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; purebasic survival guide - pb3.93
; purebasic survival guide - pb3.93
; timer_1.pb - 03.03.2004 ejn (blueznl)
; http://www.xs4all.nl/~bluez/datatalk/pure1.htm
;
; - how to make games run at the same speed on different machines
; - GetTickCount_()
;
;
; GetTickCount_() returns a counter in milliseconds, since the system started
; it's limited to 49.7 days, so it wraps around after that...
; we've also got this 'signed/unsigned' thingy going on in purebasic...
;
; t1 = GetTickCount_()      ; there is however no guarantee that t2 is bigger than t1, as there
; t2 = GetTickCount_()      ; could be a wrap, or there could be a sign change
;
; to see how much time has passed, we could do:
;
; td = t2-t1
; if td > ...
;
; so we'd start at 0, count up to 2^31-1 = 2147483647, then from -2147483647 to -1, then 0 etc.
; but... at the moment of a sign change, t2 will be smaller than t1, and... at the moment of a wrap,
; td will be smaller than 0 (makes the brain hurt)
;
; an easy way around this is simply filter out unlikely values and live with it :-) so although we have
; 2 times a mistake during the 49.7 days, at least the program will not crash out or wait unneccessary long
;
; td = t2-t1
; if td < 0 or td > ...
;
w_main_nr = 1
w_main_h = OpenWindow(w_main_nr,0,0,400,400,"test",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
;
interval = 500000                                 ; interval frequency of 1 second
ticks = interval/1000                           ; regular counter has an accuracy of millisecs
;
Debug "low performance counter GetTickCount_()"
;
t1 = 0
t2 = 0
td = 0
;
Repeat
  event = WindowEvent()
  t2 = GetTickCount_()
  td = t2-t1
  If td < 0 Or td >= ticks                      ; check if enough time passed or a wrap took place
    t1 = t2
    ;
    n = n+1                           
    Debug Str(n)+" - "+Str(t2)+" - "+FormatDate("%SS",Date())
    ;
  Else
    Delay(20)                                   ; so we don't overload the cpu while doing nothing
  EndIf
Until event = 513 Or event = #PB_Event_CloseWindow
;
; GetTickCount_() does return a timer in milliseconds, if we would like to run at a clip of 60 frames
; per second, we would have to use an interval of 1000 / 60 = 16.6 = 17 ticks... hmm...
;
; there's a high performance counter in windows as well, unfortunately purebasic does not support
; 64 bits variables yet so we will have to do a little detour using floats (brrrr)
;
Debug ""
Debug "high performance counter"
;
hf_q.LARGE_INTEGER
ht_q.LARGE_INTEGER
ht1.f = 0
ht2.f = 0
htd.f = 0
;
If QueryPerformanceFrequency_(@hf_q) = 0
  Debug "no support"
EndIf
;
; every second it has hf_q.highpart * 2^32 + hf_q.lowpart ticks... that's a lot :-)
; i don't like floats, but without 64 bit support :-(
;
hf.f = hf_q\highpart*Pow(2,32)+hf_q\lowpart
hticks.f = hf*interval/1000000                  ; ticks on the high performance counter per interval
;
Repeat
  event = WindowEvent()
  QueryPerformanceCounter_(@ht_q)
  ht1 = ht_q\highpart*Pow(2,32)+ht_q\lowpart
  htd = ht1-ht2
  If htd < 0 Or htd >= hticks                   ; check if enough time passed or a wrap took place
    ht2 = ht1
    ;
    n = n+1                           
    Debug Str(n)+" - "+Str(t2)+" - "+FormatDate("%SS",Date())
    ;
  Else
    Delay(20)                                   ; so we don't overload the cpu while doing nothing
  EndIf
Until event = 513 Or event = #PB_Event_CloseWindow

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QueryPerformanceFrequency_(Freq.LARGE_INTEGER)
Debug Pow(2,32)*Freq\highpart+Freq\lowpart/1000000