Function replace_selection 

pub fn replace_selection(
    edit: &mut TextEdit,
    config: &Config,
    metrics: &Metrics<'_>,
    text: &str,
    max_len: Option<u32>,
) -> bool

Replaces the selection with text, leaving the caret after it.

One undo item however long the text, which is the difference from typing the same characters one at a time.

A DoNotScroll field already at its plate’s edge refuses the insertion half — see is_text_overflow — but the removal half still runs upstream, because ReplaceSelection clears before it inserts. Deleting a selection therefore always works, however full the field is.

let mut edit = TextEdit::new("AB", &config, &metrics, true);
edit.set_selection(0, 1);
assert!(ops::replace_selection(&mut edit, &config, &metrics, "XYZ", None));
assert_eq!(edit.text, "XYZB");
// A caret is left after the insertion, not a selection over it.
assert_eq!(edit.selected_text(), "");
assert_eq!(edit.caret_index(), 3);

// One undo item however long the text, unlike typing it out.
ops::undo(&mut edit, &config, &metrics);
assert_eq!(edit.text, "AB");