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diff --git a/src/object-hierarchy.h b/src/object-hierarchy.h
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Authors:
+ *   MenTaLguY <mental@rydia.net>
+ *
+ * Copyright (C) 2004 MenTaLguY
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef SEEN_INKSCAPE_OBJECT_HIERARCHY_H
+#define SEEN_INKSCAPE_OBJECT_HIERARCHY_H
+
+#include <cstddef>
+#include <exception>
+#include <list>
+#include <sigc++/connection.h>
+#include <sigc++/signal.h>
+
+class SPObject;
+
+namespace Inkscape {
+
+/**
+ * An Inkscape::ObjectHierarchy is useful for situations where one wishes
+ * to keep a reference to an SPObject, but fall back on one of its ancestors
+ * when that object is removed.
+ *
+ * That cannot be accomplished simply by hooking the "release" signal of the
+ * SPObject, as by the time that signal is emitted, the object's parent
+ * field has already been cleared.
+ *
+ * There are also some subtle refcounting issues to take into account.
+ *
+ * @see SPObject
+ */
+class ObjectHierarchy {
+public:
+
+    /**
+     * Create new object hierarchy.
+     * @param top The first entry if non-NULL.
+     */
+    ObjectHierarchy(SPObject *top=nullptr);
+
+    ~ObjectHierarchy();
+
+    bool contains(SPObject *object);
+
+    sigc::connection connectAdded(const sigc::slot<void, SPObject *> &slot) {
+        return _added_signal.connect(slot);
+    }
+    sigc::connection connectRemoved(const sigc::slot<void, SPObject *> &slot) {
+        return _removed_signal.connect(slot);
+    }
+    sigc::connection connectChanged(const sigc::slot<void, SPObject *, SPObject *> &slot)
+    {
+        return _changed_signal.connect(slot);
+    }
+
+    /**
+     * Remove all entries.
+     */
+    void clear();
+
+    SPObject *top() {
+        return !_hierarchy.empty() ? _hierarchy.back().object : nullptr;
+    }
+
+    /**
+     * Trim or expand hierarchy on top such that object becomes top entry.
+     */
+    void setTop(SPObject *object);
+
+    SPObject *bottom() {
+        return !_hierarchy.empty() ? _hierarchy.front().object : nullptr;
+    }
+
+    /**
+     * Trim or expand hierarchy at bottom such that object becomes bottom entry.
+     */
+    void setBottom(SPObject *object);
+
+private:
+    struct Record {
+        Record(SPObject *o, sigc::connection c)
+        : object(o), connection(c) {}
+
+        SPObject *object;
+        sigc::connection connection;
+    };
+
+    ObjectHierarchy(ObjectHierarchy const &); // no copy
+
+    void operator=(ObjectHierarchy const &); // no assign
+
+    /**
+     * Add hierarchy from junior's parent to senior to this
+     * hierarchy's top.
+     */
+    void _addTop(SPObject *senior, SPObject *junior);
+
+    /**
+     * Add object to top of hierarchy.
+     * \pre object!=NULL.
+     */
+    void _addTop(SPObject *object);
+
+    /**
+     * Remove all objects above limit from hierarchy.
+     */
+    void _trimAbove(SPObject *limit);
+
+    /**
+     * Add hierarchy from senior to junior, in range (senior, junior], to this hierarchy's bottom.
+     */
+    void _addBottom(SPObject *senior, SPObject *junior);
+
+    /**
+     * Add object at bottom of hierarchy.
+     * \pre object!=NULL
+     */
+    void _addBottom(SPObject *object);
+
+    /**
+     * Remove all objects under given object.
+     * @param limit If NULL, remove all.
+     */
+    void _trimBelow(SPObject *limit);
+
+    Record _attach(SPObject *object);
+
+    void _detach(Record &record);
+
+    void _clear() { _trimBelow(nullptr); }
+
+    void _trim_for_release(SPObject *released);
+
+    std::list<Record> _hierarchy;
+    sigc::signal<void, SPObject *> _added_signal;
+    sigc::signal<void, SPObject *> _removed_signal;
+    sigc::signal<void, SPObject *, SPObject *> _changed_signal;
+};
+
+}
+
+#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 :