comiit

Cargo.toml

@@ -5,7 +5,7 @@
 
 [workspace]
 resolver = "3"
-members = ["libsvld", "svldcli", "svldgui"]
+members = ["libsvld", "svldcli", "svldgui", "svldplotter"]
 
 [profile.release]
 lto = "fat"

libsvld/src/lib.rs

@@ -1,6 +1,6 @@
-mod asc;
+pub mod asc;
 pub mod can_frame;
-mod motec;
+pub mod motec;
 
 use std::{
     fs::File,
@@ -30,16 +30,11 @@ struct FrameOutput {
     error_frames: Vec<ErrorFrame>,
 }
 
-fn frame_worker(
-    mmap: &[u8],
-    dbc: &Dbc,
-) -> FrameOutput {
-    let mut channel_data = HashMap::<CanId, Vec<CanFrame>>::new();
-    let mut metadatas = HashMap::<CanId, MessageMetadata>::new();
-
-    let mut unknown_ids = HashSet::<CanId>::new();
-    let mut error_frames = Vec::<ErrorFrame>::new();
-
+/// Build the LD metadata for a single CAN id from the DBC, applying the
+/// project's `ld_*`/`Frequency` attribute defaults. Returns `None` when the
+/// id is not described by the DBC (an "unknown" id). Shared by the ASC decode
+/// path and the live-CAN path so both produce identical metadata.
+pub fn build_message_metadata(dbc: &Dbc, id: CanId) -> Option<MessageMetadata> {
     let get_default = |name: &str| match dbc
         .attribute_defaults
         .iter()
@@ -56,57 +51,66 @@ fn frame_worker(
     let default_scale = get_default("ld_scale");
     let default_decimal_places = get_default("ld_decimal_places");
 
-    let mut add_metadata = |id| {
-        let msg = match dbc.messages.iter().find(|x| x.id.raw() == id) {
-            Some(msg) => msg,
-            None => {
-                unknown_ids.insert(id);
-                return;
-            }
-        };
-        let signals = &msg.signals;
-        let mut signals_meta = Vec::<SignalMetadata>::new();
-        for signal in signals {
-            let decimal_places = dbc
-                .attribute_values_signal
-                .iter()
-                .find(|x| {
-                    x.message_id.raw() == id
-                        && x.signal_name == signal.name
-                        && x.name == "ld_decimal_places"
-                })
-                .map_or(default_decimal_places, |x| match x.value {
-                    can_dbc::AttributeValue::Uint(val) => val,
-                    _ => panic!("Bad ld_decimal_places value type, expected Uint."),
-                });
-
-            signals_meta.push(SignalMetadata {
-                shift: default_shift as u16,
-                scale: default_scale as u16,
-                decimal_places: decimal_places as u16,
-                name: signal.name.clone(),
-                unit: signal.unit.clone(),
-                signal: signal.clone(),
-            });
-        }
-
-        let frequency = dbc
-            .attribute_values_message
+    let msg = dbc.messages.iter().find(|x| x.id.raw() == id)?;
+    let signals = &msg.signals;
+    let mut signals_meta = Vec::<SignalMetadata>::new();
+    for signal in signals {
+        let decimal_places = dbc
+            .attribute_values_signal
             .iter()
-            .find(|x| x.message_id.raw() == id && x.name == "Frequency")
-            .map_or(default_freqency, |x| match x.value {
+            .find(|x| {
+                x.message_id.raw() == id
+                    && x.signal_name == signal.name
+                    && x.name == "ld_decimal_places"
+            })
+            .map_or(default_decimal_places, |x| match x.value {
                 can_dbc::AttributeValue::Uint(val) => val,
-                _ => panic!("Bad Frequency value type, expected Uint."),
+                _ => panic!("Bad ld_decimal_places value type, expected Uint."),
             });
 
