Feat: Add Unsaved Changes warning on Exit/Close/Open

src/teletext/ui.py

@@ -29,6 +29,7 @@ class MainWindow(QMainWindow):
         self.clipboard = [] # List of (row, data_bytes)
         self.undo_stack = []
         self.redo_stack = []
+        self.is_modified = False
         
         # UI Components
         self.central_widget = QWidget()
@@ -130,6 +131,40 @@ class MainWindow(QMainWindow):
         # Menus
         self.create_menus()
 
+    def set_modified(self, modified: bool):
+        self.is_modified = modified
+        title = "Teletext Editor"
+        if self.current_file_path:
+            title += f" - {os.path.basename(self.current_file_path)}"
+        else:
+             title += " - Untitled"
+        
+        if self.is_modified:
+            title += " *"
+        self.setWindowTitle(title)
+
+    def maybe_save_changes(self) -> bool:
+        if not self.is_modified:
+            return True
+        
+        ret = QMessageBox.warning(self, "Unsaved Changes",
+                                  "The document has been modified.\nDo you want to save your changes?",
+                                  QMessageBox.StandardButton.Save | QMessageBox.StandardButton.Discard | QMessageBox.StandardButton.Cancel)
+        
+        if ret == QMessageBox.StandardButton.Save:
+            self.save_file()
+            return True # check if save succeeded? save_file catches exceptions but we might want to check
+        elif ret == QMessageBox.StandardButton.Discard:
+            return True
+        else:
+            return False # Cancel
+
+    def closeEvent(self, event):
+        if self.maybe_save_changes():
+            event.accept()
+        else:
+            event.ignore()
+
     def update_progress(self, current, total):
         self.progress_bar.setMaximum(total)
         self.progress_bar.setValue(current)
@@ -220,6 +255,9 @@ class MainWindow(QMainWindow):
         self.subpage_combo.setCurrentIndex(new_index)
 
     def close_file(self):
+        if not self.maybe_save_changes():
+            return
+            
         # Reset everything
         self.service = TeletextService()
         self.current_page = None
@@ -231,10 +269,19 @@ class MainWindow(QMainWindow):
         self.canvas.set_page(None)
         # Maybe reset text of hex input
         self.hex_input.clear()
+        
+        self.undo_stack.clear()
+        self.redo_stack.clear()
+        
         QMessageBox.information(self, "Closed", "File closed.")
         self.status_label.setText("Ready")
+        self.set_modified(False)
+
 
     def open_file(self):
+        if not self.maybe_save_changes():
+            return
+
         fname, _ = QFileDialog.getOpenFileName(self, "Open T42", "", "Teletext Files (*.t42);;All Files (*)")
         if fname:
             try:
@@ -248,6 +295,10 @@ class MainWindow(QMainWindow):
                 
                 self.progress_bar.setVisible(False)
                 self.status_label.setText(f"Loaded {len(self.service.pages)} pages from {os.path.basename(fname)}")
+                
+                self.undo_stack.clear()
+                self.redo_stack.clear()
+                self.set_modified(False)
             except Exception as e:
                 self.progress_bar.setVisible(False)
                 QMessageBox.critical(self, "Error", f"Failed to load file: {e}")
@@ -274,6 +325,7 @@ class MainWindow(QMainWindow):
             
             self.progress_bar.setVisible(False)
             self.status_label.setText(f"Saved {len(self.service.pages)} pages to {os.path.basename(self.current_file_path)}")
+            self.set_modified(False)
         except Exception as e:
             self.progress_bar.setVisible(False)
             QMessageBox.critical(self, "Error", f"Failed to save file: {e}")
@@ -349,6 +401,7 @@ class MainWindow(QMainWindow):
         # Limit stack size
         if len(self.undo_stack) > 50:
             self.undo_stack.pop(0)
+        self.set_modified(True)
 
     def undo(self):
         if not self.undo_stack:
@@ -362,6 +415,7 @@ class MainWindow(QMainWindow):
         snapshot = self.undo_stack.pop()
         self.restore_snapshot(snapshot)
         self.status_label.setText("Undone.")
+        self.set_modified(True)
 
     def redo(self):
         if not self.redo_stack:
@@ -375,6 +429,7 @@ class MainWindow(QMainWindow):
         snapshot = self.redo_stack.pop()
         self.restore_snapshot(snapshot)
         self.status_label.setText("Redone.")
+        self.set_modified(True)
 
     def restore_snapshot(self, snapshot: Page):
         # We need to update self.current_page content