In mousewheel event, do horizontal scroll when no vertical scroll is available in a gtkscrolledwindow
Submitted by Nelson Benítez León
Hi!, nautilus has recently added a "compact view" that is like traditional icon view but it has no vertical scrollbar, instead the icons are spread horizontally so the horizontal scrollbar is in most cases present. We have a request in nautilus (bug 555571) that the compact view could be scrolled horizontally with the mouse wheel, this is a common sense behaviour because there's no vertical scroll available, so the mousewheel should do a horizontal scroll instead.
As nautilus uses GtkScrolledWindow for the compact view, I'm attaching a patch here, and also because imho this behaviour should be default in any GtkScrolledWindow, that is, make the mouse wheel do horizontal scroll when no vertical scroll is available.