Search field (external piece)

Status: implemented as day-piece-searchfield, an external Day Piece (like day-piece-combobox) registered link-time into each backend’s renderer slice without touching day. One API: a native search input, bound two-way to a Signal<String>, realized as each toolkit’s dedicated search control.

Authoring

use day_piece_searchfield::search_field;

let query = Signal::new(String::new());
search_field(query).placeholder("Search fruit…").id("search")

search_field(query) takes a Signal<String> bound two-way: every native edit writes the text back to the signal, and setting the signal (e.g. a Clear button doing query.set(String::new())) patches the control. .placeholder(impl IntoText) sets the empty-state prompt; it accepts a constant, Signal<String>, or closure, read once for the initial value (the placeholder is fixed at build). SearchField implements Piece, so .id()/.a11y()/.frame() chain via Decorate. Like day-core’s text_field it is a width-growing leaf (grow_w = true, natural single-line height): a search field fills its row, so constrain it with .frame(w, h) if you need a fixed width.

The signal is a controlled input (§4.4): a per-build echo guard remembers the last value that arrived from the native control so bind_seeded does not patch that same value straight back (which some toolkits would re-emit as a change → a feedback loop). The programmatic-sync side is additionally guarded per backend (see the table).

Per-backend native realization

Each control reports edits through Event::TextChanged(String), the same event a built-in text field emits, so dayscript’s input: step drives the piece on every backend without touching native code. The change plumbing per backend:

• AppKit: a per-node delegate implements NSControlTextEditingDelegate::controlTextDidChange:. Programmatic setStringValue does not fire that delegate, so no suppression is needed (update only writes when the value actually differs).
• UIKit: a per-node target on UIControlEvents::EditingChanged. Programmatic setText does not fire EditingChanged, so no suppression is needed.
• GTK: GtkSearchEntry::"search-changed". That signal does fire on programmatic set_text, so a per-node suppress cell guards the sync in update.
• Qt / XAML: each carries its own C++ shim inside this crate (src/lib-qt-shim.cpp, src/lib-xaml-shim.cpp), compiled by the crate’s build.rs. The Qt shim wraps a QLineEdit (setClearButtonEnabled(true) + a leading edit-find action) and wraps programmatic setText in blockSignals. The XAML shim boxes its AutoSuggestBox into a Day handle through the day_xaml_box / day_xaml_unbox seam that day-xaml-sys exports, the same mechanism the picker/media XAML shims use, so a piece never touches day-xaml’s private handle wrapper.
• Android: carries its own Java factory (android/java/dev/daybrite/day/piece/searchfield/DaySearch.java), folded into the app’s Gradle build automatically via [package.metadata.day.android], with no edits to day-android (see docs/extending.md). A TextWatcher calls DayBridge.nativeOnEvent(id, 1, …) (kind 1 = TextChanged); the programmatic setter guards on equality (a plain EditText, so no Gradle dependency or manifest permission).

Verification

The showcase Controls page (controls.rs search_section) binds a search_field to a query signal that filters a small fruit list (Apple, Banana, Cherry, Date, Elderberry) case-insensitively. Each match is a when-gated label in a column, and a #search-result label shows the first match. A Clear button sets the signal to "" to prove the reverse binding patches the native field. The walkthrough navigates to search, types "ch" into #search-input, asserts #search-result reads Cherry (the two-way binding round-tripping the signal), taps #search-clear, and screenshots. Rust is clippy-clean (-D warnings) and cargo fmt-clean for every backend feature; host-verified for AppKit/GTK/Qt/mock, cross-compiled for iOS-sim (uikit) and Android (mdc).

Follow-ups

• Reactive placeholder (currently fixed at build).
• A submit rail (Event::Submitted on the search-action key / return) for “search on enter” semantics.
• Disabled/enabled state; scoped-search tokens (macOS NSSearchField recent-searches menu).

XAML is CI-only (built under cfg(windows) + the Windows SDK); it isn’t buildable on the macOS/Linux dev hosts.