def load_vi_bindings(registry, enable_visual_key=Always(), get_search_state=None, filter=None):
    # Note: Some key bindings have the "~IsReadOnly()" filter added. This
    #       prevents the handler to be executed when the focus is on a
    #       read-only buffer.
    #       This is however only required for those that change the ViState to
    #       INSERT mode. The `Buffer` class itself throws the
    #       `EditReadOnlyBuffer` exception for any text operations which is
    #       handled correctly. There is no need to add "~IsReadOnly" to all key
    #       bindings that do text manipulation.

    enable_visual_key = to_cli_filter(enable_visual_key)

    # Default get_search_state.
    if get_search_state is None:
        def get_search_state(cli): return cli.search_state

    handle = create_handle_decorator(registry, filter)

    # (Note: Always take the navigation bindings in read-only mode, even when
    #  ViState says different.)
    navigation_mode = (InViMode(InputMode.NAVIGATION) | IsReadOnly()) & ~ filters.HasSelection()
    insert_mode = InViMode(InputMode.INSERT) & ~ filters.HasSelection() & ~IsReadOnly()
    replace_mode = InViMode(InputMode.REPLACE) & ~ filters.HasSelection() & ~IsReadOnly()
    selection_mode = filters.HasSelection()
    operator_given = Condition(lambda cli: cli.vi_state.operator_func is not None)
    digraph_mode = Condition(lambda cli: cli.vi_state.waiting_for_digraph)

    vi_transform_functions = [
        # Rot 13 transformation
        (('g', '?'), lambda string: codecs.encode(string, 'rot_13')),

        # To lowercase
        (('g', 'u'), lambda string: string.lower()),

        # To uppercase.
        (('g', 'U'), lambda string: string.upper()),

        # Swap case.
        # (XXX: If we would implement 'tildeop', the 'g' prefix is not required.)
        (('g', '~'), lambda string: string.swapcase()),
    ]

    def check_cursor_position(event):
        """
        After every command, make sure that if we are in navigation mode, we
        never put the cursor after the last character of a line. (Unless it's
        an empty line.)
        """
        buff = event.current_buffer
        preferred_column = buff.preferred_column

        if (
                (filter is None or filter(event.cli)) and  # First make sure that this key bindings are active.

                event.cli.vi_state.input_mode == InputMode.NAVIGATION and
                buff.document.is_cursor_at_the_end_of_line and
                len(buff.document.current_line) > 0):
            buff.cursor_position -= 1

            # Set the preferred_column for arrow up/down again.
            # (This was cleared after changing the cursor position.)
            buff.preferred_column = preferred_column

    registry.on_handler_called += check_cursor_position

    @handle(Keys.Escape)
    def _(event):
        """
        Escape goes to vi navigation mode.
        """
        buffer = event.current_buffer
        vi_state = event.cli.vi_state

        if vi_state.input_mode in (InputMode.INSERT, InputMode.REPLACE):
            buffer.cursor_position += buffer.document.get_cursor_left_position()

        vi_state.reset(InputMode.NAVIGATION)

        if bool(buffer.selection_state):
            buffer.exit_selection()

    @handle('k', filter=selection_mode)
    def _(event):
        """
        Arrow up in selection mode.
        """
        event.current_buffer.cursor_up(count=event.arg)

    @handle('j', filter=selection_mode)
    def _(event):
        """
        Arrow down in selection mode.
        """
        event.current_buffer.cursor_down(count=event.arg)

    @handle('k', filter=navigation_mode)
    @handle(Keys.Up, filter=navigation_mode)
    @handle(Keys.ControlP, filter=navigation_mode)
    def _(event):
        """
        Arrow up and ControlP in navigation mode go up.
        """
        b = event.current_buffer
        b.auto_up(count=event.arg)

    @handle('j', filter=navigation_mode)
    @handle(Keys.Down, filter=navigation_mode)
    @handle(Keys.ControlN, filter=navigation_mode)
    def _(event):
        """
        Arrow down and Control-N in navigation mode.
        """
        b = event.current_buffer
        b.auto_down(count=event.arg)

    @handle(Keys.Backspace, filter=navigation_mode)
    def _(event):
        """
        In navigation-mode, move cursor.
        """
        event.current_buffer.cursor_position += \
            event.current_buffer.document.get_cursor_left_position(count=event.arg)

    @handle(Keys.ControlV, Keys.Any, filter=insert_mode)
    def _(event):
        """
        Insert a character literally (quoted insert).
        """
        event.current_buffer.insert_text(event.data, overwrite=False)

    @handle(Keys.ControlN, filter=insert_mode)
    def _(event):
        b = event.current_buffer

        if b.complete_state:
            b.complete_next()
        else:
            event.cli.start_completion(select_first=True)

    @handle(Keys.ControlP, filter=insert_mode)
    def _(event):
        """
        Control-P: To previous completion.
        """
        b = event.current_buffer

        if b.complete_state:
            b.complete_previous()
        else:
            event.cli.start_completion(select_last=True)

    @handle(Keys.ControlY, filter=insert_mode)
    def _(event):
        """
        Accept current completion.
        """
        event.current_buffer.complete_state = None

    @handle(Keys.ControlE, filter=insert_mode)
    def _(event):
        """
        Cancel completion. Go back to originally typed text.
        """
        event.current_buffer.cancel_completion()