-        metadatas.insert(
-            id,
-            MessageMetadata {
-                id,
-                frequency: frequency as u16,
-                signals: signals_meta,
-            },
-        );
+        signals_meta.push(SignalMetadata {
+            shift: default_shift as u16,
+            scale: default_scale as u16,
+            decimal_places: decimal_places as u16,
+            name: signal.name.clone(),
+            unit: signal.unit.clone(),
+            signal: signal.clone(),
+        });
+    }
+
+    let frequency = dbc
+        .attribute_values_message
+        .iter()
+        .find(|x| x.message_id.raw() == id && x.name == "Frequency")
+        .map_or(default_freqency, |x| match x.value {
+            can_dbc::AttributeValue::Uint(val) => val,
+            _ => panic!("Bad Frequency value type, expected Uint."),
+        });
+
+    Some(MessageMetadata {
+        id,
+        frequency: frequency as u16,
+        signals: signals_meta,
+    })
+}
+
+fn frame_worker(
+    mmap: &[u8],
+    dbc: &Dbc,
+) -> FrameOutput {
+    let mut channel_data = HashMap::<CanId, Vec<CanFrame>>::new();
+    let mut metadatas = HashMap::<CanId, MessageMetadata>::new();
+
+    let mut unknown_ids = HashSet::<CanId>::new();
+    let mut error_frames = Vec::<ErrorFrame>::new();
+
+    let mut add_metadata = |id| match build_message_metadata(dbc, id) {
+        Some(meta) => {
+            metadatas.insert(id, meta);
+        }
+        None => {
+            unknown_ids.insert(id);
+        }
     };
 
     // Caller has aligned the chunk to line boundaries, so we always start at
@@ -171,6 +175,51 @@ pub struct DecodeResult {
     pub info: DecodeProcessInfo,
 }
 
+impl DecodeResult {
+    /// An empty result suitable for incrementally accumulating live CAN
+    /// frames via [`DecodeResult::push_live`]. The `info` fields that only
+    /// make sense for the file-based decode are zeroed.
+    pub fn empty() -> Self {
+        DecodeResult {
+            data: HashMap::new(),
+            metadata: HashMap::new(),
+            info: DecodeProcessInfo {
+                unknown_ids: HashSet::new(),
+                error_frames: Vec::new(),
+                date: chrono::DateTime::from_timestamp(0, 0).unwrap().naive_utc(),
+                thread_count: 0,
+                page_size: 0,
+                pages_per_chunk: 0,
+                chunk_size: 0,
+            },
+        }
+    }
+
+    /// Append a single live frame, lazily resolving its metadata from the DBC
+    /// the first time an id is seen. Frames are expected to arrive in
+    /// non-decreasing timestamp order (as they do off a live bus), so no
+    /// re-sorting is performed — `compute_signal` consumes them in order.
+    pub fn push_live(&mut self, dbc: &Dbc, frame: CanFrame) {
+        match self.data.get_mut(&frame.can_id) {
+            Some(vec) => vec.push(frame),
+            None => {
+                let id = frame.can_id;
+                self.data.insert(id, vec![frame]);
+                if !self.metadata.contains_key(&id) {
+                    match build_message_metadata(dbc, id) {
+                        Some(meta) => {
+                            self.metadata.insert(id, meta);
+                        }
+                        None => {
+                            self.info.unknown_ids.insert(id);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
 pub fn decode(dbc: &Dbc,
               asc_path: &Path) -> DecodeResult {
     let thread_count = std::thread::available_parallelism().unwrap().get();
@@ -255,6 +304,11 @@ pub fn decode(dbc: &Dbc,
     // println!("{:?}", unknown_ids);
     // println!("{:?}", error_frames);
 
+    for (_, frames) in &mut data {
+        // frames.voracious_mt_sort(thread_count);
+        frames.voracious_sort();
+    }
+
     DecodeResult {
         data,
         metadata,
@@ -274,7 +328,7 @@ pub fn decode_to_motec(dbc: &Dbc,
                        asc_path: &Path,
                        output_dir: &Path) -> DecodeProcessInfo {
     let DecodeResult {
-        mut data,
+        data,
         metadata,
         info,
     } = decode(dbc, asc_path);
@@ -285,11 +339,6 @@ pub fn decode_to_motec(dbc: &Dbc,
         .and_utc()
         .to_rfc3339_opts(chrono::SecondsFormat::Secs, true);
 
-    for (_, frames) in &mut data {
-        // frames.voracious_mt_sort(thread_count);
-        frames.voracious_sort();
-    }
-
     let msgs: Vec<MessageMetadata> = metadata.values().cloned().collect();
 
