title: Self-expanding Widget, on mouse over
body: <p>I want to implement a widget (with some edit boxes and sliders) that would open beneath or next to a button ("Opener") when I hover it. The key is it's a temporary widget - as soon as it loses focus, I want it gone. Also, I want it to pop up right next to the Opener, ideally pointing an arrow to Opener.</p>
  
  <p>So, it's basically a tooltip. But it needs to be a widget with buttons and sliders and stuff like that. Is there a clever way to implement it without making a custom widget and writing handlers for all the mouse and focus events and recomputing its ideal position every time I open it or the Opener moves?</p>