I am trying to check if the window is how much obscured by other windows. But the code always return the same value

Question

I am using this code its simple code but for some reason it always returning the partially covered despite the windows is fully covered or uncovered.

I am using this in the EnumWindows

  HDC hdc = GetDC(hWnd);
    if (hdc) {
        RECT rcClip, rcClient;
    
        switch (GetClipBox(hdc, &rcClip)) {
        case NULLREGION:
            LOGGER->info("completely covered"); break;
        case SIMPLEREGION:
            GetClientRect(hWnd, &rcClient);
            if (EqualRect(&rcClient, &rcClip)) {
                LOGGER->info("completely uncovered");
            }
            else {
                LOGGER->info("partially covered");
            }
            break;
        case COMPLEXREGION:
            LOGGER->info("partially covered");
            break;
        default:
            LOGGER->info("no result");
        }
    }