fix #862

Author: doutriaux1

Packages/vcs/Lib/VTKPlots.py

@@ -57,8 +57,14 @@ def setAnimationStepper( self, stepper ):
         plot.setAnimationStepper( stepper )
 
   def interact(self,*args,**kargs):
-      warnings.warn("Press 'Q' to exit interactive mode and continue script execution")
+      if self.renWin is None:
+          warnings.warn("Cannot interact if you did not open the canvas yet")
+          return
       interactor = self.renWin.GetInteractor()
+      if interactor is None:
+          warnings.warn("Cannot start interaction. Blank plot?")
+          return
+      warnings.warn("Press 'Q' to exit interactive mode and continue script execution")
       interactor.Start()
 
   def leftButtonPressEvent(self,obj,event):

testing/vcs/CMakeLists.txt

@@ -33,6 +33,14 @@ add_test(vcs_test_clear_empy_canvas
   ${CMAKE_INSTALL_PREFIX}/bin/python
   ${cdat_SOURCE_DIR}/testing/vcs/test_clear_empty_canvas.py
   )
+add_test(vcs_test_interact_no_open
+  ${CMAKE_INSTALL_PREFIX}/bin/python
+  ${cdat_SOURCE_DIR}/testing/vcs/test_vcs_interact_no_open.py
+  )
+add_test(vcs_test_interact_no_plot
+  ${CMAKE_INSTALL_PREFIX}/bin/python
+  ${cdat_SOURCE_DIR}/testing/vcs/test_vcs_interact_no_plot.py
+  )
 
 add_test(vcs_test_colorcells
   ${CMAKE_INSTALL_PREFIX}/bin/python