DirectOptionMenu: Fix popup menu reset of the popup marker's pos

Also defines popupMarker_pos and raises an assertion error if #showPopupMenu() is called when no items have been specified.

Fixes #636
Closes #637

direct/src/gui/DirectOptionMenu.py

@@ -22,10 +22,12 @@ class DirectOptionMenu(DirectButton):
             # List of items to display on the popup menu
             ('items',       [],             self.setItems),
             # Initial item to display on menu button
-            # Can be an interger index or the same string as the button
+            # Can be an integer index or the same string as the button
             ('initialitem', None,           DGG.INITOPT),
             # Amount of padding to place around popup button indicator
             ('popupMarkerBorder', (.1, .1), None),
+            # The initial position of the popup marker
+            ('popupMarker_pos', (0, 0, 0), None),
             # Background color to use to highlight popup menu items
             ('highlightColor', (.5, .5, .5, 1), None),
             # Extra scale to use on highlight popup menu items
@@ -42,6 +44,8 @@ class DirectOptionMenu(DirectButton):
         DirectButton.__init__(self, parent)
         # Record any user specified frame size
         self.initFrameSize = self['frameSize']
+        # Record any user specified popup marker position
+        self.initPopupMarkerPos = self['popupMarker_pos']
         # Create a small rectangular marker to distinguish this button
         # as a popup menu button
         self.popupMarker = self.createcomponent(
@@ -168,8 +172,13 @@ class DirectOptionMenu(DirectButton):
         else:
             # Or base it upon largest item
             bounds = [self.minX, self.maxX, self.minZ, self.maxZ]
-        pm.setPos(bounds[1] + pmw/2.0, 0,
-                  bounds[2] + (bounds[3] - bounds[2])/2.0)
+        if self.initPopupMarkerPos:
+            # Use specified position
+            pmPos = list(self.initPopupMarkerPos)
+        else:
+            # Or base the position on the frame size.
+            pmPos = [bounds[1] + pmw/2.0, 0, bounds[2] + (bounds[3] - bounds[2])/2.0]
+        pm.setPos(pmPos[0], pmPos[1], pmPos[2])
         # Adjust popup menu button to fit all items (or use user specified
         # frame size
         bounds[1] += pmw
@@ -184,6 +193,12 @@ class DirectOptionMenu(DirectButton):
         Adjust popup position if default position puts it outside of
         visible screen region
         """
+
+        # Needed attributes (such as minZ) won't be set unless the user has specified
+        # items to display. Let's assert that we've given items to work with.
+        items = self['items']
+        assert items and len(items) > 0, 'Cannot show an empty popup menu! You must add items!'
+
         # Show the menu
         self.popupMenu.show()
         # Make sure its at the right scale