Keep Window Open

Question

Running C++, OpenGL and graphics output with Visual Studio.

Running OpenGL with a graphics window, when I execute, the window immediately closes at the program end before I can see what is happening. How does one keep the window open that has been created until ready to close, Sid Kraft

Answer 1

Need to re-phrase, using the glutInit function in OpenGL, C++, Sid Kraft

Answer 2

Keep the app alive by running the Windows message loop until the window is closed. In a Windows desktop app, the program stays in its while loop until the user closes the window and exits the application.

For closing behavior:

• When the user clicks Close or presses Alt+F4, the window receives WM_CLOSE.
• If WM_CLOSE is not handled, DefWindowProc destroys the window by default.
• When the window is being destroyed, it receives WM_DESTROY.
• In the main window, handle WM_DESTROY by calling PostQuitMessage(0), which posts WM_QUIT and ends the message loop.

Typical pattern:

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE, PWSTR, int nCmdShow)
{
    // register class, create window, show window...

    MSG msg = {};
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return 0;
}

If confirmation is needed before closing, handle WM_CLOSE and call DestroyWindow(hwnd) only when ready:

case WM_CLOSE:
    if (MessageBox(hwnd, L"Really quit?", L"My application", MB_OKCANCEL) == IDOK)
    {
        DestroyWindow(hwnd);
    }
    return 0;

For an OpenGL window specifically, create the rendering context during window creation and release it when the window is closed, after making the rendering context not current.

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• Closing the Window
• Module 1. Your First Windows Program
• Creating a Rendering Context and Making It Current
• Deleting a Rendering Context