PureBasic Forums - English

Code: Select all

;NeHe's First Polygon Tutorial (Lesson 2)
;http://nehe.gamedev.net
;Credits: Nico Gruener, Dreglor, traumatic
;Author: hagibaba
;Date: 3 Jan 2007
;Note: up-to-date with PB v4.02 (Windows)

;Section for standard constants, structures, macros and declarations

XIncludeFile "OpenGL.pbi" ;include the gl.h constants

;wingdi.h constants
#DM_BITSPERPEL=$40000
#DM_PELSWIDTH=$80000
#DM_PELSHEIGHT=$100000

;winuser.h constants
#CDS_FULLSCREEN=4
#DISP_CHANGE_SUCCESSFUL=0
#SC_MONITORPOWER=$F170

Procedure.w LoWord(value.l) ;windef.h macro
 ProcedureReturn (value & $FFFF)
EndProcedure

Procedure.w HiWord(value.l) ;windef.h macro
 ProcedureReturn ((value >> 16) & $FFFF)
EndProcedure

Import "glu32.lib"
 gluPerspective(fovy.d,aspect.d,zNear.d,zFar.d) ;sets up a perspective projection matrix
EndImport

Import "opengl32.lib"
 glClearDepth(depth.d) ;specifies the clear value for the depth buffer
EndImport

;Start of Lesson 2

Global hDC.l ;Private GDI Device Context
Global hRC.l ;Permanent Rendering Context
Global hWnd.l ;Holds Our Window Handle
Global hInstance.l ;Holds The Instance Of The Application

Global Dim keys.b(256) ;Array Used For The Keyboard Routine
Global active.b=#True ;Window Active Flag Set To TRUE By Default
Global fullscreen.b=#True ;Fullscreen Flag Set To Fullscreen Mode By Default

Declare.l WndProc(hWnd.l,uMsg.l,wParam.l,lParam.l) ;Declaration For WndProc

Procedure ReSizeGLScene(width.l,height.l) ;Resize And Initialize The GL Window

 If height=0 : height=1 : EndIf ;Prevent A Divide By Zero Error
 
 glViewport_(0,0,width,height) ;Reset The Current Viewport
 
 glMatrixMode_(#GL_PROJECTION) ;Select The Projection Matrix
 glLoadIdentity_() ;Reset The Projection Matrix
 
 gluPerspective(45.0,Abs(width/height),0.1,100.0) ;Calculate The Aspect Ratio Of The Window
 
 glMatrixMode_(#GL_MODELVIEW) ;Select The Modelview Matrix
 glLoadIdentity_() ;Reset The Modelview Matrix
 
EndProcedure

Procedure.l InitGL() ;All Setup For OpenGL Goes Here

 glShadeModel_(#GL_SMOOTH) ;Enable Smooth Shading
 glClearColor_(0.0,0.0,0.0,0.5) ;Black Background
 glClearDepth(1.0) ;Depth Buffer Setup
 glEnable_(#GL_DEPTH_TEST) ;Enables Depth Testing
 glDepthFunc_(#GL_LEQUAL) ;The Type Of Depth Testing To Do
 glHint_(#GL_PERSPECTIVE_CORRECTION_HINT,#GL_NICEST) ;Really Nice Perspective Calculations  
 
 ProcedureReturn #True ;Initialization Went OK

EndProcedure
  
Procedure.l DrawGLScene() ;Here's Where We Do All The Drawing

 glClear_(#GL_COLOR_BUFFER_BIT | #GL_DEPTH_BUFFER_BIT) ;Clear Screen And Depth Buffer
 glLoadIdentity_() ;Reset The Current Modelview Matrix
 
 glTranslatef_(-1.5,0.0,-6.0) ;Move Left 1.5 Units And Into The Screen 6.0
 
 glBegin_(#GL_TRIANGLES) ;Drawing Using Triangles
  glVertex3f_( 0.0, 1.0, 0.0) ;Top
  glVertex3f_(-1.0,-1.0, 0.0) ;Bottom Left
  glVertex3f_( 1.0,-1.0, 0.0) ;Bottom Right
 glEnd_() ;Finished Drawing The Triangle
 
 glTranslatef_(3.0,0.0,0.0) ;Move Right 3 Units
 
 glBegin_(#GL_QUADS) ;Draw A Quad
  glVertex3f_(-1.0, 1.0, 0.0) ;Top Left
  glVertex3f_( 1.0, 1.0, 0.0) ;Top Right
  glVertex3f_( 1.0,-1.0, 0.0) ;Bottom Right
  glVertex3f_(-1.0,-1.0, 0.0) ;Bottom Left
 glEnd_() ;Done Drawing The Quad
 