     // println!("Messages: {}", msgs.len());

libsvld/src/motec.rs

@@ -97,7 +97,7 @@ pub fn get_metadata_total_count(
 /// `bytes_le`). Mirrors `calc_bits` + `calc_signed_bits` + factor/offset in
 /// _ref_lib/src/process.cc.
 #[inline]
-fn extract_signal(bytes_le: u64, sig: &Signal) -> f64 {
+pub fn extract_signal(bytes_le: u64, sig: &Signal) -> f64 {
     let size = sig.size;
     let shifted = match sig.byte_order {
         ByteOrder::BigEndian => bytes_le.swap_bytes() >> (64 - size - sig.start_bit),

svldplotter/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "svldplotter"
+version = "0.1.0"
+edition = "2024"
+
+[[bin]]
+name = "svldplotter"
+test = false
+bench = false
+
+[dependencies]
+libsvld = { path = "../libsvld" }
+can-dbc = "9.1"
+
+eframe = {
+       version = "0.34",
+       features = ["persistence"]
+}
+egui = "0.34"
+egui_plot = "0.35"
+egui_ltreeview = "0.7"
+fuzzy-matcher = "0.3"
+rfd = "0.17"
+socketcan = "3.6.1"

svldplotter/src/can_live.rs

@@ -0,0 +1,63 @@
+//! Live CAN bus source (Linux/SocketCAN).
+//!
+//! Opens a SocketCAN interface and spawns a background thread that reads CAN
+//! frames, converting each into the same `libsvld::can_frame::CanFrame` the
+//! ASC decoder produces. Frames are streamed back over an `mpsc` channel so
+//! the UI thread can drain them without blocking. Timestamps are seconds
+//! elapsed since the listener was opened, mirroring the relative timebase the
+//! ASC files use.
+
+use std::sync::mpsc::{channel, Receiver};
+use std::thread;
+use std::time::Instant;
+
+use libsvld::can_frame::{CanFrame, Direction};
+use socketcan::{CanFrame as ScFrame, EmbeddedFrame, Frame, Socket};
+
+/// Open `iface` (e.g. `"can0"`) and start streaming frames.
+///
+/// Returns a receiver that yields decoded [`CanFrame`]s until the interface
+/// errors out or the receiver is dropped. The reader runs on its own thread.
+pub fn spawn_reader(iface: &str) -> std::io::Result<Receiver<CanFrame>> {
+    let socket = socketcan::CanSocket::open(iface)?;
+    let (tx, rx) = channel::<CanFrame>();
+    let start = Instant::now();
+
+    thread::spawn(move || {
+        loop {
+            let frame = match socket.read_frame() {
+                Ok(frame) => frame,
+                // A read error (interface down, etc.) ends the stream.
+                Err(_) => break,
+            };
+
+            // Only data frames carry signal payloads; ignore remote/error
+            // frames for plotting purposes.
+            let data_frame = match frame {
+                ScFrame::Data(d) => d,
+                _ => continue,
+            };
+
+            let payload = data_frame.data();
+            let dlc = payload.len().min(8);
+            let mut data = [0u8; 8];
+            data[..dlc].copy_from_slice(&payload[..dlc]);
+
+            let cf = CanFrame {
+                timestamp: start.elapsed().as_secs_f64(),
+                channel: 0,
+                can_id: data_frame.raw_id(),
+                direction: Direction::Rx,
+                dlc: dlc as u8,
+                data,
+            };
+
+            // Receiver dropped → UI no longer interested, stop reading.
+            if tx.send(cf).is_err() {
+                break;
+            }
+        }
+    });
+
+    Ok(rx)
+}

