title: Resize and reposition window to span all monitors
body: <p>Hi all I am working on a small cross-platform hobby/educational project which takes screenshot of all monitors and overlays all monitors with one wide window. Now on Windows and GTK systems this is no problem. But I am having issues on OSX:</p>
  
  <ol>
  <li>First major issue is that the window is not covering the non-work areas of the dock and the menubar at top.</li>
  <li>It won't resize to span multiple monitors.</li>
  </ol>
  
  <p>Is there any programattic way to accomplish this? Users really like when a screenshot is taken that it overlays all monitors with the capture and then they crop and click upload to image service etc. I just want to bring them the same experience on OSX.</p>
  
  <p>Thanks</p>