Fix synchronization issue in Vizrank(s)

When the widget received e.g. new data, it called `initialize`,
which set `keep_running` to `False` and the `saved_state` to `None`.
When `run` stopped (a bit later), it saved the current state to
`saved_state`, overriding `None` set by `initialize`.

Author: janezd

Orange/widgets/visualize/owmosaic.py

@@ -343,7 +343,7 @@ def set_data(self, data):
             self.bar_button.setDisabled(not disc_class)
         self.interior_coloring = \
             self.CLASS_DISTRIBUTION if disc_class else self.PEARSON
-        self.vizrank.initialize()
+        self.vizrank.stop_and_reset()
         self.vizrank_button.setEnabled(
             self.data is not None and self.data.domain.class_var is not None
             and len(self.data.domain.attributes) >= 1 and len(self.data) > 1)
@@ -377,7 +377,7 @@ def clear_selection(self):
         self.send_selection()
 
     def coloring_changed(self):
-        self.vizrank.initialize()
+        self.vizrank.stop_and_reset()
         self.update_graph()
 
     def reset_graph(self):

Orange/widgets/visualize/utils/__init__.py

@@ -90,6 +90,7 @@ def __init__(self, master):
         self.master = master
 
         self.keep_running = False
+        self.schedule_initialize = False
         self.saved_state = None
         self.saved_progress = 0
         self.scores = []
@@ -168,13 +169,21 @@ def initialize(self):
         e.g. from `set_data` handler.
         """
         self.keep_running = False
+        self.schedule_initialize = False
         self.saved_state = None
         self.saved_progress = 0
         self.scores = []
         self.rank_model.clear()
         self.button.setText("Start")
         self.button.setEnabled(self.check_preconditions())
 
+    def stop_and_reset(self):
+        if self.keep_running:
+            self.schedule_initialize = True
+            self.keep_running = False
+        else:
+            self.initialize()
+
     def check_preconditions(self):
         """Check whether there is sufficient data for ranking."""
         return True
@@ -245,9 +254,12 @@ def run(self):
             progress.advance(self.saved_progress)
             for state in self.iterate_states(self.saved_state):
                 if not self.keep_running:
-                    self.saved_state = state
-                    self.saved_progress = progress.count
-                    self._select_first_if_none()
+                    if self.schedule_initialize:
+                        self.initialize()
+                    else:
+                        self.saved_state = state
+                        self.saved_progress = progress.count
+                        self._select_first_if_none()
                     return
                 score = self.compute_score(state)
                 if score is not None: