//! Headless checks for Timeline keyframes as a person uses them: dragging keys over many frames
//! in one gesture (the drag used to end after the first frame), Shift-snapping, Ctrl+C /
//! Ctrl+V, which the windowing layer delivers as clipboard events rather than key presses.

use effectcraft_engine::Session;
use effectcraft_engine::project::LayerId;
use effectcraft_ui_egui::EffectcraftApp;
use egui::{Event, Pos2, pos2};
use egui_kittest::Harness;
use serde_json::json;

/// A 4 s, 30 fps comp with a Box layer whose Opacity has keys at 0 s and 1 s, revealed in the
/// Timeline; returns the harness, the layer and the property uid.
fn harness() -> (Harness<'static, EffectcraftApp>, LayerId, u64) {
    let mut s = Session::default();
    s.execute("comp.new", json!({"name": "Keys", "width": 320, "height": 180, "frameRate": 30, "duration": 4})).unwrap();
    s.execute("layer.newSolid", json!({"name": "Box", "color": "#e04020", "width": 80, "height": 80})).unwrap();
    let id = s.active_comp().unwrap().layers[0].id;
    for (t, v) in [(0.0, 0.0), (1.0, 100.0)] {
        s.execute("prop.addKey", json!({"layer": id.0, "path": "transform/opacity", "time": t, "value": v})).unwrap();
    }
    let uid = s.active_comp().unwrap().layer(id).unwrap().props.prop("transform/opacity").unwrap().uid;
    s.execute("layer.select", json!({"layers": [id.0]})).unwrap();
    let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).build_eframe(|_| EffectcraftApp::new(s));
    h.run_steps(3);
    let ctx = h.ctx.clone();
    effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "timeline.reveal.opacity", json!({})).unwrap();
    h.run_steps(4);
    (h, id, uid)
}

fn key_times(h: &Harness<'_, EffectcraftApp>, id: LayerId) -> Vec<f64> {
    let l = h.state().session.active_comp().unwrap().layer(id).unwrap().clone();
    l.props.prop("transform/opacity").unwrap().keys.iter().map(|k| (k.time.seconds() * 30.0).round() / 30.0).collect()
}

/// Screen centres of the property's keys, left to right.
fn keys(h: &Harness<'_, EffectcraftApp>, uid: u64) -> Vec<Pos2> {
    let mut ks: Vec<Pos2> =
        h.state().auto.query(&format!("timeline.key.{uid}.")).iter().map(|e| pos2(e.rect[0] + e.rect[2] / 2.0, e.rect[1] + e.rect[3] / 2.0)).collect();
    ks.sort_by(|a, b| a.x.total_cmp(&b.x));
    ks
}

/// Press at `from`, move to `to` in small steps (a real drag), release.
fn drag(h: &mut Harness<'_, EffectcraftApp>, from: Pos2, to: Pos2, modifiers: egui::Modifiers) {
    h.input_mut().events.push(Event::PointerMoved(from));
    h.step();
    h.input_mut().events.push(Event::ModifiersChanged(modifiers));
    h.input_mut().events.push(Event::PointerButton { pos: from, button: egui::PointerButton::Primary, pressed: true, modifiers });
    h.step();
    for i in 1..=24 {
        h.input_mut().events.push(Event::PointerMoved(from + (to - from) * (i as f32 / 24.0)));
        h.step();
    }
    h.input_mut().events.push(Event::PointerButton { pos: to, button: egui::PointerButton::Primary, pressed: false, modifiers });
    h.step();
    h.input_mut().events.push(Event::ModifiersChanged(Default::default()));
    h.run_steps(2);
}

#[test]
fn a_key_drag_follows_the_pointer_for_its_whole_length() {
    let (mut h, id, uid) = harness();
    let ks = keys(&h, uid);
    assert_eq!(ks.len(), 2);
    let px_per_s = ks[1].x - ks[0].x;
    // Drag the 1 s key to where 2.5 s is: many frames, one gesture.
    let to = pos2(ks[1].x + px_per_s * 1.5, ks[1].y);
    drag(&mut h, ks[1], to, Default::default());
    let ts = key_times(&h, id);
    assert!((ts[1] - 2.5).abs() <= 2.0 / 30.0, "the key follows the whole drag: {ts:?}");
    let steps = h.state().session.history.undo.iter().filter(|(l, _)| l == "Move Keyframes").count();
    assert_eq!(steps, 1, "one undo step per drag");
    // Shift snaps it to the current time indicator (at 0.5 s), from a few pixels away.
    h.state_mut().session.set_time(effectcraft_engine::time::Tick::from_seconds_f64(0.5));
    h.run_steps(2);
    let ks = keys(&h, uid);
    let near = pos2(ks[0].x + px_per_s * 0.5 + 4.0, ks[1].y);
    drag(&mut h, ks[1], near, egui::Modifiers { shift: true, ..Default::default() });
    assert_eq!(key_times(&h, id)[1], 0.5, "snapped to the current time");
}

#[test]
fn ctrl_c_and_ctrl_v_copy_and_paste_keys_at_the_current_time() {
    let (mut h, id, uid) = harness();
    let ks = keys(&h, uid);
    // Click the 1 s key to select it, Ctrl+C (a clipboard event, not a key press).
    h.input_mut().events.push(Event::PointerMoved(ks[1]));
    h.step();
    h.input_mut().events.push(Event::PointerButton { pos: ks[1], button: egui::PointerButton::Primary, pressed: true, modifiers: Default::default() });
    h.step();
    h.input_mut().events.push(Event::PointerButton { pos: ks[1], button: egui::PointerButton::Primary, pressed: false, modifiers: Default::default() });
    h.run_steps(2);
    assert_eq!(h.state().session.state.selected_keys.len(), 1);
    h.input_mut().events.push(Event::Copy);
    h.step();
    let copied: Vec<String> = h
        .output()
        .platform_output
        .commands
        .iter()
        .filter_map(|c| match c {
            egui::OutputCommand::CopyText(t) => Some(t.clone()),
            _ => None,
        })
        .collect();
    assert_eq!(copied, ["EffectCraft: 1 keyframe"], "the system clipboard is filled, so Ctrl+V sends a paste event");
    assert!(h.state().session.state.clip_is_keys);
    // Move to 3 s, Ctrl+V: the key lands there.
    h.state_mut().session.set_time(effectcraft_engine::time::Tick::from_seconds_f64(3.0));
    h.input_mut().events.push(Event::Paste("EffectCraft: 1 keyframe".into()));
    h.run_steps(2);
    assert_eq!(key_times(&h, id), vec![0.0, 1.0, 3.0]);
}

fn click_with(h: &mut Harness<'_, EffectcraftApp>, p: Pos2, modifiers: egui::Modifiers) {
    h.input_mut().events.push(Event::PointerMoved(p));
    h.step();
    h.input_mut().events.push(Event::ModifiersChanged(modifiers));
    h.input_mut().events.push(Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed: true, modifiers });
    h.step();
    h.input_mut().events.push(Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed: false, modifiers });
    h.step();
    h.input_mut().events.push(Event::ModifiersChanged(Default::default()));
    h.run_steps(2);
}

#[test]
fn shift_click_toggles_and_ctrl_click_switches_interpolation() {
    let (mut h, id, uid) = harness();
    let ks = keys(&h, uid);
    let shift = egui::Modifiers { shift: true, ..Default::default() };
    click_with(&mut h, ks[0], Default::default());
    click_with(&mut h, ks[1], shift);
    assert_eq!(h.state().session.state.selected_keys.len(), 2, "Shift+click adds");
    click_with(&mut h, ks[1], shift);
    assert_eq!(h.state().session.state.selected_keys.len(), 1, "and takes out again");
    let key =
        |h: &Harness<'_, EffectcraftApp>| h.state().session.active_comp().unwrap().layer(id).unwrap().props.prop("transform/opacity").unwrap().keys[0].clone();
    // Ctrl+click: Linear → Auto Bezier → Linear.
    click_with(&mut h, ks[0], egui::Modifiers::COMMAND);
    assert!(key(&h).auto_bezier, "Auto Bezier");
    click_with(&mut h, ks[0], egui::Modifiers::COMMAND);
    assert_eq!(key(&h).out_interp, effectcraft_engine::keyframe::Interp::Linear);
    // Ctrl+Alt+click: Hold.
    click_with(&mut h, ks[0], egui::Modifiers { alt: true, ..egui::Modifiers::COMMAND });
    assert_eq!(key(&h).out_interp, effectcraft_engine::keyframe::Interp::Hold);
}

/// Clicking a key in the Timeline selects its property and layer too, as in After Effects, so
/// the Graph Editor shows the key's curve (#252).
#[test]
fn a_key_clicked_in_the_timeline_shows_in_the_graph_editor() {
    let (mut h, id, uid) = harness();
    h.state_mut().session.execute("edit.deselectAll", json!({})).unwrap();
    h.run_steps(2);
    let ks = keys(&h, uid);
    click_with(&mut h, ks[1], Default::default());
    let st = &h.state().session.state;
    assert_eq!(st.selected_keys.len(), 1);
    assert_eq!((st.selected_props.clone(), st.selected_layers.clone()), (vec![(id, uid)], vec![id]), "the key's property and layer");
    h.state_mut().ui.timeline.graph_editor = true;
    h.run_steps(4);
    assert!(h.state().auto.find(&format!("timeline.graph.key.{uid}.0.1")).is_some(), "the Graph Editor shows the key");
}

#[test]
fn graph_editor_drags_move_every_selected_key_and_shift_keeps_an_axis() {
    let (mut h, id, uid) = harness();
    let s = &mut h.state_mut().session;
    s.execute("prop.select", json!({"layer": id.0, "prop": uid})).unwrap();
    s.execute("keys.selectAll", json!({})).unwrap();
    h.state_mut().ui.timeline.graph_editor = true;
    h.run_steps(4);
    let at = |h: &Harness<'_, EffectcraftApp>, i: usize| {
        let e = h.state().auto.find(&format!("timeline.graph.key.{uid}.0.{i}")).unwrap_or_else(|| panic!("no graph key {i}")).clone();
        pos2(e.rect[0] + e.rect[2] / 2.0, e.rect[1] + e.rect[3] / 2.0)
    };
    let (k0, k1) = (at(&h, 0), at(&h, 1));
    let px_per_s = k1.x - k0.x;
    let values = |h: &Harness<'_, EffectcraftApp>| -> Vec<f64> {
        h.state().session.active_comp().unwrap().layer(id).unwrap().props.prop("transform/opacity").unwrap().keys.iter().map(|k| k.value.as_f64()).collect()
    };
    // Shift: only along time, both keys, by 0.5 s.
    drag(&mut h, k1, pos2(k1.x + px_per_s * 0.5, k1.y - 6.0), egui::Modifiers { shift: true, ..Default::default() });
    assert_eq!(key_times(&h, id), vec![0.5, 1.5], "both selected keys moved");
    assert_eq!(values(&h), vec![0.0, 100.0], "Shift kept the values");
    let undo = h.state().session.history.undo.iter().filter(|(l, _)| l == "Transform Keyframes").count();
    assert_eq!(undo, 1, "one undo step per drag");
    // Without Shift the values move too (both keys, by the same amount).
    h.run_steps(2);
    let k1 = at(&h, 1);
    drag(&mut h, k1, pos2(k1.x, k1.y + 20.0), Default::default());
    let v = values(&h);
    assert!(v[0] < 0.0 && (v[1] - 100.0 - v[0]).abs() < 1e-6, "{v:?}");
}

#[test]
fn double_click_a_key_to_edit_its_value() {
    let (mut h, id, uid) = harness();
    let k1 = keys(&h, uid)[1];
    h.input_mut().events.push(Event::PointerMoved(k1));
    h.step();
    // Both clicks inside egui's double-click time.
    for _ in 0..2 {
        h.input_mut().events.push(Event::PointerButton { pos: k1, button: egui::PointerButton::Primary, pressed: true, modifiers: Default::default() });
        h.input_mut().events.push(Event::PointerButton { pos: k1, button: egui::PointerButton::Primary, pressed: false, modifiers: Default::default() });
    }
    h.step();
    h.run_steps(2);
    assert_eq!(h.state().dialog, Some(effectcraft_ui_egui::Dialog::Form), "the value dialog opened");
    h.run_steps(2);
    assert!(h.state().auto.find("form.field.value").is_some(), "one Opacity field");
    // OK keeps the key where it is (the dialog edits the value only).
    let ok = h.state().auto.find("form.ok").expect("form.ok").clone();
    let p = pos2(ok.rect[0] + ok.rect[2] / 2.0, ok.rect[1] + ok.rect[3] / 2.0);
    h.input_mut().events.push(Event::PointerMoved(p));
    h.step();
    h.input_mut().events.push(Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed: true, modifiers: Default::default() });
    h.step();
    h.input_mut().events.push(Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed: false, modifiers: Default::default() });
    h.run_steps(2);
    assert!(h.state().dialog.is_none());
    let k = h.state().session.active_comp().unwrap().layer(id).unwrap().props.prop("transform/opacity").unwrap().keys[1].clone();
    assert_eq!((k.time.seconds(), k.value.as_f64()), (1.0, 100.0));
}

#[test]
fn k_follows_the_revealed_properties_and_auto_select_picks_the_speed_graph_for_position() {
    let (mut h, id, _) = harness();
    // A Rotation key at 2 s on a property that isn't revealed: K skips it.
    h.state_mut().session.execute("prop.addKey", json!({"layer": id.0, "path": "transform/rotation", "time": 2.0, "value": 45})).unwrap();
    h.state_mut().session.set_time(effectcraft_engine::time::Tick::from_seconds_f64(1.0));
    h.run_steps(2);
    h.input_mut().events.push(Event::Key { key: egui::Key::K, physical_key: None, pressed: true, repeat: false, modifiers: Default::default() });
    h.run_steps(2);
    assert!(h.state().session.time().seconds() > 3.9, "past the hidden key to the work area end: {}", h.state().session.time().seconds());
    // Auto-Select Graph Type: Position shows its speed (one curve), Opacity its value.
    let s = &mut h.state_mut().session;
    for (t, v) in [(0.0, [40.0, 90.0]), (1.0, [280.0, 90.0])] {
        s.execute("prop.addKey", json!({"layer": id.0, "path": "transform/position", "time": t, "value": v})).unwrap();
    }
    let pos = s.active_comp().unwrap().layer(id).unwrap().props.prop("transform/position").unwrap().uid;
    s.execute("prop.select", json!({"layer": id.0, "prop": pos})).unwrap();
    h.state_mut().ui.timeline.graph_editor = true;
    h.run_steps(4);
    assert_eq!(h.state().ui.timeline.graph_mode, "auto");
    assert!(h.state().auto.find(&format!("timeline.graph.key.{pos}.0.0")).is_some());
    assert!(h.state().auto.find(&format!("timeline.graph.key.{pos}.1.0")).is_none(), "speed graph: one curve");
    assert!(h.state().auto.find("timeline.graph.autoSelectGraphType").is_some());
    h.state_mut().ui.timeline.graph_mode = "value".into();
    h.run_steps(3);
    assert!(h.state().auto.find(&format!("timeline.graph.key.{pos}.1.0")).is_some(), "value graph: X and Y");
}

