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diff --git a/src/xml/composite-node-observer.h b/src/xml/composite-node-observer.h
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * Inkscape::XML::CompositeNodeObserver - combine multiple observers
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2018 Author
+ * Copyright 2005 MenTaLguY <mental@rydia.net>
+ * 
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef SEEN_INKSCAPE_XML_COMPOSITE_NODE_OBSERVER_H
+#define SEEN_INKSCAPE_XML_COMPOSITE_NODE_OBSERVER_H
+
+#include "inkgc/gc-alloc.h"
+#include "inkgc/gc-managed.h"
+#include "xml/node-observer.h"
+#include <list>
+
+namespace Inkscape {
+
+namespace XML {
+
+struct NodeEventVector;
+
+/**
+ * @brief An observer that relays notifications to multiple other observers
+ *
+ * This special observer keeps a list of other observer objects and sends
+ * the notifications it receives to all of them. The implementation of the class
+ * allows an observer to remove itself from this object during a method call.
+ * For the documentation of callback methods, see NodeObserver.
+ */
+class CompositeNodeObserver : public NodeObserver, public GC::Managed<> {
+public:
+    struct ObserverRecord : public GC::Managed<> {
+        explicit ObserverRecord(NodeObserver &o) : observer(o), marked(false) {}
+
+        NodeObserver &observer;
+        bool marked; //< if marked for removal
+    };
+    typedef std::list<ObserverRecord, Inkscape::GC::Alloc<ObserverRecord, Inkscape::GC::MANUAL>> ObserverRecordList;
+
+    CompositeNodeObserver()
+    : _iterating(0), _active_marked(0), _pending_marked(0) {}
+
+    /**
+     * @brief Add an observer to the list
+     * @param observer The observer object to add
+     */
+    void add(NodeObserver &observer);
+    /**
+     * @brief Remove an observer from the list
+     * @param observer The observer object to remove
+     */
+    void remove(NodeObserver &observer);
+    /**
+     * @brief Add a set of callbacks with associated data
+     * @deprecated Use add() instead
+     */
+    void addListener(NodeEventVector const &vector, void *data);
+    /**
+     * @brief Remove a set of callbacks by its associated data
+     * @deprecated Use remove() instead
+     */
+    void removeListenerByData(void *data);
+    
+    void notifyChildAdded(Node &node, Node &child, Node *prev) override;
+
+    void notifyChildRemoved(Node &node, Node &child, Node *prev) override;
+
+    void notifyChildOrderChanged(Node &node, Node &child,
+                                 Node *old_prev, Node *new_prev) override;
+
+    void notifyContentChanged(Node &node,
+                              Util::ptr_shared old_content,
+                              Util::ptr_shared new_content) override;
+
+    void notifyAttributeChanged(Node &node, GQuark name,
+                                Util::ptr_shared old_value,
+                                Util::ptr_shared new_value) override;
+
+    void notifyElementNameChanged(Node& node, GQuark old_name, GQuark new_name) override;
+
+private:
+    unsigned _iterating;
+    ObserverRecordList _active;
+    unsigned _active_marked;
+    ObserverRecordList _pending;
+    unsigned _pending_marked;
+
+    void _startIteration() { ++_iterating; }
+    void _finishIteration();
+};
+
+} // namespace XML
+} // namespace Inkscape
+
+#endif
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :