C / C++ / MFC

do
{
    if ( ! ::GetMessage( &msg, 0, 0, 0 ) )
        break;
    if ( ::CallMsgFilter( &msg, MSGF_SCROLLBAR ) )
        continue;
    pt = msg.pt;
    ::ScreenToClient(m_hWnd,&pt);
    if (msg.message == WM_LBUTTONUP)
        HandleMouseUp(pt);
    else if (msg.message == WM_MOUSEMOVE)
        HandleMouseMove(pt);
    else if (msg.message == WM_TIMER)
    {
        if ( bFirstRun )
        {
            // prevent a single click acting like a hold
            bFirstRun = false;
            // cause a 500ms pause before acting on mouse hold
            for ( int i=0; i<50; i++ )
            {
                ::Sleep(10);
                MSG peek;
                if ( PeekMessage(&peek,m_hWnd,WM_LBUTTONUP,WM_LBUTTONUP,FALSE) )
                    break;
            }
            continue;
        }
        HandleMouseDown(pt);
    }
    else
    {
        ::TranslateMessage( &msg );
        ::DispatchMessageW( &msg );
    }
} while ( msg.message != WM_LBUTTONUP );