svldplotter/src/main.rs

@@ -0,0 +1,477 @@
+mod can_live;
+mod plot;
+mod plot_list;
+mod signal;
+mod tree;
+
+use std::{
+    collections::HashMap,
+    fs,
+    path::PathBuf,
+    sync::{mpsc::{channel, Receiver}, Arc},
+    thread,
+};
+
+use can_dbc::Dbc;
+use eframe::egui;
+use libsvld::{can_frame::CanFrame, DecodeResult};
+
+use crate::plot::show_plot_panel;
+use crate::plot_list::{
+    add_signal_auto, apply_move, contains_signal, new_plot, remove_plot, remove_signal,
+    show_plot_list, PlotGroup, PlotListAction,
+};
+use crate::signal::{compute_delay_signal, compute_signal, resolve_signal};
+use crate::tree::{
+    build_tree, decode_signal_node_id, delay_node_id, show_dbc_tree, MsgNode, SignalAction,
+};
+
+fn main() {
+    let native_options = eframe::NativeOptions::default();
+    eframe::run_native(
+        "svldplotter",
+        native_options,
+        Box::new(|cc| {
+            let mut app = MyEguiApp::default();
+            // Optional CLI quick-load. Positional args are an optional DBC and
+            // ASC, intended for dev iteration:
+            //   svldplotter [DBC [ASC]]
+            // Passing `--can <iface>` (e.g. `svldplotter car.dbc --can can0`)
+            // switches to live mode: instead of reading an ASC file the
+            // plotter streams frames straight off the CAN bus and plots them
+            // in real time, using the DBC for signal metadata.
+            let args: Vec<String> = std::env::args().collect();
+            let mut positional: Vec<String> = Vec::new();
+            let mut can_iface: Option<String> = None;
+            let mut i = 1;
+            while i < args.len() {
+                match args[i].as_str() {
+                    "--can" | "-c" => {
+                        can_iface = args.get(i + 1).cloned();
+                        i += 2;
+                    }
+                    other => {
+                        positional.push(other.to_string());
+                        i += 1;
+                    }
+                }
+            }
+            if let Some(dbc) = positional.first() {
+                app.load_dbc(PathBuf::from(dbc));
+            }
+            if let Some(iface) = can_iface {
+                // Live CAN takes precedence over any ASC argument.
+                app.start_can_live(&iface, &cc.egui_ctx);
+            } else if let Some(asc) = positional.get(1) {
+                app.asc_paths.push(PathBuf::from(asc));
+                app.set_active_asc(app.asc_paths.len() - 1, Some(&cc.egui_ctx));
+            }
+            Ok(Box::new(app))
+        }),
+    )
+    .unwrap();
+}
+
+#[derive(Default, PartialEq, Eq)]
+enum LeftTab {
+    #[default]
+    Signals,
+    Files,
+}
+
+struct DecodeJob {
+    asc_index: usize,
+    asc_path: PathBuf,
+    receiver: Receiver<Arc<DecodeResult>>,
+}
+
+#[derive(Default)]
+struct MyEguiApp {
+    dbc: Option<Arc<Dbc>>,
+    dbc_path: Option<PathBuf>,
+    asc_paths: Vec<PathBuf>,
+    active_asc: Option<usize>,
+    data: Option<Arc<DecodeResult>>,
+    decode_cache: HashMap<PathBuf, Arc<DecodeResult>>,
+    pending: Option<DecodeJob>,
+    tree: Vec<MsgNode>,
+    filter: String,
+    plots: Vec<PlotGroup>,
+    next_plot_id: u64,
+    cursor_x: Option<f64>,
+    left_tab: LeftTab,
+    /// Live CAN stream receiver, present only in `--can` mode.
+    live_rx: Option<Receiver<CanFrame>>,
+    /// Growing decode result fed by the live CAN stream.
+    live_data: Option<DecodeResult>,
+    /// Latest data x-extent from the previous frame, used to detect whether
+    /// the live view is pinned to the right edge for auto-scroll.
+    live_prev_max: Option<f64>,
+}
+
+impl MyEguiApp {
+    fn load_dbc(&mut self, path: PathBuf) {
+        let Ok(text) = fs::read_to_string(&path) else {
+            return;
+        };
+        let Ok(dbc) = Dbc::try_from(text.as_str()) else {
+            return;
+        };
+        self.dbc = Some(Arc::new(dbc));
+        self.dbc_path = Some(path);
+        // DBC change invalidates the decode cache.
+        self.decode_cache.clear();
+        self.pending = None;
+        self.data = None;
+        self.tree.clear();
+        if let Some(idx) = self.active_asc {
+            self.start_or_use_cached(idx, None);
+        }
