#include <windows.h>												// Header File For Windows
#include <gl\gl.h>													// Header File For The OpenGL32 Library
#include <gl\glu.h>													// Header File For The GLu32 Library
#include "glaux.h"													// Header File For The GLaux Library

HGLRC		hRC=NULL;												// Permanent Rendering Context
HDC			hDC=NULL;												// Private GDI Device 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

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);				// Declaration For WndProc

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 InitGL(GLvoid)													// All Setup For OpenGL Goes Here
{
	glShadeModel(GL_SMOOTH);										// Enable Smooth Shading
	glClearColor(0.0f,0.0f,0.0f,0.0f);								// Black Background
	glClearDepth(1.0f);												// Depth Buffer Setup
	glEnable(GL_DEPTH_TEST);										// Enables Depth Testing
	glDepthFunc(GL_LEQUAL);											// The Type Of Depth Test To Do
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);				// Really Nice Perspective Calculations
	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 Current Modelview Matrix
	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 (!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;													// Window Class Structure
	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(FALSE);											// 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,							// Required 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 OpenGL Framework",640,480,16,fullscreen))
	{
		return 0;													// Quit If Window Was Not Created
	}
	while(!done)													// Loop That Runs Until done=TRUE
	{
		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)												// Program Active?
			{
				if (keys[VK_ESCAPE])								// Was ESC Pressed?
				{
					done=TRUE;										// ESC Signalled A Quit
				}
				else												// Not Time To Quit, Update Screen
				{
					DrawGLScene();									// Draw The Scene
					SwapBuffers(hDC);								// Swap Buffers (Double Buffering)
				}
			}
			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 / Window Mode
				// Recreate Our OpenGL Window
				if (!CreateGLWindow("NeHe's OpenGL Framework",640,480,16,fullscreen))
				{
					return 0;										// Quit If Window Was Not Created
				}
			}
		}
	}
	// Shutdown
	KillGLWindow();													// Kill The Window
	return (msg.wParam);											// Exit The Program
}