Optimize layer heights cache in SimulationView

Added logic to track which node's layer heights are cached and only recalculate the cache if the data source changes. This improves performance by avoiding unnecessary recalculations and ensures cache validity when the scene changes.

plugins/SimulationView/SimulationView.py

@@ -103,6 +103,7 @@ class SimulationView(CuraView):
 
         # Cache for layer heights to avoid recalculating on every query
         self._layer_heights_cache: dict[int, float] = {}
+        self._layer_heights_cache_node_id: Optional[int] = None  # Track which node's data is cached
 
         self._global_container_stack: Optional[ContainerStack] = None
         self._proxy = None
@@ -298,8 +299,8 @@ class SimulationView(CuraView):
         This method iterates through all layers once and stores their heights in a cache.
         Handles both sliced data (microns) and loaded gcode (millimeters).
         For layer 0 from gcode, uses thickness instead of height due to incorrect Z coordinates.
+        Only recalculates if the layer data source has changed.
         """
-        self._layer_heights_cache.clear()
         scene = self.getController().getScene()
         from cura.Scene.GCodeListDecorator import GCodeListDecorator
         
@@ -308,6 +309,15 @@ class SimulationView(CuraView):
             if not layer_data:
                 continue
             
+            # Check if we already have cached data for this node
+            current_node_id = id(node)
+            if self._layer_heights_cache_node_id == current_node_id and self._layer_heights_cache:
+                # Cache is still valid, no need to recalculate
+                return
+            # Cache is invalid or empty, recalculate
+            self._layer_heights_cache.clear()
+            self._layer_heights_cache_node_id = current_node_id
+            
             has_gcode_decorator = node.getDecorator(GCodeListDecorator) is not None
             
             # Process all layers at once
@@ -328,8 +338,13 @@ class SimulationView(CuraView):
                 else:
                     self._layer_heights_cache[layer_id] = layer.height / 1000.0
             
-            # We found layer data, no need to continue searching
-            break
+            # We found layer data and cached it, no need to continue searching
+            return
+        
+        # No layer data found - clear the cache
+        if self._layer_heights_cache_node_id is not None:
+            self._layer_heights_cache.clear()
+            self._layer_heights_cache_node_id = None
 
     def _getLayerHeight(self, layer_number: int) -> float:
         """Helper method to get the height of a specific layer in millimeters from cache.
@@ -789,6 +804,7 @@ class SimulationView(CuraView):
             Application.getInstance().getPreferences().preferenceChanged.connect(self._onPreferencesChanged)
             self._controller.getScene().getRoot().childrenChanged.connect(self._onSceneChanged)
 
+            self._calculateLayerHeightsCache()
             self.calculateColorSchemeLimits()
             self.calculateMaxLayers()
             self.calculateMaxPathsOnLayer(self._current_layer_num)