Docs

Forms and the keyboard

Text entry is the input element, input() in Rust and <Input> in TSX: a UITextField or UITextView on iOS, an EditText on Android. Typing, the caret, selection, autocorrection and autofill are the platform’s own; your app gets the text through events and can control it. NSH also keeps focused inputs above the software keyboard on its own, and gives you the keyboard’s height as a reactive value for the cases it cannot handle by itself.

guide-forms.tsx
guide-forms.tsxLive
import { type JSX, mount, Scroll, signal, Text, View, type YNode } from "nsh";
import { Input } from "nsh/base";
import { button, buttonText, desktop, field, Inspector, Panel, Stage, ui, wide } from "./palette";

const label = () => ({ fontSize: 13, color: ui().muted });

function App() {
  const name = signal("");
  const email = signal("");
  const code = signal("");
  const notes = signal("");
  const notesHeight = signal(0);
  const focused = signal("nothing");
  const sent = signal("");
  let emailInput!: YNode;
  let passwordInput!: YNode;
  let notesInput!: YNode;

  let tries = 0;
  const submit = () => sent.set(`#${++tries}: signed up ${name() || "nobody"} <${email() || "no e-mail"}>`);

  type Style = () => object;
  const nameInput = (style?: Style) => (
    <Input
      {...field({ style })}
      value={name()}
      onChange={(t) => name.set(t)}
      placeholder="Ada Lovelace"
      autoCapitalize="words"
      autoComplete="name"
      returnKeyType="next"
      submitBehavior="submit"
      onSubmit={() => emailInput.focus()}
      onFocus={() => focused.set("name")}
    />
  );
  const emailField = (style?: Style) => (
    <Input
      ref={emailInput}
      {...field({ style })}
      value={email()}
      onChange={(t) => email.set(t.trim().toLowerCase())}
      placeholder="ada@example.com"
      keyboardType="email-address"
      autoCapitalize="none"
      autoCorrect={false}
      autoComplete="email"
      returnKeyType="next"
      submitBehavior="submit"
      onSubmit={() => passwordInput.focus()}
      onFocus={() => focused.set("e-mail")}
    />
  );
  const passwordField = (style?: Style) => (
    <Input
      ref={passwordInput}
      {...field({ style })}
      masked
      autoComplete="new-password"
      placeholder="At least 8 characters"
      returnKeyType="next"
      submitBehavior="submit"
      onSubmit={() => notesInput.focus()}
      onFocus={() => focused.set("password")}
    />
  );
  const codeField = (style?: Style) => (
    <Input
      {...field({ style })}
      value={code()}
      onChange={(t) => code.set(t.replace(/[^0-9]/g, ""))}
      keyboardType="number-pad"
      autoComplete="one-time-code"
      maxLength={6}
      onFocus={() => focused.set("code")}
    />
  );
  const notesField = (style?: Style) => (
    <Input
      ref={notesInput}
      multiline
      maxLength={200}
      value={notes()}
      onChange={(t) => notes.set(t)}
      onContentSizeChange={(e) => notesHeight.set(Math.min(e.height, 120))}
      placeholder="Return adds a line"
      {...field({ style })}
      onFocus={() => focused.set("notes")}
      onBlur={() => focused.set("nothing")}
    />
  );

  // A phone: one scrolling column, full-width fields and button.
  const column = () => (
    <Scroll style={{ flex: 1, backgroundColor: ui().page }} keyboardDismissMode="on-drag" keyboardShouldPersistTaps="handled">
      <View style={{ padding: 16, paddingTop: 24, gap: 12 }}>
        <Text style={{ fontSize: 22, fontWeight: "700", color: ui().text }}>Sign up</Text>
        <Text style={label()}>Focused: {focused()}</Text>

        <Text style={label()}>Name (controlled, return goes to the next field)</Text>
        {nameInput()}

        <Text style={label()}>E-mail</Text>
        {emailField()}

        <Text style={label()}>Password (uncontrolled)</Text>
        {passwordField()}

        <Text style={label()}>Code (number pad, 6 digits)</Text>
        {codeField(() => ({ letterSpacing: 8, textAlign: "center", fontSize: 22 }))}

        <Text style={label()}>About you (grows with its text, 200 max)</Text>
        {notesField(() => ({ height: Math.max(notesHeight(), 22) + 20 }))}
        <Text style={{ ...label(), textAlign: "right" }}>{`${notes().length}/200`}</Text>

        <View onPress={submit} {...button("primary")}>
          <Text style={buttonText("primary")}>Sign up</Text>
        </View>
        <Text style={{ color: ui().up }}>{sent()}</Text>
      </View>
    </Scroll>
  );

  // A wide window: a 360-point form, each label above its field, and its
  // state beside it.
  const group = (title: string, input: JSX.Element, help?: JSX.Element) => (
    <View style={{ gap: 6 }}>
      <Text style={{ fontSize: 13, fontWeight: "500", color: ui().text }}>{title}</Text>
      {input}
      {help}
    </View>
  );
  const form = () => (
    <View style={{ flex: 1, backgroundColor: ui().page, padding: 20, paddingTop: 24, gap: 14 }}>
      <Text style={{ fontSize: 22, fontWeight: "700", color: ui().text }}>Sign up</Text>
      <View style={{ flex: 1, flexDirection: "row", gap: 16 }}>
        <Stage width={360} gap={14}>
          {group("Name", nameInput(), <Text style={label()}>Controlled; Return goes to the next field</Text>)}
          {group("E-mail", emailField())}
          {group("Password", passwordField(), <Text style={label()}>Uncontrolled</Text>)}
          {group("Code", codeField(() => ({ width: 160, letterSpacing: 6, textAlign: "center", fontSize: 16 })), <Text style={label()}>6 digits</Text>)}
          {group(
            "About you",
            notesField(() => ({ height: Math.max(notesHeight(), 20) + 14 })),
            <Text style={{ ...label(), textAlign: "right", fontVariant: ["tabular-nums"] }}>{`${notes().length}/200`}</Text>,
          )}
          <View onPress={submit} {...button("primary")}>
            <Text style={buttonText("primary")}>Sign up</Text>
          </View>
        </Stage>
        <Inspector>
          <Panel title="onFocus · onBlur">
            <Text style={{ fontSize: 13, color: ui().text }}>Focused: {focused()}</Text>
          </Panel>
          <Panel title="onSubmit" minHeight={64}>
            <Text style={{ fontSize: 13, color: ui().up }}>{sent()}</Text>
          </Panel>
          <Text style={{ fontSize: 12, color: ui().faint }}>
            {desktop ? "Tab moves between fields; Return in a field goes to the next one." : "Return goes to the next field."}
          </Text>
        </Inspector>
      </View>
    </View>
  );

  return <>{() => (wide() ? form() : column())}</>;
}

mount(App);

An input takes styles like any view (typed style methods in Rust, styles and Tailwind classes in TSX), so the fields of a form have your app’s own look. A labeled field is a short component of your own:

use nsh_core::prelude::*;

fn field(label: &'static str, value: Signal<String>, masked: bool) -> impl IntoElement {
    let focused = signal(false);
    view()
        .gap_1()
        .child(text(label).text_sm().text_color(rgb(0x737373)))
        .child(
            input()
                .value(move || value.get())
                .on_change(move |text: &str| value.set(text.to_owned()))
                .masked(masked)
                .on_focus(move || focused.set(true))
                .on_blur(move || focused.set(false))
                .rounded_lg()
                .border_1()
                .px_3()
                .py_2()
                .text_base()
                .border_color(move || if focused.get() { rgb(0x0969da) } else { rgb(0xd0d7de) }),
        )
}

#Controlled and uncontrolled inputs

An input is controlled when you pass its value (.value(..), TSX value): it shows what your signal holds, and you update the signal from the change event (.on_change(..), TSX onChange).

use nsh_core::prelude::*;

#[component]
pub fn App() -> impl IntoElement {
    let name = signal(String::new());
    view()
        .flex_1()
        .p(px(16.0))
        .pt(px(60.0))
        .gap(px(8.0))
        .child(
            input()
                .value(move || name.get())
                .on_change(move |text: &str| name.set(text.to_owned()))
                .placeholder("Your name")
                .text_size(px(17.0))
                .border_1()
                .border_color(rgb(0xd0d7de))
                .rounded(px(10.0))
                .p(px(12.0)),
        )
        .child(text(move || {
            let name = name.get();
            format!("Hello, {}", if name.is_empty() { "stranger" } else { &name })
        }))
}

Because you control the value, you can transform what the user types: .on_change(move |t: &str| tag.set(t.to_uppercase())) uppercases, onChange={(t) => code.set(t.replace(/[^0-9]/g, ""))} keeps digits only.

#Input methods

Chinese, Japanese and Korean input methods compose text before committing it: pinyin turns into 腾 once a character is chosen. onCompositionChange (Rust .on_composition_change(..)) reports the composition as it goes, { composing: true, text: "teng" } while the user types and { composing: false, text: "" } when it ends; the committed text reaches onChange before the end. On iOS, Android, macOS and the web, onChange also reports the text being composed, as those systems keep it in the input; on Windows, Linux and GPUI it reports the committed text. A controlled input keeps the composition going whatever the app does with the value: a value set while the user composes is shown once the composition ends, so an input that uppercases or filters its text takes pinyin as typed.

A search box that searches the committed text only:

let query = signal(String::new());
let composing = signal(false);
input()
    .value(move || query.get())
    .on_change(move |text: &str| {
        query.set(text.to_owned());
        if !composing.get() {
            search(text);
        }
    })
    .on_composition_change(move |e: &Composition| {
        composing.set(e.composing);
        if !e.composing {
            search(&query.get());
        }
    })

An input is uncontrolled without a value: it keeps its own text, starting at its default value (.default_value(..), TSX defaultValue), and you read it from the change or submit event when you need it. Use this for fields you only read on submit, such as a password.

#Props

In Rust, each prop is a method of input() named in snake case (.placeholder(..), .masked(true), .max_length(6), .return_key_type(ReturnKeyType::Next), .selected_range((0, 4))), with these names of their own: .keyboard_type(KeyboardType::Email) and the other KeyboardType variants, .auto_fill(AutoFill::Email) for autoComplete, .keyboard_appearance(..) and .input_accessory(..) for the ios={{ … }} props. Each event is an on_ method: .on_change(|text: &str| ..), .on_submit(|text: &str| ..), .on_focus(..), .on_blur(..), .on_selection_change(|s: &Selection| ..), .on_key_press(|key: &str| ..), .on_content_size_change(|size: &Size<Points>| ..).

PropTypeDefaultDescription
valuestringThe text, controlled by JS.
defaultValuestringThe initial text of an uncontrolled input.
placeholderstringShown while the input is empty.
maskedbooleanfalseHides the text (passwords).
keyboardTypeKeyboardType"default"The keyboard layout.
returnKeyTypeReturnKeyType"default"The return key’s label.
autoCapitalize"none" | "sentences" | "words" | "characters""sentences"Automatic capitalization.
autoCorrectbooleantrueThe system’s corrections.
autoCompleteAutoCompleteWhat the input holds, for autofill.
multilinebooleanfalseSeveral lines; return inserts a line break unless submitBehavior says otherwise.
maxLengthnumberThe most characters the user can enter.
readonlybooleanfalseThe user can select and copy the text but not change it.
autoFocusbooleanfalseFocused when it appears.
submitBehavior"submit" | "blurAndSubmit" | "newline"single line "blurAndSubmit", multiline "newline"What return does: submit and keep the focus, submit and unfocus, or insert a line break (multiline only).
pasteBehavior"insert" | "report""insert"What a paste does: insert its text, or nothing (pasting).
caretbooleantrueThe caret is drawn; false hides it.
ios={{ keyboardAppearance }}"default" | "light" | "dark""default"The keyboard’s look (iOS).
selectedRange{ start: number; end?: number }The controlled selection, in UTF-16 units.
allowFontScalingbooleantrueFollow the system text size.
maxFontSizeMultipliernumberThe upper bound of the system scale (0: none).
ios={{ inputAccessoryViewID }}stringiOS: the bar shown over the keyboard (see below).
ios={{ textContentType }}TextContentTypeiOS’s names for autoComplete values.

Events:

EventPayloadWhen
onChangetext: stringThe text changed.
onSubmit{ text }The return key was pressed in an input that submits (single line, or submitBehavior "submit" / "blurAndSubmit").
onFocus / onBlurThe input gained / lost focus.
onSelectionChange{ start, end }The caret or selection moved (UTF-16 units).
onPaste{ text, files, uris }The user pasted: text, images as Files, local files’ URLs (pasting).
onCaretMove{ bounds, pageBounds }The caret moved: where it is in the input and in the window (the caret).
onKeyPress{ key }Before the text changes: key is the typed text, "Backspace" or "Enter".
onContentSizeChange{ width, height }The text’s size changed (at the input’s width when multiline), as it is typed; an empty input reports one empty line, whatever its placeholder.
onCompositionChange{ composing, text }An input method’s composition started, changed or ended (see Input methods).

