Bind each bar to its output palette and finish the island chrome

One layer-shell window per Hyprland output now loads that output's
bread-theme palette. Notifications, history, and OSD follow the
monitor they appear on. Pin bread-theme to v0.7.4.

src/bar/clock.rs

@@ -1,11 +1,21 @@
 use crate::{App, AppInput};
 use relm4::ComponentSender;
 
+pub fn now() -> gtk4::glib::DateTime {
+    gtk4::glib::DateTime::now_local().expect("local time")
+}
+
+pub fn time() -> String {
+    let dt = now();
+    format!("{:02}:{:02}", dt.hour(), dt.minute())
+}
+
+pub fn date() -> String {
+    now().format("%a %d/%m").expect("date format").to_string()
+}
+
 pub fn current() -> String {
-    let dt = gtk4::glib::DateTime::now_local().expect("local time");
-    let date = dt.format("%a %d/%m").expect("date format");
-    let time = format!("{:02}:{:02}", dt.hour(), dt.minute());
-    format!("{} {}", date, time)
+    format!("{}  {}", date(), time())
 }
 
 pub fn spawn_ticker(sender: ComponentSender<App>) {

src/bar/control.rs

@@ -121,6 +121,7 @@ pub fn spawn_set_brightness(v: f64) {
     });
 }
 
+#[allow(dead_code)]
 pub fn spawn_set_sink(name: String) {
     relm4::spawn(async move {
         let _ = tokio::process::Command::new("pactl")

src/bar/stats.rs

@@ -25,6 +25,14 @@ pub const WIFI_MEDIUM: &str = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "
 pub const WIFI_WEAK: &str = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/assets/WiFi Weak.svg"));
 pub const WIFI_OFF: &str = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/assets/WiFi Disconnect.svg"));
 
+/// Adwaita symbolic names — these are drawn for 16px status bars, not our
+/// hand-cropped Lucide arcs.
+pub const WIFI_ICON_EXCELLENT: &str = "network-wireless-signal-excellent-symbolic";
+pub const WIFI_ICON_GOOD: &str = "network-wireless-signal-good-symbolic";
+pub const WIFI_ICON_OK: &str = "network-wireless-signal-ok-symbolic";
+pub const WIFI_ICON_WEAK: &str = "network-wireless-signal-weak-symbolic";
+pub const WIFI_ICON_OFF: &str = "network-wireless-offline-symbolic";
+
 pub const BAT_HIGH: &str = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/assets/Battery 3 Bars.svg"));
 pub const BAT_MID: &str = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/assets/Battery 2 Bars.svg"));
 pub const BAT_LOW: &str = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/assets/Battery 1 Bar.svg"));
@@ -65,6 +73,7 @@ pub struct Stats {
     pub gpu_temp: Option<f32>,
     pub net_rx_kbs: f32,
     pub net_tx_kbs: f32,
+    pub volume_pct: u8,
 }
 
 struct CpuSnapshot {
@@ -76,7 +85,7 @@ static PREV_CPU: OnceLock<Mutex<CpuSnapshot>> = OnceLock::new();
 static BAT_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
 static AC_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
 static WIFI_CACHE: LazyLock<Mutex<(String, &'static str)>> =
-    LazyLock::new(|| Mutex::new(("—".to_string(), WIFI_OFF)));
+    LazyLock::new(|| Mutex::new(("—".to_string(), WIFI_ICON_OFF)));
 static WIFI_TICK: AtomicU8 = AtomicU8::new(0);
 
 fn read_cpu() -> f32 {
@@ -271,7 +280,7 @@ fn wifi_iface() -> Option<&'static str> {
 
 async fn read_wifi() -> (String, &'static str) {
     let Some(iface) = wifi_iface() else {
-        return ("—".into(), WIFI_OFF);
+        return ("—".into(), WIFI_ICON_OFF);
     };
 
     let link_out = tokio::process::Command::new("iw")
@@ -281,7 +290,7 @@ async fn read_wifi() -> (String, &'static str) {
         .ok();
     let link_stdout = match link_out {
         Some(o) if o.status.success() => String::from_utf8_lossy(&o.stdout).into_owned(),
-        _ => return ("—".into(), WIFI_OFF),
+        _ => return ("—".into(), WIFI_ICON_OFF),
     };
 
     let mut ssid = None;
@@ -296,13 +305,14 @@ async fn read_wifi() -> (String, &'static str) {
     }
 
     let Some(ssid) = ssid else {
-        return ("—".into(), WIFI_OFF);
+        return ("—".into(), WIFI_ICON_OFF);
     };
 
     let icon = match rssi {
-        Some(r) if r >= -55 => WIFI_STRONG,
-        Some(r) if r >= -70 => WIFI_MEDIUM,
-        _ => WIFI_WEAK,
+        Some(r) if r >= -55 => WIFI_ICON_EXCELLENT,
+        Some(r) if r >= -70 => WIFI_ICON_GOOD,
+        Some(r) if r >= -80 => WIFI_ICON_OK,
+        _ => WIFI_ICON_WEAK,
     };
 