    @handle(Keys.ControlJ, filter=navigation_mode)   # XXX: only if the selected buffer has a return handler.
    def _(event):
        """
        In navigation mode, pressing enter will always return the input.
        """
        b = event.current_buffer

        if b.accept_action.is_returnable:
            b.accept_action.validate_and_handle(event.cli, b)

    # ** In navigation mode **

    # List of navigation commands: http://hea-www.harvard.edu/~fine/Tech/vi.html

    @handle(Keys.Insert, filter=navigation_mode)
    def _(event):
        " Presing the Insert key. "
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('a', filter=navigation_mode & ~IsReadOnly())
            # ~IsReadOnly, because we want to stay in navigation mode for
            # read-only buffers.
    def _(event):
        event.current_buffer.cursor_position += event.current_buffer.document.get_cursor_right_position()
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('A', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        event.current_buffer.cursor_position += event.current_buffer.document.get_end_of_line_position()
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('C', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        """
        # Change to end of line.
        # Same as 'c$' (which is implemented elsewhere.)
        """
        buffer = event.current_buffer

        deleted = buffer.delete(count=buffer.document.get_end_of_line_position())
        event.cli.clipboard.set_text(deleted)
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('c', 'c', filter=navigation_mode & ~IsReadOnly())
    @handle('S', filter=navigation_mode & ~IsReadOnly())
    def _(event):  # TODO: implement 'arg'
        """
        Change current line
        """
        buffer = event.current_buffer

        # We copy the whole line.
        data = ClipboardData(buffer.document.current_line, SelectionType.LINES)
        event.cli.clipboard.set_data(data)

        # But we delete after the whitespace
        buffer.cursor_position += buffer.document.get_start_of_line_position(after_whitespace=True)
        buffer.delete(count=buffer.document.get_end_of_line_position())
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('D', filter=navigation_mode)
    def _(event):
        buffer = event.current_buffer
        deleted = buffer.delete(count=buffer.document.get_end_of_line_position())
        event.cli.clipboard.set_text(deleted)

    @handle('d', 'd', filter=navigation_mode)
    def _(event):
        """
        Delete line. (Or the following 'n' lines.)
        """
        buffer = event.current_buffer

        # Split string in before/deleted/after text.
        lines = buffer.document.lines

        before = '\n'.join(lines[:buffer.document.cursor_position_row])
        deleted = '\n'.join(lines[buffer.document.cursor_position_row: buffer.document.cursor_position_row + event.arg])
        after = '\n'.join(lines[buffer.document.cursor_position_row + event.arg:])

        # Set new text.
        if before and after:
            before = before + '\n'

        # Set text and cursor position.
        buffer.document = Document(
            text=before + after,
            # Cursor At the start of the first 'after' line, after the leading whitespace.
            cursor_position = len(before) + len(after) - len(after.lstrip(' ')))

        # Set clipboard data
        event.cli.clipboard.set_data(ClipboardData(deleted, SelectionType.LINES))

    @handle('x', filter=selection_mode)
    def _(event):
        """
        Cut selection.
        ('x' is not an operator.)
        """
        clipboard_data = event.current_buffer.cut_selection()
        event.cli.clipboard.set_data(clipboard_data)

    @handle('i', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('I', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        event.cli.vi_state.input_mode = InputMode.INSERT
        event.current_buffer.cursor_position += \
            event.current_buffer.document.get_start_of_line_position(after_whitespace=True)

    @handle('J', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        """ Join lines. """
        for i in range(event.arg):
            event.current_buffer.join_next_line()

    @handle('J', filter=selection_mode & ~IsReadOnly())
    def _(event):
        """ Join selected lines. """
        event.current_buffer.join_selected_lines()

    @handle('n', filter=navigation_mode)
    def _(event):  # XXX: use `text_object`
        """
        Search next.
        """
        event.current_buffer.apply_search(
            get_search_state(event.cli), include_current_position=False,
            count=event.arg)

    @handle('N', filter=navigation_mode)
    def _(event):  # TODO: use `text_object`
        """
        Search previous.
        """
        event.current_buffer.apply_search(
            ~get_search_state(event.cli), include_current_position=False,
            count=event.arg)

    @handle('p', filter=navigation_mode)
    def _(event):
        """
        Paste after
        """
        event.current_buffer.paste_clipboard_data(
            event.cli.clipboard.get_data(),
            count=event.arg)

    @handle('P', filter=navigation_mode)
    def _(event):
        """
        Paste before
        """
        event.current_buffer.paste_clipboard_data(
            event.cli.clipboard.get_data(),
            before=True,
            count=event.arg)

    def paste_named_register_handler(c):
        @handle('"', c, 'p')
        def _(event):
            " Paste from named register. "
            data = event.cli.vi_state.named_registers.get(c)
            if data:
                event.current_buffer.paste_clipboard_data(data, count=event.arg)

        @handle('"', c, 'P')
        def _(event):
            " Paste (before) from named register. "
            data = event.cli.vi_state.named_registers.get(c)
            if data:
                event.current_buffer.paste_clipboard_data(
                    data, before=True, count=event.arg)

    for c in ascii_lowercase:
        paste_named_register_handler(c)


