Comment 2 for bug 524567

The way I was thinking this might be implemented is:

When the treeview selection changes, remove the buttons and set fixed-height-mode=true as mpt said, then start a timeout for 0.5s (or however long). Each time the treeview selection changes, reset the timer. Once the timer expires then set fixed-height-mode=false and show the buttons again.

We could possibly do something similar whenever the user grabs a scrollbar, but we need to look into that. There are some potentially relevant signals in GtkWidget, such as "grab-notify" and "grab-broken-event"