     (ssid, icon)
@@ -413,7 +423,8 @@ pub async fn poll() -> Stats {
     let power_watts = read_power();
     let power = power_watts.map_or_else(|| "—W".into(), |w| format!("{w:.1}W"));
     let pct = read_battery();
-    let bat = pct.map_or_else(|| "—".into(), |p| format!("{p}%"));
+    // Demo bar prints the bare number ("83"), not "83%".
+    let bat = pct.map_or_else(|| "—".into(), |p| format!("{p}"));
     let bat_icon = pct.map_or(BAT_MID, bat_level_icon);
     let ac_connected = read_ac();
     // BT and WiFi both refresh every 8 cycles (~16 s); cache in between.
@@ -442,6 +453,7 @@ pub async fn poll() -> Stats {
     let gpu_usage = read_gpu_usage();
     let gpu_temp = read_gpu_temp();
     let (net_rx_kbs, net_tx_kbs) = read_net_throughput();
+    let volume_pct = read_volume_pct();
     Stats {
         cpu: format!("{cpu:.0}%"),
         cpu_pct: cpu,
@@ -465,9 +477,30 @@ pub async fn poll() -> Stats {
         gpu_temp,
         net_rx_kbs,
         net_tx_kbs,
+        volume_pct,
     }
 }
 
+/// `wpctl get-volume` prints `Volume: 0.44 [MUTED]`. Scale to a 0–150 percent
+/// for the bar chip. Missing pipewire / wpctl degrades to 0 rather than
+/// blocking the rest of the poll.
+fn read_volume_pct() -> u8 {
+    let out = std::process::Command::new("wpctl")
+        .args(["get-volume", "@DEFAULT_AUDIO_SINK@"])
+        .output()
+        .ok();
+    let Some(o) = out.filter(|o| o.status.success()) else {
+        return 0;
+    };
+    String::from_utf8_lossy(&o.stdout)
+        .trim()
+        .strip_prefix("Volume:")
+        .and_then(|s| s.split_whitespace().next())
+        .and_then(|s| s.parse::<f64>().ok())
+        .map(|v| (v * 100.0).round().clamp(0.0, 150.0) as u8)
+        .unwrap_or(0)
+}
+
 pub fn spawn_poller(sender: ComponentSender<App>) {
     relm4::spawn(async move {
         loop {

src/bar/wifi.rs

@@ -24,6 +24,8 @@ pub struct ScanEntry {
 pub struct WifiPopoverData {
     pub profiles: Vec<(String, bool)>, // (name, is_active)
     pub scan: Vec<ScanEntry>,
+    /// False while nmcli is still listing APs — profiles must still be usable.
+    pub scan_ready: bool,
 }
 
 async fn fetch_status() -> Option<CrumbsStatus> {
@@ -73,31 +75,57 @@ async fn fetch_profile_list() -> Vec<(String, bool)> {
         .collect()
 }
 
