Providing visual feedback for clickable regions

[Johannes Zarl-Zierl]

Hi!

In KPhotoAlbum, we have a map view where the user can select images based on 
their locations. Instead of displaying all images at all times, we are 
clustering the images and showing one clickable rectangle per cluster instead 
of individual images depending on the zoom level.

Technically, our map view subclasses Marble::LayerInterface in order to draw 
the clusters onto the map.

So far, so good. The trouble begins when I try to change the mouse-cursor so 
that the user is provided with visual feedback whenever the mouse hovers over 
one of the selectable regions.

Studying the api.kde.org and the tutorials on community.kde.org I don't see 
how I could implement the behaviour described above.

What's the best way to implement this? Was I wrong in using the 
LayerInterface-approach? If so, how should I go about implementing this?

Cheers,
  Johannes


P.S.: Going slightly off-topic to my own question: did I, by any chance, 
implement the clustering part in vain and does marble provide some clustering 
algorithm out of the box?