def _default_buffer_pos_changed(self, _: Buffer) -> None:
        """When the cursor changes in the default buffer. Synchronize with
        history buffer."""
        # Only when this buffer has the focus.
        if self.app.current_buffer == self.default_buffer:
            try:
                line_no = (
                    self.default_buffer.document.cursor_position_row
                    - self.history_mapping.result_line_offset
                )

                if line_no < 0:  # When the cursor is above the inserted region.
                    raise IndexError

                history_lineno = sorted(self.history_mapping.selected_lines)[line_no]
            except IndexError:
                pass
            else:
                self.history_buffer.cursor_position = (
                    self.history_buffer.document.translate_row_col_to_index(
                        history_lineno, 0
                    )
                )
When the cursor changes in the default buffer. Synchronize with
        history buffer.
src/ptpython/history_browser.py