Add custom navigation bindings to MarkdownViewer with ToC?

[TomJGooding]

I would like to add custom navigation bindings to the builtin MarkdownViewer widget in my app. The problem is that this requires handling both the bindings for scrolling the markdown content and the cursor movements for the Table of Contents.

I've hacked together the code below which seems to work, but I am wondering if there might be a better way of doing this (that doesn't require rebuilding my own version of the MarkdownViewer in a custom widget)?

Many thanks as always for any advice!

from textual.app import App, ComposeResult
from textual.widgets import Footer, MarkdownViewer, Tree

EXAMPLE_MARKDOWN = """\
# Markdown Document

This is an example of Textual's `Markdown` widget.

## Features

Markdown syntax and extensions are supported.

- Typography *emphasis*, **strong**, `inline code` etc.
- Headers
- Lists (bullet and ordered)
- Syntax highlighted code blocks
- Tables!
"""


class MarkDownViLikeApp(App):
    BINDINGS = [
        ("k", "up", "Up"),
        ("j", "down", "Down"),
        ("q", "quit", "Quit"),
    ]

    def compose(self) -> ComposeResult:
        yield MarkdownViewer(EXAMPLE_MARKDOWN * 5, show_table_of_contents=True)
        yield Footer()

    def action_up(self) -> None:
        if isinstance(self.focused, MarkdownViewer):
            self.focused.action_scroll_up()
        elif isinstance(self.focused, Tree):
            self.focused.action_cursor_up()

    def action_down(self) -> None:
        if isinstance(self.focused, MarkdownViewer):
            self.focused.action_scroll_down()
        elif isinstance(self.focused, Tree):
            self.focused.action_cursor_down()


if __name__ == "__main__":
    app = MarkDownViLikeApp()
    app.run()