Now the editor even warns when it gets closed and there are any unsaved files.

connect_gui.py

@@ -4,3 +4,4 @@ def connect_gui(app):
     app.main_window.openFile.triggered.connect(app.file_actions.open_files)
     app.main_window.saveFile.triggered.connect(app.file_actions.save_current_file)
     app.main_window.openFileTabs.tabCloseRequested.connect(app.file_actions.close_current_file)
+    app.QTMainWindow.closeEvent = app.utils.on_close

file.py

@@ -55,6 +55,12 @@ class FileActions:
 
         self.close_file(current_file_path, tab_index)
 
+    def save_all_files(self):
+        for file_path in self.app.open_files:
+            file = self.app.open_files[file_path]
+
+            self.save_file(file.path)
+
 
 class File:
     def __init__(self, app, path, name):

utils.py

@@ -52,3 +52,25 @@ class Utils:
         binary_string = bytes(bytes_int)
 
         return binary_string
+
+    def on_close(self, event):
+        changes = False
+
+        for file_path in self.app.open_files:
+            file = self.app.open_files[file_path]
+
+            if file.not_saved:
+                changes = True
+                break
+
+        if changes:
+            save_or_not = self.unsaved_changes_popup()
+
+            match save_or_not:
+                case "save":
+                    self.app.file_actions.save_all_files()
+
+                case "cancel":
+                    event.ignore()
+
+        print("Bye!")