WIP UndoRedo: Added Undo/Redo stack, added Platter::take_snapshot(),

experimental snapshots on loading STLs and increasing / decreasing
model instances.

src/slic3r/Utils/UndoRedo.hpp

@@ -0,0 +1,58 @@
+#ifndef slic3r_Utils_UndoRedo_hpp_
+#define slic3r_Utils_UndoRedo_hpp_
+
+#include <memory>
+#include <string>
+
+namespace Slic3r {
+
+class Model;
+
+namespace GUI {
+	class Selection;
+} // namespace GUI
+
+namespace UndoRedo {
+
+struct Snapshot
+{
+	Snapshot(size_t timestamp) : timestamp(timestamp) {}
+	Snapshot(const std::string &name, size_t timestamp, size_t model_object_id) : name(name), timestamp(timestamp), model_object_id(model_object_id) {}
+	
+	std::string name;
+	size_t 		timestamp;
+	size_t 		model_object_id;
+
+	bool		operator< (const Snapshot &rhs) const { return this->timestamp < rhs.timestamp; }
+	bool		operator==(const Snapshot &rhs) const { return this->timestamp == rhs.timestamp; }
+};
+
+class StackImpl;
+
+class Stack
+{
+public:
+	// Stack needs to be initialized. An empty stack is not valid, there must be a "New Project" status stored at the beginning.
+	Stack();
+	~Stack();
+
+	// The Undo / Redo stack is being initialized with an empty model and an empty selection.
+	// The first snapshot cannot be removed.
+	void initialize(const Slic3r::Model &model, const Slic3r::GUI::Selection &selection);
+
+	// Store the current application state onto the Undo / Redo stack, remove all snapshots after m_active_snapshot_time.
+	void take_snapshot(const std::string &snapshot_name, const Slic3r::Model &model, const Slic3r::GUI::Selection &selection);
+	void load_snapshot(size_t timestamp, Slic3r::Model &model, Slic3r::GUI::Selection &selection);
+
+	// Snapshot history (names with timestamps).
+	const std::vector<Snapshot>& snapshots() const;
+
+private:
+	friend class StackImpl;
+	std::unique_ptr<StackImpl> 	pimpl;
+};
+
+}; // namespace UndoRedo
+}; // namespace Slic3r
+
+#endif /* slic3r_Utils_UndoRedo_hpp_ */