Make the Rust client the sole app

app/tests/catch_a_fling.rs

@@ -0,0 +1,166 @@
+use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
+use iris::harness::{Harness, TouchAction, TouchScript};
+use iris::prelude::*;
+use iris::sense::DRAG_SLOP;
+
+fn opened() -> (Harness, ai_app::ui::TranscriptScreen) {
+    let mut h = Harness::new(phone_size(), PHONE_SCALE);
+    let opened = ai_app::ui::fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
+    h.frame(0);
+    h.frame(PHONE_FRAME_MS);
+    (h, opened.screen)
+}
+
+fn tracked_row(h: &mut Harness, screen: &ai_app::ui::TranscriptScreen) -> (RowKey, f32) {
+    let middle = phone_size().y / 2.0;
+    let list = (screen.list)(&mut h.rsc);
+    let key = list.key_at(middle).expect("a row under the viewport");
+    let (top, _) = list.extent(key).expect("that row has an extent");
+    (key, top)
+}
+
+fn row_top(h: &mut Harness, screen: &ai_app::ui::TranscriptScreen, key: RowKey) -> f32 {
+    (screen.list)(&mut h.rsc)
+        .extent(key)
+        .expect("the tracked row is still loaded")
+        .0
+}
+
+const STEP: f32 = 2.0;
+const SAMPLES: usize = 3;
+const CATCH_X: f32 = 540.0;
+
+fn drag_from(
+    h: &mut Harness,
+    screen: &ai_app::ui::TranscriptScreen,
+    key: RowKey,
+    y0: f32,
+    t0: u64,
+    expect_tracking: bool,
+) -> u64 {
+    let before = row_top(h, screen, key);
+    h.touch(TouchAction::Down, Vec2::new(CATCH_X, y0), t0);
+    assert_eq!(
+        row_top(h, screen, key),
+        before,
+        "the down itself must not move the content, only stop it"
+    );
+    let mut t = t0;
+    for i in 1..=SAMPLES {
+        let moved = STEP * i as f32;
+        t = t0 + 8 * i as u64;
+        h.touch(TouchAction::Move, Vec2::new(CATCH_X, y0 + moved), t);
+        let travelled = row_top(h, screen, key) - before;
+        if expect_tracking {
+            assert!(
+                (travelled - moved).abs() < 0.5,
+                "sample {i}: the finger has moved {moved}px since the down and the content \
+                 {travelled:.1}px -- it is not pinned to the finger"
+            );
+        } else {
+            assert!(
+                travelled.abs() < 0.5,
+                "sample {i}: a {moved}px drag is inside DRAG_SLOP ({DRAG_SLOP}px) and must move \
+                 nothing, but the content moved {travelled:.1}px"
+            );
+        }
+    }
+    t += 8;
+    h.touch(
+        TouchAction::Up,
+        Vec2::new(CATCH_X, y0 + STEP * SAMPLES as f32),
+        t,
+    );
+    t
+}
+
+#[test]
+fn a_press_on_a_flinging_list_pins_the_content_to_the_finger() {
+    let (mut h, screen) = opened();
+
+    let flick = TouchScript::parse(include_str!("../touch/flick-120hz.touch"))
+        .unwrap_or_else(|e| panic!("flick-120hz.touch: {e}"));
+    h.replay(&flick);
+
+    let catch_at = flick.end_ms() + 150;
+    h.frames_until(
+        flick.end_ms() + PHONE_FRAME_MS,
+        catch_at - PHONE_FRAME_MS,
+        PHONE_FRAME_MS,
+    );
+    assert!(
+        (screen.list)(&mut h.rsc).is_scrolling(),
+        "the fling must still be running 150ms in, or this test catches nothing"
+    );
+
+    let (key, _) = tracked_row(&mut h, &screen);
+    drag_from(&mut h, &screen, key, 1200.0, catch_at, true);
+}
+
+#[test]
+fn a_catch_that_never_moved_is_not_a_tap_and_does_not_fling() {
+    let (mut h, screen) = opened();
+
+    let flick = TouchScript::parse(include_str!("../touch/flick-120hz.touch"))
+        .unwrap_or_else(|e| panic!("flick-120hz.touch: {e}"));
+    h.replay(&flick);
+    let catch_at = flick.end_ms() + 150;
+    h.frames_until(
+        flick.end_ms() + PHONE_FRAME_MS,
+        catch_at - PHONE_FRAME_MS,
+        PHONE_FRAME_MS,
+    );
+    assert!(
+        (screen.list)(&mut h.rsc).is_scrolling(),
+        "the fling must still be running 150ms in, or this test catches nothing"
+    );
+
+    let (key, _) = tracked_row(&mut h, &screen);
+    h.touch(TouchAction::Down, Vec2::new(CATCH_X, 1200.0), catch_at);
+    let stopped_at = row_top(&mut h, &screen, key);
+    h.touch(TouchAction::Up, Vec2::new(CATCH_X, 1200.0), catch_at + 8);
+
+    assert_eq!(
+        (screen.list)(&mut h.rsc).fling_velocity(),
+        None,
+        "a press that stopped a fling and moved nothing must not start another"
+    );
+    h.frames_until(catch_at + 16, catch_at + 500, PHONE_FRAME_MS);
+    assert!(
+        (row_top(&mut h, &screen, key) - stopped_at).abs() < 0.5,
+        "the content moved after a catch was released without moving"
+    );
+    assert_eq!(
+        h.state.opened_urls,
+        Vec::<String>::new(),
+        "a catch is not a tap: nothing under it may be followed"
+    );
+}
+
+#[test]
+fn the_same_small_drag_on_a_settled_list_moves_nothing() {
+    let (mut h, screen) = opened();
+
+    let flick = TouchScript::parse(include_str!("../touch/flick-120hz.touch"))
+        .unwrap_or_else(|e| panic!("flick-120hz.touch: {e}"));
+    h.replay(&flick);
+    let settled = h.frames_until(
+        flick.end_ms() + PHONE_FRAME_MS,
+        flick.end_ms() + 4000,
+        PHONE_FRAME_MS,
+    );
+    assert!(
+        !(screen.list)(&mut h.rsc).is_scrolling(),
