teksilo-widgets 0.9.2

// SPDX-License-Identifier: MPL-2.0
// SPDX-FileCopyrightText: 2026 FernTech

//! `TextInputField` — editable single-line text surface primitive.
//!
//! This is the raw editing primitive that powers the styled
//! [`TextInput`](crate::text_input::TextInput) composite and any
//! other widget that needs inline editable text — [`SpinBox`] being
//! the primary second consumer.
//!
//! Unlike `TextInput`, `TextInputField` paints no frame, no
//! placeholder overlay, no validation border, and hosts no trailing
//! slots: it is the focusable text area only. Compose it yourself
//! with `RectWidget`, `Padding`, icons, clear buttons, etc. to
//! build a styled control. Focus indication is the composite's
//! responsibility — the Int UI convention is to thicken the
//! enclosing frame's border to `focus_ring_width` and recolor it
//! to the accent focus-ring color.
//!
//! Features:
//! - Bound `Signal<String>` for two-way text binding.
//! - Full keyboard editing (arrow keys, Home/End, Backspace/Delete,
//!   Ctrl+X/C/V, Ctrl+A, Ctrl+Z/Y), IME commit, and pointer caret
//!   positioning and drag-select.
//! - Optional per-character input filter
//!   ([`TextInputField::char_filter`]), max-length cap
//!   ([`TextInputField::max_length`]), and read-only mode
//!   ([`TextInputField::read_only`]).
//! - Commit hooks: Enter fires
//!   [`on_submit_fn`](TextInputField::on_submit_fn) and focus loss
//!   fires [`on_blur_fn`](TextInputField::on_blur_fn).
//! - Non-editable trailing
//!   [`suffix`](TextInputField::suffix), rendered flush-right inside
//!   the field's bounds (Qt's `QSpinBox::suffix`). Caret cannot
//!   enter it; clicks past the text end clamp to the last
//!   character.
//! - Right-click context menu (Cut / Copy / Paste / Select All).
//! - AccessKit `Role::TextInput` with value, selection, and
//!   character/word boundary metadata.
//!
//! # Example
//!
//! ```ignore
//! let text = ctx.signal(String::new());
//! ctx.add(
//!     TextInputField::new(text.clone())
//!         .placeholder("Enter a name…")
//!         .char_filter(|c| !c.is_ascii_digit())
//!         .on_submit_fn(|ctx| ctx.send_intent(MyIntent::Save)),
//! );
//! ```
//!
//! [`SpinBox`]: crate::spin_box::SpinBox

mod keyboard;
pub mod mask;
mod mouse;
pub(crate) mod state;
pub mod validator;

use std::rc::Rc;
use teksilo_i18n::tr_widget;

use teksilo_canvas::{Canvas, Point, Rect, Size, SizeProposal};
use teksilo_core::accessibility::AccessNodeBuilder;
use teksilo_core::build_context::BuildContext;
use teksilo_core::event::{EventResponse, Key};
use teksilo_core::shortcut::KeyStroke;
use teksilo_core::signal::{Prop, Signal};
use teksilo_core::widget::{
    CursorIcon, EventContext, LayoutContext, PaintContext, Widget, WidgetPlacement,
};
use teksilo_core::widget_builder::HandlerSet;
use teksilo_core::widget_id::WidgetId;
use teksilo_text::text_document::{SelectionType, TextDocument};
use teksilo_text::{CursorAffinity, CursorDisplay, RichTextEngine, SharedTypesetter};
use teksilo_tokens::TextStyle;

use crate::button::InteractionState;
use crate::keystroke_format::format_keystroke;
use crate::menu_item::MenuItem;
use crate::menu_list::{MenuList, MenuSeparator};
use crate::rich_text::paint::{PaintParams, paint_frame};

pub(crate) use self::state::{CharFilter, CommandFactory};
use self::state::{SharedState, TextInputConfig, TextInputState, sync_cursor_signals};

pub use self::mask::{InputMask, MaskClass, MaskError, MaskPosition};
pub use self::validator::{ValidationFeedback, ValidationOutcome, ValidatorFn};

// The caret blink period and the debounce window are shared with every other
// text surface — see `common::editor_runtime`. They used to be re-declared
// here as private constants ("same as RichTextEditor", said the comment),
// which is exactly the kind of duplication that drifts silently: two carets
// blinking at different rates is invisible to tests and obvious to users.
use crate::common::editor_runtime::CaretPolicy;

/// Horizontal scroll margin in pixels. The caret stays at least this
/// far from the left/right edge of the viewport.
const SCROLL_MARGIN: f32 = 4.0;

/// Default text-area height when the caller does not override it
/// via [`TextInputField::text_height`]. Picked to match the Int UI
/// `text_field.height` token minus 2×border — the value the
/// `TextInput` composite reports — so a bare `TextInputField`
/// added to a tree without its composite still looks right.
const DEFAULT_TEXT_HEIGHT: f32 = 20.0;

/// The semantic purpose of a text field, surfaced to assistive technology as
/// a specialised AccessKit role (WCAG 1.3.5 Identify Input Purpose / EN 301 549).
///
/// This is the in-framework-achievable part of SC 1.3.5: a screen reader
/// announces "email, edit text" instead of a generic "edit text". The FULL
/// HTML `autocomplete`-token vocabulary (`given-name`, `postal-code`,
/// `cc-number`, …) that drives OS/browser autofill has **no representation in
/// AccessKit 0.24** and therefore cannot be exposed from Teksilo — see
/// `docs/a11y/a11y_issues.md`. Password entry is configured via
/// [`TextInputField::secure`], not here.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum InputPurpose {
    /// Ordinary free text (`Role::TextInput`).
    #[default]
    Normal,
    /// Email address (`Role::EmailInput`).
    Email,
    /// Telephone number (`Role::PhoneNumberInput`).
    Phone,
    /// URL (`Role::UrlInput`).
    Url,
    /// Numeric entry — e.g. a quantity or code (`Role::NumberInput`).
    Number,
    /// Search query (`Role::SearchInput`).
    Search,
}

impl InputPurpose {
    /// The AccessKit role for a non-secure field with this purpose.
    pub(crate) fn to_role(self) -> teksilo_core::accesskit::Role {
        use teksilo_core::accesskit::Role;
        match self {
            InputPurpose::Normal => Role::TextInput,
            InputPurpose::Email => Role::EmailInput,
            InputPurpose::Phone => Role::PhoneNumberInput,
            InputPurpose::Url => Role::UrlInput,
            InputPurpose::Number => Role::NumberInput,
            InputPurpose::Search => Role::SearchInput,
        }
    }
}

/// How a secure ([`TextInputField::secure`]) field echoes typed
/// characters. Mirrors Qt's `QLineEdit::EchoMode`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum EchoMode {
    /// Replace every character with the echo glyph (default `'•'`).
    /// The plaintext stays in the bound `Signal<String>` but never
    /// reaches the text engine while masked.
    #[default]
    Masked,
    /// Show nothing at all — not even the length. The caret stays at
    /// the start. Qt's `NoEcho`.
    NoEcho,
    /// Show plaintext while the field is focused (being edited) and
    /// re-mask on blur. Qt's `PasswordEchoOnEdit`.
    RevealWhileTyping,
}

/// How a *revealed* secure field reports to assistive technology.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum AtRevealPolicy {
    /// When revealed, expose the field as a normal `Role::TextInput`
    /// carrying the plaintext value — matching what is visibly on
    /// screen and the web `type=password ↔ type=text` swap. When
    /// masked, it reverts to `Role::PasswordInput`. (Default.)
    #[default]
    SwapRole,
    /// Always report `Role::PasswordInput` and never expose plaintext
    /// to assistive tech, even while visually revealed. Higher
    /// confidentiality at the cost of consistency with the screen.
    AlwaysProtected,
}

/// Editable single-line text surface primitive.
///
/// See the [module docs](self) for the full feature list and a
/// compositional example.
pub struct TextInputField {
    // ── Configuration (builder methods, consumed in build) ───────────
    text: Signal<String>,
    /// Enabled state, static or reactive; forwarded to the arena at build
    /// time.
    enabled: Prop<bool>,
    read_only: bool,
    max_length: Option<usize>,
    placeholder: String,
    on_submit: Option<CommandFactory>,
    on_blur: Option<CommandFactory>,
    char_filter: Option<CharFilter>,
    /// Fixed trailing label rendered inside the field's border.
    /// Accepts both plain strings and `Signal<String>` — when bound,
    /// the field re-measures the suffix and relayouts each time the
    /// signal fires, so composites like `SpinBox` can derive the
    /// suffix from the widget state (e.g. hide it while
    /// `special_value_text` is active).
    suffix: Prop<String>,
    text_height: Option<f32>,
    external_interaction: Option<Signal<InteractionState>>,

    /// Optional input mask. When set, the field auto-derives a
    /// placeholder template (`__/__/____` for `99/99/9999`) and
    /// rejects non-fitting characters via a position-aware filter
    /// composed with the user's `char_filter`. See [`InputMask`] for
    /// the grammar.
    mask: Option<InputMask>,
    /// Visible char used for unfilled editable positions in the mask
    /// template. Defaults to the theme's
    /// `text_field.mask_placeholder_char` (typically `_`).
    mask_placeholder_override: Option<char>,
    /// Validator closure called on every commit (Enter, Tab-out,
    /// blur). Returns a [`ValidationOutcome`] that drives
    /// [`feedback`](Self::validation_feedback_signal).
    validator: Option<ValidatorFn>,
    /// Published feedback signal. Composites bind to this to render
    /// the inline validation strip below the field.
    feedback: Signal<ValidationFeedback>,

    // ── Secure / password masking (set via `secure`) ────────────────
    secure: bool,
    echo_mode: EchoMode,
    echo_char: char,
    revealed: Option<Signal<bool>>,
    at_reveal_policy: AtRevealPolicy,
    allow_copy: bool,

    /// Semantic purpose → specialised AT role (WCAG 1.3.5). Ignored while the
    /// field is `secure` (password role wins).
    input_purpose: InputPurpose,

    /// ARIA combobox wiring — see [`active_descendant`](Self::active_descendant).
    active_descendant: Option<Signal<Option<WidgetId>>>,
    /// The listbox this field drives, if any — see
    /// [`controls`](Self::controls).
    controls: Option<Signal<Option<WidgetId>>>,

    // ── Internal (set during build) ─────────────────────────────────
    state: Option<SharedState>,
    /// Interaction signal actually used at runtime. Either the one
    /// supplied by a wrapping composite via
    /// [`TextInputField::interaction_signal`] or a fresh one owned
    /// by the field. Read by the focus handler to repaint a
    /// parent's focus ring / border on gain/loss.
    interaction: Signal<InteractionState>,
    /// Mirror of the inner state's `cursor_position` for external
    /// readers. Wired in `build()` via a `ctx.effect`. Composing
    /// widgets that need the caret (e.g. `DateEdit` for segment
    /// stepping) read this via [`TextInputField::caret_position`].
    caret_position: Signal<usize>,
    /// Late-bound handle to the inner `SharedState`, populated in
    /// `build()`. Lets composing widgets capture a `caret_setter`
    /// closure BEFORE the field is moved into the tree, then call
    /// it later to programmatically reposition the caret. Required
    /// because the inner state doesn't exist before `build()` runs,
    /// but the composing widget loses ownership of `self` once it
    /// hands the field to `ctx.add(...)`.
    state_slot: std::rc::Rc<std::cell::RefCell<Option<SharedState>>>,
    /// Minted with the widget, not with its state, so a [`TextFieldHandle`]
    /// taken before `build` observes the signal the built widget writes.
    focus_signal: Signal<bool>,
    /// Natural intrinsic width in logical pixels, cached at the end
    /// of `build()`. When an [`InputMask`] is set, this measures the
    /// mask's empty template (e.g. `__/__/____`) in the theme body
    /// font and adds a small caret slack — so a date / time / phone
    /// field reports a width that matches its content envelope
    /// instead of the generic 200 dp fallback. Composing widgets
    /// like `DateEdit` rely on this so their unconstrained natural
    /// width tracks the format pattern.
    natural_width: f32,
}

impl std::fmt::Debug for TextInputField {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("TextInputField")
            .field("placeholder", &self.placeholder)
            .field("enabled", &self.enabled.get())
            .field("read_only", &self.read_only)
            .finish_non_exhaustive()
    }
}

impl TextInputField {
    /// Construct a new field bound to `text`.
    pub fn new(text: Signal<String>) -> Self {
        Self {
            text,
            enabled: Prop::Static(true),
            read_only: false,
            max_length: None,
            placeholder: String::new(),
            on_submit: None,
            on_blur: None,
            char_filter: None,
            suffix: Prop::Static(String::new()),
            text_height: None,
            external_interaction: None,
            mask: None,
            mask_placeholder_override: None,
            validator: None,
            feedback: Signal::new(ValidationFeedback::Pristine),
            secure: false,
            echo_mode: EchoMode::Masked,
            echo_char: '\u{2022}',
            revealed: None,
            at_reveal_policy: AtRevealPolicy::SwapRole,
            allow_copy: true,
            input_purpose: InputPurpose::Normal,
            active_descendant: None,
            controls: None,
            state: None,
            interaction: Signal::new(InteractionState::Idle),
            caret_position: Signal::new(0),
            state_slot: std::rc::Rc::new(std::cell::RefCell::new(None)),
            focus_signal: Signal::new(false),
            natural_width: 200.0,
        }
    }

    /// Declarative placeholder string. The field itself paints
    /// nothing for placeholder — that visual is the composite
    /// parent's responsibility (`TextInput` overlays a
    /// `TextWidget`). The string is still stored here and published
    /// via AccessKit's `placeholder` property so screen readers
    /// announce it.
    pub fn placeholder(mut self, text: impl Into<String>) -> Self {
        self.placeholder = text.into();
        self
    }

    /// Set the enabled state, statically or reactively. Disabled blocks
    /// input and AccessKit interaction. Forwarded to the arena at build
    /// time.
    pub fn enabled(mut self, enabled: impl Into<Prop<bool>>) -> Self {
        self.enabled = enabled.into();
        self
    }

    /// Mark the field read-only. Caret and selection still work;
    /// inserts, deletes, paste, undo/redo, and cut are all no-ops.
    pub fn read_only(mut self, read_only: bool) -> Self {
        self.read_only = read_only;
        self
    }

    /// Hard cap on document length in `char`s (grapheme count is
    /// approximated — each `char` counts as one unit, matching
    /// `String::chars().count()`).
    pub fn max_length(mut self, max_length: usize) -> Self {
        self.max_length = Some(max_length);
        self
    }

    /// Closure fired on `Enter`. Unlike `on_blur_fn`, this does
    /// not move focus — the field stays focused and the caret
    /// stays where it was.
    pub fn on_submit_fn(mut self, f: impl Fn(&mut EventContext) + 'static) -> Self {
        self.on_submit = Some(Box::new(f));
        self
    }

    /// Closure fired once per focus-loss, after selection/scroll
    /// have been reset. SpinBox-style callers parse and reformat
    /// here; validators revalidate here.
    pub fn on_blur_fn(mut self, f: impl Fn(&mut EventContext) + 'static) -> Self {
        self.on_blur = Some(Box::new(f));
        self
    }

    /// Per-character input-filter predicate. Applied uniformly to
    /// keyboard input, IME commits, and clipboard paste so a filtered
    /// field cannot receive disallowed characters through any path.
    /// Composes with `max_length` and the built-in control/newline
    /// strip (filter runs after the strip). Whole-string validity
    /// (e.g. "at most one decimal point") is a commit-time concern
    /// for `on_blur` / `on_submit`.
    pub fn char_filter(mut self, f: impl Fn(char) -> bool + 'static) -> Self {
        self.char_filter = Some(Rc::new(f));
        self
    }

    /// Static non-editable trailing string rendered flush-right
    /// inside the field's bounds (Qt's `QSpinBox::suffix`). The
    /// caret cannot enter the suffix; clicks past the text end
    /// position the caret at the last editable character.
    ///
    /// Accepts a static `String`/`&str` or a reactive `Signal<String>` /
    /// `Prop<String>`; when bound, the field re-measures the suffix glyphs
    /// and relayouts the editable text viewport each time the signal fires.
    /// Typical use: a `SpinBox` with `special_value_text` binds an empty
    /// string to the suffix whenever the value equals `min`, and the
    /// configured unit string otherwise.
    pub fn suffix(mut self, text: impl Into<Prop<String>>) -> Self {
        self.suffix = text.into();
        self
    }

    /// Override the intrinsic text-area height. The field is a
    /// pure leaf with no theme lookup of its own; by default it
    /// reports `DEFAULT_TEXT_HEIGHT`. A wrapping composite like
    /// `TextInput` passes its theme's `text_field.height` minus
    /// border + padding here so the visuals line up with the
    /// rest of the form.
    pub fn text_height(mut self, height: f32) -> Self {
        self.text_height = Some(height);
        self
    }

    /// Bind an externally-owned `InteractionState` signal. The
    /// field writes `Focused` on focus gain and `Idle` on loss;
    /// other states (`Hovered`, `Pressed`, `Disabled`) are the
    /// composite's responsibility. When unset, the field owns a
    /// private signal that observers can still read via
    /// [`interaction`](TextInputField::interaction), but composites
    /// that drive a focus ring or border color usually want to
    /// push their own.
    pub fn interaction_signal(mut self, signal: Signal<InteractionState>) -> Self {
        self.external_interaction = Some(signal);
        self
    }

    /// Set an input mask (Qt grammar). Constrains accepted characters
    /// per position, auto-derives the empty-state template
    /// (`__/__/____` for `99/99/9999`), and routes typed chars
    /// through the mask's class filter.
    ///
    /// Composes with [`char_filter`](Self::char_filter): a char must
    /// pass *both* the mask's per-position class AND the user's
    /// `char_filter` to be accepted.
    ///
    /// On parse error (only the trailing-backslash case in practice),
    /// the mask is silently dropped — the field falls back to its
    /// no-mask behaviour rather than panicking.
    pub fn input_mask(mut self, mask: impl AsRef<str>) -> Self {
        match InputMask::parse(mask.as_ref()) {
            Ok(m) => self.mask = Some(m),
            Err(_) => self.mask = None,
        }
        self
    }

    /// Override the visible character used for unfilled editable mask
    /// positions. Default: the theme's
    /// `text_field.mask_placeholder_char` (typically `_`).
    pub fn mask_placeholder(mut self, c: char) -> Self {
        self.mask_placeholder_override = Some(c);
        self
    }

    /// Install a validator. The closure runs on every commit (Enter,
    /// Tab-out, focus loss) and returns a [`ValidationOutcome`] that
    /// drives [`validation_feedback_signal`](Self::validation_feedback_signal).
    ///
    /// **Does not run per-keystroke** — that's [`char_filter`](Self::char_filter)'s
    /// job. Mixing per-keystroke text rewriting with validation
    /// produces caret-jump bugs and is explicitly out of scope.
    pub fn validator(mut self, f: impl Fn(&str) -> ValidationOutcome + 'static) -> Self {
        self.validator = Some(Rc::new(f));
        self
    }

    /// Turn this into a secure (password) field with the given
    /// [`EchoMode`]. Masking happens at the text-engine layer (one echo
    /// glyph per source `char`), so the plaintext never reaches the
    /// shaper or glyph atlas while masked, and caret / selection /
    /// hit-test stay correct. Also defaults `allow_copy` to `false` and
    /// opts the focused node out of OS IME composition. Pair with
    /// [`revealed`](Self::revealed) for a reveal toggle.
    pub fn secure(mut self, echo_mode: EchoMode) -> Self {
        self.secure = true;
        self.echo_mode = echo_mode;
        self.allow_copy = false;
        self
    }

    /// Declare the field's semantic [`InputPurpose`] (WCAG 1.3.5), which
    /// selects a specialised AccessKit role (`EmailInput`, `PhoneNumberInput`,
    /// …) so screen readers announce the field's kind. Ignored while `secure`
    /// (the password role wins). Does not change IME behaviour — winit's
    /// `ImePurpose` has no email/number/url variants — nor drive OS autofill,
    /// which AccessKit cannot express (see `docs/a11y/a11y_issues.md`).
    pub fn input_purpose(mut self, purpose: InputPurpose) -> Self {
        self.input_purpose = purpose;
        self
    }

    /// Publish `active_descendant` pointing at the row a *separate* list is
    /// currently highlighting — the ARIA combobox pattern.
    ///
    /// Keyboard focus stays in this field while arrow keys move a highlight
    /// through a listbox elsewhere in the tree (a command palette, a
    /// type-ahead picker, a suggestion popup). Assistive technology follows
    /// the focused node's active descendant, so the announcement has to be
    /// published **here**, on the node that actually holds focus — not on the
    /// composite ancestor that owns the list. Without it the arrow keys move a
    /// highlight that is announced to nobody.
    ///
    /// Bound at `AccessibilityOnly`, so moving the highlight re-walks the AT
    /// tree without a rebuild or a repaint. Pair with [`controls`](Self::controls).
    pub fn active_descendant(mut self, active: Signal<Option<WidgetId>>) -> Self {
        self.active_descendant = Some(active);
        self
    }

    /// Publish a `controls` relation to the listbox this field drives, so an
    /// AT client can navigate from the input to the list it is filtering.
    /// The companion of [`active_descendant`](Self::active_descendant).
    pub fn controls(mut self, listbox: Signal<Option<WidgetId>>) -> Self {
        self.controls = Some(listbox);
        self
    }

    /// Override the masking glyph (default `'•'`, U+2022). Any
    /// uniform-width character works; the engine emits exactly one per
    /// source `char`.
    pub fn echo_char(mut self, c: char) -> Self {
        self.echo_char = c;
        self
    }

    /// Bind the reveal toggle. When the signal is `true` the field
    /// shows plaintext regardless of [`EchoMode`]; when `false` it
    /// masks. Shared with the eye [`IconButton::visibility_toggle`].
    ///
    /// [`IconButton::visibility_toggle`]: crate::IconButton::visibility_toggle
    pub fn revealed(mut self, revealed: Signal<bool>) -> Self {
        self.revealed = Some(revealed);
        self
    }

    /// How a *revealed* secure field reports to assistive tech. Default
    /// [`AtRevealPolicy::SwapRole`].
    pub fn at_reveal_policy(mut self, policy: AtRevealPolicy) -> Self {
        self.at_reveal_policy = policy;
        self
    }

    /// Permit (or forbid) copy / cut. Plain fields default `true`;
    /// [`secure`](Self::secure) flips the default to `false`. Even when
    /// `false`, copy is allowed while the field is revealed.
    pub fn allow_copy(mut self, allow: bool) -> Self {
        self.allow_copy = allow;
        self
    }

    /// Reactive handle on the published [`ValidationFeedback`] state.
    /// Composites bind to this to render the inline feedback strip
    /// below the field. Always present; reads `Pristine` until the
    /// first commit (or forever if no validator is installed).
    pub fn validation_feedback_signal(&self) -> Signal<ValidationFeedback> {
        self.feedback.clone()
    }

    /// The `Signal<String>` this field is bound to.
    pub fn text(&self) -> Signal<String> {
        self.text.clone()
    }

    /// Adopt an existing handle instead of minting one.
    ///
    /// For a composing widget — `TextInput` wraps this field — that must hand
    /// out a handle of its own **before** it builds the field it will delegate
    /// to. Sharing the slot and the focus signal makes the wrapper's handle and
    /// the field's the same handle, rather than two that agree by accident.
    pub fn share_handle(mut self, handle: &TextFieldHandle) -> Self {
        self.state_slot = handle.slot.clone();
        self.focus_signal = handle.focus_signal.clone();
        self
    }

    /// A live handle on this field, valid before and after `build`.
    ///
    /// The counterpart of `RichTextEditor::handle`, and the reason it exists:
    /// an application that routes Undo, Cut, Copy, Paste and Select All to
    /// "whichever text surface holds the caret" has to be able to *drive* every
    /// such surface, not only the rich editors. Without this, a menu built for
    /// those commands can only grey them out over a rename field or a search
    /// box while the field's own key handling still works — a menu that lies
    /// about what the keyboard can do.
    ///
    /// Like `caret_setter`, the handle reaches its state through the slot the
    /// widget late-populates, so it may be taken while the tree is being
    /// described and used once it is live.
    pub fn handle(&self) -> TextFieldHandle {
        TextFieldHandle {
            slot: self.state_slot.clone(),
            focus_signal: self.focus_signal.clone(),
        }
    }

    /// The interaction signal this field writes on focus changes.
    /// Call before inserting the field into the tree.
    pub fn interaction(&self) -> Signal<InteractionState> {
        self.interaction.clone()
    }

    /// Reactive caret position in the field's text (in `usize` char
    /// offsets). Updates after every keyboard or pointer action that
    /// moves the cursor. Used by composing widgets that need to know
    /// where the caret is — e.g. `DateEdit` reads this to figure out
    /// which date segment Up/Down should step.
    pub fn caret_position(&self) -> Signal<usize> {
        self.caret_position.clone()
    }

    /// Returns a callable that programmatically sets the caret
    /// position (in char offsets) on the field. Capture this on the
    /// builder BEFORE `ctx.add(...)` consumes the field; call it
    /// after a programmatic text rewrite to restore the caret to the
    /// right column instead of leaving it at the document end (the
    /// default behaviour of `cursor.insert_text`).
    ///
    /// The returned closure becomes a no-op until `build()` runs;
    /// after build it walks the field's inner state and moves the
    /// document cursor to `position`, clamped to the document
    /// length. Used by `DateEdit` / `TimeEdit` segment-stepping to
    /// keep the caret within its current segment after Up/Down.
    pub fn caret_setter(&self) -> std::rc::Rc<dyn Fn(usize)> {
        let slot = self.state_slot.clone();
        std::rc::Rc::new(move |position: usize| {
            if let Some(state) = slot.borrow().as_ref() {
                let st = state.borrow();
                st.cursor
                    .set_position(position, teksilo_text::text_document::MoveMode::MoveAnchor);
                let actual = st.cursor.position();
                if st.cursor_position.get() != actual {
                    st.cursor_position.set(actual);
                }
            }
        })
    }
}

impl Widget for TextInputField {
    fn as_any(&self) -> Option<&dyn std::any::Any> {
        Some(self)
    }

    fn build(&mut self, ctx: &mut BuildContext) -> Vec<WidgetId> {
        // Tell the framework this widget edits text.
        //
        // What it buys: an application may take `Ctrl+Z`, `Ctrl+C` and friends
        // for itself — a single Undo command over the whole app has to — and
        // registered shortcuts resolve before any widget sees the raw key. This
        // is how the host can tell that the caret is *here*, and either drive
        // this surface or step aside so it keeps its own keys. Without it, an
        // application that routes those chords silently breaks every text
        // widget it does not personally know about. See
        // `teksilo_core::text_surface`.
        ctx.register_text_surface(std::rc::Rc::new(self.handle()));
        // Resolve the interaction signal (external override wins).
        if let Some(signal) = self.external_interaction.take() {
            self.interaction = signal;
        }

        // Resolve the mask placeholder character. Caller override wins;
        // otherwise pull from the recipe constant. The theme snapshot
        // is still captured for downstream typography reads below.
        let theme_snapshot = ctx.theme_signal().get();
        let mask_placeholder_char = self
            .mask_placeholder_override
            .unwrap_or(crate::styles::recipe_text_input_style::TEXT_FIELD_MASK_PLACEHOLDER_CHAR);

        // Auto-derive placeholder from mask when none was explicitly
        // set: an empty masked field paints `__/__/____` rather than
        // a blank surface, giving the user a self-documenting template.
        if self.placeholder.is_empty()
            && let Some(ref m) = self.mask
        {
            self.placeholder = m.empty_template(mask_placeholder_char);
        }

        // Cache mask-aware natural width. When a mask is set, the
        // visual content envelope is the FILLED template — every
        // editable position holding its widest plausible glyph
        // (`0` for digits, `M` for letters, etc.) and every fixed
        // position holding its literal. Measuring the empty
        // (`__/__/____`) template instead would shortchange the
        // field by the difference between an underscore and a real
        // glyph: ~2 dp per digit slot for `0`, ~5 dp per letter
        // slot for `M`, which adds up to a multi-character shortfall
        // for date / 12h time fields. We want the natural width to
        // hold the fully-typed value without overflow.
        //
        // Without a mask the 200 dp fallback (set in `new()`) stays.
        if let Some(ref m) = self.mask {
            // Measure the worst-case glyph row PLUS one extra `M` of
            // safety: one for caret breathing room past the last
            // position, plus a defensive cushion for any per-glyph
            // measurement variance between our heuristic fallback
            // and the real glyph shaper. Without this safety char,
            // dates were observed to clip the trailing 2 characters
            // and 12h time fields clipped the AM/PM letters.
            let mut widest = worst_case_template(m);
            widest.push('M');
            let style = &theme_snapshot.typography.body;
            let measured = measure_width_px(ctx, &widest, style);
            let slack = style.size;
            self.natural_width = measured + slack;
        }

        // Compose the user's char_filter with the mask's class filter.
        // The mask doesn't know the cursor position here (this is a
        // pre-position filter), so it accepts any char that fits *any*
        // editable position class — a permissive gate that catches
        // gross mismatches (typing "a" into a digits-only mask) without
        // requiring per-keystroke position tracking. Per-position
        // gating happens at commit time via the validator.
        if let Some(ref mask) = self.mask {
            let mask_for_filter = mask.clone();
            let user_filter = self.char_filter.take();
            let combined: CharFilter = Rc::new(move |c: char| {
                // Always allow fixed-separator characters (they're
                // legitimate input even if user types them — the
                // formatter consumes them).
                let in_mask_class = mask_for_filter.positions().any(|p| match p {
                    MaskPosition::Editable { class, .. } => class.accepts(c),
                    MaskPosition::Fixed(sep) => *sep == c,
                });
                if !in_mask_class {
                    return false;
                }
                match user_filter.as_ref() {
                    Some(f) => f(c),
                    None => true,
                }
            });
            self.char_filter = Some(combined);
        }

        // Build the shared state from the configured builder values.
        let mut on_submit = self.on_submit.take().map(Rc::new);
        let mut on_blur = self.on_blur.take().map(Rc::new);

        // Wrap commit callbacks with the validator pipeline. The
        // wrapping closure: snapshots the bound text, runs the
        // validator, applies the outcome (writes feedback, mutates
        // text on `Corrected`), then chains the user's callback so
        // composites can react to the now-updated state.
        if let Some(validator) = self.validator.clone() {
            let bound_text = self.text.clone();
            let feedback = self.feedback.clone();
            let prev_on_blur = on_blur.take();
            on_blur = Some(Rc::new(Box::new({
                let validator = validator.clone();
                let feedback = feedback.clone();
                let bound_text = bound_text.clone();
                move |evt_ctx: &mut EventContext| {
                    run_validator_and_apply(&validator, &bound_text, &feedback);
                    if let Some(cb) = prev_on_blur.as_ref() {
                        cb(evt_ctx);
                    }
                }
            }) as CommandFactory));
            let prev_on_submit = on_submit.take();
            on_submit = Some(Rc::new(Box::new({
                let validator = validator.clone();
                let feedback = feedback.clone();
                let bound_text = bound_text.clone();
                move |evt_ctx: &mut EventContext| {
                    run_validator_and_apply(&validator, &bound_text, &feedback);
                    if let Some(cb) = prev_on_submit.as_ref() {
                        cb(evt_ctx);
                    }
                }
            }) as CommandFactory));
        }

        let initial_text = self.text.get();
        // `read_only_effective` snapshots the build-time state so the
        // shared TextInputState's read-only mode is set once. Disabled
        // is now arena-driven and propagates per-paint via
        // `effective_enabled`; the field's interaction handlers also
        // check `ctx.is_enabled(self_id)` for keystroke gating. The
        // shared state's read_only stays a separate, document-level
        // concept (allows selection / no edits).
        let read_only_effective = self.read_only || !self.enabled.get();

        let initial_suffix = self.suffix.get();
        let shared_state = TextInputState::new(TextInputConfig {
            initial_text,
            max_length: self.max_length,
            read_only: read_only_effective,
            on_submit,
            on_blur,
            char_filter: self.char_filter.take(),
            placeholder: self.placeholder.clone(),
            suffix: initial_suffix,
            secure: self.secure,
            echo_mode: self.echo_mode,
            echo_char: self.echo_char,
            revealed: self.revealed.clone(),
            at_reveal_policy: self.at_reveal_policy,
            allow_copy: self.allow_copy,
            focus_signal: self.focus_signal.clone(),
        });
        self.state = Some(shared_state.clone());
        // Late-populate the slot so `caret_setter()` closures captured
        // before build can now reach the inner state. Idempotent on
        // rebuild — overwrites the slot with the freshly created
        // SharedState.
        *self.state_slot.borrow_mut() = Some(shared_state.clone());

        // Reset feedback to Pristine whenever the user types — prior
        // Invalid / Corrected announcements should clear as soon as
        // the user starts editing again so they don't shout stale
        // errors at someone trying to fix them.
        {
            let feedback = self.feedback.clone();
            ctx.effect(&self.text, move |_| {
                if !matches!(feedback.get(), ValidationFeedback::Pristine) {
                    feedback.set(ValidationFeedback::Pristine);
                }
            });
        }

        // Mirror the inner state's `cursor_position` onto the field's
        // public `caret_position` so callers of `caret_position()` see
        // live caret updates. The state's signal is keyed by the
        // shared state's identity (created in `TextInputState::new`),
        // not by the field's; this effect bridges the two.
        {
            let inner = shared_state.borrow().cursor_position.clone();
            let outer = self.caret_position.clone();
            outer.set(inner.get());
            ctx.effect(&inner, move |pos| {
                if outer.get() != *pos {
                    outer.set(*pos);
                }
            });
        }

        // Bind feedback at AccessibilityOnly so the field's AT node
        // refreshes its `set_invalid` state when feedback changes.
        {
            let self_id = ctx.self_id();
            self.feedback.bind_to(
                self_id,
                ctx.binding_registry(),
                teksilo_core::binding::BindingLevel::AccessibilityOnly,
            );
        }

        // Combobox wiring: a moved highlight in the list this field drives must
        // re-walk the AT tree so the new `active_descendant` is announced.
        // AccessibilityOnly — nothing about this field's own pixels changed.
        for sig in [self.active_descendant.as_ref(), self.controls.as_ref()]
            .into_iter()
            .flatten()
        {
            sig.bind_to(
                ctx.self_id(),
                ctx.binding_registry(),
                teksilo_core::binding::BindingLevel::AccessibilityOnly,
            );
        }

        // Secure fields: flipping the reveal toggle must repaint AND
        // refresh AT. `RepaintOnly` dirties this node for the render
        // walker so `paint()` runs and re-lays-out the masked/unmasked
        // glyphs via the `needs_full_layout` flag the effect below sets
        // — without it the flag is set but nothing calls `paint()`, so
        // the visual only updates on the next unrelated repaint
        // (hover / focus). This mirrors how `text_signal` is bound for
        // edits. The parallel `AccessibilityOnly` bind swaps the AT
        // role/value (PasswordInput ↔ TextInput under SwapRole); it lives
        // in its own bucket and does not imply repaint, so both are
        // required.
        if self.secure
            && let Some(revealed) = self.revealed.clone()
        {
            let id = ctx.self_id();
            let reg = ctx.binding_registry();
            revealed.bind_to(id, reg, teksilo_core::binding::BindingLevel::RepaintOnly);
            revealed.bind_to(
                id,
                reg,
                teksilo_core::binding::BindingLevel::AccessibilityOnly,
            );
        }

        let text_signal = shared_state.borrow().text_signal.clone();

