enable the first toolpath processor after program initialization

Otherwise the "last" (based on the order of plugin initialization) toolpath
processor is selected. The load order is arbitrary - thus the initial processor
selection not determined. (we don't like this)

pycam/Gui/Project.py

@@ -640,6 +640,7 @@ class ProjectGui(object):
             # register a logging handler for displaying error messages
             pycam.Utils.log.add_gtk_gui(self.window, logging.ERROR)
             self.window.show()
+        self.settings.emit_event("notify-initialization-finished")
 
     def update_all_controls(self):
         self.update_ode_settings()

pycam/Plugins/ToolpathProcessors.py

@@ -136,6 +136,8 @@ class ToolpathProcessors(pycam.Plugins.ListPluginBase):
             self._event_handlers = (
                     ("toolpath-processor-list-changed", self._update_processors),
                     ("toolpath-selection-changed", self._update_visibility),
+                    ("notify-initialization-finished",
+                            self._activate_first_processor),
             )
             self.register_event_handlers(self._event_handlers)
             self._update_processors()
@@ -148,6 +150,13 @@ class ToolpathProcessors(pycam.Plugins.ListPluginBase):
         self.unregister_event_handlers(self._event_handlers)
         self.core.get("unregister_parameter_group")("toolpath_processor")
 
+    def _activate_first_processor(self):
+        # run this action as soon as all processors are registered
+        processors = self.core.get("get_parameter_sets")("toolpath_processor").values()
+        processors.sort(key=lambda item: item["weight"])
+        if processors:
+            self.select(processors[0])
+
     def get_selected(self):
         all_processors = self.core.get("get_parameter_sets")("toolpath_processor")
         current_name = self._proc_selector.get_value()