iris/src/android/view.rs

use crate::prelude::*;
use crate::task::RequestRedraw;
use accesskit_android::Adapter as AccessAdapter;
use android_view::{
    AccessibilityNodeInfo, AccessibilityNodeProvider, Bundle, CallbackCtx, Context,
    InputConnection, KeyEvent, MotionEvent, Rect, View, ViewPeer,
    jni::{
        JNIEnv, JavaVM,
        objects::{GlobalRef, JValue},
        sys::jint,
    },
    ndk::event::{Axis, Keycode, MotionAction},
};
use std::{cell::RefCell, marker::Sized, rc::Rc, sync::Arc, time::Instant};

use super::{
    access::{AndroidAccessSource, NullActionHandler, raise_if_enabled},
    insets::{Insets, Shared},
    render::{AndroidRedrawHandle, AndroidRenderer},
};

/// Android host state. The renderer follows the `SurfaceView` lifecycle.
/// How many frames after each `surface_changed` `render()` logs a full
/// diagnostic line for -- see the log site's own comment.
const DIAGNOSTIC_FRAMES: u64 = 10;

pub struct AndroidUiState {
    pub root: Option<StrongWidget>,
    pub renderer: Option<AndroidRenderer>,
    pub focus: Option<WeakWidget<TextEdit>>,
    pub cursor: CursorState,
    pub last_click: Instant,
    /// Previous IME preedit length, in characters.
    pub compose_len: usize,
    /// Deferred until the input callback regains access to JNI.
    pub pending_show_keyboard: bool,
    /// Also deferred until a JNI callback is available.
    pub pending_open_url: Option<String>,
    /// Filled by the native insets callback registered in `android/insets.rs`.
    shared: Rc<RefCell<Shared>>,
    pub access_adapter: AccessAdapter,
    pub access: AccessTree,
    pub frame_report: FrameReport,
    pub content_scale: f32,
    /// The last insets `render()` saw -- compared each frame so
    /// `AndroidAppState::on_insets_changed` fires only when they actually
    /// change (once at startup for the status bar, again if the device
    /// rotates), not every frame.
    last_insets: Insets,
}

impl AndroidUiState {
    fn new(shared: Rc<RefCell<Shared>>, content_scale: f32) -> Self {
        Self {
            root: None,
            renderer: None,
            focus: None,
            cursor: Default::default(),
            last_click: Instant::now(),
            compose_len: 0,
            pending_show_keyboard: false,
            pending_open_url: None,
            shared,
            access_adapter: Default::default(),
            access: AccessTree::new(),
            frame_report: FrameReport::new(),
            content_scale,
            last_insets: Insets::default(),
        }
    }

    pub fn insets(&self) -> Insets {
        self.shared.borrow().insets
    }

    pub fn insets_report(&self) -> String {
        let shared = self.shared.borrow();
        let i = shared.insets;
        if shared.updates == 0 {
            return "insets: dispatches=0 -- the platform has never called \
                    onApplyWindowInsets, so nothing below was measured"
                .to_string();
        }
        format!(
            "insets: dispatches={} left={} top={} right={} bottom={} ime_bottom={} \
             ime_visible={}",
            shared.updates, i.left, i.top, i.right, i.bottom, i.ime_bottom, i.ime_visible,
        )
    }
}

impl<Rsc: HasEvents> HasRoot<Rsc> for AndroidUiState {
    fn set_root(&mut self, rsc: &mut Rsc, root: StrongWidget) {
        self.root = Some(crate::overlay::default_overlay_root(rsc, root));
    }
}

pub trait HasAndroidUiState: Sized + 'static {
    fn android_state(&self) -> &AndroidUiState;
    fn android_state_mut(&mut self) -> &mut AndroidUiState;
}

/// Application state retained for the lifetime of one Android `View`.
///
/// [`StdRsc`] is the usual [`AndroidResources`] implementation, but the host only
/// requires the capabilities in [`AndroidResources`]. An application may add
/// its own resources by supplying another implementation.
pub trait AndroidAppState: HasAndroidUiState {
    type Resources: AndroidResources<Self>;

    #[allow(unused_variables)]
    fn back_pressed(&mut self, rsc: &mut Self::Resources) -> bool {
        false
    }
    #[allow(unused_variables)]
    fn platform_ready(&mut self, rsc: &mut Self::Resources, vm: JavaVM, view: GlobalRef) {}
    #[allow(unused_variables)]
    fn on_insets_changed(&mut self, rsc: &mut Self::Resources, insets: WindowInsets) {}
}