        // Sync external text signal → internal state. A programmatic
        // update on the bound signal rewrites the document; the
        // caret ends up at the end of the inserted text (cursor
        // behavior is documented in
        // `text_document::TextCursor::insert_text`).
        //
        // `insert_text` only enqueues a `ContentsChanged` document
        // event — `tick()` drains it on the next frame and propagates
        // the new text to `text_signal`. Frames are demand-driven, so
        // we ping `frame_request` here to guarantee a tick runs even
        // when the external writer (e.g. an HSV-canvas drag feeding a
        // spinner / hex bridge) is the only thing changing on screen.
        // Without it, the document stays in sync with the bound signal
        // but the visible glyphs lag until something else (focus, a
        // keystroke, an animation frame) wakes the loop.
        {
            let ext = self.text.clone();
            let state_for_sync = shared_state.clone();
            ctx.effect(&ext, move |new_text| {
                let st = state_for_sync.borrow();
                let current = st.document.to_plain_text().unwrap_or_default();
                if current != *new_text {
                    st.cursor.select(SelectionType::Document);
                    let _ = st.cursor.insert_text(new_text);
                    if let Some(handle) = &st.frame_request {
                        handle.set(true);
                    }
                }
            });
        }

        // Sync internal text signal → external. Every edit that
        // reaches `text_signal` also updates the caller-owned
        // signal, so observers bound to it see every keystroke
        // (after the debounce in `tick`).
        {
            let ext = self.text.clone();
            ctx.effect(&text_signal, move |new_text| {
                if ext.get() != *new_text {
                    ext.set(new_text.clone());
                }
            });
        }

        // Secure reveal toggle: flipping the bound `revealed` signal
        // swaps the laid-out glyphs wholesale (bullets ↔ plaintext), so
        // mark the layout dirty and ping the frame loop to re-lay-out.
        if self.secure
            && let Some(revealed) = self.revealed.clone()
        {
            let state_for_reveal = shared_state.clone();
            ctx.effect(&revealed, move |_| {
                let mut st = state_for_reveal.borrow_mut();
                st.needs_full_layout = true;
                if let Some(handle) = &st.frame_request {
                    handle.set(true);
                }
            });
        }

        // Swap the private engine for one sharing the app's
        // `SharedTypesetter` so glyphs land in the atlas
        // teksilo-render uploads to the GPU. When no typesetter is
        // installed (headless tests), the pre-built private
        // engine stays in place.
        if let Some(shared) = ctx.app_state::<SharedTypesetter>() {
            let mut st = self.state().borrow_mut();
            let mut engine = RichTextEngine::from_shared(shared.clone());
            engine.set_wrap_mode(teksilo_text::WrapMode::None);
            st.engine = engine;
            st.needs_full_layout = true;
        }

        // Apply theme colors to the (possibly freshly swapped-in) engine.
        // Setting them before the swap would be lost. The rich-text
        // engine stores colors in GPU-ready form, so we register an
        // effect on the theme signal that re-applies the palette on
        // every theme switch instead of capturing a single snapshot.
        //
        // The text / caret / suffix *foreground* colours are deliberately
        // NOT set here — `paint` owns them, because they depend on the
        // effective enabled state as well as the theme (see the resolve
        // block there). Selection is theme + window-active only, so it
        // stays on this effect path.
        let theme_signal = ctx.theme_signal();
        // The selection colour is also window-active-aware. `ctx.effect` can
        // only observe *mutable* signals (a derived `theme.zip(window_active)`
        // would panic), so the theme effect reads the live window-active value
        // via `.get()`, and the separate window-active effect (below, near the
        // frame handles) re-applies the selection colour reading the live
        // theme. Between them, a change to either axis re-applies correctly.
        {
            let theme = theme_signal.get();
            let colors = &theme.colors;
            let mut st = self.state().borrow_mut();
            let tint = field_selection_color(colors, ctx.window_active(), st.has_focus);
            st.selection_tint = tint;
            st.engine.set_selection_color(tint);
        }
        {
            let state = self.state().clone();
            let wa_signal = ctx.window_active_signal();
            ctx.effect(&theme_signal, move |theme| {
                let colors = &theme.colors;
                let mut st = state.borrow_mut();
                let tint = field_selection_color(colors, wa_signal.get(), st.has_focus);
                st.selection_tint = tint;
                st.engine.set_selection_color(tint);
            });
        }

        // Suffix engine: second independent `RichTextEngine` used
        // to paint the non-editable trailing string (Qt's
        // `QSpinBox` `suffix`). Shares the app's typesetter when
        // available so glyphs land in the same atlas as the main
        // document; falls back to a private engine under headless
        // tests.
        //
        // `suffix_width` is cached on `TextInputState` and drives
        // both the effective text viewport (so the scroll logic
        // keeps the caret visible without sliding text behind the
        // suffix) and the suffix paint origin at the right edge
        // of the field. When the suffix is bound to a signal, a
        // reactive effect below re-lays the engine out each time
        // the signal fires.
        let text_area_height = self.text_height.unwrap_or(DEFAULT_TEXT_HEIGHT).max(1.0);
        let needs_suffix_engine = matches!(self.suffix, Prop::Bound(_)) || {
            let st = self.state().borrow();
            !st.suffix.is_empty()
        };
        if needs_suffix_engine {
            let mut suffix_engine = if let Some(shared) = ctx.app_state::<SharedTypesetter>() {
                RichTextEngine::from_shared(shared.clone())
            } else {
                RichTextEngine::private_default()
            };
            suffix_engine.set_wrap_mode(teksilo_text::WrapMode::None);
            {
                let theme = theme_signal.get();
                let secondary = theme.colors.text_secondary.to_array();
                suffix_engine.set_text_color(secondary);
                suffix_engine.set_cursor_color(secondary);
                suffix_engine.set_selection_color([0.0, 0.0, 0.0, 0.0]);
            }
            suffix_engine.set_viewport(10_000.0, text_area_height);

            {
                let mut st = self.state().borrow_mut();
                st.suffix_engine = Some(suffix_engine);
            }
            // Initial layout from the current suffix value.
            let initial = self.state().borrow().suffix.clone();
            relayout_suffix(self.state(), &initial);
        }

        // Reactive suffix: observe the signal and re-lay out on
        // every change. `Relayout` dirty-tracking ensures the
        // surrounding layout sees the new `suffix_width` and the
        // text viewport narrows/widens accordingly.
        if let Prop::Bound(signal) = &self.suffix {
            let self_id = ctx.self_id();
            signal.bind_to(
                self_id,
                ctx.binding_registry(),
                teksilo_core::binding::BindingLevel::Relayout,
            );
            let state_for_effect = self.state().clone();
            ctx.effect(signal, move |new_text| {
                relayout_suffix(&state_for_effect, new_text);
            });
        }

        // Bind caret_visible for repaint.
        {
            let st = self.state().borrow();
            let caret_visible = st.caret_visible.clone();
            drop(st);
            let self_id = ctx.self_id();
            caret_visible.bind_to(
                self_id,
                ctx.binding_registry(),
                teksilo_core::binding::BindingLevel::RepaintOnly,
            );
        }

        // Bind text_signal at RepaintOnly AND AccessibilityOnly.
        //
        // RepaintOnly: when the text changes by any route — local
        // typing, IME, clipboard paste, the ext→internal sync
        // effect firing because a composite parent (SpinBox etc.)
        // drove the bound signal — the field must redraw. During
        // typing the caret-blink signal already keeps the widget
        // repainting, which used to mask a missing repaint trigger
        // on programmatic text changes to an unfocused field. With
        // the explicit bind, no path depends on blink.
        //
        // AccessibilityOnly: screen readers see edits as soon as
        // the text signal updates, independent of whether a paint
        // happens this frame.
        {
            let st = self.state().borrow();
            let text_signal = st.text_signal.clone();
            drop(st);
            let self_id = ctx.self_id();
            let registry = ctx.binding_registry();
            text_signal.bind_to(
                self_id,
                registry,
                teksilo_core::binding::BindingLevel::RepaintOnly,
            );
            text_signal.bind_to(
                self_id,
                registry,
                teksilo_core::binding::BindingLevel::AccessibilityOnly,
            );
        }

        // Stash frame infrastructure handles and self_id.
        {
            let mut st = self.state().borrow_mut();
            st.frame_request = Some(ctx.frame_request_handle());
            st.frame_wake_at = Some(ctx.wake_at_handle());
            st.field_widget_id = Some(ctx.self_id());
        }

        // Same dormancy discipline as `RichTextEditor`: a field parked in a
        // non-selected `Switcher` / `visible_when(false)` branch must not
        // keep the event loop awake (caret `wake_at`, frame-tick work,
        // window-active re-arm). See that widget's build for the full story.
        let activation = ctx.activation_signal(ctx.self_id());
        if activation.get() {
            ctx.request_frame();
        }

        {
            let state = self.state().clone();
            let interaction = self.interaction.clone();
            ctx.effect(&activation, move |&active| {
                if active {
                    // **Re-activated** — re-arm the frame loop. The dormant branch
                    // below does not re-arm `frame_request` (a parked surface has
                    // nothing to paint) and the frame-tick effect is skipped
                    // entirely while dormant, so nothing restarts the tick on the
                    // way back. Same defect and same fix as `RichTextEditor` /
                    // `CodeEditor`: the in-tree modal path builds content, parks it
                    // dormant, mounts it, activates it and *then* moves focus in
                    // (`present_in_tree_modal_request`), so without this a field in
                    // a dialog draws no caret at all.
                    let st = state.borrow();
                    if let Some(handle) = &st.frame_request {
                        handle.set(true);
                    }
                    return;
                }
                let mut st = state.borrow_mut();
                if st.has_focus {
                    st.has_focus = false;
                    st.focus_signal.set(false);
                    // Mirror the on_focus(false) interaction write so a
                    // Focused chrome style doesn't stick on a parked field.
                    interaction.set(InteractionState::Idle);
                }
                if st.caret_visible.get() {
                    st.caret_visible.set(false);
                }
                st.blink.reset();
            });
        }

        // Frame-tick effect: flushes pending chars, drains document
        // events, drives the caret blink, and debounces undo/redo
        // state changes.
        //
        // IMPORTANT: the mutable borrow must be dropped BEFORE
        // setting `text_signal`. Setting it fires observers
        // synchronously, which chain into the ext→internal sync
        // effect that borrows the same state. Holding `borrow_mut`
        // across `signal.set()` would panic.
        {
            let state = self.state().clone();
            let active = activation.clone();
            let tick_signal = ctx.frame_tick();
            ctx.effect(&tick_signal, move |delta| {
                if !active.get() {
                    return;
                }
                let (more, pending_text) = {
                    let mut st = state.borrow_mut();
                    let more = tick(&mut st, *delta);
                    st.has_selection.set(st.cursor.has_selection());
                    let pending = st.deferred_text_update.take();
                    (more, pending)
                };
                if let Some(text) = pending_text {
                    let st = state.borrow();
                    if st.text_signal.get() != text {
                        st.text_signal.set(text);
                    }
                }
                if more {
                    let st = state.borrow();
                    if let Some(handle) = &st.frame_request {
                        handle.set(true);
                    }
                }
            });
        }

        // Window-active effect — mirror the tree's window-active state onto the
        // field state so the frame loop (no context) can gate the caret, and
        // re-apply the window-aware selection colour (reading the live theme,
        // since `ctx.effect` can't observe a derived theme×active signal). The
        // loop may not tick while the window is inactive (animation scheduler
        // parked), so on deactivation hide the caret synchronously here and
        // request a frame so it reaches a paint pass — only while this field
        // is itself active (a dormant field must not re-arm the loop).
        {
            let state = self.state().clone();
            let active = activation.clone();
            let wa_signal = ctx.window_active_signal();
            let theme_for_sel = theme_signal.clone();
            ctx.effect(&wa_signal, move |&window_active| {
                let mut st = state.borrow_mut();
                st.window_active = window_active;
                let theme = theme_for_sel.get();
                let tint = field_selection_color(&theme.colors, window_active, st.has_focus);
                st.selection_tint = tint;
                st.engine.set_selection_color(tint);
                if window_active {
                    // Reactivated: show the caret immediately if still focused
                    // (restart the blink phase), rather than waiting one interval.
                    if st.has_focus && !st.caret_visible.get() {
                        st.caret_visible.set(true);
                    }
                    st.blink.reset();
                } else {
                    // Deactivated: hide the caret synchronously (the frame loop
                    // may not tick while the window is inactive).
                    if st.caret_visible.get() {
                        st.caret_visible.set(false);
                    }
                    st.blink.reset();
                }
                if active.get()
                    && let Some(handle) = &st.frame_request
                {
                    handle.set(true);
                }
            });
        }

        // Forward the enabled state into the arena. Disabled state no
        // longer seeded into the interaction signal — the framework's
        // arena enabled-state is the single source of truth (events
        // gated, leaves resolve Disabled role).
        let self_id = ctx.self_id();
        ctx.enabled_when(self_id, self.enabled.clone());

        // Attach handlers. Focus-origin inference mirrors the
        // `Slider` pattern: hover cached, focus event checks hover
        // to distinguish keyboard vs pointer origin for the
        // select-all-on-keyboard-focus rule.
        let hovered = std::rc::Rc::new(std::cell::Cell::new(false));
        let hovered_for_focus = hovered.clone();
        let hovered_for_hover = hovered.clone();

        let state_for_focus = self.state().clone();
        let interaction_for_focus = self.interaction.clone();
        // The selection band's tint depends on focus, so the focus handler has
        // to re-apply it — and needs the live theme to do so.
        let theme_for_focus = theme_signal.clone();
        let state_for_pointer = self.state().clone();
        let state_for_key = self.state().clone();
        let state_for_double = self.state().clone();
        let state_for_triple = self.state().clone();
        let state_for_access = self.state().clone();
        let state_for_menu = self.state().clone();

        let handlers = HandlerSet::new()
            .focusable(true)
            .cursor(CursorIcon::Text)
            // Secure fields opt the focused node out of OS IME
            // composition so the preedit / candidate window can't
            // surface plaintext. Read by the platform IME layer at
            // focus-change time (default `true` for plain fields).
            .ime_input(if self.secure {
                teksilo_core::ime::ImeContext::password()
            } else {
                teksilo_core::ime::ImeContext::text()
            })
            .on_hover(move |entered, _ctx| {
                hovered_for_hover.set(entered);
            })
            .on_focus(move |gained, ctx| {
                interaction_for_focus.set(if gained {
                    InteractionState::Focused
                } else {
                    InteractionState::Idle
                });

                let mut st = state_for_focus.borrow_mut();
                st.has_focus = gained;
                st.focus_signal.set(gained);
                // Re-tint the selection band: `has_focus` is half of what
                // decides it, so losing focus inside an active window has to
                // re-apply just as losing the window does.
                let sel_theme = theme_for_focus.get();
                let tint = field_selection_color(&sel_theme.colors, st.window_active, gained);
                st.selection_tint = tint;
                st.engine.set_selection_color(tint);
                // RevealWhileTyping shows plaintext while focused and
                // re-masks on blur — both transitions need a relayout.
                if st.secure && st.echo_mode == EchoMode::RevealWhileTyping {
                    st.needs_full_layout = true;
                }
                let mut blur_callback: Option<Rc<CommandFactory>> = None;
                if gained {
                    st.blink.restart();
                    st.caret_visible.set(true);
                    let is_keyboard = !hovered_for_focus.get();
                    drop(st);
                    if is_keyboard {
                        let st = state_for_focus.borrow();
                        st.cursor.select(SelectionType::Document);
                        drop(st);
                        sync_cursor_signals(&state_for_focus);
                    }
                    // Seed the OS IME candidate area at the caret so the
                    // first composition appears in the right place.
                    keyboard::report_ime_cursor_area(&state_for_focus, ctx);
                } else {
                    // Preserve `cursor`'s selection across focus loss
                    // — clearing it here breaks the right-click
                    // context menu path (the framework focuses the
                    // newly-mounted menu, which dispatches `FocusLost`
                    // here, and `Cut` / `Copy` invoked from the menu
                    // afterwards find an empty selection). Native
                    // macOS / Windows text fields keep the selection
                    // on blur too — typically the visual is dimmed
                    // but the selection state is preserved so the
                    // next focus-gain or context-menu invocation
                    // still operates on it.
                    st.scroll_x = 0.0;
                    st.caret_visible.set(false);
                    st.drag_state = state::DragState::Idle;
                    // Drop the IME-area dedup cache. The OS candidate area is a
                    // single per-window resource a sibling field may re-point
                    // while we are unfocused; clearing this forces the next
                    // focus-gain report to re-seed it instead of being deduped.
                    st.last_ime_area = None;
                    blur_callback = st.on_blur.clone();
                    drop(st);
                    // Abandon any in-progress composition on blur — remove
                    // the tentative preedit text from the document.
                    keyboard::clear_ime_preedit(&state_for_focus);
                    sync_cursor_signals(&state_for_focus);
                }
                if let Some(cb) = blur_callback {
                    cb(ctx);
                }
                ctx.request_frame();
            })
            .on_pointer_event(move |event, ctx| {
                mouse::handle_pointer_event(&state_for_pointer, event, ctx)
            })
            .on_key(move |event, ctx| keyboard::handle_key(&state_for_key, event, ctx))
            .on_double_tap(move |event, ctx| {
                mouse::handle_double_tap(&state_for_double, event.position, ctx)
            })
            .on_triple_tap(move |event, ctx| {
                mouse::handle_triple_tap(&state_for_triple, event.position, ctx)
            })
            .on_access_action_request(move |action, _target_node, data, ctx| {
                handle_access_action(&state_for_access, action, data, ctx)
            })
            // Right-click context menu — built fresh per click so the
            // enabled state of each item reflects the live selection /
            // clipboard state at the moment the menu opens. The framework
            // handles overlay placement, focus restoration, and dismissal.
            .context_menu(move |position, ctx| {
                let _ = ctx;
                // Framework gates pointer events on `arena.is_enabled`
                // before reaching this closure — a disabled field
                // never receives the right-click that would open the
                // context menu.
                // Reposition the caret to the click position when the
                // click lands outside the existing selection — the
                // platform convention for "right-click then Cut /
                // Copy / Paste at the new caret".
                mouse::reposition_caret_for_context_menu(&state_for_menu, position);
                Some(build_context_menu_widget(&state_for_menu))
            });

        ctx.apply_self_handlers(handlers);
        Vec::new()
    }

    fn layout_response(
        &self,
        proposal: SizeProposal,
        ctx: &LayoutContext,
    ) -> teksilo_core::widget::LayoutResponse {
        // Default unwrap is the cached natural width (mask-aware when
        // a mask is set; 200 dp fallback otherwise). Composing widgets
        // that wrap us in a constraint pass `Some(width)` and we use
        // that; the natural width is what surfaces in unconstrained
        // intrinsic queries (ZStack measurement with `unspecified()`,
        // etc.) so the chain reports a sensible content size.
        //
        // The cached `natural_width` / `text_height` are 1.0-scale baselines;
        // multiply by `ctx.text_scale` so the field box grows with the global
        // accessibility text scale (the engine grows the glyphs to match — see
        // `paint`). A caller-supplied width constraint is honored as-is.
        let scale = ctx.text_scale;
        let w = proposal
            .width
            .unwrap_or(self.natural_width * scale)
            .max(0.0);
        let h = (self.text_height.unwrap_or(DEFAULT_TEXT_HEIGHT) * scale).max(0.0);
        Size::new(w, h).into()
    }

    fn place_children(
        &self,
        bounds: Rect,
        _proposal: SizeProposal,
        _children: &mut [WidgetPlacement],
        _ctx: &LayoutContext,
    ) {
        // Layout runs before paint, so this is the authoritative point to adopt
        // the field's viewport. `sync_viewport` welds the width write to the
        // `needs_full_layout` flag it also serves as the detector for (see its
        // docs); paint calls it again as an idempotent echo.
        if let Some(state) = self.state.as_ref() {
            state.borrow_mut().sync_viewport(bounds);
        }
    }

    fn paint(&self, bounds: Rect, canvas: &mut Canvas, ctx: &PaintContext) {
        let Some(state) = self.state.as_ref() else {
            return;
        };
        let mut st = state.borrow_mut();

        // Grow the shaped text with the global accessibility scale. Must run
        // before the relayout block below so the larger glyphs are shaped this
        // frame; no-op when the scale is unchanged.
        st.apply_font_scale(ctx.text_scale);
        // Idempotent echo — `place_children` already adopted these exact bounds
        // during layout, so this is normally a no-op.
        st.sync_viewport(bounds);

        // Resolve the glyph / caret / suffix colours against the *effective*
        // enabled state, exactly as `TextWidget` and `RectWidget` resolve a
        // `ColorProp` at paint time. `paint` is the single writer of these:
        // the field shapes through a `RichTextEngine`, which takes raw GPU
        // colours and so never passes through `ColorProp::resolve` — the
        // disabled substitution that greys every role-driven leaf for free
        // cannot reach it. Doing it here (rather than as a build-time effect
        // on `effective_enabled_signal`) is also the only correct option:
        // that signal is *derived* whenever an ancestor binds `enabled`, and
        // `Signal::observe` panics on derived signals. Cheap — the engine
        // stores the colour and the render-frame builder reads it, so there
        // is no relayout and no reshaping.
        let text_color = if ctx.effective_enabled {
            ctx.theme.colors.text_primary
        } else {
            ctx.theme.colors.text_disabled
        };
        st.engine.set_text_color(text_color.to_array());
        st.engine.set_cursor_color(text_color.to_array());

        let suffix_width = st.suffix_width;
        let text_viewport_width = (bounds.width - suffix_width).max(0.0);

        st.engine.set_viewport(10_000.0, bounds.height);

        if st.needs_full_layout || !st.engine.has_full_layout() {
            st.layout_full_masked();
            st.needs_full_layout = false;
            st.content_dirty = true;
        }

        // Suppress the caret in an inactive window for every paint — the
        // authoritative gate, covering the frame between a window-active flip
        // and the build-time effect running.
        let caret_on = st.caret_visible.get() && st.has_focus && st.window_active;
        // `NoEcho` while masked lays out an *empty* source, so the real
        // document cursor (which may sit past 0) must not be handed to
        // the engine — pin the displayed caret/selection to the start.
        // The real `cursor` still tracks the true position for editing.
        let hide_all = st.echo_mode == EchoMode::NoEcho && st.should_mask();
        let (disp_pos, disp_anchor) = if hide_all {
            (0, 0)
        } else {
            (st.cursor.position(), st.cursor.anchor())
        };
        // Single-line input has no wrap → affinity is moot; the
        // default Downstream matches pre-affinity behavior.
        let cursor_display = CursorDisplay {
            position: disp_pos,
            anchor: disp_anchor,
            affinity: CursorAffinity::Downstream,
            visible: caret_on,
            selected_cells: Vec::new(),
        };
        st.engine.set_cursor(&cursor_display);

        ensure_caret_visible_h(&mut st, text_viewport_width);

        let scroll_x = st.scroll_x;

        let text_clip = Rect::new(bounds.x, bounds.y, text_viewport_width, bounds.height);
        canvas.set_clip(text_clip);

        {
            let state_ref: &mut TextInputState = &mut st;
            let TextInputState {
                ref mut engine,
                ref document,
                ref mut image_cache,
                ..
            } = *state_ref;

            engine.with_render_frame(|frame| {
                paint_frame(
                    canvas,
                    PaintParams {
                        frame,
                        origin: Point::new(bounds.x - scroll_x, bounds.y),
                        document,
                        image_cache,
                        // No inline images on this surface, so none can be missing.
                        image_resolver: None,
                        selection: None,
                        selection_color: [0.0; 4],
                        selected_image_out: None,
                        resize_preview: None,
                        draw_caret: caret_on,
                    },
                );
            });
        }

        // IME preedit underline: a thin line under the composing range so
        // the user sees the text is tentative. Single line → one segment;
        // on a secure field it sits under the masked bullets. Drawn inside
        // the text clip so it never spills past the viewport.
        if let Some(range) = st.ime_preedit_range.clone()
            && st.engine.has_full_layout()
            && range.start < range.end
        {
            let start_c = st
                .engine
                .caret_rect(range.start, CursorAffinity::Downstream);
            let end_c = st.engine.caret_rect(range.end, CursorAffinity::Downstream);
            let x0 = bounds.x - scroll_x + start_c[0];
            let x1 = bounds.x - scroll_x + end_c[0];
            let y = bounds.y + start_c[1] + start_c[3] - 1.0;
            canvas.draw_line(
                Point::new(x0, y),
                Point::new(x1, y),
                ctx.theme.colors.text_primary,
                teksilo_canvas::StrokeStyle::solid(1.0),
            );
        }

        canvas.clear_clip();

        if suffix_width > 0.0
            && let Some(suffix_engine) = st.suffix_engine.as_mut()
        {
            // The suffix dims with the value it annotates — a crisp " %"
            // beside greyed-out digits reads as a rendering bug.
            let suffix_color = if ctx.effective_enabled {
                ctx.theme.colors.text_secondary
            } else {
                ctx.theme.colors.text_disabled
            };
            suffix_engine.set_text_color(suffix_color.to_array());
            let suffix_clip = Rect::new(
                bounds.x + text_viewport_width,
                bounds.y,
                suffix_width,
                bounds.height,
            );
            canvas.set_clip(suffix_clip);
            let suffix_origin = Point::new(bounds.x + text_viewport_width, bounds.y);
            suffix_engine.with_render_frame(|frame| {
                paint_suffix_glyphs(canvas, frame, suffix_origin);
            });
            canvas.clear_clip();
        }
    }

    fn accessibility(&self, builder: &mut AccessNodeBuilder) {
        use teksilo_core::accesskit::{Action, Role};

        let Some(state) = self.state.as_ref() else {
            return;
        };
        let st = state.borrow();

        let text = st.document.to_plain_text().unwrap_or_default();

        // AT-protection tracks the *explicit* reveal toggle only — not
        // the visual `RevealWhileTyping` focus-reveal (a sighted-only
        // convenience that a screen reader shouldn't surface as
        // plaintext, and that has no AT-dirty trigger on focus). The
        // reveal signal is bound at AccessibilityOnly in `build`, so the
        // role/value swap reaches AT when it flips. `Role::PasswordInput`
        // is the sole mechanism telling AT not to speak the value —
        // accesskit has no separate `protected` flag.
        let explicitly_revealed = st.revealed.as_ref().is_some_and(|s| s.get());
        let protected = st.secure
            && match st.at_reveal_policy {
                AtRevealPolicy::AlwaysProtected => true,
                AtRevealPolicy::SwapRole => !explicitly_revealed,
            };

        if protected {
            builder.set_role(Role::PasswordInput);
            // Expose a bullet string of the right length (NoEcho hides
            // even that) so AT can announce the character count, never
            // the secret. Deliberately omit character lengths, word
            // starts, and the text selection: the caret model stays
            // opaque so no structure about the secret leaks.
            if st.echo_mode != EchoMode::NoEcho {
                let count = text.chars().count();
                if count > 0 {
                    builder.set_value(st.echo_char.to_string().repeat(count));
                }
            }
        } else {
            // Plain field, or a revealed field under `SwapRole`: report
            // as a text input exposing the real value, mirroring the web
            // `type=password ↔ type=text` swap. The specialised role from
            // `input_purpose` (WCAG 1.3.5) applies here; `Role::TextInput` is
            // the `Normal` default.
            builder.set_role(self.input_purpose.to_role());
            // Keep the value on the input node so the focus announcement is
            // unchanged: accesskit resolves `value()` from `data().value()`
            // first, falling back to the TextRun text only when unset.
            if !text.is_empty() {
                builder.set_value(&text);
            }

            // Expose the editable content as a child `Role::TextRun`, NOT as
            // `character_lengths` on the input node itself. accesskit_consumer's
            // `supports_text_ranges()` is false for a childless input that only
            // hosts character data on its own node, so the macOS adapter never
            // fires `AXSelectedTextChanged` — VoiceOver reads the value once on
            // focus but never echoes characters/words while typing. Emit the run
            // even when empty so `supports_text_ranges()` is already true before
            // the first keystroke (the change-diff's *old* node must support
            // ranges too for the notification to fire). `position()` / `anchor()`
            // are character indices (text-document is char-space), matching the
            // TextRun's `character_index` contract — correct for multibyte text.
            let char_lengths: Vec<u8> = text.chars().map(|c| c.len_utf8() as u8).collect();
            let word_starts = compute_word_starts(&text);
            let word_starts = (!word_starts.is_empty()).then_some(word_starts);
            let run_id =
                builder.push_text_run_child_on_self(0, text.clone(), char_lengths, word_starts);

            // While composing (IME preedit active), expose the composition
            // as a selection so screen readers / braille track the tentative
            // text — the composing characters are already in `value`. Falls
            // back to the live cursor/selection when not composing. (The
            // secure branch above never reaches here, so a password preedit
            // is never exposed.) Selection now references the TextRun child.
            let (anchor, pos) = match st.ime_preedit_range.clone() {
                Some(range) => (range.start, range.end),
                None => (st.cursor.anchor(), st.cursor.position()),
            };
            builder.set_text_selection_to((run_id, anchor), (run_id, pos));
        }

        if !st.placeholder.is_empty() {
            builder.set_placeholder(st.placeholder.clone());
        }

        if st.read_only {
            builder.set_read_only();
        }

        builder.add_action(Action::Focus);
        if !st.read_only {
            builder.add_action(Action::SetValue);
            builder.add_action(Action::ReplaceSelectedText);
        }
        // Only meaningful when the caret model is exposed to AT.
        if !protected {
            builder.add_action(Action::SetTextSelection);
        }

        // Validation feedback → accesskit `aria-invalid`. Surface
        // `Invalid` as `Invalid::True`; `Corrected` doesn't carry an
        // invalid marker (the data is now valid) but the composite's
        // Live region announces the correction. The framework's
        // AccessNodeBuilder doesn't yet wrap `set_invalid`, so reach
        // through `inner_mut()` which is the documented escape hatch.
        if self.feedback.get().is_invalid() {
            builder
                .inner_mut()
                .set_invalid(teksilo_core::accesskit::Invalid::True);
        }

        // ARIA combobox wiring. This node is the one that actually holds
        // keyboard focus, which is why the relation is published here and not
        // on whichever composite owns the list — AT follows the *focused*
        // node's active descendant.
        if let Some(listbox) = self.controls.as_ref().and_then(|s| s.get()) {
            builder.push_controlled(teksilo_core::accessibility::widget_id_to_node_id(listbox));
        }
        if let Some(active) = self.active_descendant.as_ref().and_then(|s| s.get()) {
            builder
                .inner_mut()
                .set_active_descendant(teksilo_core::accessibility::widget_id_to_node_id(active));
        }
    }
}

impl TextInputField {
    /// Borrow the shared state. Panics if called before `build()`
    /// has run — the state is allocated in `build()` from the
    /// builder config.
    fn state(&self) -> &SharedState {
        self.state
            .as_ref()
            .expect("TextInputField::state called before build")
    }
}

/// Adjust `scroll_x` so the caret stays within the visible viewport.
///
/// `text_viewport_width` is the portion of the viewport reserved for
/// editable text, i.e. `viewport_width - suffix_width`. Callers pass
/// the reduced width explicitly so the scroll never slides text
/// behind the non-editable suffix.
fn ensure_caret_visible_h(st: &mut TextInputState, text_viewport_width: f32) {
    if !st.engine.has_full_layout() || text_viewport_width <= 0.0 {
        return;
    }
    let pos = st.cursor.position();
    // Single-line input: no wrap, affinity is a no-op.
    let caret = st.engine.caret_rect(pos, CursorAffinity::Downstream);
    let caret_x = caret[0];
    let caret_w = caret[2].max(1.0);
    let vw = text_viewport_width;

    if caret_x - st.scroll_x < SCROLL_MARGIN {
        st.scroll_x = (caret_x - SCROLL_MARGIN).max(0.0);
    } else if caret_x + caret_w - st.scroll_x > vw - SCROLL_MARGIN {
        st.scroll_x = caret_x + caret_w - vw + SCROLL_MARGIN;
    }
}

/// Update the cached suffix text and re-run layout on the suffix
/// engine. Called from `build()` for the initial value and from
/// the reactive effect when the bound suffix signal fires.
fn relayout_suffix(state: &SharedState, new_text: &str) {
    let mut st = state.borrow_mut();
    st.suffix = new_text.to_string();
    if new_text.is_empty() {
        st.suffix_width = 0.0;
        // Leave the engine in place (cheap to reuse) but don't
        // lay out — paint skips the suffix when width is zero.
        return;
    }
    let Some(engine) = st.suffix_engine.as_mut() else {
        // No engine allocated (pure-static path that started
        // empty and never became non-empty). Allocate lazily so
        // late signal flips still render.
        return;
    };
    let doc = TextDocument::new();
    let _ = doc.set_plain_text(new_text);
    let flow = doc.snapshot_flow();
    engine.layout_full(&flow);
    st.suffix_width = engine.max_content_width();
}

/// Paint glyphs from a pre-laid-out suffix `RenderFrame` at a fixed
/// origin. Decorations, selection rectangles, and caret are ignored —
/// the suffix is plain non-editable text, so only the glyph pass is
/// needed. Kept inline (rather than reusing `paint_frame`) to avoid
/// the `TextDocument` / `ImageCache` parameters `paint_frame`
/// requires for inline images the suffix never contains.
fn paint_suffix_glyphs(canvas: &mut Canvas, frame: &teksilo_text::RenderFrame, origin: Point) {
    use teksilo_canvas::GlyphQuad as CanvasGlyphQuad;
    for g in frame.glyphs.iter() {
        let quad = CanvasGlyphQuad {
            screen: [
                g.screen[0] + origin.x,
                g.screen[1] + origin.y,
                g.screen[2],
                g.screen[3],
            ],
            atlas: g.atlas,
            color: g.color,
            is_color: g.is_color,
        };
        canvas.draw_glyph_quad(quad);
    }
}

/// Selection-highlight colour for a text field: the vivid `selection_bg_active`
/// while the host window is active, the muted `selection_bg_inactive` while it
/// is inactive — so a field's selection desaturates in a background window
/// (the universal desktop convention; the same `selection_bg_inactive` the OS
/// uses for unfocused selection).
/// The band a selection is painted in — the **active** tint only while this
/// field is the one the keystrokes would go to.
///
/// Two axes, and both are needed. The window losing focus was already handled;
/// what was missing is the field losing it *within* an active window, which is
/// the common case: click into a cell editor, then click a button, and the
/// field went on showing a fully-lit selection as though it were still taking
/// input. Two fields on screen could both look focused at once.
///
/// The selection *state* is deliberately kept across blur — see the
/// `on_focus(false)` arm, which spells out why (the right-click Copy path needs
/// it, and native fields keep it too). This is the other half of that same
/// sentence: the state is preserved, the **visual is dimmed**. Only the second
/// half was implemented.
fn field_selection_color(
    colors: &teksilo_tokens::ColorTokens,
    window_active: bool,
    has_focus: bool,
) -> [f32; 4] {
    if window_active && has_focus {
        colors.selection_bg_active.to_array()
    } else {
        colors.selection_bg_inactive.to_array()
    }
}

/// Simplified frame-loop tick for single-line text input.
fn tick(state: &mut TextInputState, delta: f32) -> bool {
    if !state.pending_chars.is_empty() {
        let batch = std::mem::take(&mut state.pending_chars);
        let _ = state.cursor.insert_text(&batch);
        state.pending_text_changed = true;
    }

    let had_events = state.drain_events();

