for #1, added newest_item() to return the top of undo/redo stack directly.

Author: hedzr

include/undo_cxx/undo-zcore.hh

@@ -449,9 +449,26 @@ namespace undo_cxx {
       }
     }
 
+    // @desc to return the focused item at undo/redo stack.
+    // @note this api relies on the invocations of one of
+    //   these apis: undo/redo.
+    // @note _position will be reset to end() once invoke()
+    //   invoked.
     MementoPtr &focused_item() { return *_position; }
     MementoPtr const &focused_item() const { return *_position; }
     std::ptrdiff_t position() { return std::distance(_saved_states.begin(), _position); }
+    Iterator newest_iterator() { return _saved_states.end(); }
+    Iterator oldest_iterator() { return _saved_states.begin(); }
+    // @desc to return the newest item at stack.
+    // @note this is NOT thread-safe, you must keep watching the
+    //   usages of iterators on multi-thread scene. Or you're working
+    //   for a ui app and it has single main ui-thread to operate
+    //   any of ui-commands.
+    MementoPtr &newest_item() {
+      auto it = _position;
+      it--;
+      return *it;
+    }
 
     auto size() const { return _saved_states.size(); }
     bool empty() const { return _saved_states.empty(); }

tests/undo.cc

@@ -120,37 +120,44 @@ namespace dp { namespace undo { namespace bugs {
 }}} // namespace dp::undo::bugs
 
 void test_undo_sys() {
-using namespace dp::undo::test;
-using namespace dp::undo::bugs;
-
-using State = std::string;
-using M = undo_cxx::undoable_cmd_system_t<State>;
-using UndoCmdT = UndoCmd<State>;
-using RedoCmdT = RedoCmd<State>;
-using FontStyleCmdT = FontStyleCmd<State>;
-
-M undoable_cmd_system;
-
-// do some stuffs
-
-undoable_cmd_system.invoke<FontStyleCmdT>("italic state1");
-undoable_cmd_system.invoke<FontStyleCmdT>("italic-bold state2");
-undoable_cmd_system.invoke<FontStyleCmdT>("underline state3");
-undoable_cmd_system.invoke<FontStyleCmdT>("italic state4");
-
-// and try to undo or redo
-
-undoable_cmd_system.invoke<UndoCmdT>("undo 1");
-undoable_cmd_system.invoke<UndoCmdT>("undo 2");
-undoable_cmd_system.invoke<RedoCmdT>("redo 1");
-undoable_cmd_system.invoke<UndoCmdT>("undo 3");
-undoable_cmd_system.invoke<UndoCmdT>("undo 4");
+  using namespace dp::undo::test;
+  using namespace dp::undo::bugs;
+
+  using State = std::string;
+  using M = undo_cxx::undoable_cmd_system_t<State>;
+  using UndoCmdT = UndoCmd<State>;
+  using RedoCmdT = RedoCmd<State>;
+  using FontStyleCmdT = FontStyleCmd<State>;
+
+  M undoable_cmd_system;
+
+  // do some stuffs
+
+  undoable_cmd_system.invoke<FontStyleCmdT>("italic state1");
+  std::cout << "  > newest item: " << *undoable_cmd_system.newest_item() << '\n';
+  undoable_cmd_system.invoke<FontStyleCmdT>("italic-bold state2");
+  undoable_cmd_system.invoke<FontStyleCmdT>("underline state3");
+  undoable_cmd_system.invoke<FontStyleCmdT>("italic state4");
+  std::cout << "  > newest item: " << *undoable_cmd_system.newest_item() << '\n';
+
+  // and try to undo or redo
+
+  undoable_cmd_system.invoke<UndoCmdT>("undo 1");
+  std::cout << "  > focused item: " << *undoable_cmd_system.focused_item() << ", newest item: " << *undoable_cmd_system.newest_item() << '\n';
+  undoable_cmd_system.invoke<UndoCmdT>("undo 2");
+  std::cout << "  > focused item: " << *undoable_cmd_system.focused_item() << ", newest item: " << *undoable_cmd_system.newest_item() << '\n';
+  undoable_cmd_system.invoke<RedoCmdT>("redo 1");
+  std::cout << "  > focused item: " << *undoable_cmd_system.focused_item() << ", newest item: " << *undoable_cmd_system.newest_item() << '\n';
+  undoable_cmd_system.invoke<UndoCmdT>("undo 3");
+  std::cout << "  > focused item: " << *undoable_cmd_system.focused_item() << ", newest item: " << *undoable_cmd_system.newest_item() << '\n';
+  undoable_cmd_system.invoke<UndoCmdT>("undo 4");
+  std::cout << "  > focused item: " << *undoable_cmd_system.focused_item() << ", newest item: " << *undoable_cmd_system.newest_item() << '\n';
 }
 
 int main() {
 
-// test_undo_basic();
-test_undo_sys();
+  // test_undo_basic();
+  test_undo_sys();
 
-return 0;
+  return 0;
 }