    @handle('r', Keys.Any, filter=navigation_mode)
    def _(event):
        """
        Replace single character under cursor
        """
        event.current_buffer.insert_text(event.data * event.arg, overwrite=True)
        event.current_buffer.cursor_position -= 1

    @handle('R', filter=navigation_mode)
    def _(event):
        """
        Go to 'replace'-mode.
        """
        event.cli.vi_state.input_mode = InputMode.REPLACE

    @handle('s', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        """
        Substitute with new text
        (Delete character(s) and go to insert mode.)
        """
        text = event.current_buffer.delete(count=event.arg)
        event.cli.clipboard.set_text(text)
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('u', filter=navigation_mode, save_before=(lambda e: False))
    def _(event):
        for i in range(event.arg):
            event.current_buffer.undo()

    @handle('V', filter=navigation_mode)
    def _(event):
        """
        Start lines selection.
        """
        event.current_buffer.start_selection(selection_type=SelectionType.LINES)

    @handle(Keys.ControlV, filter=navigation_mode)
    def _(event):
        " Enter block selection mode. "
        event.current_buffer.start_selection(selection_type=SelectionType.BLOCK)

    @handle('V', filter=selection_mode)
    def _(event):
        """
        Exit line selection mode, or go from non line selection mode to line
        selection mode.
        """
        selection_state = event.current_buffer.selection_state

        if selection_state.type != SelectionType.LINES:
            selection_state.type = SelectionType.LINES
        else:
            event.current_buffer.exit_selection()

    @handle('v', filter=navigation_mode & enable_visual_key)
    def _(event):
        " Enter character selection mode. "
        event.current_buffer.start_selection(selection_type=SelectionType.CHARACTERS)

    @handle('v', filter=selection_mode)
    def _(event):
        """
        Exit character selection mode, or go from non-character-selection mode
        to character selection mode.
        """
        selection_state = event.current_buffer.selection_state

        if selection_state.type != SelectionType.CHARACTERS:
            selection_state.type = SelectionType.CHARACTERS
        else:
            event.current_buffer.exit_selection()

    @handle(Keys.ControlV, filter=selection_mode)
    def _(event):
        """
        Exit block selection mode, or go from non block selection mode to block
        selection mode.
        """
        selection_state = event.current_buffer.selection_state

        if selection_state.type != SelectionType.BLOCK:
            selection_state.type = SelectionType.BLOCK
        else:
            event.current_buffer.exit_selection()


    @handle('a', 'w', filter=selection_mode)
    @handle('a', 'W', filter=selection_mode)
    def _(event):
        """
        Switch from visual linewise mode to visual characterwise mode.
        """
        buffer = event.current_buffer

        if buffer.selection_state and buffer.selection_state.type == SelectionType.LINES:
            buffer.selection_state.type = SelectionType.CHARACTERS

    @handle('x', filter=navigation_mode)
    def _(event):
        """
        Delete character.
        """
        text = event.current_buffer.delete(count=event.arg)
        event.cli.clipboard.set_text(text)

    @handle('X', filter=navigation_mode)
    def _(event):
        text = event.current_buffer.delete_before_cursor()
        event.cli.clipboard.set_text(text)

    @handle('y', 'y', filter=navigation_mode)
    @handle('Y', filter=navigation_mode)
    def _(event):
        """
        Yank the whole line.
        """
        text = '\n'.join(event.current_buffer.document.lines_from_current[:event.arg])
        event.cli.clipboard.set_data(ClipboardData(text, SelectionType.LINES))

    @handle('+', filter=navigation_mode)
    def _(event):
        """
        Move to first non whitespace of next line
        """
        buffer = event.current_buffer
        buffer.cursor_position += buffer.document.get_cursor_down_position(count=event.arg)
        buffer.cursor_position += buffer.document.get_start_of_line_position(after_whitespace=True)

    @handle('-', filter=navigation_mode)
    def _(event):
        """
        Move to first non whitespace of previous line
        """
        buffer = event.current_buffer
        buffer.cursor_position += buffer.document.get_cursor_up_position(count=event.arg)
        buffer.cursor_position += buffer.document.get_start_of_line_position(after_whitespace=True)

    @handle('>', '>', filter=navigation_mode)
    def _(event):
        """
        Indent lines.
        """
        buffer = event.current_buffer
        current_row = buffer.document.cursor_position_row
        indent(buffer, current_row, current_row + event.arg)

    @handle('<', '<', filter=navigation_mode)
    def _(event):
        """
        Unindent lines.
        """
        current_row = event.current_buffer.document.cursor_position_row
        unindent(event.current_buffer, current_row, current_row + event.arg)

    @handle('O', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        """
        Open line above and enter insertion mode
        """
        event.current_buffer.insert_line_above(
                copy_margin=not event.cli.in_paste_mode)
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('o', filter=navigation_mode & ~IsReadOnly())
    def _(event):
        """
        Open line below and enter insertion mode
        """
        event.current_buffer.insert_line_below(
                copy_margin=not event.cli.in_paste_mode)
        event.cli.vi_state.input_mode = InputMode.INSERT

    @handle('~', filter=navigation_mode)
    def _(event):
        """
        Reverse case of current character and move cursor forward.
        """
        buffer = event.current_buffer
        c = buffer.document.current_char

        if c is not None and c != '\n':
            c = (c.upper() if c.islower() else c.lower())
            buffer.insert_text(c, overwrite=True)

