Function render_source 

pub fn render_source(
    code: &str,
    editing: Editing<'_>,
    cx: &mut App,
) -> AnyElement

Paint a document’s own markdown source: a fence’s caret, selection and hit testing, without a fence’s box, band or copy button.

The caret is a Cursor at block 0 in Part::Code — what a document held as one fence answers to, which is how an editor holds its source. Wrapping is not optional here: a paragraph is one line of markdown, and a source view that scrolled sideways would hide most of it.