+    }
+
+    fn add_asc(&mut self, path: PathBuf) {
+        self.asc_paths.push(path);
+        if self.active_asc.is_none() {
+            self.set_active_asc(self.asc_paths.len() - 1, None);
+        }
+    }
+
+    /// Switch to a given ASC. Use the cached DecodeResult if present;
+    /// otherwise spawn a background decode and show progress via the
+    /// `pending` job.
+    fn set_active_asc(&mut self, idx: usize, ctx: Option<&egui::Context>) {
+        if idx >= self.asc_paths.len() {
+            return;
+        }
+        self.active_asc = Some(idx);
+        self.start_or_use_cached(idx, ctx);
+    }
+
+    fn start_or_use_cached(&mut self, idx: usize, ctx: Option<&egui::Context>) {
+        let Some(dbc) = self.dbc.clone() else {
+            return;
+        };
+        let path = self.asc_paths[idx].clone();
+        if self.decode_cache.contains_key(&path) {
+            self.activate_decoded(idx);
+            return;
+        }
+        let (tx, rx) = channel();
+        let dbc_for_thread = dbc;
+        let path_for_thread = path.clone();
+        let ctx_for_thread = ctx.cloned();
+        thread::spawn(move || {
+            let result = libsvld::decode(&dbc_for_thread, &path_for_thread);
+            let _ = tx.send(Arc::new(result));
+            if let Some(ctx) = ctx_for_thread {
+                ctx.request_repaint();
+            }
+        });
+        self.pending = Some(DecodeJob {
+            asc_index: idx,
+            asc_path: path,
+            receiver: rx,
+        });
+    }
+
+    /// Pull a finished decode out of `pending` and install it.
+    fn poll_pending(&mut self) {
+        let Some(job) = self.pending.as_ref() else {
+            return;
+        };
+        let Ok(result) = job.receiver.try_recv() else {
+            return;
+        };
+        let asc_index = job.asc_index;
+        let asc_path = job.asc_path.clone();
+        self.pending = None;
+        self.decode_cache.insert(asc_path, result);
+        if self.active_asc == Some(asc_index) {
+            self.activate_decoded(asc_index);
+        }
+    }
+
+    /// Point `self.data`/`self.tree` at the cached result for `idx` and
+    /// re-resolve every plotted signal against the new data.
+    fn activate_decoded(&mut self, idx: usize) {
+        let Some(dbc) = self.dbc.as_ref() else {
+            return;
+        };
+        let path = &self.asc_paths[idx];
+        let Some(data) = self.decode_cache.get(path).cloned() else {
+            return;
+        };
+        self.tree = build_tree(dbc, &data);
+        // Re-resolve plotted signals so existing plots survive an ASC switch.
+        for plot in &mut self.plots {
+            for sig in &mut plot.signals {
+                if let Some(new_sig) = resolve_signal(&data, sig.id) {
+                    *sig = new_sig;
+                }
+            }
+        }
+        self.data = Some(data);
+    }
+
+    /// Enter live CAN mode: open `iface` and start streaming frames into a
+    /// fresh, growing `DecodeResult`. Requires a DBC to already be loaded so
+    /// incoming frames can be resolved to signals.
+    fn start_can_live(&mut self, iface: &str, ctx: &egui::Context) {
+        if self.dbc.is_none() {
+            eprintln!("Cannot start live CAN: no DBC loaded.");
+            return;
+        }
+        match can_live::spawn_reader(iface) {
+            Ok(rx) => {
+                self.live_rx = Some(rx);
+                self.live_data = Some(DecodeResult::empty());
+                // Clear any file-based state so the two sources don't mix.
+                self.active_asc = None;
+                self.data = None;
+                self.tree.clear();
+                ctx.request_repaint();
+            }
+            Err(e) => {
+                eprintln!("Failed to open CAN interface '{iface}': {e}");
+            }
+        }
+    }
+
+    /// Drain any frames received from the live CAN stream, fold them into the
+    /// live `DecodeResult`, and re-resolve the tree and plotted signals so the
+    /// UI reflects the latest data. A repaint is always requested while live
+    /// so polling continues even when no frame arrived this tick.
+    fn poll_live(&mut self, ctx: &egui::Context) {
+        if self.live_rx.is_none() {
