OpenGL window always busy

Question

I have a small framework which displays a texture in borderless screen window, but when I start it, the application is showing a busy mouse icon when I activate the OpenGL window, and I cannot seem to understand where it is coming from.

The following code is the complete solution (Visual Studio 2010) and should compile as is. Unfortunately I don't even know where to start looking, thus I copied the complete code here. BasicProject creates a random texture, and pipes that into the OpenGL window.

Can anyone see why the code is stuck into a busy window? The OpenGL Callbacks are never reached, but I do not see why not.

BasicProject.cpp (entry point):

/** Sample Project for OpenGL-Display functionality
*
* Anton Roth, 2013
*/

#include "stdafx.h"
#include <conio.h>
#include <process.h>
#include <vector>
#include <Windows.h>
#include <cstdlib>
#include <ctime>
#include "OpenGL-Display.h"

void RunOpenGL(void* pParams);
bool applicationRunning = true;
HANDLE threadOGL;

int _tmain(int argc, _TCHAR* argv[]) {
    OGD::OpenGLDisplay_Init(640, 480, 200, 200, 0, "First Display");
    threadOGL = (HANDLE)_beginthread(RunOpenGL, 0, NULL);

    while(!_kbhit()) {
        Sleep(500);
    }

    applicationRunning = false;
    WaitForSingleObject( threadOGL, 500 );

    return 0;
}

void RunOpenGL(void* pParams) {
    std::vector<char> texture;
    texture.resize(640 * 480 * 3);
    std::srand(time(0));

    while(applicationRunning) {
        for(int i = 0; i < 640 * 480 * 3; ++i) {
            texture.at(i) = std::rand() % 255;
        }

        OGD::OpenGLDisplay_Wrapper(&texture.at(0), 640, 480, false, 24, 0);
        int x, y;
        OGD::OpenGLDisplay_MousePos(x, y, 0);
        Sleep(300);
    }
}

OpenGL-Display.h:

#ifndef __OPENGLDISPLAY
#define __OPENGLDISPLAY
#include <windows.h>        // Header File For Windows
#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 <vector>

namespace OGD
{
    class OpenGL_Display
    {
        public:
            OpenGL_Display(int newId);
            ~OpenGL_Display();
            void Init_Display(int width, int height, int posX, int posY, LPCSTR className);
            void DrawNewImage(int width, int height, char* imageData, bool flip, int bpp);
            void GetMouseCords(int& x, int& y);
            int ID;
        protected:
            bool CreateGLWindow(char* title, int bits, int posX, int posY, LPCSTR className);
            GLvoid ReSizeGLScene(GLsizei width, GLsizei height);
            int LoadGLTextures();
            int InitGL(GLvoid);
            void UpdateGLBuffers(int width, int height, char* imageData, int bpp);
            int DrawGLScene(bool flip);
            GLvoid KillGLWindow(GLvoid);
            HDC         hDC;        // Private GDI Device Context
            static LRESULT  CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);   // Declaration For WndProc

            HGLRC       hRC;        // Permanent Rendering Context
            HWND        hWnd;       // Holds Our Window Handle
            HINSTANCE   hInstance;      // Holds The Instance Of The Application

            bool    keys[256];          // Array Used For The Keyboard Routine
            bool    active;     // Window Active Flag Set To TRUE By Default
            bool    fullscreen; // Fullscreen Flag Set To Fullscreen Mode By Default
            bool    g_bExitThread; // end thread
            GLuint  texture;            // Bitmap image buffer
            int     g_iCounter;     // Current buffer being grabbed to
            bool    g_GLdone;   // Counter to make sure no unnecessary updates are made which cause CPU load
            int xPos;
            int yPos;
            int xPos_right;
            int yPos_right;
            int width;
            int height;
    };

    static std::vector<OGD::OpenGL_Display*> oglDisp;

    void OpenGLDisplay_Wrapper(char* image, int width, int height, bool flip, int bpp, int ID);
    void OpenGLDisplay_Init(int width, int height, int posX, int posY, int ID, LPCSTR className);
    void OpenGLDisplay_MousePos(int&x, int&y, int ID);
};

