Postpone signals in project loading to avoid incomplete data update

CURA-5056

plugins/3MFReader/ThreeMFWorkspaceReader.py

@@ -6,6 +6,7 @@ from UM.Application import Application
 
 from UM.Logger import Logger
 from UM.i18n import i18nCatalog
+from UM.Signal import postponeSignals, CompressTechnique
 from UM.Settings.ContainerStack import ContainerStack
 from UM.Settings.DefinitionContainer import DefinitionContainer
 from UM.Settings.InstanceContainer import InstanceContainer
@@ -434,6 +435,24 @@ class ThreeMFWorkspaceReader(WorkspaceReader):
     #   \param file_name
     @call_on_qt_thread
     def read(self, file_name):
+        container_registry = ContainerRegistry.getInstance()
+        signals = [container_registry.containerAdded,
+                   container_registry.containerRemoved,
+                   container_registry.containerMetaDataChanged]
+        #
+        # We now have different managers updating their lookup tables upon container changes. It is critical to make
+        # sure that the managers have a complete set of data when they update.
+        #
+        # In project loading, lots of the container-related signals are loosely emitted, which can create timing gaps
+        # for incomplete data update or other kinds of issues to happen.
+        #
+        # To avoid this, we postpone all signals so they don't get emitted immediately. But, please also be aware that,
+        # because of this, do not expect to have the latest data in the lookup tables in project loading.
+        #
+        with postponeSignals(*signals, compress = CompressTechnique.CompressSingle):
+            return self._read(file_name)
+
+    def _read(self, file_name):
         archive = zipfile.ZipFile(file_name, "r")
 
         cura_file_names = [name for name in archive.namelist() if name.startswith("Cura/")]