    // Blink only when focused AND the host window is active — the caret hides
    // in an inactive window (the universal desktop convention). The else-branch
    // below then turns it off, since `!blinking_active` now also covers the
    // window-inactive case.
    let caret_active = state.has_focus && state.window_active;
    let caret_visible = state.caret_visible.clone();
    let wake = state.frame_wake_at.clone();
    // A single-line field always blinks (no read-only/static presets), so it
    // hands the shared machine a fixed `Blinking` policy.
    state.blink.tick(
        CaretPolicy::Blinking,
        caret_active,
        &caret_visible,
        wake.as_ref(),
    );

    if state.needs_full_layout && state.viewport_width > 0.0 {
        state.layout_full_masked();
        state.needs_full_layout = false;
        state.content_dirty = true;
    }

    if state.pending_text_changed {
        let new_text = state.document.to_plain_text().unwrap_or_default();
        if state.text_signal.get() != new_text {
            state.deferred_text_update = Some(new_text);
        }
    }

    if state.debounce.tick(delta) {
        if state.pending_text_changed {
            state.pending_text_changed = false;
        }
        if let Some((cu, cr)) = state.pending_undo_redo.take() {
            if state.can_undo.get() != cu {
                state.can_undo.set(cu);
            }
            if state.can_redo.get() != cr {
                state.can_redo.set(cr);
            }
        }
    }
    let debounce_work = state.pending_text_changed || state.pending_undo_redo.is_some();

    had_events || debounce_work
}

/// Handle AccessKit actions (SetValue, SetTextSelection, Focus).
fn handle_access_action(
    state: &SharedState,
    action: teksilo_core::accesskit::Action,
    data: Option<teksilo_core::accesskit::ActionData>,
    ctx: &mut EventContext,
) -> EventResponse {
    use teksilo_core::accesskit::{Action, ActionData};

    match (action, data) {
        (Action::SetTextSelection, Some(ActionData::SetTextSelection(sel))) => {
            let st = state.borrow();
            st.cursor.set_position(
                sel.anchor.character_index,
                teksilo_text::text_document::MoveMode::MoveAnchor,
            );
            st.cursor.set_position(
                sel.focus.character_index,
                teksilo_text::text_document::MoveMode::KeepAnchor,
            );
            drop(st);
            sync_cursor_signals(state);
            ctx.request_frame();
            EventResponse::Handled
        }
        (Action::SetValue, Some(ActionData::Value(value))) => {
            let st = state.borrow();
            st.cursor.select(SelectionType::Document);
            let _ = st.cursor.insert_text(value.as_ref());
            drop(st);
            sync_cursor_signals(state);
            ctx.request_frame();
            EventResponse::Handled
        }
        (Action::ReplaceSelectedText, Some(ActionData::Value(value))) => {
            // Insert at the caret, replacing the active selection (if
            // any) — NOT the whole document like `SetValue`. This is the
            // AT-SPI (Linux) / UIA (Windows) braille-keyboard and
            // dictation insertion path; macOS routes insertion through
            // `SetValue` instead, so this never fires there. We advertise
            // the action in `accessibility()`, so we must service it.
            let st = state.borrow();
            let _ = st.cursor.insert_text(value.as_ref());
            drop(st);
            sync_cursor_signals(state);
            ctx.request_frame();
            EventResponse::Handled
        }
        (Action::Focus, _) => {
            if let Some(id) = state.borrow().field_widget_id {
                ctx.request_focus(id);
            }
            EventResponse::Handled
        }
        _ => EventResponse::Ignored,
    }
}

/// Compute word-start character indices for AccessKit.
fn compute_word_starts(text: &str) -> Vec<u8> {
    let mut starts = Vec::new();
    let mut in_word = false;
    for (char_index, ch) in text.chars().enumerate() {
        let is_word_char = ch.is_alphanumeric() || ch == '_';
        if is_word_char
            && !in_word
            && let Ok(idx) = u8::try_from(char_index)
        {
            starts.push(idx);
        }
        in_word = is_word_char;
    }
    starts
}

/// Build a fresh right-click context menu widget. Called from the
/// `.context_menu(...)` factory on every right-click, so each open
/// reads live `has_selection` / `is_empty` state when computing each
/// item's enabled flag.
fn build_context_menu_widget(state: &SharedState) -> Box<dyn Widget> {
    let st = state.borrow();
    let has_selection = st.cursor.has_selection();
    let doc_non_empty = !st.document.to_plain_text().unwrap_or_default().is_empty();
    // Secure fields suppress Cut / Copy while masked (still allowed when
    // revealed or when the developer opted in via `allow_copy`).
    let copy_allowed = st.copy_allowed();
    drop(st);

    let state_cut = state.clone();
    let state_copy = state.clone();
    let state_paste = state.clone();
    let state_select_all = state.clone();

    Box::new(
        MenuList::new()
            .item(
                MenuItem::new(tr_widget!(menu_cut()))
                    .shortcut_label(format_keystroke(KeyStroke::command(Key::X)))
                    .enabled(has_selection && copy_allowed)
                    .on_activate_fn(move |ctx| {
                        {
                            let mut st = state_cut.borrow_mut();
                            keyboard::clipboard_cut(&mut st, ctx);
                        }
                        sync_cursor_signals(&state_cut);
                        ctx.request_frame();
                    }),
            )
            .item(
                MenuItem::new(tr_widget!(menu_copy()))
                    .shortcut_label(format_keystroke(KeyStroke::command(Key::C)))
                    .enabled(has_selection && copy_allowed)
                    .on_activate_fn(move |ctx| {
                        let mut st = state_copy.borrow_mut();
                        keyboard::clipboard_copy(&mut st, ctx);
                    }),
            )
            .item(
                MenuItem::new(tr_widget!(menu_paste()))
                    .shortcut_label(format_keystroke(KeyStroke::command(Key::V)))
                    .on_activate_fn(move |ctx| {
                        {
                            let mut st = state_paste.borrow_mut();
                            keyboard::clipboard_paste(&mut st, ctx);
                        }
                        sync_cursor_signals(&state_paste);
                        ctx.request_frame();
                    }),
            )
            .item(MenuSeparator)
            .item(
                MenuItem::new(tr_widget!(menu_select_all()))
                    .shortcut_label(format_keystroke(KeyStroke::command(Key::A)))
                    .enabled(doc_non_empty)
                    .on_activate_fn(move |ctx| {
                        {
                            let st = state_select_all.borrow();
                            st.cursor.select(SelectionType::Document);
                        }
                        sync_cursor_signals(&state_select_all);
                        ctx.request_frame();
                    }),
            ),
    )
}

/// Run the validator on the bound text and update the feedback signal.
///
/// On `Corrected`, also writes the corrected text back to the bound
/// signal — the field's external→internal sync effect picks this up
/// and rewrites the document in the next frame. On `Invalid`, the
/// text is left as-typed; composites that want a "revert on invalid"
/// behaviour observe the feedback signal and rewrite the text from
/// their own source of truth (e.g., `DateEdit` reformats from its
/// `Signal<Option<Date>>`).
fn run_validator_and_apply(
    validator: &ValidatorFn,
    bound_text: &Signal<String>,
    feedback: &Signal<ValidationFeedback>,
) {
    let raw = bound_text.get();
    match validator(&raw) {
        ValidationOutcome::Valid => {
            feedback.set(ValidationFeedback::Valid);
        }
        ValidationOutcome::Corrected { corrected, message } => {
            // Write the corrected text first so observers of the
            // bound signal see the new value before the feedback
            // signal flips. Composites that bind to BOTH signals
            // (rare) will see a consistent pair: text + correction
            // notice describing the change.
            if bound_text.get() != corrected {
                bound_text.set(corrected);
            }
            feedback.set(ValidationFeedback::Corrected {
                message,
                since: std::time::Instant::now(),
            });
        }
        ValidationOutcome::Invalid { message } => {
            feedback.set(ValidationFeedback::Invalid { message });
        }
    }
}

/// Build the worst-case-glyph version of an [`InputMask`] for
/// natural-width measurement: every editable slot holds the widest
/// plausible character its class can accept, and every fixed slot
/// holds its literal. Used by `build()` to size the field's
/// intrinsic envelope so a fully-typed value never overflows the
/// reported natural width.
///
/// Per-class worst-case glyph (Inter and most UI sans-serifs):
/// - `Digit` → `0` (tabular figures are constant-width, but `0` is
///   representative for fonts that aren't)
/// - `Letter` / `Alphanumeric` / `Any` → `M` (widest cap glyph)
/// - `HexDigit` → `0`
fn worst_case_template(mask: &InputMask) -> String {
    let mut s = String::with_capacity(mask.len());
    for pos in mask.positions() {
        match pos {
            MaskPosition::Editable { class, .. } => {
                s.push(match class {
                    MaskClass::Digit | MaskClass::HexDigit => '0',
                    MaskClass::Letter | MaskClass::Alphanumeric | MaskClass::Any => 'M',
                });
            }
            MaskPosition::Fixed(c) => s.push(*c),
        }
    }
    s
}

/// Measure the advance width of `text` in logical pixels using the
/// app-wide `SharedTypesetter` (the same backend the field paints
/// with). Falls back to a per-character-class heuristic when no
/// typesetter is installed (headless tests) so the caller still gets
/// a non-zero width and any natural-width / cap logic behaves
/// reasonably even there. The fallback weights match Inter's body
/// proportions closely enough that the difference between an
/// underscore and a wide cap glyph (`M`) shows up in headless tests
/// — important for verifying the worst-case-glyph mask measurement
/// without booting a typesetter.
fn measure_width_px(ctx: &mut BuildContext, text: &str, style: &TextStyle) -> f32 {
    if text.is_empty() {
        return 0.0;
    }
    if let Some(ts) = ctx.app_state::<SharedTypesetter>() {
        let backend = ts.as_text_backend();
        let layout = backend.borrow_mut().layout_single_line(text, style, None);
        return layout.width;
    }
    let em = style.size;
    text.chars()
        .map(|c| match c {
            ' ' => 0.30,
            '_' => 0.45,
            ':' | '.' | ',' | ';' | '/' | '|' | '!' | 'i' | 'l' | 'I' => 0.30,
            '0'..='9' => 0.55,
            'M' | 'W' | 'm' | 'w' => 0.85,
            'A'..='Z' => 0.65,
            'a'..='z' => 0.50,
            _ => 0.55,
        })
        .map(|w: f32| w * em)
        .sum()
}

#[cfg(test)]
mod window_active_tests {
    use super::*;
    use teksilo_canvas::{Point, SizeProposal};
    use teksilo_core::event::{Modifiers, PointerButton, WidgetEvent};
    use teksilo_core::signal::Signal;
    use teksilo_core::widget_tree::WidgetTree;

    #[test]
    fn field_selection_color_swaps_on_window_active() {
        let colors = teksilo_core::presets::intui::light().colors;
        assert_eq!(
            field_selection_color(&colors, true, true),
            colors.selection_bg_active.to_array(),
            "active window uses the vivid selection colour"
        );
        assert_eq!(
            field_selection_color(&colors, false, true),
            colors.selection_bg_inactive.to_array(),
            "inactive window uses the muted selection colour"
        );
        assert_ne!(
            field_selection_color(&colors, true, true),
            field_selection_color(&colors, false, true)
        );
    }

    /// **A field that is not focused dims its selection, even in an active
    /// window.**
    ///
    /// Only the window axis was ever consulted, so clicking from one field to
    /// another left both showing a fully-lit selection: two controls claiming
    /// the keystrokes at once. The selection *state* is kept on blur on
    /// purpose — the `on_focus(false)` arm explains why, and native fields do
    /// the same — and this is the other half of that sentence, which had never
    /// been written.
    #[test]
    fn field_selection_color_dims_when_the_field_is_not_focused() {
        let colors = teksilo_core::presets::intui::light().colors;
        assert_eq!(
            field_selection_color(&colors, true, false),
            colors.selection_bg_inactive.to_array(),
            "an unfocused field must dim its selection even in an active window"
        );
        assert_eq!(
            field_selection_color(&colors, false, false),
            colors.selection_bg_inactive.to_array()
        );
    }

