Position palette based on event coords, fixes #4897

Instead of getting the position of the mouse later in the code,
this commit uses the coords given to sugar by Gtk that say where
the event happened.  This means that if the system is busy, or
the user is fast with the mouse, the palette will pop up where
they originally clicked.

src/sugar3/graphics/palettewindow.py

@@ -1008,14 +1008,33 @@ class Invoker(GObject.GObject):
     def notify_mouse_leave(self):
         self.emit('mouse-leave')
 
-    def notify_right_click(self):
+    def notify_right_click(self, x=None, y=None):
+        '''
+        Notify the palette invoker of a right click and expand the
+        palette as required.  The x and y args should be that of
+        where the event happened, relative to the root of the screen.
+
+        Args
+            x (float): the x coord of the event relative to the root
+                of the screen, eg. :class:`Gdk.EventTouch.x_root`
+            y (float): the y coord of the event relative to the root
+                of the screen, eg. :class:`Gdk.EventTouch.y_root`
+        '''
         self._ensure_palette_exists()
+        self._process_event(x, y)
         self.emit('right-click')
 
     def notify_toggle_state(self):
         self._ensure_palette_exists()
         self.emit('toggle-state')
 
+    def _process_event(self, x, y):
+        if x is None or y is None:
+            return
+
+        self._cursor_x = x
+        self._cursor_y = y
+
     def get_palette(self):
         return self._palette
 
@@ -1231,14 +1250,14 @@ class WidgetInvoker(Invoker):
             if self.props.toggle_palette:
                 self.notify_toggle_state()
         elif event.button == 3:
-            self.notify_right_click()
+            self.notify_right_click(event.x_root, event.y_root)
             return True
         else:
             return False
 
     def __long_pressed_event_cb(self, controller, x, y, widget):
         self._long_pressed_recognized = True
-        self.notify_right_click()
+        self.notify_right_click(x, y)
 
     def get_toplevel(self):
         return self._widget.get_toplevel()
@@ -1348,14 +1367,14 @@ class CursorInvoker(Invoker):
             if self.props.toggle_palette:
                 self.notify_toggle_state()
         if event.button == 3:
-            self.notify_right_click()
+            self.notify_right_click(event.x_root, event.y_root)
             return True
         else:
             return False
 
     def __long_pressed_event_cb(self, controller, x, y, widget):
         self._long_pressed_recognized = True
-        self.notify_right_click()
+        self.notify_right_click(x, y)
 
     def get_toplevel(self):
         return self._item.get_toplevel()
@@ -1497,7 +1516,7 @@ class TreeViewInvoker(Invoker):
             # right mouse button
             self._mouse_detector.stop()
             self._change_palette()
-            self.notify_right_click()
+            self.notify_right_click(event.x_root, event.y_root)
             return True
         else:
             return False
@@ -1507,7 +1526,7 @@ class TreeViewInvoker(Invoker):
         self._path = path
         self._column = column
         self._change_palette()
-        self.notify_right_click()
+        self.notify_right_click(x, y)
 
     def __mouse_slow_cb(self, widget):
         self._mouse_detector.stop()