#include <windows.h>		// Header File For Windows
#include <math.h>		// Header File For Windows Math Library
#include <stdio.h>		// Header File For Standard Input/Output
#include <gl\gl.h>		// Header File For The OpenGL32 Library
#include <gl\glu.h>		// Header File For The GLu32 Library
#include <gl\glaux.h>		// Header File For The Glaux Library
HDC  hDC=NULL;	   // Private GDI Device Context
HGLRC  hRC=NULL;	   // Permanent Rendering Context
HWND  hWnd=NULL;	   // Holds Our Window Handle
HINSTANCE hInstance;	   // Holds The Instance Of The Application
bool keys[256];		// Array Used For The Keyboard Routine
bool active=TRUE;		// Window Active Flag Set To TRUE By Default
bool fullscreen=TRUE;	   // Fullscreen Flag Set To Fullscreen Mode By Default
bool masking=TRUE;		// Masking On/Off
bool mp;		 // M Pressed?
bool sp;		 // Space Pressed?
bool scene;		 // Which Scene To Draw
GLuint texture[5];		// Storage For Our Five Textures
GLuint loop;		 // Generic Loop Variable
GLfloat roll;		 // Rolling Texture
GLfloat xrot;
GLfloat xspeed = 0.2;
GLfloat z = -5.0;
GLfloat as01 = 0.5f;
GLfloat as02 = 0.5f;
GLfloat as03 = 2.5f;
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);	// Declaration For WndProc
AUX_RGBImageRec *LoadBMP(char *Filename)	 // Loads A Bitmap Image
{
 FILE *File=NULL;	   // File Handle
 if (!Filename)		// Make Sure A Filename Was Given
 {
  return NULL;	   // If Not Return NULL
 }
 File=fopen(Filename,"r");	  // Check To See If The File Exists
 if (File)		// Does The File Exist?
 {
  fclose(File);	   // Close The Handle
  return auxDIBImageLoad(Filename);	// Load The Bitmap And Return A Pointer
 }
 return NULL;		// If Load Failed Return NULL
}
GLvoid ReSizeGLScene(GLsizei width, GLsizei height)	// Resize And Initialize The GL Window
{
 if (height==0)		// Prevent A Divide By Zero By
 {
  height=1;	   // Making Height Equal One
 }
 glViewport(0, 0, width, height);	 // Reset The Current Viewport
 glMatrixMode(GL_PROJECTION);	  // Select The Projection Matrix
 glLoadIdentity();	   // Reset The Projection Matrix
 // Calculate The Aspect Ratio Of The Window
 gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
 glMatrixMode(GL_MODELVIEW);	  // Select The Modelview Matrix
 glLoadIdentity();	   // Reset The Modelview Matrix
}
int LoadGLTextures()		// Load Bitmaps And Convert To Textures
{
 int Status=FALSE;	   // Status Indicator
 AUX_RGBImageRec *TextureImage[5];	 // Create Storage Space For The Texture Data
 memset(TextureImage,0,sizeof(void *)*5);	// Set The Pointer To NULL
 if ((TextureImage[0]=LoadBMP("Data/logo.bmp")) &&   // Logo Texture
	 (TextureImage[1]=LoadBMP("Data/mask2.bmp")) &&   // First Mask
	 (TextureImage[2]=LoadBMP("Data/image2.bmp")) &&   // First Image
	 (TextureImage[3]=LoadBMP("Data/mask1.bmp")) &&   // Second Mask
	 (TextureImage[4]=LoadBMP("Data/image1.bmp")))   // Second Image
 {
  Status=TRUE;	   // Set The Status To TRUE
  glGenTextures(5, &texture[0]);	 // Create Five Textures
  for (loop=0; loop<5; loop++)	 // Loop Through All 5 Textures
  {
			glBindTexture(GL_TEXTURE_2D, texture[loop]);
   glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
   glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
   glTexImage2D(GL_TEXTURE_2D, 0, 3, TextureImage[loop]->sizeX, TextureImage[loop]->sizeY,
	0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[loop]->data);
  }
 }
