1 files changed, 40 insertions, 0 deletions
diff --git a/src/object/weakptr.h b/src/object/weakptr.h
new file mode 100644
index 0000000..38db7e7
--- /dev/null
+++ b/src/object/weakptr.h
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef INKSCAPE_OBJECT_WEAKPTR_H
+#define INKSCAPE_OBJECT_WEAKPTR_H
+
+#include <sigc++/connection.h>
+
+namespace Inkscape {
+
+/**
+ * A weak pointer to an SPObject: it nulls itself upon the object's destruction.
+ */
+template <typename T>
+class SPWeakPtr final
+{
+public:
+    SPWeakPtr() = default;
+    explicit SPWeakPtr(T *obj) : _obj(obj) { attach(); }
+    SPWeakPtr &operator=(T *obj) { reset(obj); return *this; }
+    SPWeakPtr(SPWeakPtr const &other) : SPWeakPtr(other._obj) {}
+    SPWeakPtr &operator=(SPWeakPtr const &other) { reset(other._obj); return *this; }
+    ~SPWeakPtr() { detach(); }
+
+    void reset() { detach(); _obj = nullptr; }
+    void reset(T *obj) { detach(); _obj = obj; attach(); }
+    explicit operator bool() const { return _obj; }
+    T *get() const { return _obj; }
+    T &operator*() const { return *_obj; }
+    T *operator->() const { return _obj; }
+
+private:
+    T *_obj = nullptr;
+    sigc::connection _conn;
+
+    void attach() { if (_obj) _conn = _obj->connectRelease([this] (auto) { _conn.disconnect(); _obj = nullptr; }); }
+    void detach() { if (_obj) _conn.disconnect(); }
+};
+
+} // namespace Inkscape
+
+#endif // INKSCAPE_OBJECT_WEAKPTR_H