Loop or Timer?

[Drakon]

In C++, I know you use a main game loop to go through all the code constantly. But I want to know if Visual basic games usually use something like that or not, or if it all gets put on a real fast timer.

If it IS done with a loop, please tell me how.

[/\/\isanThr0p]

Timers are Evil(tm)

Do
   'here goes your code
Loop until ExitCondition

[Janus]

Here's my rather messy main loop from my engine (slightly edited):

Dim cInc As Single
Dim PerfFrequency As Currency, PerfTime As Currency, RealFPS As Double
Dim StartTime As Currency, EndTime As Currency, m_strCaption As String
    Call QueryPerformanceFrequency(PerfFrequency)
    m_Engine.DesiredFramerate = 1000 \ (1000 \ ClipValue(m_Engine.DesiredFramerate, c_lngMinFramerate, c_lngMaxFramerate))
    m_Engine.Running = True
    Do While m_Engine.Running = True
        If m_booCritical Then
            DoEvents
        Else
            If QueryPerformanceCounter(PerfTime) = 0 Then
                CurrentTime = GetTickCount
                StartTime = CurrentTime
            Else
                CurrentTime = GetTickCount
                StartTime = Int((PerfTime / PerfFrequency) * 1000)
            End If
            If LastTime = 0 Then LastTime = CurrentTime
            FramesToRender = Abs(CurrentTime - LastTime) + FramerateBuildup
            FramerateBuildup = 0
            MSPerFrame = 1000 \ m_Engine.DesiredFramerate
            FramerateBuildup = FramesToRender Mod MSPerFrame
            If m_Engine.BalanceFramerate Then
                FramesToRender = FramesToRender \ MSPerFrame
            Else
                FramesToRender = 1
            End If
            If FramesToRender > c_lngMaxFrameskip Then FramesToRender = c_lngMaxFrameskip
            If FramesToRender > 0 Then
                If m_Engine.Paused Then
                    FramesToRender = 0
                Else
                    For RenderFrames = 1 To FramesToRender
                        If m_Engine.Paused Then Else m_Engine.Update
                        IncUPS = IncUPS + 1
                        If m_Engine.Running = False Then Exit For: Exit Do
                    Next RenderFrames
                End If
                If m_Engine.Running Then Redraw
                If m_GFX.Window.WindowState = 1 Then
                Else
                    If m_Engine.Running Then m_GFX.FlipImage m_Backbuffer
                End If
                IncFPS = IncFPS + 1
            Else
                If m_Engine.HarassCPU Then Else Call SleepEx(1, True)
            End If
            If m_Engine.Running = False Then Exit Do
            If QueryPerformanceCounter(PerfTime) = 0 Then
                EndTime = GetTickCount
            Else
                EndTime = Int((PerfTime / PerfFrequency) * 1000)
            End If
            If m_Engine.Running = False Then Exit Do
            If Int(CurrentTime \ 1000) <> Int(LastTime \ 1000) Then
                CurrentFPS = IncFPS
                CurrentUPS = IncUPS
                IncFPS = 0
                IncUPS = 0
            End If
            LastTime = CurrentTime
            DoEvents
        End If
    Loop
    Shutdown

It manages to maintain very very accurate framerates, with frameskipping, all without harassing the CPU (usually CPU usage stays between 0 and 10% when running at 60fps, unless the game is really detailed at the moment).

Hope this helps, if you want some help understanding it, let me know - it's not commented :P

[Drakon]

Wheres the loop go? In its own sub? If so, where does THAT sub get put?

[/\/\isanThr0p]

well you can make a sub like this
sub MainLoop()
end sub

just place it anywhere you want
now if you want to call it you could have a button for example or just put it into the form load event

[Drakon]

My loop is called when I press a command button. But after I do, it freezes up. This is the code for my loop:

Sub Run()

Do
If GetKeyState(vbKeyA) = 1 Then
MsgBox "Key A pressed"
End If
If GetKeyState(vbKeyQ) = 1 Then
Running = False
End If
Loop Until Running = False

End Sub

[/\/\isanThr0p]

well this should work but maybe you should add a
DoEvents into the loop

and format your code...

[Drakon]

I got my loop to stop crashing, but something might be wrong with my GetKeyState thing.

Sub CheckMove()
If GetKeyState(vbKeyUp) = 1 Then
PC.xvel = PC.xpos - PC.xview
PC.yvel = PC.ypos - PC.yview
PC.xpos = PC.xpos + PC.xvel
PC.ypos = PC.ypos + PC.yvel
frmGame.Caption = PC.xpos
End If

End Sub

I put CheckMove in my loop, and then in one press it overflows. I have in a different sub setting xpos and ypos to 0, and xview and yview to 120.

[/\/\isanThr0p]

use gettickcount to check when the key was last pressed, and only allow another press after about 10ms or some value that you like... otherwise it can be really fast!

[Drakon]

How do I use it, and where do I use it?

[/\/\isanThr0p]

Sub CheckMove() 
static LastPress as long
  if lastpress<Gettickcount then
    lastpress = gettickcount +50 'this will allow a keydown all 50 milli seconds
    if GetKeyState(vbKeyUp) = 1 Then 
      PC.xvel = PC.xpos - PC.xview 
      PC.yvel = PC.ypos - PC.yview 
      PC.xpos = PC.xpos + PC.xvel 
      PC.ypos = PC.ypos + PC.yvel 
      frmGame.Caption = PC.xpos 
    end if
  End If 
End Sub

[Drakon]

Now it doesn't do anything... do I have to do anything else anywhere?

[Fox]

You have to call from inside a loop..

While DoEvents
       CheckMove
   Wend

[Drakon]

I've already done that, otherwise it would never have worked, therefore preventing the overflow