Step 3: Handling System Messages

After you have created the application window and initialized Microsoft® Direct3D®, you are ready to render the scene. In most cases, Microsoft Windows® applications monitor system messages in their message loop, and they render frames whenever no messages are in the queue. However, the CreateDevice sample project waits until a WM_PAINT message is in the queue, telling the application that it needs to redraw all or part of its window.

// The message loop.
MSG msg; 
while( GetMessage( &msg, NULL, 0, 0 ) )
{
    TranslateMessage( &msg );
    DispatchMessage( &msg );
}

Each time the loop runs, DispatchMessage calls MsgProc, which handles messages in the queue. When WM_PAINT is queued, the application calls Render, the application-defined function that will redraw the window. Then the Microsoft Win32® function ValidateRect is called to validate the entire client area.

The sample code for the message-handling function is shown below.

LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
    switch( msg )
    {
        case WM_DESTROY:
            PostQuitMessage( 0 );
            return 0;

        case WM_PAINT:
            Render();
            ValidateRect( hWnd, NULL );
            return 0;
    }

    return DefWindowProc( hWnd, msg, wParam, lParam );
}

Now that the application handles system messages, the next step is to render the display, as described in Step 4: Rendering and Displaying a Scene.