An input is styled like text: fontSize, color, fontFamily, textAlign, letterSpacing and the rest of text styles, plus borders, padding and backgrounds. The focus style (.focus(|s| ..) in Rust, the focus: Tailwind variant or focusStyle in TSX) applies while the input has focus. The placeholder’s color is .placeholder_color(..) (the placeholderColor style key, placeholder:text-*), and the caret and selection’s color is .selection_color(..) (selectionColor, selection:text-*):

input()
    .placeholder("Search")
    .rounded_lg()
    .border_1()
    .border_color(rgb(0xd4d4d8))
    .px_3()
    .py_2()
    .text_base()
    .focus(|s| s.border_color(rgb(0x3b82f6)))
    .placeholder_color(rgb(0xa1a1aa))
    .selection_color(rgb(0x2563eb))

#Keyboards and autofill

The keyboard type (.keyboard_type(..), TSX keyboardType) picks the layout:

RustTSXKeyboard
KeyboardType::Default"default"Text.
KeyboardType::Email"email-address"Text with @ and . at hand.
KeyboardType::Url"url"Text with / and .com.
KeyboardType::Number"number-pad"Digits only: no sign, no decimal separator (codes, PINs).
KeyboardType::Decimal"decimal-pad"Digits and a decimal separator.
KeyboardType::Numeric"numeric"As React Native: iOS’s decimal pad; on Android digits with a sign and a decimal separator.
KeyboardType::NumbersAndPunctuation"numbers-and-punctuation"Digits, a minus sign and punctuation (iOS’s numbers and punctuation keyboard; on Android digits with a sign and a decimal separator). Use it for negative numbers on iOS.
KeyboardType::Phone"phone-pad"A phone dial pad.

On iOS, .keyboard_appearance(KeyboardAppearance::Dark) (TSX ios={{ keyboardAppearance: "dark" }}; or light, default) gives the keyboard a light or dark look regardless of the system’s appearance, for a dark app in light mode. Android’s keyboards always follow the system’s theme.

Autofill (.auto_fill(AutoFill::Email), TSX autoComplete) tells the system what the field holds, so it can offer saved names, addresses, passwords and one-time codes from messages. Rust’s AutoFill has a variant per kind (Name, GivenName, FamilyName, Email, Tel, Username, Password, NewPassword, OneTimeCode, StreetAddress, PostalCode, Country, CreditCardNumber, Url, Birthdate, …, and Off). TSX takes these values: "name", "given-name", "family-name", "email", "tel", "username", "current-password", "new-password", "one-time-code", "street-address", "postal-code", "country", "cc-number", "cc-exp", "cc-csc", "url", "birthdate-full" and others, or "off"; iOS’s own names ("emailAddress", "oneTimeCode", …) are accepted too, in autoComplete or ios={{ textContentType }}.

use nsh_core::element::AutoFill;

input()
    .keyboard_type(KeyboardType::Email)
    .auto_capitalize(AutoCapitalize::None)
    .auto_correct(false)
    .auto_fill(AutoFill::Email)
    .placeholder("E-mail")
input().masked(true).auto_fill(AutoFill::NewPassword).placeholder("Password")
input()
    .keyboard_type(KeyboardType::Number)
    .auto_fill(AutoFill::OneTimeCode)
    .max_length(6)
    .placeholder("Code")

#The return key and moving between fields

The return key type (.return_key_type(ReturnKeyType::Next), TSX returnKeyType) labels the return key: default, done, go, next, search or send. The submit behavior (.submit_behavior(..), TSX submitBehavior) says what pressing it does:

RustTSXReturnDefault for
SubmitBehavior::BlurAndSubmit"blurAndSubmit"fires the submit event, then the input loses focussingle-line inputs
SubmitBehavior::Submit"submit"fires the submit event; the input keeps focus
SubmitBehavior::Newline"newline"inserts a line break (multiline inputs only)multiline inputs

A multiline input with "submit" or "blurAndSubmit" sends on return, as chat composers do, and still wraps its lines; on a hardware keyboard (desktops, a Mac, a tablet’s keyboard) Shift+Return or Option / Alt+Return inserts a line break. A return that commits an input method’s composition (Chinese or Japanese input, say) only commits it and never submits.

To move to the next field, keep refs to the inputs (element_ref() and .element_ref(&r) in Rust, ref in TSX) and call focus():

use nsh_core::prelude::*;

pub fn sign_in() -> impl IntoElement {
    let email = signal(String::new());
    let password = element_ref();
    let submit = move || log::info!("sign in {}", email.get());
    view()
        .flex_1()
        .p(px(16.0))
        .pt(px(60.0))
        .gap(px(12.0))
        .child(
            input()
                .value(move || email.get())
                .on_change(move |t: &str| email.set(t.to_owned()))
                .keyboard_type(KeyboardType::Email)
                .auto_capitalize(AutoCapitalize::None)
                .return_key_type(ReturnKeyType::Next)
                .submit_behavior(SubmitBehavior::Submit)
                .on_submit(move |_: &str| password.focus())
                .placeholder("E-mail"),
        )
        .child(
            input()
                .element_ref(&password)
                .masked(true)
                .return_key_type(ReturnKeyType::Go)
                .on_submit(move |_: &str| submit())
                .placeholder("Password"),
        )
}

Submitting without blurring (SubmitBehavior::Submit, submitBehavior="submit") on the first field keeps the keyboard up while focus moves, so it does not drop and rise again. A chat input that sends on return and stays focused submits the same way (see the composer below).

Both the maximum length and the submit behavior are enforced natively: the platform asks “may this character be added?” and “should return end editing?” as the user types, and NSH answers from the props without waiting for JS.

#Focus from code

An input’s ref has:

RustTSXDescription
focus()focus()Focuses the input and shows the keyboard.
blur()blur()Unfocuses it.
set_selection(start, end)setSelection(start, end?)Selects start..end (UTF-16 units); a caret when they are equal (TSX: without end).

dismiss_keyboard() in Rust and Keyboard.dismiss() from nsh in TSX unfocus whichever input has focus:

view().on_press(|| dismiss_keyboard())

#Selection

The selection event (.on_selection_change(..), TSX onSelectionChange) reports the caret and selection; the ref’s set_selection or the selected range (.selected_range(..), TSX selectedRange) set them. Positions are UTF-16 code units, as JavaScript string indices are, so in TSX text.slice(start, end) is the selected text; in Rust, slice the text’s UTF-16 units.

/// `start..end` of `text` in UTF-16 units, as inputs count.
fn utf16_slice(text: &str, start: u32, end: u32) -> String {
    let units: Vec<u16> = text.encode_utf16().collect();
    let end = (end as usize).min(units.len());
    String::from_utf16_lossy(&units[(start as usize).min(end)..end])
}

let content = signal("Select part of this text".to_owned());
let range = signal(Selection::default());
let field = element_ref();

view()
    .child(
        input()
            .element_ref(&field)
            .value(move || content.get())
            .on_change(move |t: &str| content.set(t.to_owned()))
            .on_selection_change(move |r: &Selection| range.set(*r)),
    )
    .child(text(move || {
        let r = range.get();
        format!("Selected: \"{}\"", content.with(|t| utf16_slice(t, r.start, r.end)))
    }))
    .child(
        view()
            .on_press(move || {
                let len = content.with(|t| t.encode_utf16().count()) as u32;
                field.set_selection(0, len);
            })
            .child(text("Select all")),
    )

#The caret

The caret event (.on_caret_move(..), TSX onCaretMove) says where the caret is, so that what belongs at the caret can open there: suggestions for an @ mention, a slash command’s menu, an emoji picker. bounds is a Bounds in the input (origin and size, the input’s padding and scrolling applied), as wide as the platform draws the caret and as tall as its line; pageBounds is the same box in the window (or the dialog the input is in), which an overlay takes as its anchor. The event comes while the input has the focus, whenever the caret moves: with the selection, and when the input’s text scrolls or wraps onto other lines. In Rust an overlay is placed against a box with .anchor_bounds(..).

let draft = signal(String::new());
let end = signal(0u32);
let caret = signal(None::<Bounds<Points>>);

view()
    .child(
        input()
            .multiline(true)
            .value(move || draft.get())
            .on_change(move |t: &str| draft.set(t.to_owned()))
            .on_selection_change(move |s: &Selection| end.set(s.end))
            .on_caret_move(move |e: &CaretEvent| {
                // Suggestions while the word before the caret starts with "@".
                let typed = draft.with(|t| utf16_slice(t, 0, end.get()));
                let word = typed.rsplit(char::is_whitespace).next().unwrap_or("");
                caret.set(word.starts_with('@').then_some(e.page_bounds));
            })
            .p_2(),
    )
    .child(when(
        move || caret.get().is_some(),
        move || {
            overlay()
                .anchor_bounds(move || caret.get().unwrap_or_default())
                .placement(Placement::Bottom)
                .align(Align::Start)
                .offset(px(4.0))
                .child(text("@ada"))
                .child(text("@grace"))
        },
    ))

pageBounds is where the caret was when the event came: a page that scrolls under the input moves the input but sends no event, so close the suggestions when it scrolls, or anchor them to the input itself.

#Pasting images and files

The paste event (.on_paste(..), TSX onPaste) tells what the user pasted, from the keyboard’s shortcut, a menu’s Paste or a keyboard’s image: text, files and uris. files are what the clipboard held as data, such as a screenshot or an image copied from a page or another app: Files whose bytes the app can upload or show, named image.png (or the type it is). uris are the file: URLs of files copied in a file manager, as a file drop’s. The platform reads the clipboard as the user pastes, and only then.

The input inserts the pasted text by itself, as it always does: the event comes before the onChange of that text. Images and files are never inserted, since an input holds text. With pasteBehavior "report" the input inserts nothing, and the app decides what a paste does: send a long text as an attachment, or insert a cleaned-up version. The input decides at once, from the prop, because the system asks it on the spot.

let attachments = signal(Vec::<PastedFile>::new());

input()
    .multiline(true)
    .placeholder("Message")
    .on_paste(move |e: &PasteEvent| {
        // A screenshot pasted into the message goes along as an image.
        attachments.update(|a| a.extend(e.files.iter().cloned()));
    })
    .p_2()

Upload a pasted file as any File, with fetch and FormData (form.append("image", file)); its bytes stay native until they are sent. On Android, keyboards that insert images (GIFs, stickers) report them the same way. On Linux the clipboard is read asynchronously, so the event may come after the onChange of the text it inserts. Masked inputs on macOS keep AppKit’s own paste and report nothing.

#Multiline inputs that grow

A multiline input (.multiline(true), TSX multiline) scrolls its text inside its own height. To grow it with its content, feed the content size event’s height (.on_content_size_change(..), TSX onContentSizeChange) back into its style, with a limit:

let height = signal(px(0.0));

input()
    .multiline(true)
    .placeholder("Write a comment")
    .on_content_size_change(move |e: &Size<Points>| height.set(e.height.min(px(120.0))))
    .text_size(px(16.0))
    .p(px(10.0))
    .border_1()
    .border_color(rgb(0xd0d7de))
    .rounded(px(10.0))
    .h(move || height.get().max(px(20.0)) + px(20.0))

The reported height is the text’s (at the input’s width), so add the vertical padding yourself, as above.

#Keeping inputs above the keyboard

#Inside scroll views: automatic

When the keyboard appears over a focused input that is inside a scroll view or a list, NSH gives the scroll view a bottom inset as tall as the keyboard and scrolls the input into view. This is native and needs no code. A long form is simply a scroll view of inputs:

scroll()
    .flex_1()
    .keyboard_dismiss_mode(KeyboardDismissMode::OnDrag)
    .keyboard_taps(KeyboardTaps::Handled)
    .child(view().p(px(16.0)).gap(px(12.0)) /* inputs */)

The dismiss mode (.keyboard_dismiss_mode(..), TSX keyboardDismissMode: none, on drag, interactive) lets dragging the form hide the keyboard; handled taps (.keyboard_taps(KeyboardTaps::Handled), TSX keyboardShouldPersistTaps="handled") let a tap on a button go through while the keyboard is up instead of only dismissing it. See Scrolling.

