diff -r 03f8e6d42e13 -r 2f79053c2e9a src/modeleditor.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/modeleditor.h	Fri Mar 04 11:40:19 2022 +0200
@@ -0,0 +1,98 @@
+/*
+ *  LDForge: LDraw parts authoring CAD
+ *  Copyright (C) 2013 - 2020 Teemu 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/>.
+ */
+
+#pragma once
+#include "model.h"
+
+/**
+ * @brief Provides an interface for editing a model such that signals are emitted for each edit done.
+ * User edits to models should always be done through this class.
+ */
+class ModelEditor : public QObject
+{
+	Q_OBJECT
+public:
+	ModelEditor(Model& model);
+	~ModelEditor();
+	template<typename T, typename... Args>
+	ldraw::Id<T> append(Args&&... args);
+	ldraw::id_t append(std::unique_ptr<ldraw::Object>&& object);
+	template<typename T, typename... Args>
+	ldraw::Id<T> insert(int position, Args&&... args);
+	void remove(int position);
+	template<ldraw::Property property>
+	void setObjectProperty(ldraw::id_t id, const ldraw::PropertyType<property>& value);
+	auto setObjectProperty(ldraw::id_t id, ldraw::Property property, const QVariant& value)
+		-> ldraw::Object::SetPropertyResult;
+	void setObjectPoint(ldraw::id_t id, int pointId, const glm::vec3& value);
+	template<typename T, typename Fn>
+	bool modifyObject(ldraw::Id<T> id, Fn&& function);
+	template<typename T, typename Fn>
+	bool modifyObjectAt(int position, Fn&& function);
+	const Model& model();
+Q_SIGNALS:
+	void objectAdded(int position);
+	void objectModified(int position);
+	void objectRemoved(ldraw::id_t id);
+private:
+	QSet<ldraw::id_t> modifiedObjects;
+	Model& storedModel;
+};
+
+template<ldraw::Property Property>
+void ModelEditor::setObjectProperty(const ldraw::id_t id, const ldraw::PropertyType<Property>& value)
+{
+	this->modifyObject(id, [&](ldraw::Object* object){
+		object->setProperty<Property>(value);
+	});
+}
+
+template<typename T, typename... Args>
+ldraw::Id<T> ModelEditor::append(Args&&... args)
+{
+	return this->storedModel.append<T>(args...);
+}
+
+template<typename T, typename... Args>
+ldraw::Id<T> ModelEditor::insert(int position, Args&&... args)
+{
+	return this->storedModel.insert<T>(position, args...);
+}
+
+template<typename T, typename Fn>
+bool ModelEditor::modifyObject(ldraw::Id<T> id, Fn&& function)
+{
+	QModelIndex index = this->model().find(id);
+	return this->modifyObjectAt<T>(index.row(), function);
+}
+
+template<typename T, typename Fn>
+bool ModelEditor::modifyObjectAt(int position, Fn&& function)
+{
+	if (position >= 0 and position < this->model().size())
+	{
+		T* object = dynamic_cast<T*>(this->storedModel[position]);
+		if (object != nullptr)
+		{
+			Q_EMIT this->objectModified(position);
+			function(object);
+			return true;
+		}
+	}
+	return false;
+}
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