Created attachment 251092 [details] [review]
paned: minus the size by the handle for the for_child1 computation.

I wonder if there could be side effects on child1 size allocated (ie I clamp it to a smaller size... we might want to make this conditional to when child2 cannot hold the handle size).

Fixes:
    (rhythmbox:22802): Gtk-CRITICAL **:
    _gtk_widget_get_preferred_size_for_size: assertion 'size >= -1' failed
    
    that is gtk_paned_get_preferred_size_for_opposite_orientation calls
    _gtk_widget_get_preferred_size_for_size on child2 with a negative
    size.
    
    As gtkpaned size was (32), child1 minimum size was (55) then
    for_child1 became (32) for an handle_size of (5). Thus for_child2
    ended up as (-5).