/// Resources the Android host needs to draw and dispatch application events.
///
/// This deliberately names capabilities rather than storage. Custom bundles
/// can embed or replace [`StdRsc`] as long as they implement these traits and
/// create the task receiver paired with their [`Tasks`] value.
pub trait AndroidResources<State>:
    HasTasks<State = State> + HasWidgetState + Sized + 'static
where
    State: 'static,
{
    fn new(redraw: Arc<dyn RequestRedraw>) -> (Self, TaskMsgReceiver<Self>);
}

impl<State: 'static> AndroidResources<State> for StdRsc<State> {
    fn new(redraw: Arc<dyn RequestRedraw>) -> (Self, TaskMsgReceiver<Self>) {
        StdRsc::new(redraw)
    }
}

/// Widget-facing insets in physical pixels, decoupled from JNI's integer shape.
#[derive(Clone, Copy, Default, Debug, PartialEq)]
pub struct WindowInsets {
    pub left: f32,
    pub top: f32,
    pub right: f32,
    pub bottom: f32,
    /// How much of the window the keyboard covers, in physical pixels --
    /// what a layout pads by. See `insets::Insets::ime_visible` for why
    /// "is the keyboard up" is a separate field rather than this one
    /// compared against zero.
    pub ime_bottom: f32,
    pub ime_visible: bool,
}

impl WindowInsets {
    fn from_physical(insets: Insets) -> Self {
        Self {
            left: insets.left as f32,
            top: insets.top as f32,
            right: insets.right as f32,
            bottom: insets.bottom as f32,
            ime_bottom: insets.ime_bottom as f32,
            ime_visible: insets.ime_visible,
        }
    }
}

/// The `ViewPeer` android-view dispatches every callback to. One per
/// `RustView` instance; `new_peer` (below) builds it and hands the id to
/// Java the same way android-view's own demo does.
pub struct IrisViewPeer<State: AndroidAppState> {
    pub(super) rsc: State::Resources,
    pub(super) state: State,
    task_recv: TaskMsgReceiver<State::Resources>,
    /// Converts input and Choreographer timestamps onto one monotonic clock.
    device_clock: Option<DeviceClock>,
}

impl<State: AndroidAppState> IrisViewPeer<State> {
    fn drain_tasks(&mut self) {
        while let Ok(update) = self.task_recv.try_recv() {
            update(&mut self.state, &mut self.rsc);
        }
    }

    /// One pointer sample through the sensors, plus the platform calls a
    /// handler can only ask for by raising a flag. Split out of
    /// [`Self::after_input`] because a batched `MotionEvent` carries
    /// several samples that all belong to the same *frame*
    /// (`on_touch_event`): each one is a real input frame the widgets must
    /// see, but only the last one ends the frame and asks for a redraw.
    fn run_input_frame(&mut self, ctx: &mut CallbackCtx) {
        let window_size = self.window_size();
        let ui_state = self.state.android_state_mut();
        let cursor = ui_state.cursor.clone();
        let old_focus = ui_state.focus;
        let render_state = self.rsc.ui().render_state();
        render_state
            .get()
            .run_sensors(&mut self.rsc, &mut self.state, cursor, window_size);

        let ui_state = self.state.android_state_mut();
        if old_focus != ui_state.focus
            && let Some(old) = old_focus
        {
            old.edit(&mut self.rsc).deselect();
        }
        if std::mem::take(&mut ui_state.pending_show_keyboard) {
            show_soft_input(&mut ctx.env, &ctx.view);
        }
        if let Some(url) = ui_state.pending_open_url.take() {
            super::platform::open_url(&mut ctx.env, &ctx.view, &url);
        }
    }

    /// Common tail for every callback that might have changed the cursor,
    /// the text focus, or the widget tree: run the sensors that touch
    /// input feeds, then ask for a frame if the result needs drawing.
    /// Mirrors `desktop::DesktopApp::window_event`'s tail, split across
    /// android-view's several entry points instead of winit's one.
    pub(super) fn after_input(&mut self, ctx: &mut CallbackCtx) {
        self.run_input_frame(ctx);

        self.update_ime_selection(ctx);

        let ui_state = self.state.android_state_mut();
        ui_state.cursor.end_frame();
        let render_state = self.rsc.ui().render_state();
        if render_state
            .get()
            .needs_redraw(&ui_state.root, self.rsc.widgets())
        {
            ctx.view.post_frame_callback(&mut ctx.env);
        }
    }

    fn device_clock(&mut self, event_time: i64, oldest: i64) -> DeviceClock {
        *self
            .device_clock
            .get_or_insert_with(|| DeviceClock::anchored(Instant::now(), event_time, oldest))
    }

    fn generic_motion<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        event: &MotionEvent<'local>,
    ) -> bool {
        let action = event.action_masked(&mut ctx.env);
        let event_time = event.event_time_nanos(&mut ctx.env);
        let mut clock = self.device_clock(event_time, event_time);
        let at = clock.sample(event_time);
        self.device_clock = Some(clock);

        let ui = self.state.android_state_mut();
        ui.cursor.time = at;
        ui.cursor.pos = vec2(event.x(&mut ctx.env), event.y(&mut ctx.env));
        ui.cursor.exists = !matches!(action, MotionAction::HoverExit);

        let buttons = event.button_state(&mut ctx.env);
        ui.cursor.buttons.left.update(buttons.primary());
        ui.cursor.buttons.right.update(buttons.secondary());
        ui.cursor.buttons.middle.update(buttons.teriary());

        match action {
            MotionAction::HoverEnter
            | MotionAction::HoverMove
            | MotionAction::HoverExit
            | MotionAction::ButtonPress
            | MotionAction::ButtonRelease => {}
            MotionAction::Scroll => {
                ui.cursor.scroll_delta = vec2(
                    event.axis(&mut ctx.env, Axis::Hscroll, 0),
                    event.axis(&mut ctx.env, Axis::Vscroll, 0),
                );
            }
            _ => return false,
        }

        self.after_input(ctx);
        true
    }

    fn window_size(&self) -> Vec2 {
        let ui_state = self.state.android_state();
        match &ui_state.renderer {
            Some(r) => r.size(),
            None => Vec2::ZERO,
        }
    }

    fn render(&mut self, ctx: &mut CallbackCtx, now: Instant) {
        if self.state.android_state().renderer.is_none() {
            return;
        }
        // See `AndroidAppState::on_insets_changed`'s doc comment: fires
        // exactly when insets actually differ from last frame, not every
        // frame -- most frames this is one `Insets` equality check against
        // a `Copy` struct. Done before `ui_state` is bound below, since
        // `on_insets_changed` needs `&mut self.state`/`&mut self.rsc` both.
        let ui_state = self.state.android_state();
        let current_insets = ui_state.insets();
        if current_insets != ui_state.last_insets {
            let physical = WindowInsets::from_physical(current_insets);
            log::info!(
                "iris insets: left={} top={} right={} bottom={} ime_bottom={} \
                 ime_visible={} window={:?}",
                physical.left,
                physical.top,
                physical.right,
                physical.bottom,
                physical.ime_bottom,
                physical.ime_visible,
                self.window_size(),
            );
            self.state.android_state_mut().last_insets = current_insets;
            self.state.on_insets_changed(&mut self.rsc, physical);
        }

        if crate::diagnostics::trace_enabled() {
            let ui_state = self.state.android_state();
            log::debug!(
                target: "iris::frame",
                "render(): root={:?} widgets={} active={} root_px={:?} out_size={:?}",
                ui_state.root.is_some(),
                self.rsc.widgets().len(),
                self.rsc.ui().render_state().get().active_widgets(),
                ui_state
                    .root
                    .as_ref()
                    .and_then(|r| {
                        self.rsc
                            .ui()
                            .render_state()
                            .get()
                            .window_region(r, &self.rsc)
                    }),
                self.window_size(),
            );
        }
        let frame_start = Instant::now();
        let animating = self.rsc.ui_mut().tick_animations(now);
        if animating {
            ctx.view.post_frame_callback(&mut ctx.env);
        }
        let ui_state = self.state.android_state_mut();
        self.rsc.draw(&ui_state.root);
        let ui_state = self.state.android_state_mut();
        let Some(renderer) = &mut ui_state.renderer else {
            return;
        };
        let frame_diagnostics = renderer.update(self.rsc.ui_mut());
        if renderer.frame_count() <= DIAGNOSTIC_FRAMES {
            log::info!(
                "iris frame diagnostics: frame={} masks_resized={} moves_resized={} \
                 paints_resized={} \
                 atlas_pages_grown_prev={} image_bind_group_creates_prev={} wgpu_errors={}",
                renderer.frame_count(),
                frame_diagnostics.masks_resized,
                frame_diagnostics.moves_resized,
                frame_diagnostics.paints_resized,
                frame_diagnostics.atlas_pages_grown_prev,
                frame_diagnostics.image_bind_group_creates_prev,
                renderer.wgpu_errors.snapshot().len(),
            );
        }
        let mut parts = renderer.draw();
        parts.total = frame_start.elapsed();
        self.state
            .android_state_mut()
            .frame_report
            .record(now, parts, animating);
        let render_state = self.rsc.ui().render_state();
        crate::diagnostics::log_frame(&render_state.get(), now, parts, animating);
        if crate::diagnostics::trace_enabled() {
            let ui_state = self.state.android_state();
            log::debug!(
                target: "iris::frame",
                "render(): after update active={} root_px={:?}",
                self.rsc.ui().render_state().get().active_widgets(),
                ui_state
                    .root
                    .as_ref()
                    .and_then(|r| {
                        self.rsc
                            .ui()
                            .render_state()
                            .get()
                            .window_region(r, &self.rsc)
                    }),
            );
        }

        let ui_state = self.state.android_state_mut();
        if let Some(tree_update) = ui_state.access.update(
            self.rsc.widgets(),
            &self.rsc.ui().render_state().get(),
            &self.rsc,
        ) {
            let ui_state = self.state.android_state_mut();
            if let Some(events) = ui_state.access_adapter.update_if_active(|| tree_update) {
                ctx.push_dynamic_deferred_callback(move |env, view| {
                    raise_if_enabled(env, view, events);
                });
            }
        }
    }
}

fn show_soft_input<'local>(env: &mut JNIEnv<'local>, view: &View<'local>) {
    let imm = view.input_method_manager(env);
    imm.show_soft_input(env, view, 0);
}

fn show_renderer_error<'local>(env: &mut JNIEnv<'local>, view: &View<'local>, report: &str) {
    let Ok(message) = env.new_string(report) else {
        return;
    };
    let _ = env.call_method(
        &view.0,
        "showRendererError",
        "(Ljava/lang/String;)V",
        &[JValue::Object(message.as_ref())],
    );
}

impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
    fn on_key_down<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        key_code: Keycode,
        event: &KeyEvent<'local>,
    ) -> bool {
        self.drain_tasks();
        // With no `OnBackPressedCallback` registered on the Java side, the
        // system still delivers the back gesture as a synthetic
        // `KEYCODE_BACK` through this same path -- the legacy behaviour
        // every view-based app gets by default, and enough for "the back
        // gesture as an event" without a second JNI registry. See
        // `android/insets.rs`'s doc comment for why insets could not take
        // the same shortcut.
        if key_code == Keycode::Back {
            if self.rsc.run_command(Command::Escape) != CommandResult::Unused {
                self.after_input(ctx);
                return true;
            }
            let handled = self.state.back_pressed(&mut self.rsc);
            if handled {
                self.after_input(ctx);
            }
            return handled;
        }
        if self.rsc.events().controllers.command_target_blocks_input() {
            return true;
        }
        let handled = super::input::on_key(
            &mut self.rsc,
            &mut self.state,
            &mut ctx.env,
            key_code,
            event,
        );
        if handled {
            self.after_input(ctx);
        }
        handled
    }

    fn on_touch_event<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        event: &MotionEvent<'local>,
    ) -> bool {
        self.drain_tasks();
        let action = event.action_masked(&mut ctx.env);
        // MotionEvent and layout both use physical pixels.
        let x = event.x(&mut ctx.env);
        let y = event.y(&mut ctx.env);
        // Use the event clock so batched movement keeps its real timing.
        let event_time = event.event_time_nanos(&mut ctx.env);
        let history = event.history_size(&mut ctx.env);
        let mut clock = match self.device_clock {
            Some(clock) => clock,
            None => {
                let oldest = if history > 0 {
                    event.historical_event_time_nanos(&mut ctx.env, 0)
                } else {
                    event_time
                };
                self.device_clock(event_time, oldest)
            }
        };
        // Avoid allocating trace history when input tracing is disabled.
        let trace_input = crate::diagnostics::trace_enabled();
        let mut historical_ms: Vec<(u64, f32, f32)> = Vec::new();

