Update the key bindings.

src/editor.py

@@ -195,10 +195,10 @@ def new_file():
 
     # Add keyboard shortcuts
     editor.bind('<Button-3>', show_popup_menu)
-    editor.bind('Control-C', copy)
-    editor.bind('Control-V', paste)
-    editor.bind('Control-S', save)
-    editor.bind('Control-P', load_preview)
+    editor.bind('<Control-C>', copy)
+    editor.bind('<Control-V>', paste)
+    editor.bind('<Control-S>', save)
+    editor.bind('<Control-P>', load_preview)
     editor.bind('<F1>', show_project_info)
     editor.bind('<F5>', load_preview)
 

src/error_generator.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python3
+
+"""
+Module error_generator
+======================
+
+Generate a Markdown syntax error or warning.
+"""
+
+class ErrorGenerator:
+    """
+    Class ErrorGenerator
+    ====================
+
+    The error generator for tkMarker.
+    """
+    def generate(self, level: int, text: str):
+        """
+        Function generate()
+        ===================
+
+        Generate an error.
+        """
+        match level:
+            case 0:
+                self.print('WARNING ')
+            case 1:
+                self.print('ERROR')
+        self.print(text, '\n')
+    def print(self, *values):
+        print(values, flush=True, end='')
+