    @handle('#', filter=navigation_mode)
    def _(event):
        """
        Go to previous occurence of this word.
        """
        b = event.cli.current_buffer

        search_state = get_search_state(event.cli)
        search_state.text = b.document.get_word_under_cursor()
        search_state.direction = IncrementalSearchDirection.BACKWARD

        b.apply_search(search_state, count=event.arg,
                       include_current_position=False)

    @handle('*', filter=navigation_mode)
    def _(event):
        """
        Go to next occurence of this word.
        """
        b = event.cli.current_buffer

        search_state = get_search_state(event.cli)
        search_state.text = b.document.get_word_under_cursor()
        search_state.direction = IncrementalSearchDirection.FORWARD

        b.apply_search(search_state, count=event.arg,
                       include_current_position=False)

    @handle('(', filter=navigation_mode)
    def _(event):
        # TODO: go to begin of sentence.
        # XXX: should become text_object.
        pass

    @handle(')', filter=navigation_mode)
    def _(event):
        # TODO: go to end of sentence.
        # XXX: should become text_object.
        pass

    def operator(*keys, **kw):
        """
        Register a Vi operator.

        Usage::

            @operator('d', filter=...)
            def handler(cli, text_object):
                # Do something with the text object here.
        """
        filter = kw.pop('filter', Always())
        assert not kw

        def decorator(operator_func):
            @handle(*keys, filter=~operator_given & filter & navigation_mode)
            def _(event):
                """
                Handle operator in navigation mode.
                """
                # When this key binding is matched, only set the operator
                # function in the ViState. We should execute it after a text
                # object has been received.
                event.cli.vi_state.operator_func = operator_func
                event.cli.vi_state.operator_arg = event.arg

            @handle(*keys, filter=~operator_given & filter & selection_mode)
            def _(event):
                """
                Handle operator in selection mode.
                """
                buff = event.current_buffer
                selection_state = buff.selection_state

                # Create text object from selection.
                if selection_state.type == SelectionType.LINES:
                    text_obj_type = TextObjectType.LINEWISE
                elif selection_state.type == SelectionType.BLOCK:
                    text_obj_type = TextObjectType.BLOCK
                else:
                    text_obj_type = TextObjectType.INCLUSIVE

                text_object = TextObject(
                    selection_state.original_cursor_position - buff.cursor_position,
                    type=text_obj_type)

                # Execute operator.
                operator_func(event, text_object)

                # Quit selection mode.
                buff.selection_state = None

        return decorator

    def text_object(*keys, **kw):
        """
        Register a text object function.

        Usage::

            @text_object('w', filter=..., no_move_handler=False)
            def handler(event):
                # Return a text object for this key.
                return TextObject(...)

        :param no_move_handler: Disable the move handler in navigation mode.
            (It's still active in selection mode.)
        """
        filter = kw.pop('filter', Always())
        no_move_handler = kw.pop('no_move_handler', False)
        assert not kw

        def decorator(text_object_func):
            assert callable(text_object_func)

            @handle(*keys, filter=operator_given & filter)
            def _(event):
                # Arguments are multiplied.
                vi_state = event.cli.vi_state
                event._arg = (vi_state.operator_arg or 1) * (event.arg or 1)

                # Call the text object handler.
                text_obj = text_object_func(event)
                if text_obj is not None:
                    assert isinstance(text_obj, TextObject)

                    # Call the operator function with the text object.
                    vi_state.operator_func(event, text_obj)

                # Clear operator.
                event.cli.vi_state.operator_func = None
                event.cli.vi_state.operator_arg = None

            # Register a move operation. (Doesn't need an operator.)
            if not no_move_handler:
                @handle(*keys, filter=~operator_given & filter & navigation_mode)
                def _(event):
                    " Move handler for navigation mode. "
                    text_object = text_object_func(event)
                    event.current_buffer.cursor_position += text_object.start

            @handle(*keys, filter=~operator_given & filter & selection_mode)
            def _(event):
                " Move handler for selection mode. "
                text_object = text_object_func(event)
                buff = event.current_buffer

                # When the text object has both a start and end position, like 'i(' or 'iw',
                # Turn this into a selection, otherwise the cursor.
                if text_object.end:
                    # Take selection positions from text object.
                    start, end = text_object.operator_range(buff.document)
                    start += buff.cursor_position
                    end += buff.cursor_position

                    buff.selection_state.original_cursor_position = start
                    buff.cursor_position = end

                    # Take selection type from text object.
                    if text_object.type == TextObjectType.LINEWISE:
                        buff.selection_state.type = SelectionType.LINES
                    else:
                        buff.selection_state.type = SelectionType.CHARACTERS
                else:
                    event.current_buffer.cursor_position += text_object.start

            # Make it possible to chain @text_object decorators.
            return text_object_func

        return decorator

    @text_object(Keys.Any, filter=operator_given)
    def _(event):
        """
        Unknown key binding while waiting for a text object.
        """
        event.cli.output.bell()

    #
    # *** Operators ***
    #

    def create_delete_and_change_operators(delete_only, reg_name=None):
        """
        Delete and change operators.

