Try to detect invalid events from pychan.

Sometimes, pychan sends invalid event notifications. It is probably related to changing the gui when the mouse hovers on gui elements. Random tests have given evidence to believe that pychan indicates invalid events by setting the top container's position to 0, 0. Since this position is currently unused, it can serve as invalid flag, and dropping these events seems to lead to the desired placements.

A proper fix would probably be related to this:
http://fife.trac.cvsdude.com/engine/ticket/387

Refs unknown-horizons#1717

horizons/gui/widgets/tooltip.py

@@ -22,10 +22,12 @@
 import textwrap
 from fife import fife
 from fife.extensions import pychan
+
 import horizons.main
 
 from horizons.extscheduler import ExtScheduler
 from horizons.gui.util import load_uh_widget
+from horizons.util import Callback
 
 class _Tooltip(object):
 	"""Base class for pychan widgets overloaded with tooltip functionality"""
@@ -69,6 +71,18 @@ def position_tooltip(self, event):
 		if self.gui is None:
 			self.gui = load_uh_widget('tooltip.xml')
 		widget_position = self.getAbsolutePos()
+
+		# Sometimes, we get invalid events from pychan, it is probably related to changing the
+		# gui when the mouse hovers on gui elements.
+		# Random tests have given evidence to believe that pychan indicates invalid events
+		# by setting the top container's position to 0, 0.
+		# Since this position is currently unused, it can serve as invalid flag,
+		# and dropping these events seems to lead to the desired placements
+		def get_top(w): return get_top(w.parent) if w.parent else w
+		top_pos = get_top(self).position
+		if top_pos == (0, 0):
+			return
+
 		screen_width = horizons.main.fife.engine_settings.getScreenWidth()
 		self.gui.y = widget_position[1] + y + 5
 		if (widget_position[0] + x + self.gui.size[0] + 10) <= screen_width: