Fix persistent tree view palettes

A rework of the TreeViewInvoker used by the journal and activity list.

Fixes a persistent journal entry palette that reappears in journal or
home view.  https://bugs.sugarlabs.org/ticket/4918

Also fixes an over-sensitive journal icon; with the journal mostly
empty, rapidly move the mouse from the bottom of the screen into the
lowest icon and then out again.  Before this patch, the palette was
shown.  After this patch, the mouse must rest in the icon.

Changes made:

- override _ensure_palette_exists in parent class Invoker,

- remove reference to MouseSpeedDetector, it is no longer required,

- remove enter and leave events; they are for the TreeView as a whole,
  and are not required,

- properly detect that None is returned by get_path_at_pos, when the
  coordinates are outside the TreeView cells.

Not fixed:

- moving the mouse out of the journal icon invoker does not popdown the
  palette, but it does when moving the mouse out of the activity icon in
  the activity list; so this is a problem beyond the invoker,

Tested on Fedora 18 and Ubuntu 15.10.

Test cases:

- check a click will activate item,

- check a right-click will show palette,

- check a mouse hover will show palette,

- check a brief mouse passing will not show palette,

- check if mouse leaving palette will popdown.

src/sugar3/graphics/palettewindow.py

@@ -1411,15 +1411,12 @@ class TreeViewInvoker(Invoker):
 
         self._tree_view = None
         self._motion_hid = None
-        self._leave_hid = None
         self._release_hid = None
         self._long_pressed_hid = None
         self._position_hint = self.AT_CURSOR
 
         self._long_pressed_controller = SugarGestures.LongPressController()
 
-        self._mouse_detector = MouseSpeedDetector(200, 5)
-
         self._tree_view = None
         self._path = None
         self._column = None
@@ -1431,10 +1428,6 @@ class TreeViewInvoker(Invoker):
 
         self._motion_hid = tree_view.connect('motion-notify-event',
                                              self.__motion_notify_event_cb)
-        self._enter_hid = tree_view.connect('enter-notify-event',
-                                            self.__enter_notify_event_cb)
-        self._leave_hid = tree_view.connect('leave-notify-event',
-                                            self.__leave_notify_event_cb)
         self._release_hid = tree_view.connect('button-release-event',
                                               self.__button_release_event_cb)
         self._long_pressed_hid = self._long_pressed_controller.connect(
@@ -1443,19 +1436,14 @@ class TreeViewInvoker(Invoker):
             tree_view,
             SugarGestures.EventControllerFlags.NONE)
 
-        self._mouse_detector.connect('motion-slow', self.__mouse_slow_cb)
-        self._mouse_detector.parent = tree_view
         Invoker.attach(self, tree_view)
 
     def detach(self):
         Invoker.detach(self)
         self._tree_view.disconnect(self._motion_hid)
-        self._tree_view.disconnect(self._enter_hid)
-        self._tree_view.disconnect(self._leave_hid)
         self._tree_view.disconnect(self._release_hid)
         self._long_pressed_controller.detach(self._tree_view)
         self._long_pressed_controller.disconnect(self._long_pressed_hid)
-        self._mouse_detector.disconnect_by_func(self.__mouse_slow_cb)
 
     def get_rect(self):
         return self._tree_view.get_background_area(self._path, self._column)
@@ -1464,25 +1452,27 @@ class TreeViewInvoker(Invoker):
         return self._tree_view.get_toplevel()
 
     def __motion_notify_event_cb(self, widget, event):
-        try:
-            path, column, x_, y_ = self._tree_view.get_path_at_pos(
-                int(event.x), int(event.y))
-            if path != self._path or column != self._column:
-                self._redraw_cell(self._path, self._column)
-                self._redraw_cell(path, column)
-
-                self._path = path
-                self._column = column
-
-                if self.palette is not None:
-                    self.palette.popdown(immediate=True)
-                    self.palette = None
-
-                self._mouse_detector.start()
-        except TypeError:
-            # tree_view.get_path_at_pos() fail if x,y poition is over
-            # a empty area
-            pass
+        here = self._tree_view.get_path_at_pos(int(event.x), int(event.y))
+        if here is None:
+            if self._path is not None:
+                self.notify_mouse_leave()
+            self._path = None
+            self._column = None
+            return
+
+        path, column, x_, y_ = here
+        if path != self._path or column != self._column:
+            self._redraw_cell(self._path, self._column)
+            self._redraw_cell(path, column)
+
+            self._path = path
+            self._column = column
+
+            if self.palette is not None:
+                self.palette.popdown(immediate=True)
+                self.palette = None
+
+            self.notify_mouse_enter()
 
     def _redraw_cell(self, path, column):
         area = self._tree_view.get_background_area(path, column)
@@ -1490,15 +1480,12 @@ class TreeViewInvoker(Invoker):
             self._tree_view.convert_bin_window_to_widget_coords(area.x, area.y)
         self._tree_view.queue_draw_area(x, y, area.width, area.height)
 
-    def __enter_notify_event_cb(self, widget, event):
-        self._mouse_detector.start()
-
-    def __leave_notify_event_cb(self, widget, event):
-        self._mouse_detector.stop()
-
     def __button_release_event_cb(self, widget, event):
         x, y = int(event.x), int(event.y)
-        path, column, cell_x, cell_y = self._tree_view.get_path_at_pos(x, y)
+        here = self._tree_view.get_path_at_pos(x, y)
+        if here is None:
+            return False
+        path, column, cell_x, cell_y = here
         self._path = path
         self._column = column
         if event.button == 1:
@@ -1512,10 +1499,9 @@ class TreeViewInvoker(Invoker):
                 cellrenderer.emit('clicked', path)
             # So the treeview receives it and knows a drag isn't going on
             return False
-        if event.button == 3:
+        elif event.button == 3:
             # right mouse button
-            self._mouse_detector.stop()
-            self._change_palette()
+            self._ensure_palette_exists()
             self.notify_right_click(event.x_root, event.y_root)
             return True
         else:
@@ -1525,15 +1511,10 @@ class TreeViewInvoker(Invoker):
         path, column, x_, y_ = self._tree_view.get_path_at_pos(x, y)
         self._path = path
         self._column = column
-        self._change_palette()
+        self._ensure_palette_exists()
         self.notify_right_click(x, y)
 
-    def __mouse_slow_cb(self, widget):
-        self._mouse_detector.stop()
-        self._change_palette()
-        self.emit('mouse-enter')
-
-    def _change_palette(self):
+    def _ensure_palette_exists(self):
         if hasattr(self._tree_view, 'create_palette'):
             self.palette = self._tree_view.create_palette(
                 self._path, self._column)