Speedup the layerview

We were doing a lot of re-calculations that served no purpose (and
even slowed down the rest of the application)

1 files changed, 8 insertions, 2 deletions

diff --git a/plugins/SimulationView/SimulationView.py b/plugins/SimulationView/SimulationView.py
index e7bb88e1ae..72bf1274ea 100644
--- a/plugins/SimulationView/SimulationView.py
+++ b/plugins/SimulationView/SimulationView.py
@@ -90,7 +90,6 @@ class SimulationView(CuraView):
 
         self._global_container_stack = None  # type: Optional[ContainerStack]
         self._proxy = None
-        self._controller.getScene().getRoot().childrenChanged.connect(self._onSceneChanged)
 
         self._resetSettings()
         self._legend_items = None
@@ -109,7 +108,6 @@ class SimulationView(CuraView):
         Application.getInstance().getPreferences().addPreference("layerview/show_skin", True)
         Application.getInstance().getPreferences().addPreference("layerview/show_infill", True)
 
-        Application.getInstance().getPreferences().preferenceChanged.connect(self._onPreferencesChanged)
         self._updateWithPreferences()
 
         self._solid_layers = int(Application.getInstance().getPreferences().getValue("view/top_layer_count"))
@@ -184,6 +182,8 @@ class SimulationView(CuraView):
         return self._nozzle_node
 
     def _onSceneChanged(self, node: "SceneNode") -> None:
+        if node.getMeshData() is None:
+            return
         self.setActivity(False)
         self.calculateMaxLayers()
         self.calculateMaxPathsOnLayer(self._current_layer_num)
@@ -464,6 +464,10 @@ class SimulationView(CuraView):
                 return True
 
         if event.type == Event.ViewActivateEvent:
+            # Start listening to changes.
+            Application.getInstance().getPreferences().preferenceChanged.connect(self._onPreferencesChanged)
+            self._controller.getScene().getRoot().childrenChanged.connect(self._onSceneChanged)
+
             # FIX: on Max OS X, somehow QOpenGLContext.currentContext() can become None during View switching.
             # This can happen when you do the following steps:
             #   1. Start Cura
@@ -510,6 +514,8 @@ class SimulationView(CuraView):
             self._composite_pass.setCompositeShader(self._simulationview_composite_shader)
 
         elif event.type == Event.ViewDeactivateEvent:
+            self._controller.getScene().getRoot().childrenChanged.disconnect(self._onSceneChanged)
+            Application.getInstance().getPreferences().preferenceChanged.disconnect(self._onPreferencesChanged)
             self._wireprint_warning_message.hide()
             Application.getInstance().globalContainerStackChanged.disconnect(self._onGlobalStackChanged)
             if self._global_container_stack: