Infinite scrolling ?

[Joubarbe]

Hello,

I'd like to do a simple thing : scroll a grid infinitely (using a Screen). The idea would be to wrap around the grid itself, but I don't know how to do that in PB. Would it be better to create the grid as multiple lines, or a single sprite, or multiple sprites ? I'm pretty sure there are examples of that somewhere, but I cannot find them.

Any ideas ?

[DK_PETER]

Code: Select all

EnableExplicit
InitSprite()
InitKeyboard()

Enumeration 
  #info
  #frame
EndEnumeration

Structure _bgs
  id.i
  x.i
  y.i
EndStructure

Structure POINTF
  x.f
  y.f
EndStructure

Declare.i DoInfo()

Global Dim bg._bgs(8), zcount.i, ycount.i, xcount.i, pcount.i, color.i, Radi.i, pos.POINTF, Speed.f, ev.i, ret.i

OpenWindow(0, 0, 0, 800, 600, "Scroll - Escape key to exit / Arrow keys to scroll", #PB_Window_ScreenCentered)
OpenWindowedScreen(WindowID(0), 0, 0, 800, 600, #False, 0, 0, #PB_Screen_WaitSynchronization)

For xcount = 0 To 8
  bg(xcount)\id = CreateSprite(#PB_Any, 800, 600)
  StartDrawing(SpriteOutput(bg(xcount)\id))
  DrawingMode(#PB_2DDrawing_AlphaBlend)
  For pcount = 0 To 200
    Circle(Random(797, 5), Random(597, 5), 1, RGBA(Random(255,10), Random(255,10), Random(255,10), 160))
  Next pcount
  For zcount = 0 To 800 Step 50
    LineXY(zcount, 0,  zcount, 600, $CEF8EA1C)
  Next zcount
  For zcount = 0 To 600 Step 50
    LineXY(0, zcount,  800, zcount, $CEF8EA1C)
  Next zcount
  StopDrawing()
  TransparentSpriteColor(bg(xcount)\id, 0)
Next xcount

bg(0)\x = -800 : bg(0)\y = -600
bg(1)\x =    0 : bg(1)\y = -600
bg(2)\x =  800 : bg(2)\y = -600
bg(3)\x = -800 : bg(3)\y =    0
bg(4)\x =    0 : bg(4)\y =    0
bg(5)\x =  800 : bg(5)\y =    0
bg(6)\x = -800 : bg(6)\y =  600
bg(7)\x =    0 : bg(7)\y =  600
bg(8)\x =  800 : bg(8)\y =  600

Speed = 4 : pos\x = 0 : pos\y = 0

CreateSprite(#info, 200, 20)
StartDrawing(SpriteOutput(#info))
DrawingMode(#PB_2DDrawing_Transparent)
DrawText(100 - TextWidth("Sector: 0, 0")/2, 1, "Sector: 0, 0",$CEABA21A)
StopDrawing()
TransparentSpriteColor(#info, 0)

CreateSprite(#frame, 50, 50)
StartDrawing(SpriteOutput(#frame))
LineXY(25, 0, 25, 15, $19EAEE)
LineXY(25, 35, 25, 50, $19EAEE)
LineXY(0, 25, 15, 25, $19EAEE)
LineXY(35, 25, 50, 25, $19EAEE)
StopDrawing()
TransparentSpriteColor(#frame, 0)

Repeat
  ClearScreen(0)
  Repeat
    ev = WindowEvent()
  Until ev = 0
  
  ExamineKeyboard()
  
  For xcount = 0 To 8
    With bg(xcount)
      If KeyboardPushed(#PB_Key_Right)
        \x + Speed
        pos\x + 0.01
        If \x >= 800
          \x - 1600
        EndIf
      ElseIf KeyboardPushed(#PB_Key_Left)
        \x - Speed
        pos\x - 0.01
        If \x < -800
          \x + 1600
        EndIf
      EndIf
      If KeyboardPushed(#PB_Key_Up)
        \y - Speed
        pos\y - 0.01
        If \y <= -600
          \y + 1200
        EndIf
      ElseIf KeyboardPushed(#PB_Key_Down)
        \y + Speed
        pos\y + 0.01
        If \y >= 600 
          \y - 1200
        EndIf
      EndIf
    EndWith
  Next xcount

  For xcount = 0 To 8
    DisplayTransparentSprite(bg(xcount)\id, bg(xcount)\x, bg(xcount)\y)
  Next xcount
  
  ret = doInfo()

  DisplayTransparentSprite(#info, 400 - SpriteWidth(#info)/2, 580)
  DisplayTransparentSprite(#frame, ScreenWidth()/2 - 25, ScreenHeight()/2 - 25)
  
  FlipBuffers()
  
Until KeyboardPushed(#PB_Key_Escape)

Procedure.i DoInfo()
  Static x.i, y.i
  If x = pos\x And y = pos\y
    ProcedureReturn #True
  EndIf
  x = pos\x : y = pos\y
  FreeSprite(#info)
  CreateSprite(#info, 200, 20)
  StartDrawing(SpriteOutput(#info))
  DrawingMode(#PB_2DDrawing_Transparent)
  DrawText(100 - TextWidth("Sector: " + Str(pos\x) + "," + Str(pos\y))/2, 1, "Sector: " + Str(pos\x) + "," + Str(pos\y) , $CEABA21A)
  StopDrawing()
  TransparentSpriteColor(#info,0)
  ProcedureReturn #True
EndProcedure

[Joubarbe]

Thanks, I'll try that

[firace]

@DK_PETER: very nice code, but the stars are flickering/flashing every few seconds for me (when i keep an arrow key pressed)

(edited 16/08/2015)

[firace]

@DK_PETER: very nice code, but the stars are flickering/flashing every few seconds for me (when i keep an arrow key pressed)

(edited 16/08/2015)

A minor bug, perhaps related:
Many of the stars that are initially displayed disappear as soon as the scrolling begins.