BUffer Locking - Emulation Of How Buffer unlocking works in graphics commands

[kevin]

  Emulation Of How Buffer lock and unlocking works in graphics commands


  This is not really a practical source code example rather it's a an emulation of showing the integration of buffer lock/ and unlocking and how managing those yourself can reduce remove a bottle neck when rendering pixels to a surface.  

PlayBASIC Code: [Select]

      loadfont "Courier new",1,50

      INIT()

      Frames_To_TEst=50

      do 

         Test1(Frames_To_TEST)
         Test2(Frames_To_TEST)

         Sync
      loop scancode()<>0
   
            
      

Function Test1(Frames)   
         do
            cls
            
            for lp=0 to 250
               DrawDot(frames+lp,lp,$ffffff)
            next

            print "test #1"
            print fps()
            
            sync
            Frames--
         loop Frames<0
      
EndFunction



Function Test2(Frames)   
         do
            cls
            
            lockscreen()
            for lp=0 to 250
               DrawDot(frames+lp,lp,$ffffff)
            next
            unlockscreen()

            print "test #2"
            print fps()
            
            sync
            Frames--
         loop Frames<0
      
EndFunction





   Type tLockState
         Count
         Ptr
         Pitch
         Depth
   EndType
   Dim LockState as tLockState

Function INIT()
   Dim LockState as tLockState
   LockState = new tLockState
EndFunction
   

Function LockScreen()
      State=LockState.Count

      if State=0
         LockBuffer
         NULLPixel         =point(0,0)
         lockState.ptr      = GetImagePtr(0)
         lockState.pitch   = GetImagePitch(0)
         lockState.depth   = GetImageDepth(0)
      endif   
      LockState.Count=State+1
EndFunction



Function UnLockScreen()
      State=LockState.Count
      if State>0
         State--
         LockState.Count=State
      endif
      if State=0
         unLockBuffer
      endif   
EndFunction


   //  Command set mock up


Function DrawDot(X,Y,ThisRGB)

      LockScreen()
   
      //  clip it   
      if x>=0 and X<getsurfaceWidth()
         if y>=0 and y<getsurfaceHeight()
            
            // write it to surface
            ptr=lockState.ptr
            if LockState.Depth=32
               pokeint ptr+(y*LockState.Pitch)+(x*4),ThisRGB
            endif   
         endif
      endif

      UnlockScreen()
Endfunction

Related Links)

     - PlayBASIC Documentation - LOCKBUFFER - UNLOCKBUFFER
     - A Crash Course In BASIC program Optimization