+async fn saved_ssids() -> std::collections::HashSet<String> {
+    let out = tokio::process::Command::new("nmcli")
+        .args(["-t", "-f", "NAME,TYPE", "connection", "show"])
+        .output()
+        .await;
+    let Ok(o) = out else {
+        return std::collections::HashSet::new();
+    };
+    String::from_utf8_lossy(&o.stdout)
+        .lines()
+        .filter_map(|line| {
+            let (name, ty) = line.rsplit_once(':')?;
+            if ty == "802-11-wireless" || ty == "wifi" {
+                Some(name.to_string())
+            } else {
+                None
+            }
+        })
+        .collect()
+}
+
+/// Cached AP list (no rescan). Fast enough to paint next to profiles.
 async fn fetch_scan() -> Vec<ScanEntry> {
-    let Ok(Ok(out)) = tokio::time::timeout(
-        Duration::from_secs(10),
-        tokio::process::Command::new("breadcrumbs")
-            .args(["scan-list", "--json"])
+    let out = tokio::time::timeout(
+        Duration::from_secs(4),
+        tokio::process::Command::new("nmcli")
+            .args(["-t", "-f", "SSID,SIGNAL,IN-USE", "device", "wifi", "list"])
             .output(),
     )
-    .await
-    else {
+    .await;
+    let Ok(Ok(o)) = out else {
         return vec![];
     };
-    let arr: Vec<serde_json::Value> =
-        serde_json::from_slice(&out.stdout).unwrap_or_default();
-    arr.into_iter()
-        .filter_map(|v| {
-            let ssid = v["ssid"].as_str()?.to_string();
-            if ssid.is_empty() {
+    let saved = saved_ssids().await;
+    let mut seen = std::collections::HashSet::new();
+    String::from_utf8_lossy(&o.stdout)
+        .lines()
+        .filter_map(|line| {
+            let mut parts = line.rsplitn(3, ':');
+            let _in_use = parts.next()?;
+            let signal = parts.next()?.parse::<u8>().ok().unwrap_or(0);
+            let ssid = parts.next()?.replace("\\:", ":");
+            if ssid.is_empty() || ssid == "--" || !seen.insert(ssid.clone()) {
                 return None;
             }
-            let signal = v["signal"]
-                .as_str()
-                .and_then(|s| s.parse::<u8>().ok())
-                .unwrap_or(0);
-            let saved = v["saved"].as_bool().unwrap_or(false);
-            Some(ScanEntry { ssid, signal, saved })
+            let saved = saved.contains(&ssid);
+            Some(ScanEntry {
+                ssid,
+                signal,
+                saved,
+            })
         })
         .collect()
 }
@@ -114,11 +142,32 @@ pub fn spawn_status_poller(sender: ComponentSender<App>) {
     });
 }
 
-/// Called when the popover opens — loads profiles + scan in parallel.
+/// Profiles first (so you can switch Home/Away immediately), then the
+/// cached AP list. A background rescan refreshes the list if it finds more.
 pub fn spawn_popover_load(sender: ComponentSender<App>) {
     relm4::spawn(async move {
-        let (profiles, scan) = tokio::join!(fetch_profile_list(), fetch_scan());
-        sender.input(AppInput::WifiPopoverData(WifiPopoverData { profiles, scan }));
+        let profiles = fetch_profile_list().await;
+        sender.input(AppInput::WifiPopoverData(WifiPopoverData {
+            profiles: profiles.clone(),
+            scan: vec![],
+            scan_ready: false,
+        }));
+        let scan = fetch_scan().await;
+        sender.input(AppInput::WifiPopoverData(WifiPopoverData {
+            profiles: profiles.clone(),
+            scan: scan.clone(),
+            scan_ready: true,
+        }));
+        let _ = tokio::process::Command::new("nmcli")
+            .args(["device", "wifi", "rescan"])
+            .output()
+            .await;
+        let scan = fetch_scan().await;
+        sender.input(AppInput::WifiPopoverData(WifiPopoverData {
+            profiles,
+            scan,
+            scan_ready: true,
+        }));
     });
 }
 
@@ -132,29 +181,27 @@ pub fn spawn_profile_set(name: String) {
     });
 }
 
-/// Fire-and-forget: connect to a specific saved SSID via `breadcrumbs join`.
+/// Fire-and-forget: connect to a known SSID via NetworkManager.
 pub fn spawn_join(ssid: String) {
     relm4::spawn(async move {
-        let _ = tokio::process::Command::new("breadcrumbs")
-            .args(["join", &ssid])
+        let _ = tokio::process::Command::new("nmcli")
+            .args(["device", "wifi", "connect", &ssid])
             .output()
             .await;
     });
 }
 
