feat(editor): undo/redo action buttons reflect state

editor/mainwindow.cpp

@@ -103,6 +103,15 @@ MainWindow::MainWindow(QWidget *parent)
     ui->propertiesView->init();
 
     ui->mdiArea->setTabsClosable(true);
+
+    // Undo/Redo
+    ui->actionUndo->setEnabled(false);
+    ui->actionRedo->setEnabled(false);
+
+    undoManager.SetUndoStateListener([&](bool canUndo, bool canRedo) {
+        ui->actionUndo->setEnabled(canUndo);
+        ui->actionRedo->setEnabled(canRedo);
+    });
 }
 
 void MainWindow::closeEvent(QCloseEvent* evt) {

editor/undohistory.cpp

@@ -10,6 +10,7 @@ void UndoHistory::PushState(UndoState state) {
         undoHistory.erase(undoHistory.begin(), undoHistory.begin()+maxBufferSize-(int)undoHistory.size()-1);
 
     undoHistory.push_back(state);
+    undoStateListener(!undoHistory.empty(), !redoHistory.empty());
 }
 
 void UndoHistory::Undo() {
@@ -37,6 +38,7 @@ void UndoHistory::Undo() {
     }
 
     processingUndo = false;
+    undoStateListener(!undoHistory.empty(), !redoHistory.empty());
 }
 
 void UndoHistory::Redo() {
@@ -64,4 +66,9 @@ void UndoHistory::Redo() {
     }
 
     processingUndo = false;
-}
+    undoStateListener(!undoHistory.empty(), !redoHistory.empty());
+}
+
+void UndoHistory::SetUndoStateListener(UndoStateChangedListener listener) {
+    undoStateListener = listener;
+}

editor/undohistory.h

@@ -38,16 +38,21 @@ struct UndoStateSelectionChanged {
 
 typedef std::variant<UndoStatePropertyChanged, UndoStateInstanceCreated, UndoStateInstanceRemoved, UndoStateInstanceReparented, UndoStateSelectionChanged> UndoStateChange;
 typedef std::vector<UndoStateChange> UndoState;
+typedef std::function<void(bool canUndo, bool canRedo)> UndoStateChangedListener;
 
 class UndoHistory  {
     // Ignore PushState requests
     bool processingUndo = false;
     std::deque<UndoState> undoHistory;
     std::stack<UndoState> redoHistory;
+
+    UndoStateChangedListener undoStateListener;
 public:
     int maxBufferSize = 100;
 
     void PushState(UndoState);
     void Undo();
     void Redo();
+
+    void SetUndoStateListener(UndoStateChangedListener listener);
 };