title: Make a transparent hole in a QT application
body: <p>I've got a problem where I've got 2 Qt applications on top of eachother. The top Qt application needs a transparant hole in it to show the Qt application behind it. Is there any way to do this? or is there an example somewhere in the Qt library which could help me?</p>
  <p><strong>To clarify,</strong> if I'd run the Qt application on a Windows machine I would like to see my desktop background through the transparent hole.</p>
  <p>I did find the windowOpacity property. Unfortunately this property changes the opacity of the entire application, and not just a part of the application.</p>
  <p><em><strong>Why would you ever need 2 Qt applications? Just draw them in the same Application?</strong></em>
  This is not a possibility for this project because of security reasons the applications <strong>need</strong> to be seperate. To seperate the two applications there is only limited communication between the two and can not use the same QT application.</p>
  <p>Edit: Since my question got deleted because it is not clear enough, here are 3 examples of what I am trying to achieve.</p>
  <p><strong>Example 1</strong>: Here you can see how I would like application 1 to be shown. 2 squares, 1 big square (the blue one) which is not transparent and a second square (the white one) inside the first square which is transparent (it's hard to show transparency in a picture).</p>
  <p><a href="https://i.stack.imgur.com/KeMk1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KeMk1.png" alt="Example 1" /></a></p>
  <p><strong>Example 2</strong>: Here you can see how I would like both applications to be shown. Behind the transparent square the second application is shown. When they allign perfectly there is not much to see, it just looks like 2 applications drawn over eachother.</p>
  <p><a href="https://i.stack.imgur.com/C1sIG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/C1sIG.png" alt="Example 2" /></a></p>
  <p><strong>Example 3</strong>: Here you can see how the applications should interact when the second application is not aligned in the right way. The second application can only be seen through the transparent section of the first application.</p>
  <p><a href="https://i.stack.imgur.com/qmNqZ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qmNqZ.png" alt="Example 3" /></a></p>
  <p>To repeat my original question once again:
  <em>Is it possible to create an Qt application with a see through hole?</em></p>
  <p>And my follow up:
  <em>Are there any examples in the Qt library or any other place where this is implemented?</em></p>