Merge branch 'master' into output_device

* master: (22 commits)
  Added grouping action
  LayerData now works by using decorators
  Do not cause "dictionary changed size during iteration" errors when changing view
  Adds an idle-state for the layerview slider
  Adds an idle-state for the safebutton
  Sets the platform activity on true when a model is loaded
  Sets the platform activity on true when a model is loaded
  Create functions that get & set platform activity
  Send M104 to set the temperature to 0
  Do not store files that fail to load in recent files
  feat: infill wipe dist; wireframe restructure & renaming; bugfix: draft_shield_height inherit_function
  Also add the parent class' command line arguments
  Only process the layer data if the layer view is active.
  Write to the correct variable so bed temperature is properly updated
  Correct a copy-paste error in getConnectionList
  Properly close all open USB connections on shut down
  Catch errors when trying to close the connection thread
  Enlarge the zone where you can use scrolling to look trough the layer mode.
  included retraction_extra_prime_amount
  tiniest detail concerning the padding of the layer count label
  ...

cura/BuildVolume.py

@@ -33,6 +33,7 @@ class BuildVolume(SceneNode):
 
         self.setCalculateBoundingBox(False)
 
+
     def setWidth(self, width):
         self._width = width
 

cura/CuraApplication.py

@@ -22,6 +22,7 @@ from UM.Math.Polygon import Polygon
 
 from UM.Scene.BoxRenderer import BoxRenderer
 from UM.Scene.Selection import Selection
+from UM.Scene.GroupDecorator import GroupDecorator
 
 from UM.Operations.AddSceneNodeOperation import AddSceneNodeOperation
 from UM.Operations.RemoveSceneNodeOperation import RemoveSceneNodeOperation
@@ -74,6 +75,7 @@ class CuraApplication(QtApplication):
         self._print_information = None
         self._i18n_catalog = None
         self._previous_active_tool = None
+        self._platform_activity = False
 
         self.activeMachineChanged.connect(self._onActiveMachineChanged)
 
@@ -106,6 +108,7 @@ class CuraApplication(QtApplication):
             raise RuntimeError("Could not load the backend plugin!")
 
     def addCommandLineOptions(self, parser):
+        super().addCommandLineOptions(parser)
         parser.add_argument("file", nargs="*", help="Files to load after starting the application.")
 
     def run(self):
@@ -199,6 +202,31 @@ class CuraApplication(QtApplication):
                 self._previous_active_tool = None
 
     requestAddPrinter = pyqtSignal()
+    activityChanged = pyqtSignal()
+
+    @pyqtProperty(bool, notify = activityChanged)
+    def getPlatformActivity(self):
+        return self._platform_activity
+
+    @pyqtSlot(bool)
+    def setPlatformActivity(self, activity):
+        ##Sets the _platform_activity variable on true or false depending on whether there is a mesh on the platform
+        if activity == True:
+            self._platform_activity = activity
+        elif activity == False:
+            nodes = []
+            for node in DepthFirstIterator(self.getController().getScene().getRoot()):
+                if type(node) is not SceneNode or not node.getMeshData():
+                    continue
+                nodes.append(node)
+            i = 0
+            for node in nodes:
+                if not node.getMeshData():
+                    continue
+                i += 1
+            if i <= 1: ## i == 0 when the meshes are removed using the deleteAll function; i == 1 when the last remaining mesh is removed using the deleteObject function
+                self._platform_activity = activity
+        self.activityChanged.emit()
 
     ##  Remove an object from the scene
     @pyqtSlot("quint64")
@@ -211,6 +239,7 @@ class CuraApplication(QtApplication):
         if object:
             op = RemoveSceneNodeOperation(object)
             op.push()
+            self.setPlatformActivity(False)
     
     ##  Create a number of copies of existing object.
     @pyqtSlot("quint64", int)
@@ -251,7 +280,6 @@ class CuraApplication(QtApplication):
             if type(node) is not SceneNode or not node.getMeshData():
                 continue
             nodes.append(node)
-
         if nodes:
             op = GroupedOperation()
 
@@ -259,6 +287,7 @@ class CuraApplication(QtApplication):
                 op.addOperation(RemoveSceneNodeOperation(node))
 
             op.push()
+        self.setPlatformActivity(False)
     
     ## Reset all translation on nodes with mesh data. 
     @pyqtSlot()
@@ -362,6 +391,17 @@ class CuraApplication(QtApplication):
             return
 
         self.getActiveMachine().setSettingValueByKey(key, value)
+        
+        
+    @pyqtSlot()
+    def groupSelected(self):
+        group_node = SceneNode()
+        group_decorator = GroupDecorator()
+        group_node.addDecorator(group_decorator)
+        group_node.setParent(self.getController().getScene().getRoot())
+        for node in Selection.getAllSelectedObjects():
+            node.setParent(group_node)
+            
 
     def _onActiveMachineChanged(self):
         machine = self.getActiveMachine()
@@ -401,7 +441,7 @@ class CuraApplication(QtApplication):
             op.push()
 
     def _onJobFinished(self, job):
-        if type(job) is not ReadMeshJob:
+        if type(job) is not ReadMeshJob or not job.getResult():
             return
 
         f = QUrl.fromLocalFile(job.getFileName())