Use a decorator to track Z offset

This makes it much easier to correct for Z offset after operations

CURA-196 #Ready-for-Review

cura/CuraApplication.py

@@ -37,6 +37,7 @@ from . import CameraAnimation
 from . import PrintInformation
 from . import CuraActions
 from . import MultiMaterialDecorator
+from . import ZOffsetDecorator
 
 from PyQt5.QtCore import pyqtSlot, QUrl, Qt, pyqtSignal, pyqtProperty, QEvent, Q_ENUMS
 from PyQt5.QtGui import QColor, QIcon
@@ -342,14 +343,12 @@ class CuraApplication(QtApplication):
                 continue #Grouped nodes don't need resetting as their parent (the group) is resetted)
 
             nodes.append(node)
+
         if nodes:
             op = GroupedOperation()
             for node in nodes:
-                # Ensure that the object is above the build platform
-                move_distance = node.getBoundingBox().center.y
-                if move_distance <= 0:
-                    move_distance = -node.getBoundingBox().bottom
-                op.addOperation(SetTransformOperation(node, Vector(0,move_distance,0)))
+                node.removeDecorator(ZOffsetDecorator.ZOffsetDecorator)
+                op.addOperation(SetTransformOperation(node, Vector(0,0,0)))
 
             op.push()
     
@@ -371,10 +370,8 @@ class CuraApplication(QtApplication):
 
             for node in nodes:
                 # Ensure that the object is above the build platform
-                move_distance = node.getBoundingBox().center.y
-                if move_distance <= 0:
-                    move_distance = -node.getBoundingBox().bottom
-                op.addOperation(SetTransformOperation(node, Vector(0,move_distance,0), Quaternion(), Vector(1, 1, 1)))
+                node.removeDecorator(ZOffsetDecorator.ZOffsetDecorator)
+                op.addOperation(SetTransformOperation(node, Vector(0,0,0), Quaternion(), Vector(1, 1, 1)))
 
             op.push()
             

cura/PlatformPhysics.py

@@ -17,6 +17,7 @@ from cura.ConvexHullDecorator import ConvexHullDecorator
 
 from . import PlatformPhysicsOperation
 from . import ConvexHullJob
+from . import ZOffsetDecorator
 
 import time
 import threading
@@ -69,8 +70,12 @@ class PlatformPhysics:
             # Move it downwards if bottom is above platform
             move_vector = Vector()
             if not (node.getParent() and node.getParent().callDecoration("isGroup")): #If an object is grouped, don't move it down
+                z_offset = node.callDecoration("getZOffset") if node.getDecorator(ZOffsetDecorator.ZOffsetDecorator) else 0
                 if bbox.bottom > 0:
-                    move_vector.setY(-bbox.bottom)
+                    move_vector.setY(-bbox.bottom + z_offset)
+                elif bbox.bottom < z_offset:
+                    move_vector.setY((-bbox.bottom) - z_offset)
+
             #if not Float.fuzzyCompare(bbox.bottom, 0.0):
             #   pass#move_vector.setY(-bbox.bottom)
 
@@ -149,5 +154,16 @@ class PlatformPhysics:
         self._enabled = False
 
     def _onToolOperationStopped(self, tool):
+        if tool.getPluginId() == "TranslateTool":
+            for node in Selection.getAllSelectedObjects():
+                if node.getBoundingBox().bottom < 0:
+                    if not node.getDecorator(ZOffsetDecorator.ZOffsetDecorator):
+                        node.addDecorator(ZOffsetDecorator.ZOffsetDecorator())
+
+                    node.callDecoration("setZOffset", node.getBoundingBox().bottom)
+                else:
+                    if node.getDecorator(ZOffsetDecorator.ZOffsetDecorator):
+                        node.removeDecorator(ZOffsetDecorator.ZOffsetDecorator)
+
         self._enabled = True
         self._onChangeTimerFinished()

cura/ZOffsetDecorator.py

@@ -0,0 +1,13 @@
+from UM.Scene.SceneNodeDecorator import SceneNodeDecorator
+
+##  A decorator that stores the amount an object has been moved below the platform.
+class ZOffsetDecorator(SceneNodeDecorator):
+    def __init__(self):
+        self._z_offset = 0
+
+    def setZOffset(self, offset):
+        print("setZOffset", offset)
+        self._z_offset = offset
+
+    def getZOffset(self):
+        return self._z_offset