qtvcp -qt5_graphics: allow magic comments notify to print to terminal

(PREVIEW,notify, some test) in gcode should print the text.
Most of the code was present but at the time I didn't inderstand
what the code was used for. Now it will print to the terminal.
It could be overriden in gcode_graphics.py to do something else,
thought I'm not sure what it is really useful for - debugging?
it only prints when the gcode is loaded.

src/emc/usr_intf/gremlin/qt5_graphics.py

@@ -170,11 +170,15 @@ def check_abort(self):
     def next_line(self, st):
         glcanon.GLCanon.next_line(self, st)
         self.progress.update(self.lineno)
-        # not sure if this is used - copied from AXIS code
         if self.notify:
-            print("info",self.notify_message)
+            self.output_notify_message(self.notify_message)
             self.notify = 0
 
+    # this is class patched
+    # output the text from the magic comment eg: (PREVEIW,notify,The text)
+    def output_notify_message(self, message):
+        pass
+
 ###############################
 # widget for graphics plotting
 ###############################
@@ -344,6 +348,7 @@ def load(self,filename = None):
 
         lines = open(filename).readlines()
         progress = Progress(2, len(lines))
+        # monkey patch function to call ours
         progress.emit_percent = self.emit_percent
 
         code = []
@@ -371,6 +376,8 @@ def load(self,filename = None):
                                 self.lathe_option,
                                 s, text, random, i,
                                 progress, arcdivision)
+            # monkey patched function to call ours
+            canon.output_notify_message = self.output_notify_message
             parameter = self.inifile.find("RS274NGC", "PARAMETER_FILE")
             temp_parameter = os.path.join(td, os.path.basename(parameter or "linuxcnc.var"))
             if parameter:
@@ -397,6 +404,11 @@ def load(self,filename = None):
                 pass
         self._redraw()
 
+    # monkey patched function from StatCanon class
+    def output_notify_message(self, message):
+        print("Preview Notify:", message)
+
+    # monkey patched function from Progess class
     def emit_percent(self, percent):
         self.percentLoaded.emit(percent)