OpenGL学习三十六：Windows 2D字体

(此节内容对应NEHE教程第13课)

本节主要说明OpenGL结合WINDOW 创建并使用2D字体

作法

1.声明显示列表base = glGenLists(96);
2.创建新的FONT font = CreateFont(WinAPI)
3.选择我们需要的字体 oldfont = (HFONT)SelectObject(hDC, font);(WinAPI)
4.创建显示列表 wglUseFontBitmaps(hDC, 32, 96, base);从32~128字符。
按照ASII码进行存储。显示时候也是按照此逻辑进行寻找，如A对应65 则在显示列表65进行寻找
5.设置显示列表基础值 glListBase(base - 32); 原因：假设字符A的ASII为32，那么在第4步骤上A存储在显示列表第0位。在从显示列表从0位获取A时，就需要将最开始的32编译去掉
6.使用显示列表进行文字绘制 glCallLists(strlen(text), GL_UNSIGNED_BYTE, text);


图像字体使用的是显示列表，声明N个显示列表。每个显示列表用来存放一个字符，当显示文字时调用显示列表进行绘制。其中字符的ASII码对应显示列表的值

说明：显示列表创建过程 应该在工程初始化中进行，保证仅执行一次
步骤1~4 属于显示列表创建过程，步骤5 是显示列表重定位函数，结合逻辑使用。不是必须使用函数
步骤6在文字绘制时进行调用

#include "header.h"

#include <stdarg.h>			// Header File For Variable Argument Routines


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

GLuint	base;				// Base Display List For The Font Set
GLfloat	cnt1;				// 1st Counter Used To Move Text & For Coloring
GLfloat	cnt2;				// 2nd Counter Used To Move Text & For Coloring

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 BuildFont(GLvoid)								// Build Our Bitmap Font
{
	HFONT	font;									// Windows Font ID
	HFONT	oldfont;								// Used For Good House Keeping

	base = glGenLists(96);								// Storage For 96 Characters

	font = CreateFont(	-24,							// Height Of Font
						0,					// Width Of Font
						0,					// Angle Of Escapement
						0,					// Orientation Angle
						FW_BOLD,				// Font Weight
						FALSE,					// Italic
						FALSE,					// Underline
						FALSE,					// Strikeout
						ANSI_CHARSET,				// Character Set Identifier
						OUT_TT_PRECIS,				// Output Precision
						CLIP_DEFAULT_PRECIS,			// Clipping Precision
						ANTIALIASED_QUALITY,			// Output Quality
						FF_DONTCARE|DEFAULT_PITCH,		// Family And Pitch
						"Courier New");				// Font Name

	oldfont = (HFONT)SelectObject(hDC, font);                                       // Selects The Font We Want
	wglUseFontBitmaps(hDC, 32, 96, base);		                                // Builds 96 Characters Starting At Character 32
	SelectObject(hDC, oldfont);							// Selects The Font We Want
	DeleteObject(font);								// Delete The Font
}

GLvoid KillFont(GLvoid)									// Delete The Font List
{
	glDeleteLists(base, 96);							// Delete All 96 Characters
}

GLvoid glPrint(const char *fmt, ...)					// Custom GL "Print" Routine
{
	char		text[256];					// Holds Our String
	va_list		ap;						// Pointer To List Of Arguments

	if (fmt == NULL)						// If There's No Text
		return;							// Do Nothing

	va_start(ap, fmt);						// Parses The String For Variables
	    vsprintf(text, fmt, ap);					// And Converts Symbols To Actual Numbers
	va_end(ap);							// Results Are Stored In Text

	glPushAttrib(GL_LIST_BIT);					// Pushes The Display List Bits
	glListBase(base - 32);						// Sets The Base Character to 32
	glCallLists(strlen(text), GL_UNSIGNED_BYTE, text);	        // Draws The Display List Text
	glPopAttrib();							// Pops The Display List Bits
}

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, 0.5f);				// Black Background
	glClearDepth(1.0f);						// 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

	BuildFont();							// Build The Font

	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 Screen And Depth Buffer
	glLoadIdentity();							// Reset The Current Modelview Matrix
	glTranslatef(0.0f,0.0f,-1.0f);						// Move One Unit Into The Screen
	// Pulsing Colors Based On Text Position
	glColor3f(1.0f*float(cos(cnt1)),1.0f*float(sin(cnt2)),1.0f-0.5f*float(cos(cnt1+cnt2)));
	// Position The Text On The Screen
	glRasterPos2f(-0.45f+0.05f*float(cos(cnt1)), 0.32f*float(sin(cnt2)));
 	glPrint("Active OpenGL Text With NeHe - %7.2f", cnt1);	// Print GL Text To The Screen
	cnt1+=0.051f;										// Increase The First Counter
	cnt2+=0.005f;										// Increase The First Counter
	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
	}

	KillFont();
}


BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)
{
	GLuint		PixelFormat;			        // Holds The Results After Searching For A Match
	WNDCLASS	wc;					// Windows 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 Size, 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;							// 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 Use Windowed Mode.
			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;		// 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);
				return FALSE;									// 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

	// Create The Window
	if (!(hWnd=CreateWindowEx(	dwExStyle,							// Extended Style For The Window
								"OpenGL",				// Class Name
								title,					// Window Title
								dwStyle |				// Defined Window Style
								WS_CLIPSIBLINGS |			// Required Window Style
								WS_CLIPCHILDREN,			// Required Window Style
								0, 0,					// Window Position
								WindowRect.right-WindowRect.left,	// Calculate Window Width
								WindowRect.bottom-WindowRect.top,	// Calculate Window Height
								NULL,					// No Parent Window
								NULL,					// No Menu
								hInstance,				// Instance
								NULL)))					// Dont 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 Bitmap Font 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[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 Bitmap Font Tutorial",640,480,16,fullscreen))
				{
					return 0;						// Quit If Window Was Not Created
				}
			}
		}
	}

	// Shutdown
	KillGLWindow();									// Kill The Window
	return (msg.wParam);							// Exit The Program
}