+            return;
+        }
+        // Keep the UI ticking so we keep polling the stream.
+        ctx.request_repaint();
+
+        let Some(dbc) = self.dbc.clone() else {
+            return;
+        };
+
+        // Collect first so the receiver borrow is released before we mutate
+        // `self.live_data` below.
+        let frames: Vec<CanFrame> = self
+            .live_rx
+            .as_ref()
+            .map(|rx| rx.try_iter().collect())
+            .unwrap_or_default();
+        if frames.is_empty() {
+            return;
+        }
+
+        let Some(live) = self.live_data.as_mut() else {
+            return;
+        };
+        for frame in frames {
+            live.push_live(&dbc, frame);
+        }
+
+        // Re-resolve tree and plots against the updated live data. These touch
+        // disjoint fields of `self`, so the borrows don't conflict.
+        let data = self.live_data.as_ref().unwrap();
+        self.tree = build_tree(&dbc, data);
+        for plot in &mut self.plots {
+            for sig in &mut plot.signals {
+                if let Some(new_sig) = resolve_signal(data, sig.id) {
+                    *sig = new_sig;
+                }
+            }
+        }
+    }
+
+    fn handle_signal_actions(&mut self, actions: Vec<SignalAction>) {
+        for action in actions {
+            match action {
+                SignalAction::Toggle(id) => self.toggle_plotted(id, false),
+                SignalAction::PlotDelay(sig_id) => {
+                    // The delay plot uses a distinct node id derived from the
+                    // signal, so it can coexist with the value plot.
+                    self.toggle_plotted(delay_node_id(sig_id), true);
+                }
+            }
+        }
+    }
+
+    /// Toggle whether `id` is plotted. `delay` selects the inter-frame delay
+    /// (Δt) computation instead of the signal's value.
+    fn toggle_plotted(&mut self, id: u64, delay: bool) {
+        if contains_signal(&self.plots, id) {
+            remove_signal(&mut self.plots, id);
+            return;
+        }
+        let Some((msg_id, sig_idx)) = decode_signal_node_id(id) else {
+            return;
+        };
+        // Pull from the live stream when in `--can` mode, otherwise the decoded
+        // ASC. Accessed as disjoint fields so the immutable data borrow doesn't
+        // clash with the `self.plots` mutation.
+        let data = if self.live_data.is_some() {
+            self.live_data.as_ref()
+        } else {
+            self.data.as_deref()
+        };
+        let Some(data) = data else {
+            return;
+        };
+        let sig = if delay {
+            compute_delay_signal(data, msg_id, sig_idx, id)
+        } else {
+            compute_signal(data, msg_id, sig_idx, id)
+        };
+        if let Some(sig) = sig {
+            add_signal_auto(&mut self.plots, &mut self.next_plot_id, sig);
+        }
+    }
+
+    fn handle_plot_actions(&mut self, actions: Vec<PlotListAction>) {
+        for action in actions {
+            match action {
+                PlotListAction::NewPlot => new_plot(&mut self.plots, &mut self.next_plot_id),
+                PlotListAction::Move(dd) => apply_move(&mut self.plots, dd),
+                PlotListAction::RemovePlot(id) => remove_plot(&mut self.plots, id),
+                PlotListAction::RemoveSignal(id) => remove_signal(&mut self.plots, id),
+            }
+        }
+    }
+}
+
+enum FilesAction {
+    LoadDbc(PathBuf),
+    AddAsc(PathBuf),
+    SetActive(usize),
+}
+
+fn show_files_tab(
+    ui: &mut egui::Ui,
+    dbc_path: Option<&PathBuf>,
+    asc_paths: &[PathBuf],
+    active: Option<usize>,
+) -> Vec<FilesAction> {
+    let mut actions = Vec::new();
+    ui.horizontal(|ui| {
+        if ui.button("Load DBC").clicked() {
+            if let Some(p) = rfd::FileDialog::new()
+                .add_filter("DBC files", &["dbc"])
+                .pick_file()
+            {
+                actions.push(FilesAction::LoadDbc(p));
+            }
+        }
+        let label = dbc_path
+            .map(|p| p.file_name().map(|s| s.to_string_lossy().into_owned()).unwrap_or_default())
+            .unwrap_or_else(|| "(none)".to_string());
+        ui.label(label);
+    });
