avoid uncommanded palettes

Problem #1, buddy menu appears on Sugar startup on physical hardware, or
when mouse is centre of display.

Problem #2, Terminal toolbar steals keyboard focus, when mouse is left
in home view search box at activity start time.

Regressions were introduced in the port from Gtk2 to Gtk3.

Cause is enter-notify-events that arrive because cursor is already
present in widgets as they are realised and mapped.

Fix is to capture cursor position when the widget is being created, and
ignore enter-notify-event if the same position is seen.

src/sugar3/graphics/palettewindow.py

@@ -1111,6 +1111,7 @@ class WidgetInvoker(Invoker):
 
         self._widget = None
         self._expanded = False
+        self._pointer_position = (-1, -1)
         self._enter_hid = None
         self._leave_hid = None
         self._release_hid = None
@@ -1130,6 +1131,8 @@ class WidgetInvoker(Invoker):
         else:
             self._widget = parent
 
+        self._pointer_position = _get_pointer_position(self._widget)
+
         self.notify('widget')
 
         self._enter_hid = self._widget.connect('enter-notify-event',
@@ -1206,6 +1209,9 @@ class WidgetInvoker(Invoker):
                                  gap[0], gap[1], gap[1] + gap[2])
 
     def __enter_notify_event_cb(self, widget, event):
+        if (event.x_root, event.y_root) == self._pointer_position:
+            self._pointer_position = (-1, -1)
+            return False
         if event.mode == Gdk.CrossingMode.NORMAL:
             self.notify_mouse_enter()
 
@@ -1297,6 +1303,7 @@ class CursorInvoker(Invoker):
         Invoker.__init__(self)
 
         self._position_hint = self.AT_CURSOR
+        self._pointer_position = (-1, -1)
         self._enter_hid = None
         self._leave_hid = None
         self._release_hid = None
@@ -1312,6 +1319,9 @@ class CursorInvoker(Invoker):
         Invoker.attach(self, parent)
 
         self._item = parent
+
+        self._pointer_position = _get_pointer_position(self.parent)
+
         self._enter_hid = self._item.connect('enter-notify-event',
                                              self.__enter_notify_event_cb)
         self._leave_hid = self._item.connect('leave-notify-event',
@@ -1346,6 +1356,9 @@ class CursorInvoker(Invoker):
         return rect
 
     def __enter_notify_event_cb(self, button, event):
+        if (event.x_root, event.y_root) == self._pointer_position:
+            self._pointer_position = (-1, -1)
+            return False
         if event.mode == Gdk.CrossingMode.NORMAL:
             self.notify_mouse_enter()
         return False