run on different WinXP SP2 computers:
Not so good.
% set e [clock micro] ; after 5 {puts [expr [clock micro] - $e]}
after#39
16000
Now this is more like it!
% set e [clock micro] ; after 5 {puts [expr [clock micro] - $e]}
after#5914
5055
Different machines will fail at different small values. I think this is because of the way the after command must be implemented on windows. See this page: http://www.geisswerks.com/ryan/FAQS/timing.html
How to fix it?
I'm thinking to make a seperate thread use a better Win32 timing schedule command and call the main thread. I guess this is reimplementing the after command. Anyone have a better idea?
From the web
As I mentioned earlier the default PIC resolution for the OS when it starts up is around 16 milliseconds. Let’s say that you set a periodic timer to fire every 5 milliseconds, with the PIC set at 16 milliseconds you will only be alerted every 16 milliseconds (at best). This level of accuracy is usually good enough for most applications. However, for time critical applications such as audio and video playback this resolution just is not good enough.