Adding warning to the openmc-plot-mesh-tally script and ensuring unstructured mesh filters aren't included in the app's combobox.

scripts/openmc-plot-mesh-tally

@@ -2,6 +2,7 @@
 
 """Python script to plot tally data generated by OpenMC."""
 
+
 import os
 import sys
 import argparse
@@ -19,11 +20,18 @@ from matplotlib.figure import Figure
 import matplotlib.pyplot as plt
 import numpy as np
 
-from openmc import StatePoint, MeshFilter
+from openmc import StatePoint, MeshFilter, UnstructuredMesh
 
 _COMBOBOX_SELECTED = '<<ComboboxSelected>>'
 
 
+def mesh_filter_check(filter):
+    """
+    Check that the filter is a usable mesh filter
+    """
+    return isinstance(filter, MeshFilter) and not isinstance(filter.mesh, UnstructuredMesh)
+
+
 class MeshPlotter(tk.Frame):
     def __init__(self, parent, filename):
         super().__init__(parent)
@@ -289,10 +297,17 @@ class MeshPlotter(tk.Frame):
         # Create StatePoint object and read in data
         self.datafile = StatePoint(filename)
 
+        meshes = self.datafile.meshes
+        if any(isinstance(m, UnstructuredMesh) for m in meshes.values()):
+            warn_msg = "Unstructured meshes are present in the" \
+                       " statepoint file but are not currently" \
+                       " supported by this script"
+            messagebox.showwarning("Unstructured Meshes", message=warn_msg)
+
         # Find which tallies are mesh tallies
         self.meshTallies = []
         for itally, tally in self.datafile.tallies.items():
-            if any([isinstance(f, MeshFilter) for f in tally.filters]):
+            if any([mesh_filter_check(f) for f in tally.filters]):
                 self.meshTallies.append(itally)
 
         if not self.meshTallies: