Typed controllers

Keep the accepted value in Rust and project its presentation into Slint. The slint_kit facade reexports core values and weak-window adapters. A view token is only valid within its model generation; it is never the application's stable identity.

Run and read the complete typed application: native field, validation, stable selection and every signal connected.

Field drafts and accepted values

FieldBinding<T, E> connects a FieldController<T, E> to a publisher. Choose a domain type for T and an error enum for E. Its constructor accepts the initial accepted value, ownership, commit policy, absence policy, parser, formatter, error formatter and projection publisher.

Feed editor changes into edited(&str), wire blur and submit to commit, and use cancel or reset for explicit actions. Publish FieldProjection.draft, access, validation and error back into the view. The publisher should capture window.as_weak() and upgrade it only while updating the window. Keep the binding alive with the window's controller.

Do not replace the editor or rewrite its text on every keystroke. Native Slint text editing owns selection, caret, undo and IME. Formatting belongs at the acceptance boundary. See the complete field bindings in the showcase and editor signals.

Validation and form submission

begin_validation() returns a ValidationGeneration; retain that ticket with the asynchronous request. finish_validation(ticket, errors) ignores a result superseded by a newer draft. Do not identify requests by a mutable row index. FormCoordinator similarly uses submission tickets and typed field keys. A submit button only emits the form action; the host owns validation and persistence.

Stable keyed selection

SelectBinding<K> retains stable application keys and publishes SelectProjection rows, active and selected tokens, availability, open state and generation. Its activate(token, generation) rejects stale input. reconcile changes the source options; query filters the view without removing the accepted key. Duplicate keys are an error.

Use on_intent for SelectionIntent::Commit(K) and SelectionIntent::Clear. Under controlled ownership, acknowledge the accepted key with set_selected. The bind_select! macro wires the conventional window contract; its required rows, select-state and select-* callbacks are documented in the public macro source.

SelectionAvailability distinguishes Absent, Available and Unavailable. A selected item hidden by filtering or removed from the current model is not automatically an instruction to clear the domain value. See KitSelect and navigation examples.

Exact numbers and civil time

Use DecimalValue, Money, CurrencyMetadata and explicit NumberLocale, DecimalScale and RoundingPolicy. Slider positions and color byte projections are renderer values; they do not replace exact accepted amounts. Parse civil dates and local times with the core types, then resolve a zone explicitly. An ambiguous local time requires an explicit choice; never silently pick an instant.

Overlays and feedback

Keep FocusRegistry and the exact opener in the host controller. Dialog and drawer primitives present focus requests; register real focus targets and restore the opener on close. A tooltip needs one window-level KitTooltipLayer, mounted after the content. ToastQueue owns toast lifetimes; pointer and focus pauses use distinct ToastPause sources so overlapping interactions do not resume a toast prematurely.