 ProcedureReturn #True ;Everything Went OK
 
EndProcedure

Procedure KillGLWindow() ;Properly Kill The Window

 If fullscreen ;Are We In Fullscreen Mode?
  ChangeDisplaySettings_(#Null,0) ;If So Switch Back To The Desktop
  ShowCursor_(#True) ;Show Mouse Pointer
 EndIf
 
 If hRC ;Do We Have A Rendering Context?
  If wglMakeCurrent_(#Null,#Null)=0 ;Are We Able To Release The DC And RC Contexts?
   MessageBox_(#Null,"Release Of DC And RC Failed.","SHUTDOWN ERROR",#MB_OK | #MB_ICONINFORMATION)
  EndIf
  If wglDeleteContext_(hRC)=0 ;Are We Able To Delete The RC?
   MessageBox_(#Null,"Release Rendering Context Failed.","SHUTDOWN ERROR",#MB_OK | #MB_ICONINFORMATION)
  EndIf
  hRC=#Null ;Set RC To NULL
 EndIf
 
 If hDC And ReleaseDC_(hWnd,hDC)=0 ;Are We Able To Release The DC
  MessageBox_(#Null,"Release Device Context Failed.","SHUTDOWN ERROR",#MB_OK | #MB_ICONINFORMATION)
  hDC=#Null ;Set DC To NULL
 EndIf
 
 If hWnd And DestroyWindow_(hWnd)=0 ;Are We Able To Destroy The Window?
   MessageBox_(#Null,"Could Not Release hWnd.","SHUTDOWN ERROR",#MB_OK | #MB_ICONINFORMATION)
   hWnd=#Null ;Set hWnd To NULL
 EndIf
 
 If UnregisterClass_("OpenGL",hInstance)=0 ;Are We Able To Unregister Class
  MessageBox_(#Null,"Could Not Unregister Class.","SHUTDOWN ERROR",#MB_OK | #MB_ICONINFORMATION)
  hInstance=#Null ;Set hInstance To NULL
 EndIf
 
EndProcedure

;This Code Creates Our OpenGL Window. Parameters Are:
;title - Title To Appear At The Top Of The Window
;width - Width Of The GL Window Or Fullscreen Mode
;height - Height Of The GL Window Or Fullscreen Mode
;bits - Number Of Bits To Use For Color (8/16/24/32)
;fullscreenflag - Use Fullscreen Mode (TRUE) Or Windowed Mode (FALSE)

Procedure.b CreateGLWindow(title.s,width.l,height.l,bits.l,fullscreenflag.b)

 Protected PixelFormat.l ;Holds The Results After Searching For A Match
 Protected wc.WNDCLASS ;Windows Class Structure
 Protected dwExStyle.l ;Window Extended Style
 Protected dwStyle.l ;Window Style
 Protected WindowRect.RECT ;Grabs Rectangle Upper Left / Lower Right Values
 Protected wpos.POINT ;Window position
 
 WindowRect\left=0 ;Set Left Value To 0
 WindowRect\right=width ;Set Right Value To Requested Width
 WindowRect\top=0 ;Set Top Value To 0
 WindowRect\bottom=height ;Set Bottom Value To Requested Height
 
 fullscreen=fullscreenflag ;Set The Global Fullscreen Flag
 
 hInstance=GetModuleHandle_(#Null) ;Grab An Instance For Our Window
 
 wc\style=#CS_HREDRAW | #CS_VREDRAW | #CS_OWNDC ;Redraw On Size, And Own DC For Window
 wc\lpfnWndProc=@WndProc() ;WndProc Handles Messages
 wc\cbClsExtra=0 ;No Extra Window Data
 wc\cbWndExtra=0 ;No Extra Window Data
 wc\hInstance=hInstance ;Set The Instance
 wc\hIcon=LoadIcon_(#Null,#IDI_WINLOGO) ;Load The Default Icon
 wc\hCursor=LoadCursor_(#Null,#IDC_ARROW) ;Load The Arrow Pointer
 wc\hbrBackground=#Null ;No Background Required For GL
 wc\lpszMenuName=#Null ;We Don't Want A Menu
 wc\lpszClassName=@"OpenGL" ;Set The Class Name  
 