        :param delete_only: Create an operator that deletes, but doesn't go to insert mode.
        :param reg_name: Copy the deleted text to this named register instead of the clipboard.
        """
        if reg_name:
            handler_keys = ('"', reg_name, 'cd'[delete_only])
        else:
            handler_keys = 'cd'[delete_only]

        @operator(*handler_keys, filter=~IsReadOnly())
        def delete_or_change_operator(event, text_object):
            clipboard_data = None
            buff = event.current_buffer

            if text_object:
                new_document, clipboard_data = text_object.cut(buff)
                buff.document = new_document

            # Set deleted/changed text to clipboard or named register.
            if clipboard_data and clipboard_data.text:
                if reg_name:
                    event.cli.named_registers[reg_name] = clipboard_data
                else:
                    event.cli.clipboard.set_data(clipboard_data)

            # Only go back to insert mode in case of 'change'.
            if not delete_only:
                event.cli.vi_state.input_mode = InputMode.INSERT

    for c in tuple(ascii_lowercase) + (None, ):
        create_delete_and_change_operators(False, reg_name=c)
        create_delete_and_change_operators(True, reg_name=c)

    def create_transform_handler(transform_func, *a):
        @operator(*a, filter=~IsReadOnly())
        def _(event, text_object):
            """
            Apply transformation (uppercase, lowercase, rot13, swap case).
            """
            buff = event.current_buffer
            start, end = text_object.operator_range(buff.document)

            if start < end:
                # Transform.
                buff.transform_region(
                    buff.cursor_position + start,
                    buff.cursor_position + end,
                    transform_func)

                # Move cursor
                buff.cursor_position += (text_object.end or text_object.start)

    for k, f in vi_transform_functions:
        create_transform_handler(f, *k)

    @operator('y')
    def yank_handler(event, text_object):
        """
        Yank operator. (Copy text.)
        """
        _, clipboard_data = text_object.cut(event.current_buffer)
        if clipboard_data.text:
            event.cli.clipboard.set_data(clipboard_data)

    def create_yank_selection_handler(c):
        @operator('"', c, 'y')
        def _(event, text_object):
            " Yank selection to named register 'c'. "
            _, clipboard_data = text_object.cut(event.current_buffer)
            event.cli.vi_state.named_registers[c] = clipboard_data

    for c in ascii_lowercase:
        create_yank_selection_handler(c)

    @operator('>')
    def _(event, text_object):
        """
        Indent.
        """
        buff = event.current_buffer
        from_, to = text_object.get_line_numbers(buff)
        indent(buff, from_, to + 1, count=event.arg)

    @operator('<')
    def _(event, text_object):
        """
        Unindent.
        """
        buff = event.current_buffer
        from_, to = text_object.get_line_numbers(buff)
        unindent(buff, from_, to + 1, count=event.arg)

    @operator('g', 'q')
    def _(event, text_object):
        """
        Reshape text.
        """
        buff = event.current_buffer
        from_, to = text_object.get_line_numbers(buff)
        reshape_text(buff, from_, to)

    #
    # *** Text objects ***
    #

    @text_object('b')
    def _(event):
        """ Move one word or token left. """
        return TextObject(event.current_buffer.document.find_start_of_previous_word(count=event.arg) or 0)

    @text_object('B')
    def _(event):
        """ Move one non-blank word left """
        return TextObject(event.current_buffer.document.find_start_of_previous_word(count=event.arg, WORD=True) or 0)

    @text_object('$')
    def key_dollar(event):
        """ 'c$', 'd$' and '$':  Delete/change/move until end of line. """
        return TextObject(event.current_buffer.document.get_end_of_line_position())

    @text_object('w')
    def _(event):
        """ 'word' forward. 'cw', 'dw', 'w': Delete/change/move one word.  """
        return TextObject(event.current_buffer.document.find_next_word_beginning(count=event.arg) or
                            event.current_buffer.document.get_end_of_document_position())

    @text_object('W')
    def _(event):
        """ 'WORD' forward. 'cW', 'dW', 'W': Delete/change/move one WORD.  """
        return TextObject(event.current_buffer.document.find_next_word_beginning(count=event.arg, WORD=True) or
                            event.current_buffer.document.get_end_of_document_position())

    @text_object('e')
    def _(event):
        """ End of 'word': 'ce', 'de', 'e' """
        end = event.current_buffer.document.find_next_word_ending(count=event.arg)
        return TextObject(end - 1 if end else 0, type=TextObjectType.INCLUSIVE)

    @text_object('E')
    def _(event):
        """ End of 'WORD': 'cE', 'dE', 'E' """
        end = event.current_buffer.document.find_next_word_ending(count=event.arg, WORD=True)
        return TextObject(end - 1 if end else 0, type=TextObjectType.INCLUSIVE)

    @text_object('i', 'w', no_move_handler=True)
    def _(event):
        """ Inner 'word': ciw and diw """
        start, end = event.current_buffer.document.find_boundaries_of_current_word()
        return TextObject(start, end)

    @text_object('a', 'w', no_move_handler=True)
    def _(event):
        """ A 'word': caw and daw """
        start, end = event.current_buffer.document.find_boundaries_of_current_word(include_trailing_whitespace=True)
        return TextObject(start, end)

