Find the correct column index in adjust_vertical

components/script/textinput.rs

@@ -301,8 +301,11 @@ impl<T: ClipboardProvider> TextInput<T> {
             return;
         }
 
+
+        let col = self.lines[self.edit_point.line][..self.edit_point.index].chars().count();
+
         self.edit_point.line = target_line as usize;
-        self.edit_point.index = min(self.current_line_length(), self.edit_point.index);
+        self.edit_point.index = len_of_first_n_chars(&self.lines[self.edit_point.line], col);
     }
 
     /// Adjust the editing point position by a given number of bytes. If the adjustment

tests/unit/script/textinput.rs

@@ -244,6 +244,19 @@ fn test_textinput_adjust_vertical() {
     assert_eq!(textinput.edit_point.index, 1);
 }
 
+#[test]
+fn test_textinput_adjust_vertical_multibyte() {
+    let mut textinput = text_input(Lines::Multiple, "áé\nae");
+
+    textinput.adjust_horizontal_by_one(Direction::Forward, Selection::NotSelected);
+    assert_eq!(textinput.edit_point.line, 0);
+    assert_eq!(textinput.edit_point.index, 2);
+
+    textinput.adjust_vertical(1, Selection::NotSelected);
+    assert_eq!(textinput.edit_point.line, 1);
+    assert_eq!(textinput.edit_point.index, 1);
+}
+
 #[test]
 fn test_textinput_adjust_horizontal() {
     let mut textinput = text_input(Lines::Multiple, "abc\nde\nf");