OpenGL入门笔记（一）

#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 <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

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, 0.5f);                // 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
    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
    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
    }
}

/**//*    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)    */
 
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 OpenGL Framework",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)                                // 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 / Windowed 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
}