+        "the fling must have stopped, or this is the same case as the test above"
+    );
+
+    let (key, _) = tracked_row(&mut h, &screen);
+    drag_from(
+        &mut h,
+        &screen,
+        key,
+        1200.0,
+        settled + PHONE_FRAME_MS,
+        false,
+    );
+}

app/tests/fence_fling.rs

@@ -0,0 +1,193 @@
+use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
+use iris::harness::{Harness, TouchAction};
+use iris::prelude::*;
+
+fn fence_scroll_in(h: &Harness, top: f32, bottom: f32) -> Option<(WidgetId, PixelRegion)> {
+    let render_handle = h.rsc.ui.render_state();
+    let render_state = render_handle.get();
+    render_state
+        .active
+        .keys()
+        .copied()
+        .filter(|&id| {
+            h.rsc
+                .ui
+                .widgets
+                .get_dyn(id)
+                .and_then(|w| w.as_any().downcast_ref::<ScrollArea>())
+                .is_some_and(|s| s.axis() == Axis::X)
+        })
+        .find_map(|id| {
+            let r = render_state.window_region(&id, &h.rsc)?;
+            (r.top_left.y >= top && r.bot_right.y <= bottom).then_some((id, r))
+        })
+}
+
+fn is_scrolling(h: &Harness, id: WidgetId) -> bool {
+    h.rsc
+        .ui
+        .widgets
+        .get_dyn(id)
+        .and_then(|w| w.as_any().downcast_ref::<ScrollArea>())
+        .expect("the fence's scroll area is still drawn")
+        .is_scrolling()
+}
+
+fn amt(h: &Harness, id: WidgetId) -> f32 {
+    h.rsc
+        .ui
+        .widgets
+        .get_dyn(id)
+        .and_then(|w| w.as_any().downcast_ref::<ScrollArea>())
+        .expect("the fence's scroll area is still drawn")
+        .amt()
+}
+
+#[test]
+fn a_flick_across_a_code_fence_keeps_moving_after_the_finger_leaves() {
+    use ai_app::client::transcript_fold::{TranscriptItem, TranscriptRow};
+
+    let mut h = Harness::new(phone_size(), PHONE_SCALE);
+    let opened = ai_app::ui::fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
+    let mut screen = opened.screen;
+    h.frame(0);
+    h.frame(PHONE_FRAME_MS);
+
+    let fence = TranscriptRow::Single(TranscriptItem::AssistantMsg {
+        seq: 9_000_000,
+        text: "```\none two three four five six seven eight nine ten eleven twelve \
+               thirteen fourteen fifteen sixteen seventeen eighteen twenty twentyone\n```"
+            .to_string(),
+        settled: true,
+    });
+    screen.push_row(&mut h.rsc, &fence);
+    (screen.list)(&mut h.rsc).jump_to_end();
+    h.frame(100);
+    h.frame(108);
+
+    let key = ai_app::ui::row::row_key(&fence.key());
+    let (top, bottom) = (screen.list)(&mut h.rsc)
+        .extent(key)
+        .expect("the fence row is on screen");
+    let (fence_scroll, box_) = fence_scroll_in(&h, top, bottom)
+        .expect("the pushed fence draws a horizontal scroll area of its own");
+    assert_eq!(amt(&h, fence_scroll), 0.0, "a fence opens at its start");
+
+    let y = (box_.top_left.y + box_.bot_right.y) / 2.0;
+
+    h.touch(TouchAction::Down, Vec2::new(900.0, y), 200);
+    for (i, x) in [860.0, 800.0, 720.0, 620.0].into_iter().enumerate() {
+        h.touch(TouchAction::Move, Vec2::new(x, y), 208 + 8 * i as u64);
+    }
+    h.touch(TouchAction::Up, Vec2::new(620.0, y), 240);
+
+    let at_release = amt(&h, fence_scroll);
+    assert!(
+        at_release > 0.0,
+        "the flick itself must have panned the fence, got {at_release}"
+    );
+
+    let mut t = 240;
+    while t <= 740 {
+        h.frame(t);
+        t += PHONE_FRAME_MS;
+    }
+    let coasted = amt(&h, fence_scroll);
+    assert!(
+        coasted > at_release + 1.0,
+        "the fence stopped dead at the release: {at_release} -> {coasted}"
+    );
+
+    let settled = coasted;
+    while t <= 4_000 {
+        h.frame(t);
+        t += PHONE_FRAME_MS;
+    }
+    let after = amt(&h, fence_scroll);
+    assert!(
+        after >= settled,
+        "a fling must not run backwards: {settled} -> {after}"
+    );
+    let last = after;
+    h.frame(t);
+    assert_eq!(last, amt(&h, fence_scroll), "the fling never settled");
+}
+
+#[test]
+fn a_drag_away_from_a_coasting_fence_scrolls_the_list_and_leaves_it_coasting() {
+    use ai_app::client::transcript_fold::{TranscriptItem, TranscriptRow};
+
+    let mut h = Harness::new(phone_size(), PHONE_SCALE);
+    let opened = ai_app::ui::fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
+    let mut screen = opened.screen;
+    h.frame(0);
+    h.frame(PHONE_FRAME_MS);
+
+    let fence = TranscriptRow::Single(TranscriptItem::AssistantMsg {
+        seq: 9_000_000,
+        text: format!(
+            "```\n{}\n```",
+            (1..=200)
+                .map(|i| format!("word{i}"))
+                .collect::<Vec<_>>()
+                .join(" ")
+        ),
+        settled: true,
+    });
+    screen.push_row(&mut h.rsc, &fence);
+    (screen.list)(&mut h.rsc).jump_to_end();
+    h.frame(100);
+    h.frame(108);
+
+    let key = ai_app::ui::row::row_key(&fence.key());
+    let (top, bottom) = (screen.list)(&mut h.rsc)
+        .extent(key)
+        .expect("the fence row is on screen");
+    let (fence_scroll, box_) = fence_scroll_in(&h, top, bottom)