 for (loop=0; loop<5; loop++)	  // Loop Through All 5 Textures
 {
  if (TextureImage[loop])	  // If Texture Exists
  {
   if (TextureImage[loop]->data)	// If Texture Image Exists
   {
	free(TextureImage[loop]->data);   // Free The Texture Image Memory
   }
   free(TextureImage[loop]);	// Free The Image Structure
  }
 }
 return Status;		// Return The Status
}
int InitGL(GLvoid)		// All Setup For OpenGL Goes Here
{
 if (!LoadGLTextures())	   // Jump To Texture Loading Routine
 {
  return FALSE;	   // If Texture Didn't Load Return FALSE
 }
 glClearColor(1.0f, 1.0f, 0.0f, 0.0f);	 // Clear The Background Color To Yellow
 glClearDepth(1.0);	   // Enables Clearing Of The Depth Buffer
 glEnable(GL_DEPTH_TEST);	  // Enable Depth Testing
 glShadeModel(GL_SMOOTH);	  // Enables Smooth Color Shading
 glEnable(GL_TEXTURE_2D);	  // Enable 2D Texture Mapping
 return TRUE;		// Initialization Went OK
}
int DrawGLScene(GLvoid)		// Here's Where We Do All The Drawing
{
 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);   // Clear The Screen And The Depth Buffer
 glLoadIdentity();	   // Reset The Modelview Matrix
 glTranslatef(0.0f,0.0f,-2.0f);	  // Move Into The Screen 5 Units
	 glTranslatef(0.0f,0.0f,z);	  // Translate Into/Out Of The Screen By z
  glRotatef(xrot,1.0f,0.0f,0.0f);	  // Rotate On The X Axis By xrot
	
	glBindTexture(GL_TEXTURE_2D, texture[0]);	// Select Our Logo Texture
 glBegin(GL_QUADS);	   // Start Drawing A Textured Quad
  glTexCoord2f(0.0f, -roll+0.0f); glVertex3f(-1.1f, -1.1f,  0.0f); // Bottom Left
  glTexCoord2f(3.0f, -roll+0.0f); glVertex3f( 1.1f, -1.1f,  0.0f); // Bottom Right
  glTexCoord2f(3.0f, -roll+3.0f); glVertex3f( 1.1f,  1.1f,  0.0f); // Top Right
  glTexCoord2f(0.0f, -roll+3.0f); glVertex3f(-1.1f,  1.1f,  0.0f); // Top Left
 glEnd();		// Done Drawing The Quad
	 xrot+=xspeed;		// Add xspeed To xrot
 glEnable(GL_BLEND);	   // Enable Blending
 glDisable(GL_DEPTH_TEST);	  // Disable Depth Testing
 if (masking)		// Is Masking Enabled?
 {
  glBlendFunc(GL_DST_COLOR,GL_ZERO);	// Blend Screen Color With Zero (Black)
 }
 if (scene)		// Are We Drawing The Second Scene?
 {
  glTranslatef(0.0f,0.0f,-1.0f);	 // Translate Into The Screen One Unit
  glRotatef(roll*360,0.0f,0.0f,1.0f);	// Rotate On The Z Axis 360 Degrees
  if (masking)	   // Is Masking On?
  {   glBindTexture(GL_TEXTURE_2D, texture[3]);  // Select The Second Mask Texture
   glBegin(GL_QUADS);	 // Start Drawing A Textured Quad
	glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.1f, -1.1f,  0.0f); // Bottom Left
	glTexCoord2f(as01, 0.0f); glVertex3f( 1.1f, -1.1f,  0.0f); // Bottom Right
	glTexCoord2f(as01, as01); glVertex3f( 1.1f,  1.1f,  0.0f); // Top Right
	glTexCoord2f(0.0f, as01); glVertex3f(-1.1f,  1.1f,  0.0f); // Top Left
   glEnd();	  // Done Drawing The Quad
  }
  
  glBlendFunc(GL_ONE, GL_ONE);	 // Copy Image 2 Color To The Screen
  glBindTexture(GL_TEXTURE_2D, texture[4]);   // Select The Second Image Texture
  glBegin(GL_QUADS);	  // Start Drawing A Textured Quad
   glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.1f, -1.1f,  0.0f); // Bottom Left
   glTexCoord2f(as01, 0.0f); glVertex3f( 1.1f, -1.1f,  0.0f); // Bottom Right
   glTexCoord2f(as01, as01); glVertex3f( 1.1f,  1.1f,  0.0f); // Top Right
   glTexCoord2f(0.0f, as01); glVertex3f(-1.1f,  1.1f,  0.0f); // Top Left
  glEnd();	   // Done Drawing The Quad
 }
 else		 // Otherwise
 {
  if (masking)	   // Is Masking On?