+    ui.separator();
+    ui.horizontal(|ui| {
+        if ui.button("Add ASC").clicked() {
+            if let Some(p) = rfd::FileDialog::new()
+                .add_filter("ASC files", &["asc"])
+                .pick_file()
+            {
+                actions.push(FilesAction::AddAsc(p));
+            }
+        }
+        ui.label(format!("{} file(s)", asc_paths.len()));
+    });
+    egui::ScrollArea::vertical().show(ui, |ui| {
+        for (i, path) in asc_paths.iter().enumerate() {
+            let name = path
+                .file_name()
+                .map(|s| s.to_string_lossy().into_owned())
+                .unwrap_or_else(|| path.display().to_string());
+            if ui.selectable_label(active == Some(i), name).clicked() {
+                actions.push(FilesAction::SetActive(i));
+            }
+        }
+    });
+    actions
+}
+
+impl eframe::App for MyEguiApp {
+    fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
+        self.poll_pending();
+
+        let ctx = ui.ctx().clone();
+        self.poll_live(&ctx);
+        egui::Panel::left(egui::Id::new("LeftPanel"))
+            .resizable(true)
+            .show_inside(ui, |ui| {
+                let plot_actions = egui::Panel::bottom(egui::Id::new("PlotList"))
+                    .resizable(true)
+                    .default_size(220.0)
+                    .show_inside(ui, |ui| show_plot_list(ui, &self.plots))
+                    .inner;
+                let (toggles, files_actions) = egui::CentralPanel::default()
+                    .show_inside(ui, |ui| {
+                        ui.horizontal(|ui| {
+                            ui.selectable_value(
+                                &mut self.left_tab,
+                                LeftTab::Signals,
+                                "Signals",
+                            );
+                            ui.selectable_value(
+                                &mut self.left_tab,
+                                LeftTab::Files,
+                                "Files",
+                            );
+                        });
+                        ui.separator();
+                        match self.left_tab {
+                            LeftTab::Signals => (
+                                show_dbc_tree(ui, &mut self.filter, &self.tree),
+                                Vec::new(),
+                            ),
+                            LeftTab::Files => (
+                                Vec::new(),
+                                show_files_tab(
+                                    ui,
+                                    self.dbc_path.as_ref(),
+                                    &self.asc_paths,
+                                    self.active_asc,
+                                ),
+                            ),
+                        }
+                    })
+                    .inner;
+                self.handle_signal_actions(toggles);
+                self.handle_plot_actions(plot_actions);
+                for action in files_actions {
+                    match action {
+                        FilesAction::LoadDbc(p) => self.load_dbc(p),
+                        FilesAction::AddAsc(p) => self.add_asc(p),
+                        FilesAction::SetActive(i) => self.set_active_asc(i, Some(&ctx)),
+                    }
+                }
+            });
+        show_plot_panel(
+            ui,
+            &self.plots,
+            &mut self.cursor_x,
+            self.live_rx.is_some(),
+            &mut self.live_prev_max,
+        );
+
+        if let Some(job) = self.pending.as_ref() {
+            let name = job
+                .asc_path
+                .file_name()
+                .map(|s| s.to_string_lossy().into_owned())
+                .unwrap_or_else(|| job.asc_path.display().to_string());
+            egui::Modal::new(egui::Id::new("DecodingModal")).show(&ctx, |ui| {
+                ui.set_min_width(280.0);
+                ui.vertical_centered(|ui| {
+                    ui.heading("Decoding...");
+                    ui.add_space(6.0);
+                    ui.label(name);
+                    ui.add_space(6.0);
+                    ui.spinner();
+                });
+            });
+        }
+    }
+}