+        .expect("the pushed fence draws a horizontal scroll area of its own");
+    let y = (box_.top_left.y + box_.bot_right.y) / 2.0;
+
+    h.touch(TouchAction::Down, Vec2::new(900.0, y), 200);
+    for (i, x) in [860.0, 800.0, 720.0, 620.0].into_iter().enumerate() {
+        h.touch(TouchAction::Move, Vec2::new(x, y), 208 + 8 * i as u64);
+    }
+    h.touch(TouchAction::Up, Vec2::new(620.0, y), 240);
+    h.frame(248);
+    assert!(
+        is_scrolling(&h, fence_scroll),
+        "the fence has to still be coasting for this to be the reported case",
+    );
+
+    let probe = box_.top_left.y - 500.0;
+    let row = (screen.list)(&mut h.rsc)
+        .key_at(probe)
+        .expect("a row that far up the screen");
+    let (row_top, row_bottom) = (screen.list)(&mut h.rsc).extent(row).expect("its extent");
+    let from = (row_top + row_bottom) / 2.0;
+
+    let list_before = (screen.list)(&mut h.rsc).anchor_position_display();
+    let fence_before = amt(&h, fence_scroll);
+    h.touch(TouchAction::Down, Vec2::new(540.0, from), 256);
+    let mut t = 264;
+    for i in 1..=8 {
+        h.touch(
+            TouchAction::Move,
+            Vec2::new(540.0, from + 20.0 * i as f32),
+            t,
+        );
+        t += 8;
+    }
+    h.touch(TouchAction::Up, Vec2::new(540.0, from + 160.0), t);
+
+    assert_ne!(
+        list_before,
+        (screen.list)(&mut h.rsc).anchor_position_display(),
+        "the drag was nowhere near the fence, so it belongs to the list",
+    );
+    assert!(
+        amt(&h, fence_scroll) > fence_before,
+        "the fence's fling must carry on through a gesture that was never \
+         its own: {fence_before} -> {}",
+        amt(&h, fence_scroll),
+    );
+}

app/tests/gesture_cancel.rs

@@ -0,0 +1,150 @@
+use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
+use iris::harness::{Harness, TouchAction, TouchScript};
+use iris::prelude::*;
+
+fn opened() -> (Harness, ai_app::ui::TranscriptScreen) {
+    let mut h = Harness::new(phone_size(), PHONE_SCALE);
+    let opened = ai_app::ui::fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
+    h.frame(0);
+    h.frame(PHONE_FRAME_MS);
+    (h, opened.screen)
+}
+
+fn script(name: &str, text: &str) -> TouchScript {
+    TouchScript::parse(text).unwrap_or_else(|e| panic!("{name}: {e}"))
+}
+
+fn tracked_row(h: &mut Harness, screen: &ai_app::ui::TranscriptScreen) -> (RowKey, f32) {
+    let middle = phone_size().y / 2.0;
+    let list = (screen.list)(&mut h.rsc);
+    let key = list.key_at(middle).expect("a row under the viewport");
+    let (top, _) = list.extent(key).expect("that row has an extent");
+    (key, top)
+}
+
+fn row_top(h: &mut Harness, screen: &ai_app::ui::TranscriptScreen, key: RowKey) -> f32 {
+    (screen.list)(&mut h.rsc)
+        .extent(key)
+        .expect("the tracked row is still loaded")
+        .0
+}
+
+#[test]
+fn a_cancelled_flick_does_not_fling() {
+    let (mut h, screen) = opened();
+    let flick = script(
+        "flick-cancelled",
+        include_str!("../touch/flick-cancelled.touch"),
+    );
+    h.replay(&flick);
+
+    assert_eq!(
+        (screen.list)(&mut h.rsc).fling_velocity(),
+        None,
+        "a gesture the platform took away must not fling"
+    );
+
+    let (key, settled) = tracked_row(&mut h, &screen);
+    let end = flick.end_ms() + 1_000;
+    let mut t = flick.end_ms();
+    while t <= end {
+        h.frame(t);
+        t += PHONE_FRAME_MS;
+    }
+    let now = row_top(&mut h, &screen, key);
+    assert!(
+        (now - settled).abs() < 0.5,
+        "the list kept moving after a cancelled gesture: {settled} -> {now}"
+    );
+}
+
+#[test]
+fn a_press_ended_by_a_cancel_leaves_no_origin_for_the_next_one() {
+    let (mut h, screen) = opened();
+
+    h.touch(TouchAction::Down, Vec2::new(540.0, 700.0), 0);
+    h.touch(TouchAction::Cancel, Vec2::new(540.0, 700.0), 8);
+
+    let (key, before) = tracked_row(&mut h, &screen);
+
+    h.touch(TouchAction::Down, Vec2::new(540.0, 1900.0), 200);
+    h.touch(TouchAction::Up, Vec2::new(540.0, 1900.0), 250);
+
+    let after = row_top(&mut h, &screen, key);
+    assert!(
+        (after - before).abs() < 0.5,
+        "a tap after a cancelled press panned the list by {}px, the distance between them",
+        after - before
+    );
+    assert_eq!(
+        (screen.list)(&mut h.rsc).fling_velocity(),
+        None,
+        "and it must not have flung either"
+    );
+}
+
+#[test]
+fn panning_a_code_fence_then_tapping_elsewhere_moves_nothing() {
+    use ai_app::client::transcript_fold::{TranscriptItem, TranscriptRow};
+
+    let (mut h, mut screen) = opened();
+    let fence = TranscriptRow::Single(TranscriptItem::AssistantMsg {
+        seq: 9_000_000,
+        text: "```\none two three four five six seven eight nine ten eleven twelve\n\
+               thirteen fourteen fifteen sixteen seventeen eighteen nineteen\n```"
+            .to_string(),
+        settled: true,
+    });
+    let para = TranscriptRow::Single(TranscriptItem::AssistantMsg {
+        seq: 9_000_001,
+        text: "A plain paragraph with nothing to tap in it, only words, so that a \
+               press here is a press on ordinary text and nothing else."
+            .to_string(),
+        settled: true,
+    });
+    screen.push_row(&mut h.rsc, &fence);
+    screen.push_row(&mut h.rsc, &para);
+    (screen.list)(&mut h.rsc).jump_to_end();
+    h.frame(100);
+    h.frame(108);
+
+    let key = ai_app::ui::row::row_key(&fence.key());
+    let (top, bottom) = (screen.list)(&mut h.rsc)
+        .extent(key)
+        .expect("the fence row is on screen");
+    let y = (top + bottom) / 2.0;
+    assert!(
+        y > 0.0 && y < phone_size().y,
+        "the fence row has to be on screen to be pressed: {top}..{bottom}"
+    );
+
+    h.touch(TouchAction::Down, Vec2::new(800.0, y), 200);
+    for (i, x) in [760.0, 700.0, 620.0, 540.0].into_iter().enumerate() {
+        h.touch(TouchAction::Move, Vec2::new(x, y), 208 + 8 * i as u64);
+    }
+    h.touch(TouchAction::Up, Vec2::new(540.0, y), 248);
+
+    let (tracked, before) = tracked_row(&mut h, &screen);
+
+    let para_key = ai_app::ui::row::row_key(&para.key());
+    let (ptop, pbottom) = (screen.list)(&mut h.rsc)
+        .extent(para_key)
+        .expect("the paragraph row is on screen");
+    h.touch(
+        TouchAction::Down,
+        Vec2::new(540.0, (ptop + pbottom) / 2.0),
+        400,
+    );
+    h.touch(
+        TouchAction::Up,
+        Vec2::new(540.0, (ptop + pbottom) / 2.0),
+        450,
+    );
+
+    let after = row_top(&mut h, &screen, tracked);
+    assert!(
+        (after - before).abs() < 0.5,
+        "a tap after panning a code fence moved the transcript by {}px",
+        after - before
+    );
+}

app/tests/input_log_roundtrip.rs

@@ -0,0 +1,144 @@
+use std::process::{Command, Stdio};
+use std::sync::{Mutex, OnceLock};
+
+use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
+use iris::harness::{Harness, TouchScript};
+
+struct CaptureLogger {
+    lines: Mutex<Vec<(log::Level, String)>>,
+}
+
+static LOGGER: OnceLock<CaptureLogger> = OnceLock::new();
+
+impl log::Log for CaptureLogger {
+    fn enabled(&self, _metadata: &log::Metadata) -> bool {
+        true
+    }
+    fn log(&self, record: &log::Record) {
+        self.lines
+            .lock()
+            .unwrap()
+            .push((record.level(), record.args().to_string()));
+    }
+    fn flush(&self) {}
+}
+
+fn logger() -> &'static CaptureLogger {
+    let logger = LOGGER.get_or_init(|| CaptureLogger {
+        lines: Mutex::new(Vec::new()),
+    });
+    let _ = log::set_logger(logger);
+    log::set_max_level(log::LevelFilter::Debug);
+    logger
+}
+
+fn drain(logger: &CaptureLogger) -> Vec<(log::Level, String)> {
+    std::mem::take(&mut *logger.lines.lock().unwrap())
+}
+
+fn opened() -> (Harness, ai_app::ui::TranscriptScreen) {
+    let mut h = Harness::new(phone_size(), PHONE_SCALE);
+    let opened = ai_app::ui::fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
+    h.frame(0);
+    h.frame(PHONE_FRAME_MS);
+    (h, opened.screen)
+}
+
+#[test]
+fn tracing_is_silent_off_and_round_trips_the_flick_on() {
+    let logger = logger();
+
+    iris::diagnostics::set_trace(false);
+    drain(logger); // whatever `opened()` itself logged while building
+    let (mut h, screen) = opened();
+    drain(logger); // and whatever opening logged
+    let flick = TouchScript::parse(include_str!("../touch/flick-120hz.touch"))
+        .unwrap_or_else(|e| panic!("flick-120hz.touch: {e}"));
+    h.replay(&flick);
+    let _ = (screen.list)(&mut h.rsc); // touch the screen the same way a real caller would
+    let quiet = drain(logger);
+    let debug_lines: Vec<_> = quiet
+        .iter()
+        .filter(|(level, _)| *level == log::Level::Debug)
+        .collect();
+    assert!(
+        debug_lines.is_empty(),
+        "tracing is off, but the ring would still have held these `debug!` lines: {debug_lines:#?}"
+    );
+
+    iris::diagnostics::set_trace(true);
+    let (mut h, screen) = opened();
+    drain(logger);
+    h.replay(&flick);
+    let _ = (screen.list)(&mut h.rsc);
+    let traced = drain(logger);
+    iris::diagnostics::set_trace(false); // leave it off for any test after this one
+
+    let input_lines: Vec<&str> = traced
+        .iter()
+        .filter(|(_, msg)| msg.contains("iris input: action="))
+        .map(|(_, msg)| msg.as_str())
+        .collect();
+    assert_eq!(
+        input_lines.len(),
+        flick.samples.len(),
+        "expected one `iris::input` line per replayed sample, got:\n{input_lines:#?}"
+    );
+    let frame_lines: Vec<&str> = traced
+        .iter()
+        .filter(|(_, msg)| msg.starts_with("iris frame:"))
+        .map(|(_, msg)| msg.as_str())
+        .collect();
+    assert!(
+        !frame_lines.is_empty(),
+        "expected at least one `iris::frame` line once tracing was on"
+    );
+    for line in &frame_lines {
+        assert!(
+            !line.contains("layout=0ns"),
+            "a frame that redrew should not report zero layout time: {line}"
+        );
+    }
+
+    let report = input_lines.join("\n");
+    let script_path = concat!(
+        env!("CARGO_MANIFEST_DIR"),
+        "/../iris/benches/report_to_touch.py"
+    );
+    let mut child = Command::new("python3")
+        .arg(script_path)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .expect("python3 must be on PATH to run report_to_touch.py");
+    {
+        use std::io::Write;
+        child
+            .stdin
+            .take()
+            .unwrap()
+            .write_all(report.as_bytes())
+            .unwrap();
+    }
+    let output = child.wait_with_output().expect("report_to_touch.py exited");
+    assert!(
+        output.status.success(),
+        "report_to_touch.py failed: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let touch_text = String::from_utf8(output.stdout).expect("report_to_touch.py wrote UTF-8");
+    let round_tripped =
+        TouchScript::parse(&touch_text).unwrap_or_else(|e| panic!("round-tripped script: {e}"));
+
+    assert_eq!(
+        round_tripped.samples.len(),
+        flick.samples.len(),
+        "round trip produced a different number of samples:\n{touch_text}"
+    );
+    for (original, back) in flick.samples.iter().zip(round_tripped.samples.iter()) {
+        assert_eq!(original.t_ms, back.t_ms);
+        assert_eq!(original.action, back.action);
+        assert_eq!(original.pos, back.pos);
+    }
+}

app/tests/phone_screen.rs

@@ -0,0 +1,270 @@
+use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
+use iris::harness::{Harness, TouchScript};
+use iris::prelude::*;
+
+fn opened() -> (Harness, ai_app::ui::TranscriptScreen) {
+    let mut h = Harness::new(phone_size(), PHONE_SCALE);
+    let opened = ai_app::ui::fixture::open(&mut h.rsc, &mut h.state).expect("the fixture folds");
+    h.frame(0);
+    h.frame(PHONE_FRAME_MS);
+    (h, opened.screen)
+}
+
+fn script(name: &str, text: &str) -> TouchScript {
+    TouchScript::parse(text).unwrap_or_else(|e| panic!("{name}: {e}"))
+}
+
+fn offset(h: &mut Harness, screen: &ai_app::ui::TranscriptScreen) -> String {
+    (screen.list)(&mut h.rsc).anchor_position_display()
+}
+
+#[test]
+fn a_recorded_flick_releases_with_a_velocity_and_flings_the_list() {
+    let (mut h, screen) = opened();
+    let before = offset(&mut h, &screen);
+
+    let flick = script("flick-120hz", include_str!("../touch/flick-120hz.touch"));
+    h.replay(&flick);
+
+    let velocity = (screen.list)(&mut h.rsc)
+        .fling_velocity()
+        .expect("the flick must release as a pan with a velocity, not a tap");
+    assert!(
+        (velocity - 15_250.0).abs() < 20.0,
+        "expected ~15250px/s from velocity_reference.py, got {velocity}"
+    );
+
+    const REFERENCE_MS: u64 = 2071;
+    const REFERENCE_PX: f32 = 11057.0;
+    let end = flick.end_ms() + REFERENCE_MS * 2;
+    let mut settled_at = None;
+    let mut t = flick.end_ms();
+    let middle = phone_size().y / 2.0;
+    let mut travelled = 0.0f32;
+    let mut tracked: Option<(RowKey, f32)> = None;
+    while t <= end {
+        h.frame(t);
+        let list = (screen.list)(&mut h.rsc);
+        tracked =
+            match tracked.and_then(|(key, was)| list.extent(key).map(|(now, _)| (key, was, now))) {
+                Some((key, was, now)) => {
+                    travelled += (now - was).abs();
+                    Some((key, now))
+                }
+                None => list
+                    .key_at(middle)
+                    .and_then(|key| list.extent(key).map(|(top, _)| (key, top))),
+            };
+        if settled_at.is_none() && !(screen.list)(&mut h.rsc).is_scrolling() {
+            settled_at = Some(t);
+        }
+        t += PHONE_FRAME_MS;
+    }
+
+    let after = offset(&mut h, &screen);
+    assert_ne!(
+        before, after,
+        "the fling ticks must have moved the list off where the flick left it"
+    );
+    let settled_at = settled_at.expect("the fling must stop on its own, not run forever");
+    let ran_for = settled_at - flick.end_ms();
+    assert!(
+        ran_for >= REFERENCE_MS - PHONE_FRAME_MS * 2,
+        "the fling stopped after {ran_for}ms against the spline reference's {REFERENCE_MS}ms"
+    );
+    assert!(
+        ran_for <= REFERENCE_MS + PHONE_FRAME_MS * 2,
+        "the fling ran {ran_for}ms against the spline reference's {REFERENCE_MS}ms"
+    );
+    assert!(
+        travelled >= REFERENCE_PX * 0.8,
+        "the fling travelled {travelled:.0}px against the spline reference's {REFERENCE_PX:.0}px"
+    );
+}
+
+#[test]
