Arch: Add property to switch to true north

When enabled, the whole coin scene graph is rotated by the declination
property of the site. So one can see the whole geometry oriented like in
real life.

src/Mod/Arch/ArchSite.py

@@ -686,6 +686,12 @@ class _ViewProviderSite(ArchFloor._ViewProviderFloor):
         if not "SolarDiagramColor" in pl:
             vobj.addProperty("App::PropertyColor","SolarDiagramColor","Site",QT_TRANSLATE_NOOP("App::Property","The color of the solar diagram"))
             vobj.SolarDiagramColor = (0.16,0.16,0.25)
+        if not "Orientation" in pl:
+            vobj.addProperty("App::PropertyEnumeration", "Orientation", "Site", QT_TRANSLATE_NOOP(
+                "App::Property", "When set to 'True North' the whole geometry will be rotated to match the true north of this site"))
+            
+            vobj.Orientation = ["Project North", "True North"]
+            vobj.Orientation = "Project North"
 
     def onDocumentRestored(self,vobj):
 
@@ -748,6 +754,7 @@ class _ViewProviderSite(ArchFloor._ViewProviderFloor):
             self.onChanged(obj.ViewObject,"SolarDiagram")
         elif prop == "Declination":
             self.onChanged(obj.ViewObject,"SolarDiagramPosition")
+            self.updateTrueNorthRotation()
         elif prop == "Terrain":
             self.updateCompassLocation(obj)
         elif prop == "Compass":
@@ -787,7 +794,40 @@ class _ViewProviderSite(ArchFloor._ViewProviderFloor):
                 self.updateCompassVisibility(self.Object)
             else:
                 self.compass.hide()
+        elif prop == 'Orientation':
+            if vobj.Orientation == 'True North':
+                self.addTrueNorthRotation()
+            else:
+                self.removeTrueNorthRotation()
     
+    def addTrueNorthRotation(self):
+        if hasattr(self, 'trueNorthRotation') and self.trueNorthRotation is not None:
+            return
+        
+        from pivy import coin
+        
+        self.trueNorthRotation = coin.SoTransform()
+
+        sg = FreeCADGui.ActiveDocument.ActiveView.getSceneGraph()
+        sg.insertChild(self.trueNorthRotation, 0)
+
+        self.updateTrueNorthRotation()
+    
+    def removeTrueNorthRotation(self):
+        if hasattr(self, 'trueNorthRotation') and self.trueNorthRotation is not None:
+            sg = FreeCADGui.ActiveDocument.ActiveView.getSceneGraph()
+
+            sg.removeChild(self.trueNorthRotation)
+            self.trueNorthRotation = None
+    
+    def updateTrueNorthRotation(self):
+        if hasattr(self, 'trueNorthRotation') and self.trueNorthRotation is not None:
+            from pivy import coin
+            
+            angle = self.Object.Declination.Value
+
+            self.trueNorthRotation.rotation.setValue(coin.SbVec3f(0, 0, 1), math.radians(-angle))
+
     def updateCompassVisibility(self, obj):
         if not hasattr(self, 'compass'):
             return