-/// Fire-and-forget: save a new network with its password, then join it.
+/// Save in breadcrumbs (if the CLI still accepts `add`) and connect with nmcli.
 pub fn spawn_add_and_join(ssid: String, password: String) {
     relm4::spawn(async move {
-        let added = tokio::process::Command::new("breadcrumbs")
+        let _ = tokio::process::Command::new("breadcrumbs")
             .args(["add", &ssid, &password])
             .output()
             .await;
-        if matches!(added, Ok(o) if o.status.success()) {
-            let _ = tokio::process::Command::new("breadcrumbs")
-                .args(["join", &ssid])
-                .output()
-                .await;
-        }
+        let _ = tokio::process::Command::new("nmcli")
+            .args(["device", "wifi", "connect", &ssid, "password", &password])
+            .output()
+            .await;
     });
 }
 

src/bar/workspaces.rs

@@ -1,7 +1,12 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::time::Instant;
+
 use futures_lite::StreamExt;
+use gtk4::glib::ControlFlow;
 use gtk4::prelude::*;
 use hyprland::{
-    data::{Workspace, Workspaces},
+    data::{Monitors, Workspaces},
     event_listener::{Event, EventStream},
     prelude::*,
     shared::WorkspaceId,
@@ -10,16 +15,62 @@ use relm4::ComponentSender;
 
 use crate::AppInput;
 
-/// Fetches the current workspace list + active workspace and pushes both to
-/// the app — used both for the initial state and to re-sync after the event
-/// stream reconnects (state may have changed while we were disconnected).
+/// Stock Hyprland accepts `hyprctl dispatch workspace N`. Lua-config
+/// Hyprland (BOS) rewrites that as `hl.dispatch(workspace N)`, which is
+/// a syntax error — the working form is `hl.dsp.focus({workspace=N})`.
+async fn switch_workspace(id: hyprland::shared::WorkspaceId) {
+    let arg = id.to_string();
+    let stock = tokio::process::Command::new("hyprctl")
+        .args(["dispatch", "workspace", &arg])
+        .output()
+        .await;
+    if let Ok(o) = &stock {
+        let err = String::from_utf8_lossy(&o.stderr);
+        let out = String::from_utf8_lossy(&o.stdout);
+        if o.status.success() && !err.contains("hl.dispatch") && !out.contains("hl.dispatch") {
+            return;
+        }
+    }
+    let expr = format!("hl.dispatch(hl.dsp.focus({{workspace={arg}}}))");
+    let lua = tokio::process::Command::new("hyprctl")
+        .args(["eval", &expr])
+        .output()
+        .await;
+    match lua {
+        Ok(o) if o.status.success() => {}
+        Ok(o) => eprintln!(
+            "breadbar: workspace {arg}: {}",
+            String::from_utf8_lossy(&o.stderr)
+        ),
+        Err(e) => eprintln!("breadbar: workspace {arg}: {e}"),
+    }
+}
+
+/// Stretch to the old→new span, then snap onto the destination — CSS
+/// transitions cannot widen a pill across two buttons, so the trail's
+/// Fixed allocation is interpolated on the frame clock instead.
+const STRETCH_MS: f64 = 220.0;
+const SNAP_MS: f64 = 380.0;
+
+/// Full workspace + per-monitor active snapshot. Each bar filters this to
+/// its own output so a second display does not inherit the laptop's set.
 async fn sync_state(sender: &ComponentSender<crate::App>) {
-    if let Ok(ws) = Workspaces::get_async().await {
-        sender.input(AppInput::WorkspaceList(ws.to_vec()));
-    }
-    if let Ok(active) = Workspace::get_active_async().await {
-        sender.input(AppInput::ActiveWorkspace(active.id));
+    let workspaces = Workspaces::get_async()
+        .await
+        .map(|w| w.to_vec())
+        .unwrap_or_default();
+    let mut actives = std::collections::HashMap::new();
+    if let Ok(mons) = Monitors::get_async().await {
+        for m in mons {
+            if !m.disabled {
+                actives.insert(m.name, m.active_workspace.id);
+            }
+        }
     }
+    sender.input(AppInput::WorkspaceSync {
+        workspaces,
+        actives,
+    });
 }
 
 pub fn spawn_watcher(sender: ComponentSender<crate::App>) {
@@ -41,13 +92,21 @@ pub fn spawn_watcher(sender: ComponentSender<crate::App>) {
             while let Some(Ok(event)) = stream.next().await {
                 backoff = std::time::Duration::from_millis(500);
                 match event {
-                    Event::WorkspaceChanged(data) => {
-                        sender.input(AppInput::ActiveWorkspace(data.id));
+                    Event::WorkspaceChanged(_)
+                    | Event::WorkspaceAdded(_)
+                    | Event::WorkspaceDeleted(_) => {
+                        sync_state(&sender).await;
                     }
-                    Event::WorkspaceAdded(_) | Event::WorkspaceDeleted(_) => {
-                        if let Ok(ws) = Workspaces::get_async().await {
-                            sender.input(AppInput::WorkspaceList(ws.to_vec()));
-                        }
+                    Event::MonitorAdded(data) => {
+                        sender.input(AppInput::MonitorAdded(data.name));
+                        sync_state(&sender).await;
+                    }
+                    Event::MonitorRemoved(name) => {
+                        sender.input(AppInput::MonitorRemoved(name));
+                        sync_state(&sender).await;
+                    }
+                    Event::ActiveWindowChanged(_) => {
+                        sender.input(AppInput::DismissPanels);
                     }
                     _ => {}
                 }
@@ -65,17 +124,233 @@ pub fn spawn_watcher(sender: ComponentSender<crate::App>) {
     });
 }
 
