The triangle is not displayed in OpenGL application

Question

I'm trying to make my first polygon.

Because I wrote a code, complied it and voila ... the triangle is not displayed :(

What is wrong with this code?

#pragma once

#include <Windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <gl\GL.h>
#include <gl\glu.h>
#include <gl\glut.h>

HDC         hDC=NULL;
HGLRC       hRC=NULL;

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height);
int GL_init( GLvoid );
int GL_drawit( GLvoid );

typedef struct {
    HWND hWnd;
} Glab_t;

static Glab_t glab;

char szClassName[ ] = "GLab";

static LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
    switch (message) {
        case WM_DESTROY:
            PostQuitMessage (0);
            break;
        case WM_SIZE:
            GL_ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));
            break;
        default:
            return DefWindowProc (hwnd, message, wParam, lParam);
    }
    return 0;
}


int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    MSG messages;
    RECT rect;
    WNDCLASSEX wndClass;
    int screenWidth, screenHeight;
    int x, y, w, h;
    GLuint      PixelFormat;

    screenWidth = GetSystemMetrics(SM_CXSCREEN);
    screenHeight = GetSystemMetrics(SM_CYSCREEN);

    rect.left = (screenWidth - 582) / 2;
    rect.top = (screenHeight - 358) / 2;
    rect.right = rect.left + 582;
    rect.bottom = rect.top + 358;

    x = rect.left;
    y = rect.top;
    w = 640;
    h = 480;


    wndClass.hInstance = hInstance;
    wndClass.lpszClassName = szClassName;
    wndClass.lpfnWndProc = WindowProcedure;
    wndClass.style = CS_DBLCLKS;
    wndClass.cbSize = sizeof (WNDCLASSEX);
    wndClass.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hCursor = LoadCursor (NULL, IDC_ARROW);
    wndClass.lpszMenuName = NULL;
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);

    if (!RegisterClassEx (&wndClass)) {
        return 0;
    }

    glab.hWnd = CreateWindowEx (
           0,
           szClassName,
           "GLab - OpenGL",
           WS_OVERLAPPEDWINDOW,
           x,
           y,
           w,
           h,
           HWND_DESKTOP,
           NULL,
           hInstance,
           NULL 
           );

    static  PIXELFORMATDESCRIPTOR pfd=  {
        sizeof(PIXELFORMATDESCRIPTOR),
        1,
        PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
        PFD_TYPE_RGBA,
        16, // Can be 32 tough :)
        0, 0, 0, 0, 0, 0,
        0,
        0,
        0,
        0, 0, 0, 0, 
        16, 
        0,
        0,
        PFD_MAIN_PLANE, 
        0,
        0, 0, 0 
    };

    if (!(hDC=GetDC(glab.hWnd))) {
        MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) {
        MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!SetPixelFormat(hDC,PixelFormat,&pfd)) {
        MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(hRC=wglCreateContext(hDC))) {
        MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!wglMakeCurrent(hDC,hRC)) {
        MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    ShowWindow (glab.hWnd, nCmdShow);
    SetForegroundWindow(glab.hWnd);
    SetFocus(glab.hWnd);
    GL_ReSizeGLScene( w, h );

    if (!GL_init() ) {
        MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return false;
    }

    if( !GL_drawit() ) {
        MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return false;
    }

    while (GetMessage (&messages, NULL, 0, 0)) {
        TranslateMessage(&messages);
        DispatchMessage(&messages);
    }

    return messages.wParam;
}

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height) {
    if (height==0) {
        height=1;
    }

    glViewport(0,0,width,height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

int GL_init( GLvoid ) {
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    return true;
}

int GL_drawit( GLvoid ) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(-1.5f,0.0f,-6.0f);
    glBegin(GL_TRIANGLES);
        glVertex3f( 0.0f, 1.0f, 0.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);
    glEnd();            
    return true;
}

Using MC Visual C++ 2010 Express and OpenGL 1.4.

