title: Form background transparency but still have click events
body: <p>I have been trying to work out if this is possible.</p>
  
  <p>Essentially what I want is to have a form with a border as normal but with a transparent background.  In this area I want a live display of what's behind (a video feed is highly likely) into which I can capture the click events to display further information onto my overly form.</p>
  
  <p>Currently I have tried to use Form.TransparencyKey and BackColor but I then lose the click events in the transparent sections of the from.  I have also attempted to use a 99% transparent png as the BackgroundImage, but this just gives a dark gray background.</p>
  
  <p>I have noted if I draw to the gap (ie a simple line) I can capture the click events over these, just not the transparent sections.  Is there way I could draw a semi transparent rectangle in the on paint first maybe?</p>
  
  <p>I would like this to be mono compatible if at all possible.</p>