Invalidate Tracked Object

When the user clicks an object, the tracker needs to be drawn around the newly selected object. This code invalidates the extra area occupied by the tracker.

To add update hints to OnLButtonDown

• Use ClassView to jump to the implementation of CContainerView::OnLButtonDown and replace the following code:

  Invalidate();    
  pItemHit->m_rect = tracker.m_rect;
  

  with this code:

  pItemHit->InvalidateItem();
  pItemHit->m_rect = tracker.m_rect;
  pItemHit->InvalidateItem();