this fixes an error with buffer overflow when a user clicks very fast in the preview while a program is running. Fixes #2631

Author: gmoccapy

src/emc/usr_intf/gremlin/gremlin.py

@@ -490,6 +490,13 @@ def select_prime(self, x, y):
 
     @rs274.glcanon.with_context
     def select_fire(self, widget, event):
+        # if program is running, do not update the line:
+        # if the user clicks in the preview, 
+        # Highlighting the line can cause an error with buffer OverflowError
+        #print("DEBUG NORBERT",self.stat.state, linuxcnc.RCS_EXEC)
+        if self.stat.state == linuxcnc.RCS_EXEC:
+            return
+ 
         if not self.select_primed: return
         x, y = self.select_primed
         self.select_primed = None