 If RegisterClass_(wc)=0 ;Attempt To Register The Window Class
  MessageBox_(#Null,"Failed To Register The Window Class.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 If fullscreen ;Attempt Fullscreen Mode?
 
  Protected dmScreenSettings.DEVMODE ;Device Mode
  dmScreenSettings\dmSize=SizeOf(DEVMODE) ;Size Of The Devmode Structure
  dmScreenSettings\dmFields=#DM_BITSPERPEL | #DM_PELSWIDTH | #DM_PELSHEIGHT ;bit flags to specify the members of DEVMODE that were initialized
  dmScreenSettings\dmBitsPerPel=bits ;Selected Bits Per Pixel
  dmScreenSettings\dmPelsWidth=width ;Selected Screen Width in pixels
  dmScreenSettings\dmPelsHeight=height ;Selected Screen Height in pixels
  
  ;Try To Set Selected Mode And Get Results. Note: CDS_FULLSCREEN Gets Rid Of Start Bar
  If ChangeDisplaySettings_(dmScreenSettings,#CDS_FULLSCREEN)<>#DISP_CHANGE_SUCCESSFUL
   ;If The Mode Fails, Offer Two Options. Quit Or Use Windowed Mode
   If MessageBox_(#Null,"The Requested Fullscreen Mode Is Not Supported By"+Chr(10)+"Your Video Card. Use Windowed Mode Instead?","NeHe GL",#MB_YESNO | #MB_ICONEXCLAMATION)=#IDYES
    fullscreen=#False ;Windowed Mode Selected.  Fullscreen = FALSE
   Else
    ;Pop Up A Message Box Letting User Know The Program Is Closing
    MessageBox_(#Null,"Program Will Now Close.","ERROR",#MB_OK | #MB_ICONSTOP)
    ProcedureReturn #False
   EndIf
  EndIf
  
 EndIf
 
 If fullscreen ;Are We Still In Fullscreen Mode?
  dwExStyle=#WS_EX_APPWINDOW ;Window Extended Style
  dwStyle=#WS_POPUP ;Windows Style
  ShowCursor_(#False) ;Hide Mouse Pointer
 Else
  dwExStyle=#WS_EX_APPWINDOW | #WS_EX_WINDOWEDGE ;Window Extended Style
  dwStyle=#WS_OVERLAPPEDWINDOW ;Windows Style
 EndIf
 
 AdjustWindowRectEx_(WindowRect,dwStyle,#False,dwExStyle) ;Adjust Window To True Requested Size
 
 If fullscreen=0 ;if not fullscreen mode calculate screen centered window
  wpos\x=(GetSystemMetrics_(#SM_CXSCREEN)/2)-((WindowRect\right-WindowRect\left)/2)
  wpos\y=(GetSystemMetrics_(#SM_CYSCREEN)/2)-((WindowRect\bottom-WindowRect\top)/2)
 EndIf
 