/// #284: in the Graph Editor, dragging the handle of one selected key moves the same handle of
/// every selected key with it (After Effects), in one undo step.
#[test]
fn a_graph_handle_drag_moves_the_handles_of_every_selected_key() {
    let (mut h, id, uid) = harness();
    let s = &mut h.state_mut().session;
    s.execute("prop.addKey", json!({"layer": id.0, "path": "transform/opacity", "time": 2.0, "value": 0.0})).unwrap();
    s.execute("prop.select", json!({"layer": id.0, "prop": uid})).unwrap();
    s.execute("keys.selectAll", json!({})).unwrap();
    s.execute("keys.easyEase", json!({})).unwrap();
    h.state_mut().ui.timeline.graph_editor = true;
    h.run_steps(4);
    // (in, out) influence of each key.
    let influences = |h: &Harness<'_, EffectcraftApp>| -> Vec<(f64, f64)> {
        let l = h.state().session.active_comp().unwrap().layer(id).unwrap().clone();
        let keys = l.props.prop("transform/opacity").unwrap().keys.clone();
        keys.iter().map(|k| (k.in_ease.first().map_or(0.0, |e| e.influence), k.out_ease.first().map_or(0.0, |e| e.influence))).collect()
    };
    let before = influences(&h);
    let handle = |h: &Harness<'_, EffectcraftApp>, key: usize| {
        let e = h.state().auto.find(&format!("timeline.graph.handle.{uid}.0.{key}.out")).unwrap_or_else(|| panic!("no handle {key}")).clone();
        pos2(e.rect[0] + e.rect[2] / 2.0, e.rect[1] + e.rect[3] / 2.0)
    };
    let px_per_s = {
        let at = |i: usize| h.state().auto.find(&format!("timeline.graph.key.{uid}.0.{i}")).unwrap().rect[0];
        at(1) - at(0)
    };
    let (k0, k1) = (handle(&h, 0), handle(&h, 1));
    let undo = h.state().session.history.undo.len();
    // Key 1's out handle 0.2 s further out (the keys are 1 s apart): key 0's goes along.
    drag(&mut h, k1, k1 + egui::vec2(px_per_s * 0.2, 0.0), Default::default());
    let after = influences(&h);
    for i in [0, 1] {
        assert!((after[i].1 - before[i].1 - 0.2).abs() < 0.01, "key {i}: {:?} → {:?}", before[i], after[i]);
    }
    assert_eq!((after[1].0, after[2].0), (before[1].0, before[2].0), "the in handles stay");
    assert_eq!(h.state().session.history.undo.len(), undo + 1, "one undo step");
    assert!((handle(&h, 0).x - k0.x - px_per_s * 0.2).abs() < 2.0, "key 0's handle moved on screen");
}