    @text_object('i', 'W', no_move_handler=True)
    def _(event):
        """ Inner 'WORD': ciW and diW """
        start, end = event.current_buffer.document.find_boundaries_of_current_word(WORD=True)
        return TextObject(start, end)

    @text_object('a', 'W', no_move_handler=True)
    def _(event):
        """ A 'WORD': caw and daw """
        start, end = event.current_buffer.document.find_boundaries_of_current_word(WORD=True, include_trailing_whitespace=True)
        return TextObject(start, end)

    @text_object('a', 'p', no_move_handler=True)
    def _(event):
        """
        Auto paragraph.
        """
        start = event.current_buffer.document.start_of_paragraph()
        end = event.current_buffer.document.end_of_paragraph(count=event.arg)
        return TextObject(start, end)

    @text_object('^')
    def key_circumflex(event):
        """ 'c^', 'd^' and '^': Soft start of line, after whitespace. """
        return TextObject(event.current_buffer.document.get_start_of_line_position(after_whitespace=True))

    @text_object('0', no_move_handler=True)
    def key_zero(event):
        """
        'c0', 'd0': Hard start of line, before whitespace.
        (The move '0' key is implemented elsewhere, because a '0' could also change the `arg`.)
        """
        return TextObject(event.current_buffer.document.get_start_of_line_position(after_whitespace=False))

    def create_ci_ca_handles(ci_start, ci_end, inner):
                # TODO: 'dab', 'dib', (brackets or block) 'daB', 'diB', Braces.
                # TODO: 'dat', 'dit', (tags (like xml)
        """
        Delete/Change string between this start and stop character. But keep these characters.
        This implements all the ci", ci<, ci{, ci(, di", di<, ca", ca<, ... combinations.
        """
        @text_object('ai'[inner], ci_start, no_move_handler=True)
        @text_object('ai'[inner], ci_end, no_move_handler=True)
        def _(event):
            if ci_start == ci_end:
                # Quotes
                start = event.current_buffer.document.find_backwards(ci_start, in_current_line=False)
                end = event.current_buffer.document.find(ci_end, in_current_line=False)
            else:
                # Brackets
                start = event.current_buffer.document.find_enclosing_bracket_left(ci_start, ci_end)
                end = event.current_buffer.document.find_enclosing_bracket_right(ci_start, ci_end)

            if start is not None and end is not None:
                offset = 0 if inner else 1
                return TextObject(start + 1 - offset, end + offset)
            else:
                # Nothing found.
                return TextObject(0)

    for inner in (False, True):
        for ci_start, ci_end in [('"', '"'), ("'", "'"), ("`", "`"),
                                 ('[', ']'), ('<', '>'), ('{', '}'), ('(', ')')]:
            create_ci_ca_handles(ci_start, ci_end, inner)

    @text_object('{')
    def _(event):
        """
        Move to previous blank-line separated section.
        Implements '{', 'c{', 'd{', 'y{'
        """
        index = event.current_buffer.document.start_of_paragraph(count=event.arg, before=True)
        return TextObject(index)

    @text_object('}')
    def _(event):
        """
        Move to next blank-line separated section.
        Implements '}', 'c}', 'd}', 'y}'
        """
        index = event.current_buffer.document.end_of_paragraph(count=event.arg, after=True)
        return TextObject(index)

    @text_object('f', Keys.Any)
    def _(event):
        """
        Go to next occurance of character. Typing 'fx' will move the
        cursor to the next occurance of character. 'x'.
        """
        event.cli.vi_state.last_character_find = CharacterFind(event.data, False)
        match = event.current_buffer.document.find(event.data, in_current_line=True, count=event.arg)
        if match:
            return TextObject(match, type=TextObjectType.INCLUSIVE)
        else:
            return TextObject(0)

    @text_object('F', Keys.Any)
    def _(event):
        """
        Go to previous occurance of character. Typing 'Fx' will move the
        cursor to the previous occurance of character. 'x'.
        """
        event.cli.vi_state.last_character_find = CharacterFind(event.data, True)
        return TextObject(event.current_buffer.document.find_backwards(event.data, in_current_line=True, count=event.arg) or 0)

    @text_object('t', Keys.Any)
    def _(event):
        """
        Move right to the next occurance of c, then one char backward.
        """
        event.cli.vi_state.last_character_find = CharacterFind(event.data, False)
        match = event.current_buffer.document.find(event.data, in_current_line=True, count=event.arg)
        if match:
            return TextObject(match - 1, type=TextObjectType.INCLUSIVE)
        else:
            return TextObject(0)

    @text_object('T', Keys.Any)
    def _(event):
        """
        Move left to the previous occurance of c, then one char forward.
        """
        event.cli.vi_state.last_character_find = CharacterFind(event.data, True)
        match = event.current_buffer.document.find_backwards(event.data, in_current_line=True, count=event.arg)
        return TextObject(match + 1 if match else 0)

    def repeat(reverse):
        """
        Create ',' and ';' commands.
        """
        @text_object(',' if reverse else ';')
        def _(event):
            # Repeat the last 'f'/'F'/'t'/'T' command.
            pos = 0
            vi_state = event.cli.vi_state

            type = TextObjectType.EXCLUSIVE

            if vi_state.last_character_find:
                char = vi_state.last_character_find.character
                backwards = vi_state.last_character_find.backwards

                if reverse:
                    backwards = not backwards

                if backwards:
                    pos = event.current_buffer.document.find_backwards(char, in_current_line=True, count=event.arg)
                else:
                    pos = event.current_buffer.document.find(char, in_current_line=True, count=event.arg)
                    type = TextObjectType.INCLUSIVE
            if pos:
                return TextObject(pos, type=type)
            else:
                return TextObject(0)
    repeat(True)
    repeat(False)