 ;CreateWindowEx_(Extended Window Style, Class Name, Window Title, Window Style, Window X Position, Window Y Position, Width, Height, No Parent Window, No Menu, Instance, No Creation Data)
 hWnd=CreateWindowEx_(dwExStyle,"OpenGL",title,dwStyle | #WS_CLIPSIBLINGS | #WS_CLIPCHILDREN,wpos\x,wpos\y,WindowRect\right-WindowRect\left,WindowRect\bottom-WindowRect\top,#Null,#Null,hInstance,#Null)
 If hWnd=0
  KillGLWindow() ;Reset The Display
  MessageBox_(#Null,"Window Creation Error.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 Protected pfd.PIXELFORMATDESCRIPTOR ;pfd Tells Windows How We Want Things To Be
 pfd\nSize=SizeOf(PIXELFORMATDESCRIPTOR) ;Size Of This Structure
 pfd\nVersion=1 ;Version Number
 pfd\dwFlags=#PFD_SUPPORT_OPENGL | #PFD_DOUBLEBUFFER | #PFD_DRAW_TO_WINDOW ;Format Must Support Window, OpenGL, Double Buffering
 pfd\iPixelType=#PFD_TYPE_RGBA ;Request An RGBA Format
 pfd\cColorBits=bits ;Select Our Color Depth
 pfd\cRedBits=0 ;Color Bits Ignored
 pfd\cRedShift=0
 pfd\cGreenBits=0
 pfd\cGreenShift=0
 pfd\cBlueBits=0
 pfd\cBlueShift=0
 pfd\cAlphaBits=0 ;No Alpha Buffer
 pfd\cAlphaShift=0 ;Shift Bit Ignored
 pfd\cAccumBits=0 ;No Accumulation Buffer
 pfd\cAccumRedBits=0 ;Accumulation Bits Ignored
 pfd\cAccumGreenBits=0
 pfd\cAccumBlueBits=0
 pfd\cAccumAlphaBits=0
 pfd\cDepthBits=16 ;16Bit Z-Buffer (Depth Buffer)
 pfd\cStencilBits=0 ;No Stencil Buffer
 pfd\cAuxBuffers=0 ;No Auxiliary Buffer
 pfd\iLayerType=#PFD_MAIN_PLANE ;Main Drawing Layer
 pfd\bReserved=0 ;Reserved
 pfd\dwLayerMask=0 ;Layer Masks Ignored
 pfd\dwVisibleMask=0
 pfd\dwDamageMask=0
 
 hDC=GetDC_(hWnd)
 If hDC=0 ;Did We Get A Device Context?
  KillGLWindow() ;Reset The Display
  MessageBox_(#Null,"Can't Create A GL Device Context.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 PixelFormat=ChoosePixelFormat_(hDC,pfd)
 If PixelFormat=0 ;Did Windows Find A Matching Pixel Format?
  KillGLWindow() ;Reset The Display
  MessageBox_(#Null,"Can't Find A Suitable PixelFormat.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 If SetPixelFormat_(hDC,PixelFormat,pfd)=0 ;Are We Able To Set The Pixel Format?
  KillGLWindow() ;Reset The Display
  MessageBox_(#Null,"Can't Set The PixelFormat.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 hRC=wglCreateContext_(hDC)
 If hRC=0 ;Are We Able To Get A Rendering Context?
  KillGLWindow() ;Reset The Display
  MessageBox_(#Null,"Can't Create A GL Rendering Context.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 If wglMakeCurrent_(hDC,hRC)=0 ;Try To Activate The Rendering Context
  KillGLWindow() ;Reset The Display
  MessageBox_(#Null,"Can't Activate The GL Rendering Context.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 ShowWindow_(hWnd,#SW_SHOW) ;Show The Window
 SetForegroundWindow_(hWnd) ;Slightly Higher Priority
 SetFocus_(hWnd) ;Sets Keyboard Focus To The Window
 ReSizeGLScene(width,height) ;Set Up Our Perspective GL Screen
 
 If InitGL()=0 ;Initialize Our Newly Created GL Window
  KillGLWindow() ;Reset The Display
  MessageBox_(#Null,"Initialization Failed.","ERROR",#MB_OK | #MB_ICONEXCLAMATION)
  ProcedureReturn #False
 EndIf
 
 ProcedureReturn #True ;Success
 
EndProcedure

Procedure.l WndProc(hWnd.l,uMsg.l,wParam.l,lParam.l)

 Select uMsg ;Check For Windows Messages
 
  Case #WM_ACTIVATE ;Watch For Window Activate Message
   If HiWord(wParam)=0 ;Check Minimization State
    active=#True ;Program Is Active
   Else
    active=#False ;Program Is No Longer Active
   EndIf
   ProcedureReturn 0 ;Return To The Message Loop
   
  Case #WM_SYSCOMMAND ;Intercept System Commands
   Select wParam ;Check System Calls
    Case #SC_SCREENSAVE ;Screensaver Trying To Start?
     ProcedureReturn 0 ;Prevent From Happening
    Case #SC_MONITORPOWER ;Monitor Trying To Enter Powersave?
     ProcedureReturn 0 ;Prevent From Happening
   EndSelect
   