#endif

OpenGL-Display.cpp:

/** Based on code by NeHe tutorials
    Adapted to display live camera display with OpenGL
*/

#include "OpenGL-Display.h"

using namespace OGD;

OpenGL_Display::OpenGL_Display(int newId)
{
    xPos = -1;
    yPos = -1;
    ID = newId;
    width = 1;
    height = 1;
}

OpenGL_Display::~OpenGL_Display()
{
    KillGLWindow();
}

void OpenGL_Display::Init_Display(int newWidth, int newHeight, int posX, int posY, LPCSTR inputName)
{
    width = newWidth;
    height = newHeight;
    className = inputName;

    if (!CreateGLWindow((char*)className, 24, posX, posY, className))
    {
        throw;
    }   
}

LRESULT CALLBACK OpenGL_Display::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_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_SIZE:                               // Resize The OpenGL Window
        {
            oglDisp.at(0)->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);
}


bool OpenGL_Display::CreateGLWindow(char* title, int bits, int posX, int posY, LPCSTR className)
{
    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

    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 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    = className;                                // Set The Class Name

    RegisterClass(&wc);                                         // Return FALSE

    dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;           // Window Extended Style
    dwStyle=WS_VISIBLE | WS_POPUP | WS_CLIPSIBLINGS | WS_CLIPCHILDREN;;                         // Windows Style

    AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle);     // Adjust Window To True Requested Size
    //HWND hwndC = GetConsoleWindow();
    // Create The Window
    hWnd=CreateWindowEx(    dwExStyle,                          // Extended Style For The Window
                                className,                          // Class Name
                                title,                              // Window Title
                                //WS_OVERLAPPEDWINDOW,
                                dwStyle |                           // Defined Window Style
                                WS_CLIPSIBLINGS |                   // Required Window Style
                                WS_CLIPCHILDREN,                    // Required Window Style
                                posX, posY,                         // 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);

    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
    };

    hDC=GetDC(hWnd);

    PixelFormat=ChoosePixelFormat(hDC,&pfd);

    SetPixelFormat(hDC,PixelFormat,&pfd);

    hRC=wglCreateContext(hDC);

    wglMakeCurrent(hDC,hRC);

    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

    InitGL();

    return TRUE;                                    // Success
}


int OpenGL_Display::LoadGLTextures()                                    // Load Bitmaps And Convert To Textures
{
    // Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit

    glGenTextures(1, &texture);                 // Create The Texture
    // Typical Texture Generation Using Data From The Bitmap
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST); // Minimizing filter, in case display is smaller image size
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST); // Magnifying filter, in case display is smaller image size

    return 1;                                       // Return The Status
}

GLvoid OpenGL_Display::ReSizeGLScene(GLsizei newWidth, GLsizei newHeight)       // Resize And Initialize The GL Window
{
    width = newWidth;
    height = newHeight;
}

int OpenGL_Display::InitGL(GLvoid)                                      // All Setup For OpenGL Goes Here
{
    if (!LoadGLTextures())                              // Jump To Texture Loading Routine
    {
        return FALSE;                                   // If Texture Didn't Load Return FALSE
    }

    return TRUE;                                        // Initialization Went OK
}

void OpenGL_Display::GetMouseCords(int& x, int& y)      // All Setup For OpenGL Goes Here
{
    x = xPos;
    y = yPos;
}

void OpenGL_Display::UpdateGLBuffers(int width, int height, char* imageData, int bpp) {
    glBindTexture(GL_TEXTURE_2D, texture); 
    switch(bpp) {
    case 8:  glTexImage2D(GL_TEXTURE_2D, 0, GL_INTENSITY, width, height, 0, GL_RED, GL_UNSIGNED_BYTE, imageData); break;
    case 16: glTexImage2D(GL_TEXTURE_2D, 0, GL_INTENSITY, width, height, 0, GL_RED, GL_UNSIGNED_SHORT, imageData); break;
    case 24: glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, imageData); break;
    default: return;
    }