+fn a_tap_on_a_row_moves_nothing() {
+    let (mut h, screen) = opened();
+    let before = offset(&mut h, &screen);
+
+    h.replay(&script("tap", include_str!("../touch/tap.touch")));
+
+    assert_eq!(
+        (screen.list)(&mut h.rsc).fling_velocity(),
+        None,
+        "a tap must not fling"
+    );
+    h.frames_until(100, 400, PHONE_FRAME_MS);
+    assert_eq!(before, offset(&mut h, &screen), "a tap must scroll nothing");
+    assert_eq!(
+        h.state.opened_urls,
+        Vec::<String>::new(),
+        "no link was under this tap"
+    );
+}
+
+#[test]
+fn a_long_press_and_drag_selects_text() {
+    let (mut h, screen) = opened();
+    let before = offset(&mut h, &screen);
+
+    h.replay(&script(
+        "long-press",
+        include_str!("../touch/long-press.touch"),
+    ));
+
+    let selected = screen
+        .selected_text(&mut h.rsc)
+        .expect("a long-press then drag must leave text selected");
+    assert!(
+        !selected.trim().is_empty(),
+        "the selection covered no characters: {selected:?}"
+    );
+    assert_eq!(
+        before,
+        offset(&mut h, &screen),
+        "a selection must not also pan the list"
+    );
+}
+
+#[test]
+fn a_tap_after_selection_deselects_text() {
+    let (mut h, screen) = opened();
+    h.replay(&script(
+        "select-then-tap",
+        "0 down 300 1000\n\
+         520 move 300 1000\n\
+         560 move 700 1000\n\
+         600 move 900 1000\n\
+         640 up 900 1000\n\
+         800 down 540 1000\n\
+         880 up 540 1000",
+    ));
+
+    assert_eq!(
+        screen.selected_text(&mut h.rsc),
+        None,
+        "an ordinary tap after a selection must dismiss it"
+    );
+    assert_eq!(
+        h.state.opened_urls,
+        Vec::<String>::new(),
+        "the deselecting tap must be consumed rather than activating content"
+    );
+}
+
+#[test]
+fn the_composer_sits_above_a_simulated_ime_inset() {
+    let (mut h, screen) = opened();
+    let height = h.size().y;
+    let field_bottom = |h: &mut Harness| {
+        h.rsc
+            .ui
+            .render_state()
+            .get()
+            .window_region(&screen.composer.field, &h.rsc)
+            .expect("the composer field is on screen")
+            .bot_right
+            .y
+    };
+
+    let closed = field_bottom(&mut h);
+    assert!(
+        closed <= height,
+        "the composer is off the bottom of the window even with no keyboard: {closed} > {height}"
+    );
+
+    let ime = 1000.0;
+    screen.composer.set_bottom_inset(&mut h.rsc, ime);
+    h.frame(PHONE_FRAME_MS * 2);
+
+    let open = field_bottom(&mut h);
+    assert!(
+        open <= height - ime,
+        "the keyboard covers the composer: its bottom is at {open}, the IME starts at {}",
+        height - ime
+    );
+    assert!(
+        (closed - open - ime).abs() < 1.0,
+        "the composer moved {} for a {ime}px inset",
+        closed - open
+    );
+}
+
+#[test]
+fn a_space_in_the_composer_finishes_layout() {
+    let (mut h, screen) = opened();
+    screen.composer.set_bottom_inset(&mut h.rsc, 1000.0);
+    h.frame(PHONE_FRAME_MS * 2);
+    h.state.set_focus(Some(screen.composer.field));
+    screen.composer.field.edit(&mut h.rsc).set_cursor_byte(0);
+
+    for text in ["h", "i", " "] {
+        screen.composer.field.edit(&mut h.rsc).insert(text);
+        h.frame(PHONE_FRAME_MS);
+    }
+
+    assert_eq!(screen.composer.field.edit(&mut h.rsc).text.text(), "hi ");
+    let region = h
+        .rsc
+        .ui
+        .render_state()
+        .get()
+        .window_region(&screen.composer.field, &h.rsc)
+        .expect("the composer field is drawn");
+    let size = region.bot_right - region.top_left;
+    assert!(
+        size.x > phone_size().x / 2.0,
+        "the field shrink-wrapped to the short message: {region:?}"
+    );
+    assert!(
+        size.y < 30.0 * PHONE_SCALE,
+        "the trailing space wrapped onto a second line: {region:?}"
+    );
+}
+
+#[test]
+fn a_newline_leaves_the_caret_inside_the_composers_padding() {
+    let (mut h, screen) = opened();
+    let height = h.size().y;
+    let ime = 1000.0;
+    screen.composer.set_bottom_inset(&mut h.rsc, ime);
+    h.frame(PHONE_FRAME_MS * 2);
+
+    h.state.set_focus(Some(screen.composer.field));
+    screen.composer.field.edit(&mut h.rsc).set_cursor_byte(0);
+    for _ in 0..12 {
+        screen.composer.field.edit(&mut h.rsc).insert("a\n");
+        h.frame(PHONE_FRAME_MS);
+    }
+    let render_handle = h.rsc.ui.render_state();
+    let render_state = render_handle.get();
+    let message = render_state
+        .debug(h.rsc.widgets(), "Message")
+        .find(|a| !a.primitives.is_empty())
+        .expect("the composer field is drawn");
