title: OS X: How to pass mouse drag events through a view to superview
body: <p>I am building an app using Swift for OS X where I have a <code>NSTabView</code> that I can drag images into.  For each image that is dragged in, it adds a new tab and the <code>NSTabViewItem</code> contains a <code>NSImageView</code> that holds the <code>NSImage</code> that was dragged in.</p>
  
  <p>I created a subclass of the <code>NSTabView</code> class that handles the drag operations.</p>
  
  <p>I have the code working where it is taking the dragged images and creating the new tabs correctly.  However, once there is an <code>NSImageView</code> showing (after dragging in), now, when dragging new images, it appears the <code>NSImageView</code> is blocking the dragging information and does not receive the drag operation. Therefore, I can only drag new images if i put them at the edge just over the <code>NSImageView</code> showing the previously dragged image.</p>
  
  <p>Is there a way to make the <code>NSImageView</code> transparent to the mouse drag events so that they pass through to the <code>NSTabView</code> below?</p>
  
  <p>I have tried setting <code>NSImageView.enabled</code> to false, and also trying to override the <code>hitTest</code> of the <code>NSImageView</code>.  But none of these seem to be working.</p>