Skip displaying pan/zoom navigate mode in toolbar.

It doesn't add much over the button state and the button tooltip (note
that the state isn't even displayed when the cursor is over an axes, as
the coordinates take precedence), and collides with other possible
end-user customizations of the toolbar (currently, end-users can
override the coordinate string via format_coord, but not the navigate
mode string).

Author: anntzer

lib/matplotlib/backend_bases.py

@@ -3150,15 +3150,11 @@ def _mouse_event_to_message(event):
                             if data_str:
                                 s = s + '\n' + data_str
                 return s
+        return ""
 
     def mouse_move(self, event):
         self._update_cursor(event)
-
-        s = self._mouse_event_to_message(event)
-        if s is not None:
-            self.set_message(s)
-        else:
-            self.set_message(self.mode)
+        self.set_message(self._mouse_event_to_message(event))
 
     def _zoom_pan_handler(self, event):
         if self.mode == _Mode.PAN:
@@ -3189,7 +3185,6 @@ def pan(self, *args):
             self.canvas.widgetlock(self)
         for a in self.canvas.figure.get_axes():
             a.set_navigate_mode(self.mode._navigate_mode)
-        self.set_message(self.mode)
 
     _PanInfo = namedtuple("_PanInfo", "button axes cid")
 
@@ -3245,7 +3240,6 @@ def zoom(self, *args):
             self.canvas.widgetlock(self)
         for a in self.canvas.figure.get_axes():
             a.set_navigate_mode(self.mode._navigate_mode)
-        self.set_message(self.mode)
 
     _ZoomInfo = namedtuple("_ZoomInfo", "direction start_xy axes cid cbar")
 

lib/matplotlib/backend_tools.py

@@ -336,8 +336,6 @@ def send_message(self, event):
 
         from matplotlib.backend_bases import NavigationToolbar2
         message = NavigationToolbar2._mouse_event_to_message(event)
-        if message is None:
-            message = ' '
         self.toolmanager.message_event(message, self)