/// #457: on a Timeline narrower than the Graph Editor's whole button row, the buttons that don't
/// fit go to a "»" menu at the end of the bar instead of being cut off; each stays reachable and
/// works from there.
#[test]
fn graph_editor_buttons_that_do_not_fit_move_to_the_more_menu() {
    let (mut h, _, _) = harness();
    h.set_size(egui::vec2(1280.0, 800.0));
    h.state_mut().ui.timeline.graph_editor = true;
    h.run_steps(4);
    let ids = [
        "autoSelectGraphType",
        "valueGraph",
        "speedGraph",
        "showSelected",
        "autoZoom",
        "fit",
        "fitSelection",
        "snap",
        "reference",
        "transformBox",
        "separateDimensions",
        "interpolationHold",
        "interpolationLinear",
        "interpolationAuto",
        "easyEaseEasy",
        "easyEaseInEase",
        "easyEaseOutEase",
    ];
    let graph = h.state().auto.find("timeline.graph").expect("the Graph Editor is shown").rect;
    let right = graph[0] + graph[2];
    let shown: Vec<&str> = ids.iter().copied().filter(|id| h.state().auto.find(&format!("timeline.graph.{id}")).is_some()).collect();
    for id in &shown {
        let r = h.state().auto.find(&format!("timeline.graph.{id}")).unwrap().rect;
        assert!(r[0] + r[2] <= right, "{id} is drawn past the bar's right edge");
    }
    let more = h.state().auto.find("timeline.graph.more").expect("the buttons that don't fit are in a menu").rect;
    assert!(more[0] + more[2] <= right);
    let p = pos2(more[0] + more[2] / 2.0, more[1] + more[3] / 2.0);
    let click = |h: &mut Harness<'_, EffectcraftApp>, p: Pos2| {
        h.input_mut().events.push(Event::PointerMoved(p));
        h.input_mut().events.push(Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed: true, modifiers: Default::default() });
        h.step();
        h.input_mut().events.push(Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed: false, modifiers: Default::default() });
        h.run_steps(3);
    };
    click(&mut h, p);
    let hidden: Vec<&str> = ids.iter().copied().filter(|id| h.state().auto.find(&format!("timeline.graph.more.{id}")).is_some()).collect();
    assert_eq!(shown.len() + hidden.len(), ids.len(), "every button is on the bar or in the menu: {shown:?} + {hidden:?}");
    assert!(hidden.contains(&"transformBox"), "{hidden:?}");
    let before = h.state().ui.timeline.graph_transform_box;
    let item = h.state().auto.find("timeline.graph.more.transformBox").unwrap().rect;
    click(&mut h, pos2(item[0] + item[2] / 2.0, item[1] + item[3] / 2.0));
    assert_eq!(h.state().ui.timeline.graph_transform_box, !before, "the menu item runs the button");
}

/// #355, #491: with three layers selected the Properties panel heads "(3) Selected Objects"; its
/// stopwatch animates Position on all three (one undo step) and scrubbing X moves all three by
/// the same amount.
#[test]
fn properties_panel_edits_every_selected_layer() {
    let mut s = Session::default();
    s.execute("comp.new", json!({"name": "Three", "width": 320, "height": 180, "frameRate": 30, "duration": 4})).unwrap();
    let mut ids = vec![];
    for (i, c) in ["#e04020", "#20e040", "#2040e0"].iter().enumerate() {
        let l = s.execute("layer.newSolid", json!({"color": c, "width": 40, "height": 40})).unwrap()["layer"].as_u64().unwrap();
        s.execute("prop.set", json!({"layer": l, "path": "transform/position", "value": [60.0 + 80.0 * i as f64, 90.0]})).unwrap();
        ids.push(l);
    }
    s.execute("layer.select", json!({"layers": ids})).unwrap();
    let first = s.state.selected_layers[0];
    let uid = s.active_comp().unwrap().layer(first).unwrap().props.prop("transform/position").unwrap().uid;
    let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).build_eframe(|_| EffectcraftApp::new(s));
    h.state_mut().show_panel(effectcraft_ui_egui::dock::PanelKind::Properties);
    h.run_steps(4);
    assert_eq!(h.state().auto.find("properties.selectedObjects").map(|e| e.label.clone()), Some("(3) Selected Objects".into()));
    let pos = |h: &Harness<'_, EffectcraftApp>, l: u64| {
        h.state().session.active_comp().unwrap().layer(LayerId(l)).unwrap().props.prop("transform/position").unwrap().clone()
    };
    let at = |h: &Harness<'_, EffectcraftApp>, id: &str| {
        let e = h.state().auto.find(id).unwrap_or_else(|| panic!("no {id}"));
        pos2(e.rect[0] + e.rect[2] / 2.0, e.rect[1] + e.rect[3] / 2.0)
    };
    let sw = at(&h, &format!("properties.prop.{uid}.stopwatch"));
    h.input_mut().events.push(Event::PointerMoved(sw));
    h.step();
    h.input_mut().events.push(Event::PointerButton { pos: sw, button: egui::PointerButton::Primary, pressed: true, modifiers: Default::default() });
    h.step();
    h.input_mut().events.push(Event::PointerButton { pos: sw, button: egui::PointerButton::Primary, pressed: false, modifiers: Default::default() });
    h.run_steps(3);
    assert!(ids.iter().all(|l| pos(&h, *l).is_animated()), "every selected layer's stopwatch");
    h.state_mut().session.execute("edit.undo", json!({})).unwrap();
    h.run_steps(2);
    assert!(ids.iter().all(|l| !pos(&h, *l).is_animated()), "one undo step");
    // Scrub X: each layer moves by the same amount.
    let before: Vec<f64> = ids.iter().map(|l| pos(&h, *l).value.components()[0]).collect();
    let x = at(&h, &format!("properties.prop.{uid}.value.0"));
    drag(&mut h, x, x + egui::vec2(30.0, 0.0), Default::default());
    let after: Vec<f64> = ids.iter().map(|l| pos(&h, *l).value.components()[0]).collect();
    let d = after[0] - before[0];
    assert!(d.abs() > 1.0, "the scrub moved X: {before:?} → {after:?}");
    for (a, b) in after.iter().zip(&before) {
        assert!((a - b - d).abs() < 1e-6, "same change on every layer: {before:?} → {after:?}");
    }
}

/// #770: Proportional Scrubbing (After Effects 26.2). With three layers selected, a Ctrl+Alt
/// (Cmd+Opt) scrub of Position X in the Timeline leaves the first selected layer where it is,
/// moves the last by the whole change and the middle one by half, whichever layer is scrubbed.
#[test]
fn ctrl_alt_scrub_in_the_timeline_is_proportional() {
    let mut s = Session::default();
    s.execute("comp.new", json!({"name": "Three", "width": 320, "height": 180, "frameRate": 30, "duration": 4})).unwrap();
    let mut ids = vec![];
    for c in ["#e04020", "#20e040", "#2040e0"] {
        let l = s.execute("layer.newSolid", json!({"color": c, "width": 40, "height": 40})).unwrap()["layer"].as_u64().unwrap();
        s.execute("prop.set", json!({"layer": l, "path": "transform/position", "value": [100.0, 90.0]})).unwrap();
        ids.push(l);
    }
    // Selection order: the first created, then the second, then the third.
    for (i, l) in ids.iter().enumerate() {
        s.execute("layer.select", json!({"layers": [l], "add": i > 0})).unwrap();
    }
    let middle = ids[1];
    let uid = s.active_comp().unwrap().layer(LayerId(middle)).unwrap().props.prop("transform/position").unwrap().uid;
    let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).build_eframe(|_| EffectcraftApp::new(s));
    h.run_steps(3);
    let ctx = h.ctx.clone();
    effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "timeline.reveal.position", json!({})).unwrap();
    h.run_steps(4);
    let x = |h: &Harness<'_, EffectcraftApp>, l: u64| {
        h.state().session.active_comp().unwrap().layer(LayerId(l)).unwrap().props.prop("transform/position").unwrap().value.components()[0]
    };
    let e = h.state().auto.find(&format!("timeline.prop.{uid}.value.0")).cloned().expect("the middle layer's Position X shows");
    let from = pos2(e.rect[0] + e.rect[2] / 2.0, e.rect[1] + e.rect[3] / 2.0);
    let ctrl_alt = egui::Modifiers { alt: true, ctrl: true, command: true, ..Default::default() };
    drag(&mut h, from, from + egui::vec2(40.0, 0.0), ctrl_alt);
    let moved: Vec<f64> = ids.iter().map(|l| x(&h, *l) - 100.0).collect();
    assert!(moved[2] > 1.0, "the last selected layer moved: {moved:?}");
    assert!(moved[0].abs() < 1e-9, "the first selected layer stays: {moved:?}");
    assert!((moved[1] - moved[2] / 2.0).abs() < 1e-6, "the middle one moves by half: {moved:?}");
}