    @text_object('h')
    @text_object(Keys.Left)
    def _(event):
        """ Implements 'ch', 'dh', 'h': Cursor left. """
        return TextObject(event.current_buffer.document.get_cursor_left_position(count=event.arg))

    @text_object('j', no_move_handler=True)
    def _(event):
        """ Implements 'cj', 'dj', 'j', ... Cursor up. """
        return TextObject(event.current_buffer.document.get_cursor_down_position(count=event.arg), type=TextObjectType.LINEWISE)

    @text_object('k', no_move_handler=True)
    def _(event):
        """ Implements 'ck', 'dk', 'k', ... Cursor up. """
        return TextObject(event.current_buffer.document.get_cursor_up_position(count=event.arg), type=TextObjectType.LINEWISE)

    @text_object('l')
    @text_object(' ')
    @text_object(Keys.Right)
    def _(event):
        """ Implements 'cl', 'dl', 'l', 'c ', 'd ', ' '. Cursor right. """
        return TextObject(event.current_buffer.document.get_cursor_right_position(count=event.arg))

    @text_object('H')
    def _(event):
        """
        Moves to the start of the visible region. (Below the scroll offset.)
        Implements 'cH', 'dH', 'H'.
        """
        w = find_window_for_buffer_name(event.cli, event.cli.current_buffer_name)
        b = event.current_buffer

        if w and w.render_info:
            # When we find a Window that has BufferControl showing this window,
            # move to the start of the visible area.
            pos = (b.document.translate_row_col_to_index(
                       w.render_info.first_visible_line(after_scroll_offset=True), 0) -
                   b.cursor_position)

        else:
            # Otherwise, move to the start of the input.
            pos = -len(b.document.text_before_cursor)
        return TextObject(pos, type=TextObjectType.LINEWISE)

    @text_object('M')
    def _(event):
        """
        Moves cursor to the vertical center of the visible region.
        Implements 'cM', 'dM', 'M'.
        """
        w = find_window_for_buffer_name(event.cli, event.cli.current_buffer_name)
        b = event.current_buffer

        if w and w.render_info:
            # When we find a Window that has BufferControl showing this window,
            # move to the center of the visible area.
            pos = (b.document.translate_row_col_to_index(
                       w.render_info.center_visible_line(), 0) -
                   b.cursor_position)

        else:
            # Otherwise, move to the start of the input.
            pos = -len(b.document.text_before_cursor)
        return TextObject(pos, type=TextObjectType.LINEWISE)

    @text_object('L')
    def _(event):
        """
        Moves to the end of the visible region. (Above the scroll offset.)
        """
        w = find_window_for_buffer_name(event.cli, event.cli.current_buffer_name)
        b = event.current_buffer

        if w and w.render_info:
            # When we find a Window that has BufferControl showing this window,
            # move to the end of the visible area.
            pos = (b.document.translate_row_col_to_index(
                       w.render_info.last_visible_line(before_scroll_offset=True), 0) -
                   b.cursor_position)

        else:
            # Otherwise, move to the end of the input.
            pos = len(b.document.text_after_cursor)
        return TextObject(pos, type=TextObjectType.LINEWISE)

    @handle('z', '+', filter=navigation_mode|selection_mode)
    @handle('z', 't', filter=navigation_mode|selection_mode)
    @handle('z', Keys.ControlJ, filter=navigation_mode|selection_mode)
    def _(event):
        """
        Scrolls the window to makes the current line the first line in the visible region.
        """
        w = find_window_for_buffer_name(event.cli, event.cli.current_buffer_name)
        b = event.cli.current_buffer
        w.vertical_scroll = b.document.cursor_position_row

    @handle('z', '-', filter=navigation_mode|selection_mode)
    @handle('z', 'b', filter=navigation_mode|selection_mode)
    def _(event):
        """
        Scrolls the window to makes the current line the last line in the visible region.
        """
        w = find_window_for_buffer_name(event.cli, event.cli.current_buffer_name)

        # We can safely set the scroll offset to zero; the Window will meke
        # sure that it scrolls at least enough to make the cursor visible
        # again.
        w.vertical_scroll = 0

    @handle('z', 'z', filter=navigation_mode|selection_mode)
    def _(event):
        """
        Center Window vertically around cursor.
        """
        w = find_window_for_buffer_name(event.cli, event.cli.current_buffer_name)
        b = event.cli.current_buffer

        if w and w.render_info:
            info = w.render_info

            # Calculate the offset that we need in order to position the row
            # containing the cursor in the center.
            scroll_height = info.window_height // 2

            y = max(0, b.document.cursor_position_row - 1)
            height = 0
            while y > 0:
                line_height = info.get_height_for_line(y)

                if height + line_height < scroll_height:
                    height += line_height
                    y -= 1
                else:
                    break

            w.vertical_scroll = y

    @text_object('%')
    def _(event):
        """
        Implements 'c%', 'd%', '%, 'y%' (Move to corresponding bracket.)
        If an 'arg' has been given, go this this % position in the file.
        """
        buffer = event.current_buffer

        if event._arg:
            # If 'arg' has been given, the meaning of % is to go to the 'x%'
            # row in the file.
            if 0 < event.arg <= 100:
                absolute_index = buffer.document.translate_row_col_to_index(
                    int((event.arg * buffer.document.line_count - 1) / 100), 0)
                return TextObject(absolute_index - buffer.document.cursor_position, type=TextObjectType.LINEWISE)
            else:
                return TextObject(0)  # Do nothing.

