From b2874ec0dce77a1f1cc72a54ef420b9cdc223f6b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Tr=C3=B6ger?= <stefantroeger@gmx.net>
Date: Tue, 8 Aug 2017 18:16:41 +0200
Subject: [PATCH] Keep backlink consitent during undo/redo. issue 0003150

---
 src/App/Transactions.cpp | 18 ++++++++--
 src/Mod/Test/Document.py | 71 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/src/App/Transactions.cpp b/src/App/Transactions.cpp
index 414891be79..6a1c6378cf 100644
--- a/src/App/Transactions.cpp
+++ b/src/App/Transactions.cpp
@@ -339,9 +339,18 @@ TransactionDocumentObject::~TransactionDocumentObject()
 void TransactionDocumentObject::applyDel(Document &Doc, TransactionalObject *pcObj)
 {
     if (status == Del) {
-        // simply filling in the saved object
+        
         DocumentObject* obj = static_cast<DocumentObject*>(pcObj);
-        Doc._remObject(obj);
+
+        //Make sure the backlinks of all linked objects are updated. As the links of the removed
+        //object are never set to [] they also do not remove the backlink. But as they are 
+        //not in the document anymore we need to remove them anyway to ensure a correct graph
+        auto list = obj->getOutList();
+        for(auto link : list)
+            link->_removeBackLink(obj);
+        
+        // simply filling in the saved object
+        Doc._remObject(obj);       
     }
 }
 
@@ -350,6 +359,11 @@ void TransactionDocumentObject::applyNew(Document &Doc, TransactionalObject *pcO
     if (status == New) {
         DocumentObject* obj = static_cast<DocumentObject*>(pcObj);
         Doc._addObject(obj, _NameInDocument.c_str());
+        
+        //make sure the backlinks of all linked objects are updated
+        auto list = obj->getOutList();
+        for(auto link : list)
+            link->_addBackLink(obj);
     }
 }
 
diff --git a/src/Mod/Test/Document.py b/src/Mod/Test/Document.py
index e05b54ec4d..353a55fe46 100644
--- a/src/Mod/Test/Document.py
+++ b/src/Mod/Test/Document.py
@@ -764,6 +764,77 @@ class UndoRedoCases(unittest.TestCase):
     self.assertEqual(self.Doc.RedoNames,[])
     self.assertEqual(self.Doc.RedoCount,0)
 
+  def testUndoInList(self):
+    
+    self.Doc.UndoMode = 1
+      
+    self.Doc.openTransaction("Box")
+    self.Box = self.Doc.addObject('Part::Box')
+    self.Doc.commitTransaction()
+
+    self.Doc.openTransaction("Cylinder")
+    self.Cylinder = self.Doc.addObject('Part::Cylinder')
+    self.Doc.commitTransaction()
+    
+    self.Doc.openTransaction("Fuse")
+    self.Fuse1 = self.Doc.addObject('Part::MultiFuse', 'Fuse')
+    self.Fuse1.Shapes = [self.Box, self.Cylinder]
+    self.Doc.commitTransaction()
+    
+    print self.Box.InList
+    self.Doc.undo()
+    print self.Box.InList
+    self.failUnless(len(self.Box.InList) == 0)
+    self.failUnless(len(self.Cylinder.InList) == 0)      
+    
+    self.Doc.redo()
+    self.failUnless(len(self.Box.InList) == 1)
+    self.failUnless(self.Box.InList[0] == self.Doc.Fuse)
+    self.failUnless(len(self.Cylinder.InList) == 1)  
+    self.failUnless(self.Cylinder.InList[0] == self.Doc.Fuse)
+      
+  def testUndoIssue0003150(self):
+  
+    self.Doc.UndoMode = 1
+  
+    self.Doc.openTransaction("Box")
+    self.Box = self.Doc.addObject('Part::Box')
+    self.Doc.commitTransaction()
+
+    self.Doc.openTransaction("Cylinder")
+    self.Cylinder = self.Doc.addObject('Part::Cylinder')
+    self.Doc.commitTransaction()
+
+    self.Doc.openTransaction("Fuse")
+    self.Fuse1 = self.Doc.addObject('Part::MultiFuse')
+    self.Fuse1.Shapes = [self.Box, self.Cylinder]
+    self.Doc.commitTransaction()
+    self.Doc.recompute()
+
+    self.Doc.openTransaction("Sphere")
+    self.Sphere = self.Doc.addObject('Part::Sphere')
+    self.Doc.commitTransaction()
+
+    self.Doc.openTransaction("Fuse")
+    self.Fuse2 = self.Doc.addObject('Part::MultiFuse')
+    self.Fuse2.Shapes = [self.Fuse1, self.Sphere]
+    self.Doc.commitTransaction()
+    self.Doc.recompute()
+
+    self.Doc.openTransaction("Part")
+    self.Part = self.Doc.addObject('App::Part')
+    self.Doc.commitTransaction()
+
+    self.Doc.openTransaction("Drag")
+    self.Part.addObject(self.Fuse2)
+    self.Doc.commitTransaction()
+
+    #3 undos show the problem of failing recompute
+    self.Doc.undo()
+    self.Doc.undo()
+    self.Doc.undo()
+    self.failUnless(self.Doc.recompute() >= 0)
+
   def tearDown(self):
     # closing doc
     FreeCAD.closeDocument("UndoTest")