-pub fn make_button(id: WorkspaceId, name: &str, active: WorkspaceId) -> gtk4::Button {
+pub fn make_button(
+    id: WorkspaceId,
+    name: &str,
+    active: WorkspaceId,
+    occupied: bool,
+) -> gtk4::Button {
     let btn = gtk4::Button::with_label(name);
     btn.add_css_class("workspace-btn");
+    if occupied {
+        btn.add_css_class("occupied");
+    }
     if id == active {
         btn.add_css_class("active");
     }
+    btn.set_valign(gtk4::Align::Center);
+    btn.set_vexpand(false);
+    btn.set_size_request(-1, crate::CHIP_HEIGHT);
     btn.connect_clicked(move |_| {
-        use hyprland::dispatch::{Dispatch, DispatchType, WorkspaceIdentifierWithSpecial};
-        let _ = Dispatch::call(DispatchType::Workspace(WorkspaceIdentifierWithSpecial::Id(
-            id,
-        )));
+        relm4::spawn(async move {
+            switch_workspace(id).await;
+        });
     });
     btn
 }
+
+#[derive(Clone, Copy)]
+struct Geom {
+    x: f64,
+    y: f64,
+    w: f64,
+    h: f64,
+}
+
+struct TrailInner {
+    tick: Option<gtk4::TickCallbackId>,
+    geom: Geom,
+}
+
+/// Overlay + Fixed pill sitting *behind* the workspace buttons. The
+/// Overlay's measured size comes from the button row; the pill is the
+/// main child so it paints underneath and never steals clicks.
+pub struct WorkspaceTrail {
+    pub overlay: gtk4::Overlay,
+    pub buttons: gtk4::Box,
+    host: gtk4::Fixed,
+    pill: gtk4::Box,
+    inner: Rc<RefCell<TrailInner>>,
+}
+
+impl WorkspaceTrail {
+    pub fn new() -> Self {
+        let overlay = gtk4::Overlay::new();
+        overlay.add_css_class("workspace-overlay");
+        overlay.set_valign(gtk4::Align::Center);
+        overlay.set_vexpand(false);
+
+        let host = gtk4::Fixed::new();
+        host.set_can_target(false);
+
+        let pill = gtk4::Box::new(gtk4::Orientation::Horizontal, 0);
+        pill.add_css_class("workspace-trail");
+        pill.set_can_target(false);
+        pill.set_visible(false);
+        host.put(&pill, 0.0, 0.0);
+
+        let buttons = gtk4::Box::new(gtk4::Orientation::Horizontal, 2);
+        buttons.set_halign(gtk4::Align::Fill);
+        buttons.set_valign(gtk4::Align::Center);
+        buttons.set_vexpand(false);
+
+        overlay.set_child(Some(&host));
+        overlay.add_overlay(&buttons);
+        overlay.set_measure_overlay(&buttons, true);
+
+        let inner = Rc::new(RefCell::new(TrailInner {
+            tick: None,
+            geom: Geom {
+                x: 0.0,
+                y: 0.0,
+                w: 0.0,
+                h: 0.0,
+            },
+        }));
+
+        Self {
+            overlay,
+            buttons,
+            host,
+            pill,
+            inner,
+        }
+    }
+
+    pub fn cancel(&self) {
+        if let Some(id) = self.inner.borrow_mut().tick.take() {
+            id.remove();
+        }
+    }
+
+    pub fn clear(&self) {
+        self.cancel();
+        self.pill.set_visible(false);
+        self.inner.borrow_mut().geom.w = 0.0;
+    }
+
+    pub fn place(&self, btn: &gtk4::Button) {
+        self.cancel();
+        if let Some(g) = button_geom(btn, &self.overlay) {
+            self.apply(&g);
+            return;
+        }
+        // First map: the button exists but has no allocation yet.
+        let pill = self.pill.clone();
+        let host = self.host.clone();
+        let btn = btn.clone();
+        let inner = self.inner.clone();