        else:
            # Move to the corresponding opening/closing bracket (()'s, []'s and {}'s).
            match = buffer.document.find_matching_bracket_position()
            if match:
                return TextObject(match, type=TextObjectType.INCLUSIVE)
            else:
                return TextObject(0)

    @text_object('|')
    def _(event):
        # Move to the n-th column (you may specify the argument n by typing
        # it on number keys, for example, 20|).
        return TextObject(event.current_buffer.document.get_column_cursor_position(event.arg - 1))

    @text_object('g', 'g')
    def _(event):
        """
        Implements 'gg', 'cgg', 'ygg'
        """
        d = event.current_buffer.document

        if event._arg:
            # Move to the given line.
            return TextObject(d.translate_row_col_to_index(event.arg - 1, 0) - d.cursor_position, type=TextObjectType.LINEWISE)
        else:
            # Move to the top of the input.
            return TextObject(d.get_start_of_document_position(), type=TextObjectType.LINEWISE)

    @text_object('g', '_')
    def _(event):
        """
        Go to last non-blank of line.
        'g_', 'cg_', 'yg_', etc..
        """
        return TextObject(
            event.current_buffer.document.last_non_blank_of_current_line_position(), type=TextObjectType.INCLUSIVE)

    @text_object('g', 'e')
    def _(event):
        """
        Go to last character of previous word.
        'ge', 'cge', 'yge', etc..
        """
        prev_end = event.current_buffer.document.find_previous_word_ending(count=event.arg)
        return TextObject(prev_end - 1 if prev_end is not None else 0, type=TextObjectType.INCLUSIVE)

    @text_object('g', 'E')
    def _(event):
        """
        Go to last character of previous WORD.
        'gE', 'cgE', 'ygE', etc..
        """
        prev_end = event.current_buffer.document.find_previous_word_ending(count=event.arg, WORD=True)
        return TextObject(prev_end - 1 if prev_end is not None else 0, type=TextObjectType.INCLUSIVE)

    @text_object('G')
    def _(event):
        """
        Go to the end of the document. (If no arg has been given.)
        """
        buf = event.current_buffer
        return TextObject(buf.document.translate_row_col_to_index(buf.document.line_count - 1, 0) -
                          buf.cursor_position, type=TextObjectType.LINEWISE)

    #
    # *** Other ***
    #

    @handle('G', filter=HasArg())
    def _(event):
        """
        If an argument is given, move to this line in the  history. (for
        example, 15G)
        """
        event.current_buffer.go_to_history(event.arg - 1)

    for n in '0123456789':
        @handle(n, filter=navigation_mode|selection_mode|operator_given)
        def _(event):
            """
            Always handle numberics in navigation mode as arg.
            """
            if event.data in '123456789' or (event._arg and event.data == '0'):
                event.append_to_arg_count(event.data)
            elif event.data == '0':
                buffer = event.current_buffer
                buffer.cursor_position += buffer.document.get_start_of_line_position(after_whitespace=False)

    @handle(Keys.Any, filter=replace_mode)
    def _(event):
        """
        Insert data at cursor position.
        """
        event.current_buffer.insert_text(event.data, overwrite=True)

    @handle(Keys.ControlX, Keys.ControlL, filter=insert_mode)
    def _(event):
        """
        Pressing the ControlX - ControlL sequence in Vi mode does line
        completion based on the other lines in the document and the history.
        """
        event.current_buffer.start_history_lines_completion()

    @handle(Keys.ControlX, Keys.ControlF, filter=insert_mode)
    def _(event):
        """
        Complete file names.
        """
        # TODO
        pass

    @handle(Keys.ControlK, filter=insert_mode)
    def _(event):
        " Insert digraph. "
        event.cli.vi_state.waiting_for_digraph = True

    for key1, key2, symbol in DIGRAPHS:
        @handle(key1, key2, filter=digraph_mode)
        def _(event, symbol=symbol):
            " Insert digraph. "
            event.current_buffer.insert_text(six.unichr(symbol))
            event.cli.vi_state.waiting_for_digraph = False

    @handle(Keys.Any, filter=digraph_mode)
    def _(event):
        " Unknown digraph sequence. "
        event.cli.output.bell()
        event.cli.vi_state.waiting_for_digraph = False
Ensures token is well-formed and hasn't expired, and extracts client_id.
dataset/ETHPy150Open jonathanslenders/python-prompt-toolkit/prompt_toolkit/key_binding/bindings/vi.py/load_vi_bindings--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/python-compat-runtime/appengine-compat/exported_appengine_sdk/google/appengine/api/channel/channel_service_stub.py/ChannelServiceStub.validate_token_and_extract_client_id