#Content outside scroll views

A message bar pinned to the bottom of a screen is not in a scroll view, so nothing moves it. Pad the screen’s bottom by CSS’s env(keyboard-inset-height) (paddingBottom: "env(keyboard-inset-height)", Tailwind pb-[env(keyboard-inset-height)], Rust .pb_keyboard()): it makes room at the bottom as tall as the keyboard, animated natively with the keyboard.

use nsh_core::prelude::*;

pub fn chat_screen() -> impl IntoElement {
    let draft = signal(String::new());
    let send = move || {
        let text = draft.get();
        if !text.trim().is_empty() {
            log::info!("send {text}");
        }
        draft.set(String::new());
    };
    view()
        .flex_1()
        .pb_keyboard()
        .child(scroll().flex_1().keyboard_dismiss_mode(KeyboardDismissMode::Interactive) /* messages */)
        .child(
            view()
                .flex_row()
                .p(px(8.0))
                // Above the home indicator, unless the keyboard covers it.
                .pb(move || {
                    px(8.0) + if keyboard_height() > px(0.0) { px(0.0) } else { safe_area().bottom }
                })
                .child(
                    input()
                        .value(move || draft.get())
                        .on_change(move |t: &str| draft.set(t.to_owned()))
                        .multiline(true)
                        .submit_behavior(SubmitBehavior::Submit)
                        .return_key_type(ReturnKeyType::Send)
                        .on_submit(move |_: &str| send())
                        .placeholder("Message")
                        .flex_1()
                        .max_h(px(120.0)),
                ),
        )
}

Padding (.pb_keyboard()) shrinks the content above while the background reaches the bottom of the screen; a bottom margin (marginBottom: "env(keyboard-inset-height)", .mb_keyboard()) ends the whole view at the top of the keyboard. calc(env(keyboard-inset-height) + <length>) (Rust .pb_keyboard_plus(..), .mb_keyboard_plus(..)) adds a length, such as minus the height of a tab bar below the view.

The full height suits a view that reaches the bottom of the surface, as a screen’s content does. On an Android host whose window resizes for the keyboard, the window itself shrinks and the variable is 0. See Keyboard.

#The keyboard accessor

keyboard_height() and keyboard_duration() in Rust, and keyboardFrame() from nsh in TSX (a { height, duration }), are reactive: how far the keyboard reaches into the surface (0 when hidden; the bottom safe area under it included) and its animation’s duration in seconds. Read them for anything custom: hide a floating button while typing, or size a panel. A layout that changes with them moves with the keyboard when it animates on the keyboard’s curve: LayoutAnimation.configureNext({ duration: keyboardFrame().duration * 1000, update: { type: "keyboard" } }) (Rust: LayoutCurve::Keyboard), as env(keyboard-inset-height) does.

view().child(when(
    || keyboard_height() == px(0.0),
    || view().absolute().right(px(16.0)).bottom(px(16.0)), /* … */
))

#A bar over the keyboard (iOS): InputAccessoryView

input_accessory_view(id) in Rust and InputAccessoryView from nsh/mobile in TSX show a bar attached to the top of the keyboard while an input that names it has focus: iOS’s inputAccessoryView. It moves with the keyboard natively, including during interactive dismissal. It takes no room where it is placed in the tree; inputs refer to it by its id (.input_accessory(id), TSX ios={{ inputAccessoryViewID }} and nativeID):

use nsh_core::prelude::*;

pub fn note() -> impl IntoElement {
    let content = signal(String::new());
    let field = element_ref();
    view()
        .p(px(16.0))
        .child(
            input()
                .element_ref(&field)
                .value(move || content.get())
                .on_change(move |t: &str| content.set(t.to_owned()))
                .input_accessory("note-bar")
                .placeholder("A note"),
        )
        .child(
            input_accessory_view("note-bar").bg(rgb(0xf6f8fa)).child(
                view()
                    .flex_row()
                    .items_center()
                    .p(px(8.0))
                    .child(
                        text(move || format!("{} characters", content.with(|t| t.chars().count())))
                            .flex_1()
                            .text_color(rgb(0x57606a)),
                    )
                    .child(
                        text("Done")
                            .on_press(move || field.blur())
                            .text_color(rgb(0x0969da))
                            .font_weight(FontWeight::SEMIBOLD),
                    ),
            ),
        )
}

The bar is as wide as the window and as tall as its content. Input accessories are iOS’s: on Android the bar is an empty hidden view, so place those controls elsewhere there, for example above the input (os() == Os::Android in Rust, platform.os === "android" in TSX).