2006-04-26  Kristian Rietveld  <kris@imendio.com>

	* gtk/gtktreeview.c (node_is_visible): new function,
	(validate_visible_area): when a node is validated, only queue a
	redraw for that node, not for the entire widget (a redraw for the
	entire widget is only needed when the sizes change, and
	_queue_resize() will take care of that),
	(do_validate_rows): do not queue a redraw, redraws are only needed
	for changes in the visible area and validate_visible_area() takes
	care of that,
	(gtk_tree_view_row_inserted): for fixed height mode, only queue
	a resize and redraw if the node is visible, else no redraw is needed.