  {
   glBindTexture(GL_TEXTURE_2D, texture[1]);  // Select The First Mask Texture
   glBegin(GL_QUADS);	 // Start Drawing A Textured Quad
	glTexCoord2f(roll+0.0f, 0.0f); glVertex3f(-as03, -as03,  0.0f); // Bottom Left
	glTexCoord2f(roll+as02, 0.0f); glVertex3f( as03, -as03,  0.0f); // Bottom Right
	glTexCoord2f(roll+as02, as02); glVertex3f( as03,  as03,  0.0f); // Top Right
	glTexCoord2f(roll+0.0f, as02); glVertex3f(-as03,  as03,  0.0f); // Top Left
   glEnd();	  // Done Drawing The Quad
  }
  glBlendFunc(GL_ONE, GL_ONE);	 // Copy Image 1 Color To The Screen
  glBindTexture(GL_TEXTURE_2D, texture[2]);   // Select The First Image Texture
  glBegin(GL_QUADS);	  // Start Drawing A Textured Quad
   glTexCoord2f(roll+0.0f, 0.0f); glVertex3f(-as03, -as03,  0.0f); // Bottom Left
   glTexCoord2f(roll+as02, 0.0f); glVertex3f( as03, -as03,  0.0f); // Bottom Right
   glTexCoord2f(roll+as02, as02); glVertex3f( as03,  as03,  0.0f); // Top Right
   glTexCoord2f(roll+0.0f, as02); glVertex3f(-as03,  as03,  0.0f); // Top Left
  glEnd();	   // Done Drawing The Quad
 }
 glEnable(GL_DEPTH_TEST);	  // Enable Depth Testing
 glDisable(GL_BLEND);	   // Disable Blending
 roll+=0.002f;		// Increase Our Texture Roll Variable
 if (roll>1.0f)		// Is Roll Greater Than One
 {
  roll-=1.0f;	   // Subtract 1 From Roll
 }
 return TRUE;		// Everything Went OK
}
  
GLvoid KillGLWindow(GLvoid)	   // 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
 }
 if (hRC)		// Do We Have A Rendering Context?
 {
  if (!wglMakeCurrent(NULL,NULL))	 // Are We Able To Release The DC And RC Contexts?
  {
   MessageBox(NULL,"Release Of DC And RC Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
  }
  
  if (!wglDeleteContext(hRC))	 // Are We Able To Delete The RC?
  {
   MessageBox(NULL,"Release Rendering Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
  }
  hRC=NULL;	   // Set RC To NULL
 }
 
 if (hDC && !ReleaseDC(hWnd,hDC))	 // 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
 }
 if (hWnd && !DestroyWindow(hWnd))	 // 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
 }
 if (!UnregisterClass("OpenGL",hInstance))	// Are We Able To Unregister Class
 {
  MessageBox(NULL,"Could Not Unregister Class.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
  hInstance=NULL;	   // Set hInstance To NULL
 }
}
BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)
{
 GLuint  PixelFormat;	  // Holds The Results After Searching For A Match
 WNDCLASS wc;
 DWORD  dwExStyle;	  // Window Extended Style
 DWORD  dwStyle;	  // Window Style
 RECT WindowRect;	   // Grabs Rectangle Upper Left / Lower Right Values
 WindowRect.left=(long)0;	  // Set Left Value To 0
 WindowRect.right=(long)width;	  // Set Right Value To Requested Width
 WindowRect.top=(long)0;	   // Set Top Value To 0
 WindowRect.bottom=(long)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 Move, And Own DC For Window
 wc.lpfnWndProc  = (WNDPROC) 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))	  // Attempt To Register The Window Class
 {
  MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);
  return FALSE;	   // Exit And Return FALSE
 }
 if (fullscreen)		// Attempt Fullscreen Mode?
