title: Make a non-rectangular area draggable
body: <p>To make a widget draggable, it has to be passed to a <a href="https://api.flutter.dev/flutter/widgets/Draggable-class.html" rel="nofollow noreferrer">Draggable</a> like so:</p>
  <pre><code>                 Draggable&lt;String&gt;(
                      data:  &quot;SomeDateToBeDragged&quot;,
                      child: Container(
                        width: 300,
                        height: 200,
                        alignment: Alignment.center,
                        color: Colors.purple,
                        child: Image.network(
                          'https://someServer.com/dog.jpg',
                          fit: BoxFit.cover,
                        ),
                      ),
                      ...
  </code></pre>
  <p>As far as I know, a Widget is something rectangular. At least, I found nothing else than rectangular widgets.</p>
  <p>I'd like to build a sketching app. Thus, I'd like to make a 'two dimensional' connector [a Line between two points] draggable.</p>
  <p><strong>How to I make a line draggable?</strong></p>
  <p>In other words: I'd like to make a click initiate a drag only if the drag e.g. is on a painted area and not on transparent background of the area. If I would draw a circle, it would drag if the circle would be clicked. If clicked some pixel outside the circle, it should not start a drag.</p>