candy-focus

A tiny, dependency-free focus ring for full-window terminal UIs: an ordered set of focusable regions with a single focused member and wrap-around Tab/Shift-Tab traversal.

It is the "which panel has focus" state for a TUI layout. Register each focusable region (sidebar, content grid, filter bar…), map Tab to next() and Shift-Tab to previous(), and give the region returned by current() an accent border when you render. The ring carries no rendering or key decoding of its own, so it composes with any candy-core model without pulling in dependencies.

Install

composer require sugarcraft/candy-focus

Quick start

use SugarCraft\Focus\FocusRing;

$ring = FocusRing::of('sidebar', 'grid', 'filter'); // 'sidebar' is focused

$ring = $ring->next();        // → 'grid'
$ring = $ring->next();        // → 'filter'
$ring = $ring->next();        // → 'sidebar' (wraps)
$ring = $ring->previous();    // → 'filter' (wraps the other way)
$ring = $ring->focus('grid'); // jump straight to a region

$ring->current();             // 'grid'
$ring->isFocused('grid');     // true

Wire it into a candy-core model's update():

if ($msg instanceof KeyMsg && $msg->type === KeyType::Tab) {
    $ring = $msg->shift ? $this->ring->previous() : $this->ring->next();
    return [$this->withRing($ring), null];
}

…and let each region style itself in view():

$style = $ring->isFocused('sidebar') ? $accentBorder : $plainBorder;

Behaviour

• A non-empty ring always has exactly one focused region; an empty ring focuses nothing (current() is null, index() is -1).
• register() appends to the traversal order and focuses the region only when the ring was empty; re-registering an existing id is a no-op.
• unregister() keeps focus on the same region where possible; removing the focused region shifts focus to whatever takes its slot (clamped to the end), and emptying the ring clears focus.
• next() / previous() wrap around and are no-ops with fewer than two regions.
• Immutable — every mutator returns a new FocusRing and leaves the receiver untouched, so it slots into the immutable-model (TEA) pattern.

API

Method	Description
FocusRing::new()	An empty ring.
FocusRing::of(string ...$ids)	A ring of regions (duplicates dropped), focusing the first.
register(string $id): self	Add a region to the end of the order.
unregister(string $id): self	Remove a region, preserving focus where possible.
focus(string $id): self	Focus a specific registered region.
next(): self / previous(): self	Tab / Shift-Tab traversal (wrapping).
current(): ?string	The focused region id, or null.
isFocused(string $id): bool	Whether $id is the focused region.
has(string $id): bool	Whether $id is registered.
index(): int	Focused position, or -1 when empty.
ids(): list<string>	Registered region ids in traversal order.
count(): int / isEmpty(): bool	Size helpers.

License

MIT © Joe Huss