 {
  DEVMODE dmScreenSettings;	 // Device Mode
  memset(&dmScreenSettings,0,sizeof(dmScreenSettings));  // Makes Sure Memory's Cleared
  dmScreenSettings.dmSize=sizeof(dmScreenSettings);  // Size Of The Devmode Structure
  dmScreenSettings.dmPelsWidth = width;   // Selected Screen Width
  dmScreenSettings.dmPelsHeight = height;   // Selected Screen Height
  dmScreenSettings.dmBitsPerPel = bits;	// Selected Bits Per Pixel
  dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;
  // 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 Run In A Window.
   if (MessageBox(NULL,"The Requested Fullscreen Mode Is Not Supported By\nYour Video Card. Use Windowed Mode Instead?","NeHe GL",MB_YESNO|MB_ICONEXCLAMATION)==IDYES)
   {
	fullscreen=FALSE;	// Select Windowed Mode (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);
	return FALSE;	 // Exit And Return FALSE
   }
  }
 }
 if (fullscreen)		// Are We Still In Fullscreen Mode?
 {
  dwExStyle=WS_EX_APPWINDOW;	 // Window Extended Style
  dwStyle=WS_POPUP;	  // Windows Style
  ShowCursor(TRUE);	  // Hide Mouse Pointer
 }
 else
 {
  dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;   // Window Extended Style
  dwStyle=WS_OVERLAPPEDWINDOW;	 // Windows Style
 }
 AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle);  // Adjust Window To True Requested Size
 if (!(hWnd=CreateWindowEx( dwExStyle,	// Extended Style For The Window
	 "OpenGL",	// Class Name
	 title,	 // Window Title
	 WS_CLIPSIBLINGS |   // Required Window Style
	 WS_CLIPCHILDREN |   // Required Window Style
	 dwStyle,	// Selected Window Style
	 0, 0,	 // Window Position
	 WindowRect.right-WindowRect.left, // Calculate Adjusted Window Width
	 WindowRect.bottom-WindowRect.top, // Calculate Adjusted Window Height
	 NULL,	 // No Parent Window
	 NULL,	 // No Menu
	 hInstance,	// Instance
	 NULL)))	 // Don't Pass Anything To WM_CREATE
 {
  KillGLWindow();	   // Reset The Display
  MessageBox(NULL,"Window Creation Error.","ERROR",MB_OK|MB_ICONEXCLAMATION);
  return FALSE;	   // Return FALSE
 }
 static PIXELFORMATDESCRIPTOR pfd=	 // pfd Tells Windows How We Want Things To Be
 {
  sizeof(PIXELFORMATDESCRIPTOR),	 // Size Of This Pixel Format Descriptor
  1,		// Version Number
  PFD_DRAW_TO_WINDOW |	  // Format Must Support Window
  PFD_SUPPORT_OPENGL |	  // Format Must Support OpenGL
  PFD_DOUBLEBUFFER,	  // Must Support Double Buffering
  PFD_TYPE_RGBA,	   // Request An RGBA Format
  bits,		// Select Our Color Depth
  0, 0, 0, 0, 0, 0,	  // Color Bits Ignored
  0,		// No Alpha Buffer
  0,		// Shift Bit Ignored
  0,		// No Accumulation Buffer
  0, 0, 0, 0,	   // Accumulation Bits Ignored
  16,		// 16Bit Z-Buffer (Depth Buffer)
  0,		// No Stencil Buffer
  0,		// No Auxiliary Buffer
  PFD_MAIN_PLANE,	   // Main Drawing Layer
  0,		// Reserved
  0, 0, 0		// Layer Masks Ignored
 };
 if (!(hDC=GetDC(hWnd)))	   // Did We Get A Device Context?
 {
  KillGLWindow();	   // Reset The Display
  MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
  return FALSE;	   // Return FALSE
 }
 if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd)))	// Did Windows Find A Matching Pixel Format?
 {
  KillGLWindow();	   // Reset The Display
  MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
  return FALSE;	   // Return FALSE
 }
 if(!SetPixelFormat(hDC,PixelFormat,&pfd))	// Are We Able To Set The Pixel Format?