        if matches!(action, MotionAction::Move) {
            // Android orders history oldest-first; `sample` checks monotonicity.
            for pos in 0..history {
                let hx = event.historical_axis(&mut ctx.env, Axis::X, 0, pos);
                let hy = event.historical_axis(&mut ctx.env, Axis::Y, 0, pos);
                let ht = event.historical_event_time_nanos(&mut ctx.env, pos);
                let sample_at = clock.sample(ht);
                if trace_input {
                    historical_ms.push((clock.ms_since_anchor(ht), hx, hy));
                }
                let ui_state = self.state.android_state_mut();
                ui_state.cursor.pos = vec2(hx, hy);
                ui_state.cursor.time = sample_at;
                self.run_input_frame(ctx);
            }
        }

        let event_at = clock.sample(event_time);
        let event_ms = clock.ms_since_anchor(event_time);
        self.device_clock = Some(clock);
        let ui_state = self.state.android_state_mut();
        ui_state.cursor.time = event_at;
        match action {
            MotionAction::Down => {
                ui_state.cursor.pos = vec2(x, y);
                ui_state.cursor.exists = true;
                ui_state.cursor.buttons.left.update(true);
            }
            MotionAction::Move => {
                ui_state.cursor.pos = vec2(x, y);
            }
            MotionAction::Up => {
                ui_state.cursor.pos = vec2(x, y);
                ui_state.cursor.buttons.left.update(false);
            }
            MotionAction::Cancel => {
                ui_state.cursor.pos = vec2(x, y);
                ui_state.cursor.buttons.left.update(false);
                ui_state.cursor.cancelled = true;
            }
            _ => return false,
        }
        if trace_input {
            let action_word = match action {
                MotionAction::Down => "down",
                MotionAction::Move => "move",
                MotionAction::Up => "up",
                MotionAction::Cancel => "cancel",
                _ => "other",
            };
            crate::sense::log_input_event(action_word, x, y, event_ms, &historical_ms);
        }
        self.after_input(ctx);
        true
    }

    fn on_generic_motion_event<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        event: &MotionEvent<'local>,
    ) -> bool {
        self.drain_tasks();
        self.generic_motion(ctx, event)
    }

    fn on_hover_event<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        event: &MotionEvent<'local>,
    ) -> bool {
        let action = event.action(&mut ctx.env);
        let x = event.x(&mut ctx.env);
        let y = event.y(&mut ctx.env);
        let access_events = {
            let render_handle = self.rsc.ui().render_state();
            let render_state = render_handle.get();
            let mut source = AndroidAccessSource {
                widgets: self.rsc.widgets(),
                render: &render_state,
                rsc: &self.rsc,
            };
            self.state
                .android_state_mut()
                .access_adapter
                .on_hover_event(&mut source, action, x, y)
        };
        if let Some(events) = access_events {
            ctx.push_dynamic_deferred_callback(move |env, view| {
                raise_if_enabled(env, view, events);
            });
            true
        } else {
            self.drain_tasks();
            self.generic_motion(ctx, event)
        }
    }

    fn on_focus_changed<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        gain_focus: bool,
        _direction: i32,
        _previously_focused_rect: Option<&Rect<'local>>,
    ) {
        self.drain_tasks();
        if !gain_focus {
            let ui_state = self.state.android_state_mut();
            if let Some(focus) = ui_state.focus.take() {
                focus.edit(&mut self.rsc).deselect();
            }
        }
        self.after_input(ctx);
    }

    fn on_attached_to_window(&mut self, _ctx: &mut CallbackCtx) {
        self.drain_tasks();
    }

    fn surface_changed<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        holder: &android_view::SurfaceHolder<'local>,
        _format: i32,
        width: i32,
        height: i32,
    ) {
        self.drain_tasks();
        // The layout canvas and wgpu surface are separate and both use physical pixels.
        self.rsc.ui_mut().resize((width as f32, height as f32));

        // Resizing preserves GPU resources; recreating a destroyed surface does not.
        let already_live = self.state.android_state().renderer.is_some();
        log::info!(
            "iris surface: surface_changed {width}x{height} already_live={already_live} \
             glyphs_cached={} atlas_pages={}",
            self.rsc.ui().text.atlas.glyph_count(),
            self.rsc.ui().text.atlas.page_count(),
        );
        if already_live {
            let ui_state = self.state.android_state_mut();
            ui_state
                .renderer
                .as_mut()
                .expect("checked Some above")
                .resize(width as u32, height as u32);
            self.render(ctx, Instant::now());
            return;
        }

        let window = holder.surface(&mut ctx.env).to_native_window(&mut ctx.env);
        // `content_scale` reaches `AndroidRenderer` only for the
        // Diagnostics page's report text now -- window size and the
        // shader's window uniform are physical pixels throughout (see the
        // `resize` call above), not divided by it.
        let content_scale = self.state.android_state().content_scale;
        match AndroidRenderer::new(window, width as u32, height as u32, content_scale) {
            Ok(renderer) => {
                // A genuinely new renderer means a genuinely new GPU
                // device, holding none of the textures the old one did --
                // while the CPU side of them (`UiData::textures`, and the
                // glyph atlas built on it) lives on `self.rsc` and
                // survives. So every slot has to be uploaded again, and
                // `Textures::reupload` queues exactly that, in slot order.
                //
                // It replaces clearing them, which threw away the *slot
                // numbering* as well as the pixels: every `TextureHandle`
                // a live widget still held -- one per icon or image on
                // screen, and one per folded card at the time -- then
                // named a slot nothing recognised, and the next frame
                // panicked in `image_bind_group` ("texture slot 89 is not
                // a live standalone image: None"). Re-uploading also keeps
                // the glyph atlas, so an app switch no longer re-rasterises
                // every glyph on screen. This only runs on the branch that
                // actually builds a new renderer, never on the reuse
                // branch above, where the textures are still on the device
                // that holds them.
                log::info!(
                    "iris surface: new renderer built ({:?}), re-uploading textures: \
                     glyphs={} pages={}",
                    renderer.adapter_backend,
                    self.rsc.ui().text.atlas.glyph_count(),
                    self.rsc.ui().text.atlas.page_count(),
                );
                self.rsc.ui_mut().textures.reupload();
                self.rsc.ui_mut().paints.reupload();
                self.state.android_state_mut().renderer = Some(renderer);
                self.render(ctx, Instant::now());
            }
            Err(report) => {
                log::error!("iris renderer init failed: {}", report.replace('\n', " | "));
                ctx.push_dynamic_deferred_callback(move |env, view| {
                    show_renderer_error(env, view, &report);
                });
            }
        }
    }

    fn surface_destroyed<'local>(
        &mut self,
        _ctx: &mut CallbackCtx<'local>,
        _holder: &android_view::SurfaceHolder<'local>,
    ) {
        log::info!(
            "iris surface: surface_destroyed, tearing the renderer down \
             (glyphs_cached={} atlas_pages={})",
            self.rsc.ui().text.atlas.glyph_count(),
            self.rsc.ui().text.atlas.page_count(),
        );
        self.state.android_state_mut().renderer = None;
    }

    fn do_frame(&mut self, ctx: &mut CallbackCtx, frame_time_nanos: i64) {
        self.drain_tasks();
        // The vsync this frame is for, dated on the same ruler touch
        // samples are (`DeviceClock`), rather than `Instant::now()` here:
        // this callback runs some variable distance after that vsync --
        // behind `drain_tasks`, behind whatever else the UI thread was
        // doing -- and anything advanced by that variable amount moves
        // unevenly between frames the display shows evenly. `at` rather
        // than `sample`, since a frame time is not part of the touch
        // samples' own ordering.
        let now = self
            .device_clock(frame_time_nanos, frame_time_nanos)
            .at(frame_time_nanos);
        self.render(ctx, now);
    }

