Add MaterialsModel to make material list update upon metadata change

This new model inherits from InstanceContainersModel. The only change is that it updates when the metadata of a material container changes. This is needed to make the list of materials update when the material diameter changes.

Contributes to issue CURA-2822.

cura/CuraApplication.py

@@ -48,6 +48,7 @@ from UM.Settings.ContainerRegistry import ContainerRegistry
 from UM.Settings.SettingFunction import SettingFunction
 from cura.Settings.MachineNameValidator import MachineNameValidator
 from cura.Settings.ProfilesModel import ProfilesModel
+from cura.Settings.MaterialsModel import MaterialsModel
 from cura.Settings.QualityAndUserProfilesModel import QualityAndUserProfilesModel
 from cura.Settings.SettingInheritanceManager import SettingInheritanceManager
 from cura.Settings.UserProfilesModel import UserProfilesModel
@@ -717,6 +718,7 @@ class CuraApplication(QtApplication):
 
         qmlRegisterType(ContainerSettingsModel, "Cura", 1, 0, "ContainerSettingsModel")
         qmlRegisterSingletonType(ProfilesModel, "Cura", 1, 0, "ProfilesModel", ProfilesModel.createProfilesModel)
+        qmlRegisterType(MaterialsModel, "Cura", 1, 0, "MaterialsModel")
         qmlRegisterType(QualityAndUserProfilesModel, "Cura", 1, 0, "QualityAndUserProfilesModel")
         qmlRegisterType(UserProfilesModel, "Cura", 1, 0, "UserProfilesModel")
         qmlRegisterType(MaterialSettingsVisibilityHandler, "Cura", 1, 0, "MaterialSettingsVisibilityHandler")

cura/Settings/MaterialsModel.py

@@ -0,0 +1,21 @@
+# Copyright (c) 2017 Ultimaker B.V.
+# Cura is released under the terms of the AGPLv3 or higher.
+
+from UM.Settings.ContainerRegistry import ContainerRegistry #To listen for changes to the materials.
+from UM.Settings.Models.InstanceContainersModel import InstanceContainersModel #We're extending this class.
+
+##  A model that shows a list of currently valid materials.
+class MaterialsModel(InstanceContainersModel):
+    def __init__(self, parent = None):
+        super().__init__(parent)
+
+        ContainerRegistry.getInstance().containerMetaDataChanged.connect(self._onContainerMetaDataChanged)
+
+    ##  Called when the metadata of the container was changed.
+    #
+    #   This makes sure that we only update when it was a material that changed.
+    #
+    #   \param container The container whose metadata was changed.
+    def _onContainerMetaDataChanged(self, container):
+        if container.getMetaDataEntry("type") == "material": #Only need to update if a material was changed.
+            self._update()

resources/qml/Preferences/MaterialsPage.qml

@@ -20,7 +20,7 @@ UM.ManagementPage
         objectList.positionViewAtBeginning();
     }
 
-    model: UM.InstanceContainersModel
+    model: Cura.MaterialsModel
     {
         filter:
         {