    GLenum mError = glGetError();

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
}

int OpenGL_Display::DrawGLScene(bool flip)                                  // Here's Where We Do All The Drawing
{
    if (height==0)                                      // Prevent A Divide By Zero
    {
        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(25.0f,1.0f,0.1f,100.0f);

    glMatrixMode(GL_MODELVIEW);                         // Select The Modelview Matrix
    glLoadIdentity();                                   // Reset The Modelview Matrix

    glEnable(GL_TEXTURE_2D);                            // Enable Texture Mapping
    glShadeModel(GL_SMOOTH);                            // Enable Smooth Shading
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);               // Black Background
    glClearDepth(1.0f);                                 // Depth Buffer Setup
    glDisable(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

    GLenum mError = glGetError();
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
    glLoadIdentity();                                   // Reset The View
    glTranslatef(0.0f,0.0f,-5.0f);
    mError = glGetError();
    glBindTexture(GL_TEXTURE_2D, texture);
    mError = glGetError();
    glColor4f(1.0, 1.0, 1.0, 1.0);
    mError = glGetError();

    if(flip)
    {
        glBegin(GL_QUADS);
            // Front Face
            glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  0.5f);
            glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  0.5f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  0.5f);
            glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  0.5f);
        glEnd();
        mError = glGetError();
    }
    else
    {
        glBegin(GL_QUADS);
            // Front Face
            glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, -1.0f,  0.5f);
            glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, -1.0f,  0.5f);
            glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,  1.0f,  0.5f);
            glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,  1.0f,  0.5f);
        glEnd();
        mError = glGetError();
    }
    mError = glGetError();  
    return TRUE;                                        // Keep Going
}

GLvoid OpenGL_Display::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?
    {
        wglMakeCurrent(NULL,NULL);
        wglDeleteContext(hRC);
        hRC=NULL;                                       // Set RC To NULL
    }

    ReleaseDC(hWnd,hDC);

    DestroyWindow(hWnd);

    UnregisterClass("OpenGL_Display",hInstance);
}

void OpenGL_Display::DrawNewImage(int width, int height, char* imageData, bool flip, int bpp)
{
    BOOL returnVal = wglMakeCurrent(hDC, hRC);

    UpdateGLBuffers(width, height, imageData, bpp); 
    DrawGLScene(flip);
    SwapBuffers(hDC);
    wglMakeCurrent(NULL, NULL);
}

void OGD::OpenGLDisplay_Init(int width, int height, int posX, int posY, int ID, LPCSTR className)
{
    for(unsigned int i = 0; i < oglDisp.size(); ++i) {
        if(oglDisp.at(i)->ID == ID) {
            return;
        }
    }

    oglDisp.push_back(new OGD::OpenGL_Display(ID));
    oglDisp.at(oglDisp.size()-1)->Init_Display(width, height, posX, posY, className); //by default this ID is latest
    wglMakeCurrent(NULL, NULL);
    GLenum mError = glGetError();
}

void OGD::OpenGLDisplay_Wrapper(char* image, int width, int height, bool flip, int bpp, int ID)
{
    for(unsigned int i = 0; i < oglDisp.size(); ++i) {
        if(oglDisp.at(i)->ID == ID) {
            oglDisp.at(i)->DrawNewImage(width, height, image, flip, bpp);   
            return;
        }
    }   
}

Answer 1

Even though your window is OpenGL-based, you should create a message loop and repeatedly call GetMessage, TranslateMessage and DispatchMessage. Handle WM_PAINT even though it doesn't need to draw anything. If you don't do this, Windows will think your application doesn't respond, and shows the busy cursor (or worse, shows the 'Application not responding' dialogue.)