<ul>
<li>if the mouse is over a selected region, or no region, use all selected
regions, or</li>
<li>if the mouse is over an unselected region, use just that region.</li>
</ul>
</li>
<ul>
<li>if the mouse is over a selected region, or no region, use all selected
regions, or</li>
<li>if the mouse is over an unselected region, use just that region.</li>
</ul>
</li>