    /// Where `AndroidRedrawHandle::request_redraw` (`android/render.rs`)
    /// actually lands: `View.postDelayed`'s Runnable resolves to this, on
    /// the UI thread, which is what makes it safe to call from a background
    /// task's own thread when `post_frame_callback`'s `Choreographer`
    /// requirement (a `Looper` on the *calling* thread) is not. Same body
    /// as `do_frame` -- draining tasks and rendering immediately is a
    /// perfectly good answer to "a background fetch has new state," and
    /// avoids a second frame-scheduling path to keep in sync with the real
    /// one.
    fn delayed_callback(&mut self, ctx: &mut CallbackCtx) {
        self.drain_tasks();
        self.render(ctx, Instant::now());
    }

    fn as_input_connection(&mut self) -> Option<&mut dyn InputConnection> {
        Some(self)
    }

    fn as_accessibility_node_provider(&mut self) -> Option<&mut dyn AccessibilityNodeProvider> {
        Some(self)
    }
}

impl<State: AndroidAppState> AccessibilityNodeProvider for IrisViewPeer<State> {
    fn create_accessibility_node_info<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        virtual_view_id: jint,
    ) -> AccessibilityNodeInfo<'local> {
        let render_handle = self.rsc.ui().render_state();
        let render_state = render_handle.get();
        let mut source = AndroidAccessSource {
            widgets: self.rsc.widgets(),
            render: &render_state,
            rsc: &self.rsc,
        };
        let ui_state = self.state.android_state_mut();
        AccessibilityNodeInfo(ui_state.access_adapter.create_accessibility_node_info(
            &mut source,
            &mut ctx.env,
            &ctx.view.0,
            virtual_view_id,
        ))
    }

    fn find_focus<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        focus_type: jint,
    ) -> AccessibilityNodeInfo<'local> {
        let render_handle = self.rsc.ui().render_state();
        let render_state = render_handle.get();
        let mut source = AndroidAccessSource {
            widgets: self.rsc.widgets(),
            render: &render_state,
            rsc: &self.rsc,
        };
        let ui_state = self.state.android_state_mut();
        AccessibilityNodeInfo(ui_state.access_adapter.find_focus(
            &mut source,
            &mut ctx.env,
            &ctx.view.0,
            focus_type,
        ))
    }

    fn perform_action<'local>(
        &mut self,
        ctx: &mut CallbackCtx<'local>,
        virtual_view_id: jint,
        action: jint,
        arguments: &Bundle<'local>,
    ) -> bool {
        let Some(action) =
            accesskit_android::PlatformAction::from_java(&mut ctx.env, action, &arguments.0)
        else {
            return false;
        };
        let ui_state = self.state.android_state_mut();
        let Some(events) = ui_state.access_adapter.perform_action(
            &mut NullActionHandler,
            virtual_view_id,
            &action,
        ) else {
            return false;
        };
        ctx.push_dynamic_deferred_callback(move |env, view| {
            raise_if_enabled(env, view, events);
        });
        true
    }
}

/// Registers `IrisViewPeer<State>`'s native methods and builds one on every
/// `newViewPeer` call from Java. `State`'s app crate wraps this in a
/// concrete `extern "system" fn` (a generic function cannot be handed to
/// `register_view_class`, which wants a plain function pointer) -- see
/// `iris/android-app/src/lib.rs`.
pub fn new_peer<'local, State: AndroidAppState>(
    mut env: JNIEnv<'local>,
    view: View<'local>,
    context: Context<'local>,
    init: fn(AndroidUiState, &mut State::Resources) -> State,
) -> android_view::jni::sys::jlong {
    // `DisplayMetrics.density` -- physical pixels per dp on this device.
    // Read once here, at the one point in this file already handed a
    // `Context`, and carried on `AndroidUiState` from then on (see
    // `content_scale`'s field comment for what depends on it).
    let content_scale = context
        .resources(&mut env)
        .display_metrics(&mut env)
        .density(&mut env);
    log::info!("iris: new_peer content_scale={content_scale}");
    let vm = env.get_java_vm().unwrap();
    let global_view = env.new_global_ref(&view.0).unwrap();
    let redraw: Arc<dyn RequestRedraw> = Arc::new(AndroidRedrawHandle::new(vm, global_view));
    let (mut rsc, task_recv) = State::Resources::new(redraw);
    rsc.ui_mut().set_density(content_scale);
    let shared = Rc::new(RefCell::new(Shared::default()));
    let ui_state = AndroidUiState::new(shared.clone(), content_scale);
    let mut state = init(ui_state, &mut rsc);
    let platform_vm = env.get_java_vm().unwrap();
    let platform_view = env.new_global_ref(&view.0).unwrap();
    state.platform_ready(&mut rsc, platform_vm, platform_view);
    let peer = IrisViewPeer {
        rsc,
        state,
        task_recv,
        device_clock: None,
    };
    let id = android_view::register_view_peer(peer);
    super::insets::register(id, shared);
    id
}