Added warning when trying to load project with objects on buildplate

CURA-1263

plugins/3MFReader/ThreeMFWorkspaceReader.py

@@ -145,6 +145,7 @@ class ThreeMFWorkspaceReader(WorkspaceReader):
         self._dialog.setActiveMode(active_mode)
         self._dialog.setMachineName(machine_name)
         self._dialog.setMaterialLabels(material_labels)
+        self._dialog.setHasObjectsOnPlate(Application.getInstance().getPlatformActivity)
         self._dialog.show()
 
         # Block until the dialog is closed.

plugins/3MFReader/WorkspaceDialog.py

@@ -38,6 +38,7 @@ class WorkspaceDialog(QObject):
         self._quality_type = ""
         self._machine_name = ""
         self._material_labels = []
+        self._objects_on_plate = False
 
     machineConflictChanged = pyqtSignal()
     qualityChangesConflictChanged = pyqtSignal()
@@ -49,6 +50,15 @@ class WorkspaceDialog(QObject):
     qualityTypeChanged = pyqtSignal()
     machineNameChanged = pyqtSignal()
     materialLabelsChanged = pyqtSignal()
+    objectsOnPlateChanged = pyqtSignal()
+
+    @pyqtProperty(bool, notify=objectsOnPlateChanged)
+    def hasObjectsOnPlate(self):
+        return self._objects_on_plate
+
+    def setHasObjectsOnPlate(self, objects_on_plate):
+        self._objects_on_plate = objects_on_plate
+        self.objectsOnPlateChanged.emit()
 
     @pyqtProperty("QVariantList", notify = materialLabelsChanged)
     def materialLabels(self):

plugins/3MFReader/WorkspaceDialog.qml

@@ -284,6 +284,19 @@ UM.Dialog
                     width: parent.width / 3
                 }
             }
+            Item // Spacer
+            {
+                height: spacerHeight
+                width: height
+            }
+            Label
+            {
+                text: catalog.i18nc("@action:warning", "Loading a project will clear all models on the buildplate")
+                visible: manager.hasObjectsOnPlate
+                color: "red"
+                width: parent.width
+                wrapMode: Text.Wrap
+            }
         }
     }
     rightButtons: [