Prefer a read-only material in findDefaultMaterial.

Contributes to CURA-4243.

1 files changed, 10 insertions, 4 deletions

diff --git a/cura/Settings/CuraContainerStack.py b/cura/Settings/CuraContainerStack.py
index bf001c7f08..9e30e3dd66 100755
--- a/cura/Settings/CuraContainerStack.py
+++ b/cura/Settings/CuraContainerStack.py
@@ -487,11 +487,17 @@ class CuraContainerStack(ContainerStack):
             search_criteria.pop("name", None)
             materials = ContainerRegistry.getInstance().findInstanceContainers(**search_criteria)
 
-        if materials:
-            return materials[0]
+        if not materials:
+            Logger.log("w", "Could not find a valid material for stack {stack}", stack = self.id)
+            return None
+
+        for material in materials:
+            # Prefer a read-only material
+            if ContainerRegistry.getInstance().isReadOnly(material.getId()):
+                return material
+
+        return materials[0]
 
-        Logger.log("w", "Could not find a valid material for stack {stack}", stack = self.id)
-        return None
 
     ##  Find the quality that should be used as "default" quality.
     #