  Case #WM_CLOSE ;Did We Receive A Close Message?
   PostQuitMessage_(0) ;Send A Quit Message 
   ProcedureReturn 0 ;Jump Back
   
  Case #WM_KEYDOWN ;Is A Key Being Held Down?
   keys(wParam)=#True ;If So, Mark It As TRUE
   ProcedureReturn 0 ;Jump Back
   
  Case #WM_KEYUP ;Has A Key Been Released?
   keys(wParam)=#False ;If So, Mark It As FALSE
   ProcedureReturn 0 ;Jump Back
   
  Case #WM_SIZE ;Resize The OpenGL Window
   ReSizeGLScene(LoWord(lParam),HiWord(lParam)) ;LoWord=Width, HiWord=Height
   ProcedureReturn 0 ;Jump Back
   
 EndSelect
 
 ;Pass All Unhandled Messages To DefWindowProc
 ProcedureReturn DefWindowProc_(hWnd,uMsg,wParam,lParam)
 
EndProcedure

Procedure.l WinMain() ;Main Program

 Protected msg.MSG ;Windows Message Structure
 Protected done.b ;Bool Variable To Exit Loop
 
 ;Ask The User Which Screen Mode They Prefer
 If MessageBox_(#Null,"Would You Like To Run In Fullscreen Mode?","Start FullScreen?",#MB_YESNO | #MB_ICONQUESTION)=#IDNO
  fullscreen=#False ;Windowed Mode
 EndIf
 
 If CreateGLWindow("NeHe's First Polygon Tutorial",640,480,16,fullscreen)=0 ;Create The Window
  ProcedureReturn 0 ;Quit If Window Was Not Created
 EndIf
 
 While done=#False ;Loop That Runs While done=FALSE
 
  If PeekMessage_(msg,#Null,0,0,#PM_REMOVE) ;Is There A Message Waiting?
  
   If msg\message=#WM_QUIT ;Have We Received A Quit Message?
    done=#True ;If So done=TRUE
   Else ;If Not, Deal With Window Messages
    TranslateMessage_(msg) ;Translate The Message
    DispatchMessage_(msg) ;Dispatch The Message
   EndIf
   
  Else ;If There Are No Messages
  
   ;Draw The Scene. Watch For ESC Key And Quit Messages From DrawGLScene()
   If (active And DrawGLScene()=0) Or keys(#VK_ESCAPE) ;Active? Was There A Quit Received?
    done=#True ;ESC or DrawGLScene Signalled A Quit
   Else ;Not Time To Quit, Update Screen
    SwapBuffers_(hDC) ;Swap Buffers (Double Buffering)
   EndIf
   
   If keys(#VK_F1) ;Is F1 Being Pressed?
    keys(#VK_F1)=#False ;If So Make Key FALSE
    KillGLWindow() ;Kill Our Current Window
    fullscreen=~fullscreen & 1 ;Toggle Fullscreen / Windowed Mode
    ;Recreate Our OpenGL Window
    If CreateGLWindow("NeHe's First Polygon Tutorial",640,480,16,fullscreen)=0
     ProcedureReturn 0 ;Quit If Window Was Not Created
    EndIf
   EndIf
   
  EndIf
  
 Wend
 
 ;Shutdown
 KillGLWindow() ;Kill The Window
 End ;Exit The Program
 
EndProcedure

WinMain() ;run the main program

Code: Select all

;NeHe's Your First Polygon Tutorial (Lesson 2) 
;http://nehe.gamedev.net 
;http://nehe.gamedev.net/tutorial/your_first_polygon/13002/
;Credits: Nico Gruener, Dreglor, traumatic, hagibaba
;Author: MPz
;Date: 04 Oct 2021
;Note: up-to-date with PB v5.73 (Windows)