    /// ...and the live field re-tints as focus comes and goes, rather than
    /// keeping whatever colour it was built with.
    #[test]
    fn a_field_re_tints_its_selection_when_focus_leaves_it() {
        let colors = teksilo_core::presets::intui::light().colors;
        let mut tree = WidgetTree::new().with_theme(teksilo_core::presets::intui::light());
        let a = tree.add(TextInputField::new(Signal::new("hello".to_string())));
        let b = tree.add(TextInputField::new(Signal::new("world".to_string())));
        tree.layout(SizeProposal::exact(200.0, 40.0));

        let tint = |tree: &WidgetTree, id| {
            tree.widget_as_any(id)
                .and_then(|w| w.downcast_ref::<TextInputField>())
                .and_then(|f| f.state.as_ref())
                .map(|st| st.borrow().selection_tint)
                .expect("a built field")
        };

        tree.focus(a);
        assert_eq!(
            tint(&tree, a),
            colors.selection_bg_active.to_array(),
            "the focused field paints its selection live"
        );

        tree.focus(b);
        assert_eq!(
            tint(&tree, a),
            colors.selection_bg_inactive.to_array(),
            "focus moved to another field and the first kept a lit selection"
        );
        assert_eq!(tint(&tree, b), colors.selection_bg_active.to_array());
    }

    #[test]
    fn caret_hidden_when_window_inactive() {
        let text = Signal::new("hello".to_string());
        let mut tree = WidgetTree::new().with_theme(teksilo_core::presets::intui::light());
        let id = tree.add(TextInputField::new(text));
        tree.layout(SizeProposal::exact(200.0, 40.0));
        let _ = tree.render();

        // Reach the built field's shared state (created lazily in build()) to
        // observe the caret-gate inputs directly — the caret paints as an
        // engine-internal fill, not a top-level decoration.
        let state = tree
            .widget_as_any(id)
            .and_then(|a| a.downcast_ref::<TextInputField>())
            .map(|f| f.state().clone())
            .expect("built TextInputField is reachable via as_any");

        // Focus the field by clicking its centre.
        let b = tree.bounds(id);
        tree.dispatch_event(WidgetEvent::PointerDown {
            position: Point::new(b.x + b.width / 2.0, b.y + b.height / 2.0),
            button: PointerButton::Primary,
            modifiers: Modifiers::NONE,
        });
        // One frame so the blink turns the caret on (on_focus sets it on; the
        // 500 ms interval hasn't elapsed after a single 16 ms tick).
        tree.request_frame();
        tree.tick_animations(std::time::Duration::from_millis(16));
        tree.layout(SizeProposal::exact(200.0, 40.0));

        assert!(state.borrow().has_focus, "field took focus");
        assert!(state.borrow().window_active);
        assert!(
            state.borrow().caret_visible.get(),
            "caret visible when focused in an active window"
        );

        // Window blur: caret hidden (effect clears it synchronously).
        tree.set_window_active(false);
        assert!(!state.borrow().window_active);
        assert!(
            !state.borrow().caret_visible.get(),
            "caret hidden while the window is inactive"
        );

        // Reactivate: caret returns immediately (field still holds focus).
        tree.set_window_active(true);
        assert!(
            state.borrow().caret_visible.get(),
            "caret restored on window reactivate"
        );
    }
}

/// **A key the platform decorates with control text must still bubble.**
///
/// These dispatch `KeyDown` with the `text` a real keyboard carries. Every
/// synthetic helper in the workspace sends `text: None`, which skips the branch
/// under test entirely — so a test written with `press_key` passes on the bug.
#[cfg(test)]
mod key_text_bubbling_tests {
    use super::*;
    use std::cell::Cell;
    use teksilo_canvas::{Point, SizeProposal};
    use teksilo_core::WidgetBuilder;
    use teksilo_core::event::{Modifiers, PointerButton, WidgetEvent};
    use teksilo_core::signal::Signal;
    use teksilo_core::widget_tree::WidgetTree;

    /// Dispatch one `KeyDown` to a focused field that sits *inside* a widget
    /// carrying an `on_key`, and report whether that outer handler saw it.
    ///
    /// The nesting is the point. Hanging the handler on the field itself puts
    /// it on the same node the click focuses, above the field's own handler
    /// rather than behind it, and the bubble under test never happens — which
    /// is exactly how an earlier version of this test passed on the bug.
    fn outer_handler_sees(key: Key, text: Option<&str>, field: TextInputField) -> bool {
        let seen = Rc::new(Cell::new(false));
        let seen_for_handler = seen.clone();
        let mut tree = WidgetTree::new().with_theme(teksilo_core::presets::intui::light());
        let outer = tree.add(crate::primitives::VStack::new().child(field).on_key(
            move |_ev, _ctx| {
                seen_for_handler.set(true);
                EventResponse::Handled
            },
        ));
        tree.layout(SizeProposal::exact(200.0, 40.0));

        let b = tree.bounds(outer);
        let centre = Point::new(b.x + b.width / 2.0, b.y + b.height / 2.0);
        tree.dispatch_event(WidgetEvent::PointerDown {
            position: centre,
            button: PointerButton::Primary,
            modifiers: Modifiers::NONE,
        });
        tree.dispatch_event(WidgetEvent::PointerUp {
            position: centre,
            button: PointerButton::Primary,
            modifiers: Modifiers::NONE,
        });
        let focused = tree.focused().expect("the click focused something");
        assert_ne!(
            focused, outer,
            "focus must land on the field, or nothing below the outer handler is being tested"
        );

        tree.dispatch_event(WidgetEvent::KeyDown {
            key,
            modifiers: Modifiers::NONE,
            text: text.map(str::to_string),
        });
        seen.get()
    }

    /// The bug: winit gives Escape `text: Some("\u{1b}")`, the field had no
    /// `Escape` arm so it fell into the printable-character branch, the control
    /// character was filtered out, and the empty result was read as "input
    /// rejected" — which swallows the key. Escape therefore never left a
    /// focused field, and anything above it that closes on Escape stayed open.
    #[test]
    fn escape_bubbles_out_of_a_field_even_carrying_its_control_text() {
        assert!(
            outer_handler_sees(
                Key::Escape,
                Some("\u{1b}"),
                TextInputField::new(Signal::new("hello".to_string()))
            ),
            "Escape must reach the widget above the field"
        );
    }

    /// ...and it made no difference with `text: None`, which is why the whole
    /// suite went green on the bug. Kept so the two cases stay visibly paired.
    #[test]
    fn escape_bubbles_out_of_a_field_without_text() {
        assert!(outer_handler_sees(
            Key::Escape,
            None,
            TextInputField::new(Signal::new("hello".to_string()))
        ));
    }

    /// The other half of the guard, and the reason it is written against the
    /// *text* rather than the `Key` variant: a character the field's filter
    /// rejects is still swallowed, so a digits-only field does not let a
    /// rejected letter fall through and match a shortcut.
    ///
    /// A typed letter arrives as `Key::A`, not `Key::Character('a')`, so a
    /// variant test here would have silently stopped swallowing letters.
    #[test]
    fn a_filter_rejected_character_is_still_swallowed() {
        let digits_only = TextInputField::new(Signal::new(String::new()))
            .char_filter(|c: char| c.is_ascii_digit());
        assert!(
            !outer_handler_sees(Key::A, Some("a"), digits_only),
            "a rejected letter must not bubble into a shortcut match"
        );
    }
}

/// A live handle on a [`TextInputField`] — its text-editing commands, for a
/// caller outside the widget.
///
/// Every method is a no-op before the field is built (and after it is
/// destroyed), which is the honest answer rather than a panic: a menu row bound
/// to a field that is no longer on screen should do nothing, not crash.
#[derive(Clone)]
pub struct TextFieldHandle {
    slot: std::rc::Rc<std::cell::RefCell<Option<SharedState>>>,
    focus_signal: Signal<bool>,
}

impl std::fmt::Debug for TextFieldHandle {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("TextFieldHandle")
            .field("live", &self.slot.borrow().is_some())
            .field("focused", &self.focus_signal.get())
            .finish()
    }
}

impl TextFieldHandle {
    /// A handle not yet attached to any field — for a composing widget that
    /// hands one out before building the field it will delegate to. Every
    /// method answers "nothing" until [`TextInputField::share_handle`] binds it.
    pub fn detached() -> Self {
        Self {
            slot: std::rc::Rc::new(std::cell::RefCell::new(None)),
            focus_signal: Signal::new(false),
        }
    }

    /// `true` while this field holds the keyboard focus. Observable, so a
    /// router can follow the caret without polling.
    pub fn focused_signal(&self) -> Signal<bool> {
        self.focus_signal.clone()
    }

    /// Is the widget built and still alive?
    pub fn is_live(&self) -> bool {
        self.slot.borrow().is_some()
    }

    fn with<R>(&self, f: impl FnOnce(&mut TextInputState) -> R) -> Option<R> {
        let slot = self.slot.borrow();
        let state = slot.as_ref()?;
        let mut st = state.borrow_mut();
        Some(f(&mut st))
    }

    /// The field's current text.
    pub fn text(&self) -> String {
        self.with(|st| st.document.to_plain_text().unwrap_or_default())
            .unwrap_or_default()
    }

    /// Is any text selected right now?
    pub fn has_selection(&self) -> bool {
        self.with(|st| st.cursor.has_selection()).unwrap_or(false)
    }

    /// May this field's content be copied at all? A password field says no —
    /// see [`TextInputField::allow_copy`].
    pub fn allows_copy(&self) -> bool {
        self.with(|st| st.allow_copy).unwrap_or(false)
    }

    /// Is the field refusing edits? Cut and Paste are meaningless when it is.
    pub fn is_read_only(&self) -> bool {
        self.with(|st| st.read_only).unwrap_or(true)
    }

    /// Select the whole field.
    pub fn select_all(&self) {
        self.with(|st| st.cursor.select(SelectionType::Document));
    }

    /// Copy the selection to the clipboard.
    pub fn copy(&self, ctx: &EventContext) {
        self.with(|st| keyboard::clipboard_copy(st, ctx));
    }

    /// Cut the selection to the clipboard.
    pub fn cut(&self, ctx: &EventContext) {
        self.with(|st| keyboard::clipboard_cut(st, ctx));
    }

    /// Paste over the selection.
    pub fn paste(&self, ctx: &EventContext) {
        self.with(|st| keyboard::clipboard_paste(st, ctx));
    }

    /// Undo this field's own last edit.
    pub fn undo(&self) {
        self.with(|st| {
            let _ = st.document.undo();
        });
    }

    /// Redo this field's own last undone edit.
    pub fn redo(&self) {
        self.with(|st| {
            let _ = st.document.redo();
        });
    }

    /// Is there anything to undo? Debounced like the editor's twin.
    pub fn can_undo(&self) -> Signal<bool> {
        self.with(|st| st.can_undo.clone())
            .unwrap_or_else(|| Signal::new(false))
    }

    /// Is there anything to redo?
    pub fn can_redo(&self) -> Signal<bool> {
        self.with(|st| st.can_redo.clone())
            .unwrap_or_else(|| Signal::new(false))
    }
}

// ── The framework's uniform view of a text-editing widget ────────────────────

impl teksilo_core::text_surface::TextSurface for TextFieldHandle {
    fn can_undo(&self) -> bool {
        TextFieldHandle::can_undo(self).get()
    }

    fn can_redo(&self) -> bool {
        TextFieldHandle::can_redo(self).get()
    }

    fn undo(&self) {
        TextFieldHandle::undo(self);
    }

    fn redo(&self) {
        TextFieldHandle::redo(self);
    }

    fn has_selection(&self) -> bool {
        TextFieldHandle::has_selection(self)
    }

    fn is_read_only(&self) -> bool {
        TextFieldHandle::is_read_only(self)
    }

    fn allows_copy(&self) -> bool {
        TextFieldHandle::allows_copy(self)
    }

    fn cut(&self, ctx: &teksilo_core::widget::EventContext<'_>) {
        TextFieldHandle::cut(self, ctx);
    }

    fn copy(&self, ctx: &teksilo_core::widget::EventContext<'_>) {
        TextFieldHandle::copy(self, ctx);
    }

    fn paste(&self, ctx: &teksilo_core::widget::EventContext<'_>) {
        TextFieldHandle::paste(self, ctx);
    }

    /// A one-line field carries no formatting to strip, so the plain paste
    /// *is* the paste. Answering "nothing" here would make Edit ▸ Paste without
    /// formatting silently dead over a rename box.
    fn paste_plain(&self, ctx: &teksilo_core::widget::EventContext<'_>) {
        TextFieldHandle::paste(self, ctx);
    }

    fn select_all(&self) {
        TextFieldHandle::select_all(self);
    }
}