The Windows Operating System and applications are event-driven. Describe how a Windows application is decoding event...

   

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The Windows Operating System and applications are event-driven. Describe how a Windows application is decoding event messages in its main message procedure WndProc. How does the application decode a WM_COMMAND message to call the DialogBox? Refer to the source code example below. Discuss how such an approach is beneficial for interactive applications. LRESULT CALLBACK WndProc (HWND hWnd, UINT message, WPARAM wParam, LPARAM 1Param) { int wmId, wmEvent; PAINTSTRUCT ps; HDC hdc; switch (message) { case WM_COMMAND: wm Id = LOWORD (wParam); wmEvent = HIWORD (wParam); // Parse the menu selections: switch (wmId) } { case IDM_ABOUT: break; case IDM_EXIT: DialogBox (hInst, MAKEINTRESOURCE (IDD_ABOUTBOX), hwnd, About); DestroyWindow(hWnd); default: break; return DefWindowProc(hWnd, message, wParam, 1Param); } break; case WM_PAINT: hdc = BeginPaint (hWnd, &ps); // TODO: Add any drawing code here... EndPaint (hWnd, &ps); break; case WM_DESTROY: default: } return 0; PostQuitMessage(0); break; return DefWindowProc(hWnd, message, wParam, 1Param); The Windows Operating System and applications are event-driven. Describe how a Windows application is decoding event messages in its main message procedure WndProc. How does the application decode a WM_COMMAND message to call the DialogBox? Refer to the source code example below. Discuss how such an approach is beneficial for interactive applications. LRESULT CALLBACK WndProc (HWND hWnd, UINT message, WPARAM wParam, LPARAM 1Param) { int wmId, wmEvent; PAINTSTRUCT ps; HDC hdc; switch (message) { case WM_COMMAND: wm Id = LOWORD (wParam); wmEvent = HIWORD (wParam); // Parse the menu selections: switch (wmId) } { case IDM_ABOUT: break; case IDM_EXIT: DialogBox (hInst, MAKEINTRESOURCE (IDD_ABOUTBOX), hwnd, About); DestroyWindow(hWnd); default: break; return DefWindowProc(hWnd, message, wParam, 1Param); } break; case WM_PAINT: hdc = BeginPaint (hWnd, &ps); // TODO: Add any drawing code here... EndPaint (hWnd, &ps); break; case WM_DESTROY: default: } return 0; PostQuitMessage(0); break; return DefWindowProc(hWnd, message, wParam, 1Param);