+    let caret = render_state.primitive_corners(message.primitives.last().unwrap().slot, &h.rsc);
+    let bar_bottom = height - ime;
+    let padding = 12.0 * PHONE_SCALE;
+    assert!(
+        caret.bot_right.y < bar_bottom - padding / 2.0,
+        "the caret is in the bar's bottom padding: it ends at {}, the bar's edge is {bar_bottom} \
+         and its padding is {padding}px",
+        caret.bot_right.y,
+    );
+
+    let mask = h.rsc.ui.masks[message.mask.idx()];
+    let bar = render_state.primitive_corners(mask.primitive, &h.rsc);
+    let visible_content_top = message
+        .primitives
+        .iter()
+        .map(|p| render_state.primitive_corners(p.slot, &h.rsc))
+        .filter(|r| r.bot_right.y > bar.top_left.y)
+        .map(|r| r.top_left.y)
+        .fold(f32::INFINITY, f32::min);
+    assert!(
+        visible_content_top > bar.top_left.y,
+        "the composer's first visible line is clipped above its bar: content starts at {visible_content_top}, bar starts at {}",
+        bar.top_left.y,
+    );
+}

app/tests/top_edge.rs

@@ -0,0 +1,256 @@
+use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
+use iris::harness::Harness;
+use iris::prelude::*;
+
+const HEADER_H: f32 = 300.0;
+const HEADER: Srgba8 = Srgba8::new(28, 28, 34, 255);
+
+fn opened() -> (Harness, ai_app::ui::TranscriptScreen) {
+    let mut h = Harness::new(phone_size(), PHONE_SCALE);
+    let (opened, tree) = ai_app::ui::fixture::build_screen(&mut h.rsc).expect("the fixture folds");
+    let content = WidgetPtr::new().add(&mut h.rsc);
+    content(&mut h.rsc).set(tree);
+    let root = (rect(HEADER).height(abs(HEADER_H)), content.height(rest(1)))
+        .span(Dir::DOWN)
+        .add_strong(&mut h.rsc)
+        .any();
+    h.state.set_root(&mut h.rsc, root);
+    h.frame(0);
+    h.frame(PHONE_FRAME_MS);
+    (h, opened.screen)
+}
+
+fn list_box(h: &Harness, screen: &ai_app::ui::TranscriptScreen) -> PixelRegion {
+    h.rsc
+        .ui
+        .render_state()
+        .get()
+        .window_region(&screen.list.id(), &h.rsc)
+        .expect("the list is on screen")
+}
+
+fn drawn_rows(h: &Harness, screen: &ai_app::ui::TranscriptScreen) -> Vec<(f32, f32)> {
+    let render_handle = h.rsc.ui.render_state();
+    let render_state = render_handle.get();
+    let mut rows: Vec<(f32, f32)> = render_state
+        .active
+        .get(&screen.list.id())
+        .expect("the list is drawn")
+        .children
+        .iter()
+        .filter_map(|id| render_state.window_region(id, &h.rsc))
+        .map(|px| (px.top_left.y, px.bot_right.y))
+        .collect();
+    rows.sort_by(|a, b| a.0.total_cmp(&b.0));
+    rows
+}
+
+fn scrolled(h: &mut Harness, screen: &ai_app::ui::TranscriptScreen, amount: f32, t: u64) -> u64 {
+    (screen.list)(&mut h.rsc).scroll(amount);
+    h.frame(t);
+    t + PHONE_FRAME_MS
+}
+
+#[test]
+fn the_row_across_the_top_edge_is_drawn() {
+    let (mut h, screen) = opened();
+    let top = list_box(&h, &screen).top_left.y;
+    let mut t = PHONE_FRAME_MS * 2;
+
+    for _ in 0..60 {
+        t = scrolled(&mut h, &screen, 40.0, t);
+        let rows = drawn_rows(&h, &screen);
+        let first = *rows.first().expect("something is on screen");
+        assert!(
+            first.0 <= top + 0.5,
+            "a band of {:.1}px under the header belongs to no row: rows start at {:.1}, the list \
+             at {top:.1}",
+            first.0 - top,
+            first.0,
+        );
+        assert!(
+            first.1 > top,
+            "the row across the top edge was culled: it ends at {:.1}, above the list's own \
+             {top:.1}",
+            first.1,
+        );
+    }
+}
+
+#[test]
+fn the_list_is_clipped_to_its_own_box() {
+    let (h, screen) = opened();
+    let render_handle = h.rsc.ui.render_state();
+    let render_state = render_handle.get();
+    let active = render_state.active.get(&screen.list.id()).expect("drawn");
+    assert!(
+        active.mask != MaskIdx::NONE,
+        "the transcript's list is drawn with nothing clipping it",
+    );
+    let clip = render_state.mask_region(active.mask, &h.rsc);
+    let list = list_box(&h, &screen);
+    assert!(
+        clip.top_left.y >= list.top_left.y - 0.5 && clip.bot_right.y <= list.bot_right.y + 0.5,
+        "the clip {clip:?} reaches outside the list's own box {list:?}, so a row straddling an \
+         edge still draws past it",
+    );
+
+    let rows = render_state
+        .active
+        .get(&screen.list.id())
+        .expect("the list is drawn")
+        .children
+        .clone();
+    let mut checked = 0;
+    for row in rows {
+        for prim in primitives_under(&h, row) {
+            assert!(
