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What's new in 5.0

A release about the keyboard. A key press stops being the console's own type and becomes one with room for the modifier that terminal reports and the console type could not hold; a binding stops being a list of positions and becomes something built. The break is the type itself — Migrating to 5.0 is the two-line change most applications need, and the changelog is the full record.

A key press has room for Command​

ConsoleKeyInfo stores Shift, Alt and Control as three booleans, and there is no fourth slot. The key next to the space bar — Command on a Mac, the Windows key elsewhere — needs one, and a terminal does report it: one more bit in the same modifier field as the rest.

public ViewRoute Handle(KeyPress key) =>
    key is { Key: ConsoleKey.LeftArrow, Modifiers: KeyModifiers.Super } ? ViewKind.Default : ViewRoute.None;

That bit is not a curiosity. On a Mac terminal, Option is spoken for by the characters it types, so Alt never reaches an application at all and every binding built on it is unreachable. Command is what that keyboard has going spare, and a binding wearing it relabels itself for the machine it runs on: Cmd+← on a Mac, Win+← elsewhere.

A whole keymap moves onto it at once, because rewriting thirty bindings by hand is how an application ends up with twenty-eight of them rewritten:

builder.UseKeymap(new ArlecchinoKeymap().Replacing(KeyModifiers.Alt, KeyModifiers.Super));

A binding is built, not listed​

KeyBinding used to carry its second combination as two more positional parameters, which allowed exactly one alternative and read as four keys in a row at the call site. Now the binding is the combination it is named after, and everything else is added to it:

new KeyBinding(ConsoleKey.Insert, KeyModifiers.Control)
    .AddAlternative(ConsoleKey.C, KeyModifiers.Control | KeyModifiers.Shift);

Call AddAlternative as often as there are habits to answer to. What is written on the keys screen is the combination the binding is named after; the alternatives are matched and never drawn, so a screen lists one key per command however many reach it.

Two keystrokes, one command​

A terminal hands on a handful of combinations and no more. Option is spoken for, Command belongs to the window, and what is left on a Mac are the letters held with Control — and there are not thirty of those. A leader spends one of them and hands back the alphabet behind it:

new KeyBinding(ConsoleKey.X, KeyModifiers.Control).ThenKey(ConsoleKey.T);

While a leader is half typed, the hints box stops listing the keys that are out of reach and lists what finishes the chord instead, so the second key is read rather than remembered. An application that turned the hints box off still gets this one: turning it off says something about the keys of a screen, not about a key half pressed.

Opens and Closes ask about the two halves, and Matches answers false for a chord, so a leader on its own runs nothing. Keyboard is where the whole of it is written down.