Answer 1

You need a SwapBuffers() call in there after you render your scene:

#include <Windows.h>
#include <GL/GL.h>
#include <GL/GLU.h>

HDC         hDC=NULL;
HGLRC       hRC=NULL;

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height);
int GL_init( GLvoid );
int GL_drawit( GLvoid );

typedef struct {
    HWND hWnd;
} Glab_t;

static Glab_t glab;

char szClassName[ ] = "GLab";

static LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
    switch (message) {
        case WM_DESTROY:
            PostQuitMessage (0);
            break;
        case WM_SIZE:
            GL_ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));
            break;
        default:
            return DefWindowProc (hwnd, message, wParam, lParam);
    }
    return 0;
}


int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    MSG messages;
    RECT rect;
    WNDCLASSEX wndClass;
    int screenWidth, screenHeight;
    int x, y, w, h;
    GLuint      PixelFormat;

    screenWidth = GetSystemMetrics(SM_CXSCREEN);
    screenHeight = GetSystemMetrics(SM_CYSCREEN);

    rect.left = (screenWidth - 582) / 2;
    rect.top = (screenHeight - 358) / 2;
    rect.right = rect.left + 582;
    rect.bottom = rect.top + 358;

    x = rect.left;
    y = rect.top;
    w = 640;
    h = 480;


    wndClass.hInstance = hInstance;
    wndClass.lpszClassName = szClassName;
    wndClass.lpfnWndProc = WindowProcedure;
    wndClass.style = CS_DBLCLKS;
    wndClass.cbSize = sizeof (WNDCLASSEX);
    wndClass.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wndClass.hCursor = LoadCursor (NULL, IDC_ARROW);
    wndClass.lpszMenuName = NULL;
    wndClass.cbClsExtra = 0;
    wndClass.cbWndExtra = 0;
    wndClass.hbrBackground = (HBRUSH)(COLOR_BTNFACE + 1);

    if (!RegisterClassEx (&wndClass)) {
        return 0;
    }

    glab.hWnd = CreateWindowEx (
           0,
           szClassName,
           "GLab - OpenGL",
           WS_OVERLAPPEDWINDOW,
           x,
           y,
           w,
           h,
           HWND_DESKTOP,
           NULL,
           hInstance,
           NULL 
           );

    static  PIXELFORMATDESCRIPTOR pfd=  {
        sizeof(PIXELFORMATDESCRIPTOR),
        1,
        PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
        PFD_TYPE_RGBA,
        16, // Can be 32 tough :)
        0, 0, 0, 0, 0, 0,
        0,
        0,
        0,
        0, 0, 0, 0, 
        16, 
        0,
        0,
        PFD_MAIN_PLANE, 
        0,
        0, 0, 0 
    };

    if (!(hDC=GetDC(glab.hWnd))) {
        MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) {
        MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!SetPixelFormat(hDC,PixelFormat,&pfd)) {
        MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if (!(hRC=wglCreateContext(hDC))) {
        MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    if(!wglMakeCurrent(hDC,hRC)) {
        MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return FALSE;
    }

    ShowWindow (glab.hWnd, nCmdShow);
    SetForegroundWindow(glab.hWnd);
    SetFocus(glab.hWnd);
    GL_ReSizeGLScene( w, h );

    if (!GL_init() ) {
        MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
        return false;
    }

    while (GetMessage (&messages, NULL, 0, 0)) {
        TranslateMessage(&messages);
        DispatchMessage(&messages);

        if( !GL_drawit() ) {
            MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
            return false;
        }
        SwapBuffers(hDC);
    }

    return messages.wParam;
}

GLvoid GL_ReSizeGLScene(GLsizei width, GLsizei height) {
    if (height==0) {
        height=1;
    }

    glViewport(0,0,width,height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

int GL_init( GLvoid ) {
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
    return true;
}

int GL_drawit( GLvoid ) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(-1.5f,0.0f,-6.0f);
    glBegin(GL_TRIANGLES);
        glVertex3f( 0.0f, 1.0f, 0.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);
    glEnd();            
    return true;
}

EDIT: I also moved your GL_drawit() call to the event loop so it redraws in response to resize events. Well, any event at all really.

Answer 2

Getting OpenGL windows initialized is tricky and hardware dependent. Suggest you try your OpenGL code first in a window built by GLUT. After it's working there, if something about GLUT won't work in your application, you can grok its sources to see how to initialize your own OpenGL window.