Procedure ReSizeGLScene(width.l,height.l) ;Resize And Initialize The GL Window

 If height=0 : height=1 : EndIf ;Prevent A Divide By Zero Error
 
 ResizeGadget(0, 0, 0, width, height)
 
 glViewport_(0,0,width,height) ;Reset The Current Viewport
 
 glMatrixMode_(#GL_PROJECTION) ;Select The Projection Matrix
 glLoadIdentity_() ;Reset The Projection Matrix
 
 gluPerspective_(45.0,Abs(width/height),0.1,100.0) ;Calculate The Aspect Ratio Of The Window
 
 glMatrixMode_(#GL_MODELVIEW) ;Select The Modelview Matrix
 glLoadIdentity_() ;Reset The Modelview Matrix
 
EndProcedure

Procedure DrawScene(Gadget)
  SetGadgetAttribute(Gadget, #PB_OpenGL_SetContext, #True)
  
  glPushMatrix_()                  ; Save the original Matrix coordinates
  glMatrixMode_(#GL_MODELVIEW)
  glClear_ (#GL_COLOR_BUFFER_BIT | #GL_DEPTH_BUFFER_BIT)
 
  glTranslatef_(-1.5,0.0,-6.0)
  
  glBegin_(#GL_TRIANGLES);                      // Drawing Using Triangles
    glVertex3f_( 0.0, 1.0, 0.0);              // Top
    glVertex3f_(-1.0,-1.0, 0.0);              // Bottom Left
    glVertex3f_( 1.0,-1.0, 0.0);              // Bottom Right
  glEnd_();                            // Finished Drawing The Triangle
  
  glTranslatef_(3,0.0,0.0);                   // Move Right 3 Units
  
  glBegin_(#GL_QUADS);                      // Draw A Quad
    glVertex3f_( 1.0, 1.0, 0.0);              // Top Right
    glVertex3f_(-1.0, 1.0, 0.0);              // Top Left
    glVertex3f_(-1.0,-1.0, 0.0);              // Bottom Left
    glVertex3f_( 1.0,-1.0, 0.0);              // Bottom Right
  glEnd_();

  glPopMatrix_()

  SetGadgetAttribute(Gadget, #PB_OpenGL_FlipBuffers, #True)
EndProcedure

Procedure CreateGLWindow(title.s,WindowWidth.l,WindowHeight.l,bits.l=16,fullscreenflag.b=0,Vsync.b=0)
  
  If InitKeyboard() = 0 Or InitSprite() = 0 Or InitMouse() = 0
    MessageRequester("Error", "Can't initialize Keyboards or Mouse", 0)
    End
  EndIf

  If fullscreenflag
    hWnd = OpenWindow(0, 0, 0, WindowWidth, WindowHeight, title, #PB_Window_BorderLess|#PB_Window_Maximize )
    OpenWindowedScreen(WindowID(0), 0, 0,WindowWidth(0),WindowHeight(0)) 
  Else  
    hWnd = OpenWindow(0, 1, 1, WindowWidth, WindowHeight, title,#PB_Window_MinimizeGadget |  #PB_Window_MaximizeGadget | #PB_Window_SizeGadget ) 
    OpenWindowedScreen(WindowID(0), 1, 1, WindowWidth,WindowHeight) 
  EndIf
  
  If bits = 24
    OpenGlFlags + #PB_OpenGL_24BitDepthBuffer
  EndIf
  
  If Vsync = 0
    OpenGlFlags + #PB_OpenGL_NoFlipSynchronization
  EndIf
  
  OpenGLGadget(0, 0, 0, WindowWidth(0),WindowHeight(0),OpenGlFlags)
  
  SetActiveGadget(0) 
  
  ReSizeGLScene(WindowWidth(0),WindowHeight(0))
  ;hDC = GetDC_(hWnd)
  
EndProcedure

CreateGLWindow("OpenGL Lesson 2",640,480,16)

Repeat
  
  Repeat 
    Event = WindowEvent()
    
    Select Event
      Case #PB_Event_CloseWindow
        Quit = 1
      Case #PB_Event_SizeWindow  
        ReSizeGLScene(WindowWidth(0),WindowHeight(0)) ;LoWord=Width, HiWord=Height
    EndSelect
  
  Until Event = 0
  
  ExamineKeyboard()
  
  If KeyboardPushed(#PB_Key_Escape) ;  Esc key to exit
    Quit = 1
  EndIf 

  DrawScene(0)
  Delay(20)
Until Quit = 1