Issue a warning on discrete data

Author: ajdapretnar

Orange/widgets/visualize/owheatmap.py

@@ -692,7 +692,11 @@ def set_column_split_var(self, var: Optional[Variable]):
     def update_heatmaps(self):
         if self.data is not None:
             self.clear_scene()
-            self.clear_messages()
+            self.Error.clear()
+            self.Warning.clear()
+            self.Information.row_clust.clear()
+            self.Information.col_clust.clear()
+            self.Information.sampled.clear()
             if self.col_clustering != Clustering.None_ and \
                     len(self.data.domain.attributes) < 2:
                 self.Error.not_enough_features()

Orange/widgets/visualize/tests/test_owheatmap.py

@@ -72,6 +72,9 @@ def test_information_message(self):
         self.assertFalse(self.widget.Information.active)
         self.send_signal(self.widget.Inputs.data, data[:21])
         self.assertTrue(self.widget.Information.active)
+        data = Table("heart_disease.tab")[:10]
+        self.send_signal(self.widget.Inputs.data, data)
+        self.assertTrue(self.widget.Information.discrete_ignored.is_shown())
 
     def test_settings_changed(self):
         self.send_signal(self.widget.Inputs.data, self.data)