Creating Borderless Windows with Aero Features in QT/C

Achieving a borderless window in Windows comes with limitations, such as lacking Aero shadow, snap, minimization animation, and shake. To overcome this challenge, we can leverage the power of Spy and the DWMAPI calls.

Handling WM_NCCALCSIZE Message

To hide the window's border, intercept the WM_NCCALCSIZE message in the WindowProc:

case WM_NCCALCSIZE: {
    if (window->is_borderless) {
        return 0;
    } else {
        return DefWindowProc(hwnd, msg, wparam, lparam);
    }
}

Enabling Aero Shadow

To add an Aero shadow, use the DwmExtendFrameIntoClientArea function:

MARGINS borderless = {1,1,1,1};
DwmExtendFrameIntoClientArea(hwnd, &borderless);

Adding Aero Snap, Maximizing, and Minimizing

For these features to work, the window style should include:

WS_POPUP | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX | WS_CAPTION

Caution Regarding Alpha Channel Transparency

When using DwmExtendFrameIntoClientArea, a small frame may be visible through transparent elements in the client area. Consider using a non-transparent background or brush.

Example Project

A simple project demonstrates the use of these techniques. Pressing F11 toggles between borderless and windowed mode, while F12 toggles the Aero shadow on and off.

Conclusion

By implementing these steps and leveraging the DWMAPI, it is possible to create borderless windows in QT/C with the desired Aero features. This provides a seamless and enhanced user experience for your applications.