diff -r a74f2ff353b8 -r b376645315ab src/misc/documentPointer.cc
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/misc/documentPointer.cc	Sat Mar 29 05:26:10 2014 +0200
@@ -0,0 +1,76 @@
+/*
+ *  LDForge: LDraw parts authoring CAD
+ *  Copyright (C) 2013, 2014 Santeri Piippo
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "documentPointer.h"
+#include "../ldDocument.h"
+#include "../miscallenous.h"
+
+LDDocumentPointer::LDDocumentPointer()  : m_pointer (null) {}
+
+// =============================================================================
+//
+LDDocumentPointer::LDDocumentPointer (LDDocument* ptr) :
+	m_pointer (ptr)
+{
+	addReference ();
+}
+
+// =============================================================================
+//
+LDDocumentPointer::LDDocumentPointer (const LDDocumentPointer& other) :
+	m_pointer (other.pointer())
+{
+	addReference ();
+}
+
+// =============================================================================
+//
+LDDocumentPointer::~LDDocumentPointer()
+{
+	removeReference();
+}
+
+// =============================================================================
+//
+void LDDocumentPointer::addReference()
+{
+	if (pointer() != null)
+		pointer()->addReference (this);
+}
+
+// =============================================================================
+//
+void LDDocumentPointer::removeReference()
+{
+	if (pointer() != null)
+		pointer()->removeReference (this);
+}
+
+// =============================================================================
+//
+LDDocumentPointer& LDDocumentPointer::operator= (LDDocument* ptr)
+{
+	if (ptr != pointer())
+	{
+		removeReference();
+		setPointer (ptr);
+		addReference();
+	}
+
+	return *this;
+}
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