on.mouse_press = function(x,y, mouse_button)
	print('mouse press', x,y)
	local node_id = to_node(x,y)
	if node_id then
		App.set_clipboard(Nodes[node_id].url)
		Cursor_node = Nodes[node_id]
		return
	end
	-- pan surface
	Pan = {x=Viewport.x+x/Viewport.zoom, y=Viewport.y+y/Viewport.zoom}
end