+        let id = self.overlay.add_tick_callback(move |ov, _| {
+            let Some(g) = button_geom(&btn, ov) else {
+                return ControlFlow::Continue;
+            };
+            apply_geom(&host, &pill, &inner, &g);
+            inner.borrow_mut().tick = None;
+            ControlFlow::Break
+        });
+        self.inner.borrow_mut().tick = Some(id);
+    }
+
+    pub fn stretch(&self, from: Option<&gtk4::Button>, to: &gtk4::Button) {
+        let from_g = self.from_geom(from);
+        if let Some(to_g) = button_geom(to, &self.overlay) {
+            self.stretch_geom(from_g, to_g);
+            return;
+        }
+        // Destination just appeared (empty workspace becoming active) and
+        // has no allocation yet. Wait one layout pass, then stretch from
+        // the last pill — don't snap via place().
+        self.cancel();
+        let overlay = self.overlay.clone();
+        let pill = self.pill.clone();
+        let host = self.host.clone();
+        let inner = self.inner.clone();
+        let btn = to.clone();
+        let id = self.overlay.add_tick_callback(move |ov, _| {
+            let Some(to_g) = button_geom(&btn, ov) else {
+                return ControlFlow::Continue;
+            };
+            inner.borrow_mut().tick = None;
+            stretch_geom_on(&overlay, &host, &pill, &inner, from_g, to_g);
+            ControlFlow::Break
+        });
+        self.inner.borrow_mut().tick = Some(id);
+    }
+
+    fn from_geom(&self, from: Option<&gtk4::Button>) -> Option<Geom> {
+        let st = self.inner.borrow();
+        if self.pill.is_visible() && st.geom.w > 0.5 {
+            return Some(st.geom);
+        }
+        drop(st);
+        from.and_then(|b| button_geom(b, &self.overlay))
+    }
+
+    fn stretch_geom(&self, from_g: Option<Geom>, to_g: Geom) {
+        stretch_geom_on(
+            &self.overlay,
+            &self.host,
+            &self.pill,
+            &self.inner,
+            from_g,
+            to_g,
+        );
+    }
+
+    fn apply(&self, g: &Geom) {
+        apply_geom(&self.host, &self.pill, &self.inner, g);
+    }
+}
+
+fn button_geom(btn: &gtk4::Button, overlay: &gtk4::Overlay) -> Option<Geom> {
+    let r = btn.compute_bounds(overlay)?;
+    let w = f64::from(r.width());
+    let h = f64::from(r.height());
+    if w < 1.0 || h < 1.0 {
+        return None;
+    }
+    Some(Geom {
+        x: f64::from(r.x()),
+        y: f64::from(r.y()),
+        w,
+        h,
+    })
+}
+
+fn apply_geom(host: &gtk4::Fixed, pill: &gtk4::Box, inner: &Rc<RefCell<TrailInner>>, g: &Geom) {
+    inner.borrow_mut().geom = Geom {
+        x: g.x,
+        y: g.y,
+        w: g.w,
+        h: g.h,
+    };
+    pill.set_size_request(g.w.max(1.0).round() as i32, g.h.max(1.0).round() as i32);
+    host.move_(pill, g.x, g.y);
+    pill.set_visible(true);
+}
+
+fn lerp(a: f64, b: f64, t: f64) -> f64 {
+    a + (b - a) * t
+}
+
+fn lerp_geom(a: &Geom, b: &Geom, t: f64) -> Geom {
+    Geom {
+        x: lerp(a.x, b.x, t),
+        y: lerp(a.y, b.y, t),
+        w: lerp(a.w, b.w, t),
+        h: lerp(a.h, b.h, t),
+    }
+}
+
+fn ease(t: f64) -> f64 {
+    let t = t.clamp(0.0, 1.0);
+    t * t * (3.0 - 2.0 * t)
+}
+
+/// Approximates the demo's cubic-bezier(.22, 1.4, .36, 1) snap.
+fn ease_overshoot(t: f64) -> f64 {
+    let t = t.clamp(0.0, 1.0);
+    let c = 1.4;
+    let t1 = t - 1.0;
+    1.0 + t1 * t1 * ((c + 1.0) * t1 + c)
+}