This event is triggered when one of the mouse buttons is released on the control. Button identifies the mouse button that 
        triggered the event. Flags describes the state of the [Shift] and [Ctrl] 
        keys, and the mouse buttons. X and Y specify the control client 
        coordinates where the event occurred.
      
          
            | Button Number | 
            Button | 
          
          
            | 1 | 
            Left | 
          
          
            | 2 | 
            Right | 
          
          
            | 4 | 
            Middle | 
          
        
        
      
          
            | Flags bit | 
            Value | 
            Meaning | 
          
          
            | 0 | 
            1 | 
            Left mouse button pressed | 
          
          
            | 1 | 
            2 | 
            Right mouse button pressed | 
          
          
            | 2 | 
             4 | 
             [Shift] key pressed | 
          
          
            | 3 | 
             8 | 
             [Ctrl] key pressed | 
          
          
            | 4 | 
             16 | 
             Middle mouse button pressed |