Enum Edit 

#[non_exhaustive]
pub enum Edit {
    Insert(char),
    Backspace,
    Delete,
    Left,
    Right,
    WordLeft,
    WordRight,
    Home,
    End,
    KillToStart,
    KillToEnd,
    KillWordLeft,
    KillWordRight,
    Yank,
    HistoryPrev,
    HistoryNext,
}

One editing command for an Editor.

Edit is the boundary between the terminal and the editor. The host reads key events however its platform delivers them — a raw-mode terminal library, a GUI text field, a test script — and maps each one to an Edit; the editor applies it to the line and reports whether anything changed. Keeping the mapping on the host’s side means the editor never touches a terminal and any keymap (Emacs, Vi-style, custom) is a lookup table away.

Motions and deletions work in display units: a visible character together with any zero-width characters attached to it, such as a combining accent. The cursor never stops inside a unit. A word is a run of identifier characters (Unicode XID_Continue: letters, digits, _, combining marks); everything else separates words.

The usual Emacs/readline bindings are noted on each variant as a guide; they are not built in.

The enum is #[non_exhaustive], so new commands can arrive in a minor release. Hosts build Edit values rather than matching on them, so this costs nothing in practice.

Examples

use repl_lang::{Edit, Editor};

let mut editor = Editor::new();
for c in "print x".chars() {
    editor.apply(Edit::Insert(c));
}
assert!(editor.apply(Edit::WordLeft));    // cursor before `x`
assert!(editor.apply(Edit::KillToStart)); // removes "print "
assert_eq!(editor.line(), "x");
assert!(editor.apply(Edit::Yank));        // and puts it back
assert_eq!(editor.line(), "print x");

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Insert(char)

Inserts a character at the cursor and moves the cursor past it.

Control characters ('\n', '\t', escape, and the rest of the C0/C1 ranges) are refused: they have no printable form on a single line, and a terminal key handler should turn them into commands instead. So are the bidirectional formatting characters (U+061C, U+200E, U+200F, U+202A to U+202E, U+2066 to U+2069), which are invisible and change how the text around them is displayed.

Backspace

Deletes the display unit before the cursor. Backspace, Ctrl-H.

Delete

Deletes the display unit under the cursor. Delete, Ctrl-D on a non-empty line.

Left

Moves one display unit left. ←, Ctrl-B.

Right

Moves one display unit right. →, Ctrl-F.

WordLeft

Moves to the start of the current or previous word. Ctrl-←, Alt-B.

WordRight

Moves to the end of the current or next word. Ctrl-→, Alt-F.

Home

Moves to the start of the line. Home, Ctrl-A.

End

Moves to the end of the line. End, Ctrl-E.

KillToStart

Cuts everything before the cursor into the kill buffer. Ctrl-U.

KillToEnd

Cuts everything from the cursor to the end into the kill buffer. Ctrl-K.

KillWordLeft

Cuts the word before the cursor into the kill buffer. Ctrl-W, Alt-Backspace.

KillWordRight

Cuts the word after the cursor into the kill buffer. Alt-D.

Yank

Inserts the kill buffer at the cursor. Ctrl-Y.

HistoryPrev

Replaces the line with the previous (older) history entry. The first step saves the line being typed so HistoryNext can return to it. ↑, Ctrl-P.

HistoryNext

Replaces the line with the next (newer) history entry, or restores the line that was being typed when browsing started. ↓, Ctrl-N.

Trait Implementations

impl Clone for Edit

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Edit

impl Debug for Edit

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Edit

impl Hash for Edit

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Edit

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Edit