 {
  KillGLWindow();	   // Reset The Display
  MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
  return FALSE;	   // Return FALSE
 }
 if (!(hRC=wglCreateContext(hDC)))	 // 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);
  return FALSE;	   // Return FALSE
 }
 if(!wglMakeCurrent(hDC,hRC))	  // Try To Activate The Rendering Context
 {
  KillGLWindow();	   // Reset The Display
  MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
  return FALSE;	   // Return FALSE
 }
 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())		// Initialize Our Newly Created GL Window
 {
  KillGLWindow();	   // Reset The Display
  MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
  return FALSE;	   // Return FALSE
 }
 return TRUE;		// Success
}
LRESULT CALLBACK WndProc( HWND hWnd,	 // Handle For This Window
	UINT uMsg,	 // Message For This Window
	WPARAM wParam,	 // Additional Message Information
	LPARAM lParam)	 // Additional Message Information
{
 switch (uMsg)		// Check For Windows Messages
 {
  case WM_ACTIVATE:	  // Watch For Window Activate Message
  {
   if (!HIWORD(wParam))	 // Check Minimization State
   {
	active=TRUE;	 // Program Is Active
   }
   else
   {
	active=FALSE;	 // Program Is No Longer Active
   }
   return 0;	  // Return To The Message Loop
  }
  
  case WM_SYSCOMMAND:	  // Intercept System Commands
  {
   switch (wParam)	  // Check System Calls
   {
	case SC_SCREENSAVE:	// Screensaver Trying To Start?
	case SC_MONITORPOWER:	// Monitor Trying To Enter Powersave?
	return 0;	 // Prevent From Happening
   }
   break;	   // Exit
  }
  
  case WM_CLOSE:	   // Did We Receive A Close Message?
  {
   PostQuitMessage(0);	 // Send A Quit Message
   return 0;	  // Jump Back
  }
  case WM_KEYDOWN:	  // Is A Key Being Held Down?
  {
   keys[wParam] = TRUE;	 // If So, Mark It As TRUE
   return 0;	  // Jump Back
  }
  case WM_KEYUP:	   // Has A Key Been Released?
  {
   keys[wParam] = FALSE;	 // If So, Mark It As FALSE
   return 0;	  // Jump Back
  }
  case WM_SIZE:	   // Resize The OpenGL Window
  {
   ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));  // LoWord=Width, HiWord=Height
   return 0;	  // Jump Back
  }
 }
 // Pass All Unhandled Messages To DefWindowProc
 return DefWindowProc(hWnd,uMsg,wParam,lParam);
}   

int WINAPI WinMain( HINSTANCE hInstance,	// Instance
   HINSTANCE hPrevInstance,	// Previous Instance
   LPSTR  lpCmdLine,	// Command Line Parameters
   int  nCmdShow)	// Window Show State
{
 MSG msg;		// Windows Message Structure
 BOOL done=FALSE;	   // 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
 }
 // Create Our OpenGL Window
 if (!CreateGLWindow("NeHe's Masking Tutorial",640,480,16,fullscreen))
 {
  return 0;	   // Quit If Window Was Not Created
 }
 while(!done)		// 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
   }
  }
  else		// If There Are No Messages
  {
   // Draw The Scene.  Watch For ESC Key And Quit Messages From DrawGLScene()
   if ((active && !DrawGLScene()) || 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)
	if (keys[' '] && !sp)	// Is Space Being Pressed?
	{
	 sp=TRUE;	// Tell Program Spacebar Is Being Held
	 scene=!scene;	// Toggle From One Scene To The Other
	}
	if (!keys[' '])	 // Has Spacebar Been Released?
	{
	 sp=FALSE;	// Tell Program Spacebar Has Been Released
	}
	if (keys['M'] && !mp)	// Is M Being Pressed?
	{
	 mp=TRUE;	// Tell Program M Is Being Held
	 masking=!masking;   // Toggle Masking Mode OFF/ON
	}
	if (!keys['M'])	 // Has M Been Released?
	{
	 mp=FALSE;	// Tell Program That M Has Been Released
	}
	if (keys[VK_F1])	// Is F1 Being Pressed?
	{
	 keys[VK_F1]=FALSE;   // If So Make Key FALSE
	 KillGLWindow();	// Kill Our Current Window
	 fullscreen=!fullscreen;   // Toggle Fullscreen / Windowed Mode
	 // Recreate Our OpenGL Window
	 if (!CreateGLWindow("NeHe's Masking Tutorial",640,480,16,fullscreen))
	 {
	  return 0;   // Quit If Window Was Not Created
	 }
	}
   }
  }
 }
 // Shutdown
 KillGLWindow();		// Kill The Window
 return (msg.wParam);	   // Exit The Program
}