+                mask_chain(&h, prim).contains(&active.mask),
+                "a primitive of row {row:?} clips to {:?}, a chain that never reaches the list's \
+                 own mask {:?}",
+                mask_chain(&h, prim),
+                active.mask,
+            );
+            checked += 1;
+        }
+    }
+    assert!(
+        checked > 0,
+        "no row primitive was checked, so this test asserted nothing",
+    );
+}
+
+fn primitives_under(h: &Harness, id: WidgetId) -> Vec<MaskIdx> {
+    let render_handle = h.rsc.ui.render_state();
+    let render_state = render_handle.get();
+    let Some(active) = render_state.active.get(&id) else {
+        return Vec::new();
+    };
+    let mut out: Vec<MaskIdx> = active
+        .primitives
+        .iter()
+        .filter(|p| p.binding != IMAGE_BINDING)
+        .map(|p| render_state.primitives.instance(p.slot).mask_idx)
+        .collect();
+    for child in &active.children {
+        out.extend(primitives_under(h, *child));
+    }
+    out
+}
+
+fn mask_chain(h: &Harness, mask: MaskIdx) -> Vec<MaskIdx> {
+    let mut chain = Vec::new();
+    let mut at = mask;
+    while at != MaskIdx::NONE {
+        assert!(
+            !chain.contains(&at),
+            "the mask chain from {mask:?} loops back to {at:?}",
+        );
+        chain.push(at);
+        at = h.rsc.ui.masks[at.idx()].parent;
+    }
+    chain
+}
+
+#[test]
+fn rows_that_have_left_the_viewport_are_not_drawn() {
+    let (mut h, screen) = opened();
+    let list = list_box(&h, &screen);
+    let mut t = PHONE_FRAME_MS * 2;
+    let bounded = |rows: &[(f32, f32)], leg: &str, step: usize| {
+        assert!(
+            rows.len() <= 24,
+            "{leg} {step}: {} rows drawn for one 2012px viewport",
+            rows.len(),
+        );
+    };
+    let inside = |rows: &[(f32, f32)], leg: &str, step: usize| {
+        for &(top, bottom) in rows {
+            assert!(
+                bottom > list.top_left.y - 0.5 && top < list.bot_right.y + 0.5,
+                "{leg} {step}: a row at ({top:.1}, {bottom:.1}) is outside the list's box \
+                 {list:?} and was drawn anyway",
+            );
+        }
+    };
+
+    for step in 0..40 {
+        t = scrolled(&mut h, &screen, 400.0, t);
+        bounded(&drawn_rows(&h, &screen), "measuring", step);
+    }
+    for step in 0..40 {
+        t = scrolled(&mut h, &screen, -400.0, t);
+        let rows = drawn_rows(&h, &screen);
+        bounded(&rows, "forward", step);
+        inside(&rows, "forward", step);
+    }
+    for step in 0..40 {
+        t = scrolled(&mut h, &screen, 400.0, t);
+        let rows = drawn_rows(&h, &screen);
+        bounded(&rows, "back", step);
+        inside(&rows, "back", step);
+    }
+}
+
+#[test]
+fn the_row_across_the_bottom_edge_is_drawn() {
+    let (mut h, screen) = opened();
+    let list = list_box(&h, &screen);
+    let mut t = PHONE_FRAME_MS * 2;
+
+    for _ in 0..40 {
+        t = scrolled(&mut h, &screen, 37.0, t);
+        let rows = drawn_rows(&h, &screen);
+        let last = *rows.last().expect("something is on screen");
+        assert!(
+            last.1 >= list.bot_right.y - 0.5,
+            "a band of {:.1}px above the composer belongs to no row",
+            list.bot_right.y - last.1,
+        );
+        assert!(
+            last.0 < list.bot_right.y,
+            "the row across the bottom edge was culled: it starts at {:.1}, below the list's own \
+             {:.1}",
+            last.0,
+            list.bot_right.y,
+        );
+    }
+}
+
+#[test]
+fn scrolling_past_the_first_row_settles_on_it() {
+    let (mut h, screen) = opened();
+    let list = list_box(&h, &screen);
+    let mut t = PHONE_FRAME_MS * 2;
+
+    for _ in 0..60 {
+        t = scrolled(&mut h, &screen, 100_000.0, t);
+    }
+    let rows = drawn_rows(&h, &screen);
+    let first = *rows.first().expect("the first row is on screen");
+    assert!(
+        (first.0 - list.top_left.y).abs() < 0.5,
+        "the transcript is parked {:.1}px past its own first row, so the top of the list is blank",
+        first.0 - list.top_left.y,
+    );
+}
+
+#[test]
+fn scrolling_past_the_last_row_settles_on_it() {
+    let (mut h, screen) = opened();
+    let list = list_box(&h, &screen);
+    let mut t = PHONE_FRAME_MS * 2;
+
+    for _ in 0..20 {
+        t = scrolled(&mut h, &screen, -100_000.0, t);
+    }
+
+    let rows = drawn_rows(&h, &screen);
+    let last = *rows.last().expect("the last row is on screen");
+    assert!(
+        (last.1 - list.bot_right.y).abs() < 0.5,
+        "the transcript is parked {:.1}px past its own last row, so the bottom of the list is \
+         blank",
+        list.bot_right.y - last.1,
+    );
+}