notes for working with Textual in Python

When working with Textual, here are some notes:

1. Widgets have a lot of CPU overhead, since each one invokes callbacks during mount/compose and things have to be laid out, styled, etc. Therefore, prefer to use Widget.render() -> Text to return a text representation of large, static content. Save Widget.compose() for containers and layouts.

2. Use egregious background colors to figure out the boundary of widget, like background: green. Since borders are so wide (one character/row) setting a border like you might do in HTML doesn’t work quite as well.

3. Rich doesn’t have access to class styles or CSS styling provided at the Textual level. This causes a temptation to use lots of small widgets, but see #1. Instead, inspect the app stylesheet and resolve the style you want into a Rich.Style and pass into Rich.Text(..., style=style).