svldplotter/src/plot.rs

@@ -0,0 +1,225 @@
+use eframe::egui;
+use egui::ecolor::Hsva;
+use egui::{Color32, Vec2b};
+use egui_plot::{AxisHints, Legend, Line, Plot, PlotBounds, PlotPoint, PlotPoints, VPlacement};
+
+use crate::plot_list::{majority_unit, PlotGroup};
+use crate::signal::{decimate, nearest_y, PlottedSignal};
+
+const MIN_PLOT_HEIGHT: f32 = 80.0;
+const Y_AXIS_MIN_THICKNESS: f32 = 48.0;
+
+/// Split points into runs separated by x-gaps larger than `threshold`,
+/// so the line is broken across holes in the data instead of bridged.
+fn split_at_gaps(points: Vec<PlotPoint>, threshold: f64) -> Vec<Vec<PlotPoint>> {
+    let mut segments = Vec::new();
+    let mut current = Vec::new();
+    let mut prev_x: Option<f64> = None;
+    for p in points {
+        if let Some(px) = prev_x {
+            if p.x - px > threshold && !current.is_empty() {
+                segments.push(std::mem::take(&mut current));
+            }
+        }
+        prev_x = Some(p.x);
+        current.push(p);
+    }
+    if !current.is_empty() {
+        segments.push(current);
+    }
+    segments
+}
+
+fn full_x_range(plots: &[PlotGroup]) -> (f64, f64) {
+    let signals = plots.iter().flat_map(|p| p.signals.iter());
+    let min = signals
+        .clone()
+        .filter_map(|s| s.points.first().map(|p| p.x))
+        .fold(f64::INFINITY, f64::min);
+    let max = signals
+        .filter_map(|s| s.points.last().map(|p| p.x))
+        .fold(f64::NEG_INFINITY, f64::max);
+    (min, max)
+}
+
+/// Per-plot signal color. Index-based with golden-ratio hue spacing so
+/// neighbours on the same plot stay visually distinct.
+fn color_for_index(index: usize) -> Color32 {
+    const GOLDEN_RATIO_CONJUGATE: f32 = 0.618_034;
+    let hue = (index as f32 * GOLDEN_RATIO_CONJUGATE).fract();
+    Hsva::new(hue, 0.85, 0.9, 1.0).into()
+}
+
+fn line_label(sig: &PlottedSignal, cursor_x: Option<f64>) -> String {
+    let unit_suffix = if sig.unit.is_empty() {
+        String::new()
+    } else {
+        format!(" [{}]", sig.unit)
+    };
+    match cursor_x.and_then(|x| nearest_y(&sig.points, x)) {
+        Some(v) => format!("{}: {:.4}{}", sig.label, v, unit_suffix),
+        None => format!("{}{}", sig.label, unit_suffix),
+    }
+}
+
+/// Clamp the visible x-range to [0, x_max]. Preserves the current zoom
+/// width when possible; if the zoomed-out width exceeds the data range,
+/// just snaps to the full range.
+///
+/// In live mode, if the view's right edge was pinned to the latest sample
+/// (`prev_max`, the data extent from the previous frame), the window is
+/// scrolled right to keep the right edge at the new `x_max` so the plot
+/// auto-follows incoming data. Panning away from the edge disengages this.
+fn clamp_x_bounds(
+    plot_ui: &mut egui_plot::PlotUi,
+    x_max: f64,
+    live: bool,
+    prev_max: Option<f64>,
+) {
+    if !x_max.is_finite() {
+        return;
+    }
+    let bounds = plot_ui.plot_bounds();
+    let lo = bounds.min();
+    let hi = bounds.max();
+    let mut new_lo_x = lo[0];
+    let mut new_hi_x = hi[0];
+    let width = new_hi_x - new_lo_x;
+
+    if live && width < x_max {
+        // Pinned when the right edge sits at (or past) the previous extent.
+        // A tiny epsilon absorbs float error from last frame's snap.
+        let pinned = match prev_max {
+            Some(p) => new_hi_x >= p - width * 1e-3,
+            None => true,
+        };
+        if pinned {
+            new_hi_x = x_max;
+            new_lo_x = x_max - width;
+        }
+    }
+
+    if width >= x_max {
+        new_lo_x = 0.0;
+        new_hi_x = x_max;
+    } else {
+        if new_lo_x < 0.0 {
+            new_lo_x = 0.0;
+            new_hi_x = new_lo_x + width;
+        }
+        if new_hi_x > x_max {
+            new_hi_x = x_max;
+            new_lo_x = new_hi_x - width;
+        }
+    }
+
+    if new_lo_x != lo[0] || new_hi_x != hi[0] {
+        plot_ui.set_plot_bounds(PlotBounds::from_min_max(
+            [new_lo_x, lo[1]],
+            [new_hi_x, hi[1]],
+        ));
+    }
+}
+
+pub fn show_plot_panel(
+    ui: &mut egui::Ui,
+    plots: &[PlotGroup],
+    cursor_x: &mut Option<f64>,
+    live: bool,
+    prev_max: &mut Option<f64>,
+) {
+    egui::CentralPanel::default().show_inside(ui, |ui| {
+        if plots.is_empty() {
+            ui.centered_and_justified(|ui| {
+                ui.label("Click a signal in the tree to plot it.");
+            });
+            return;
+        }
+
+        let (full_min, full_max) = full_x_range(plots);
+        // Snapshot the previous frame's extent for the auto-follow decision,
+        // then record this frame's for the next one.
+        let follow_prev_max = *prev_max;
+        if full_max.is_finite() {
+            *prev_max = Some(full_max);
+        }
+        let link_group = ui.id().with("plot-link");
+        let plot_count = plots.len();
+        let plot_height =
+            (ui.available_height() / plot_count as f32).max(MIN_PLOT_HEIGHT);
+
+        let prev_cursor_x = *cursor_x;
+        let mut new_cursor_x: Option<f64> = None;
+
+        for (plot_index, plot_group) in plots.iter().enumerate() {
+            let is_first = plot_index == 0;
+            let is_last = plot_index + 1 == plot_count;
+
+            let mut x_axes: Vec<AxisHints> = Vec::new();
+            if is_first {
+                x_axes.push(AxisHints::new_x().placement(VPlacement::Top));
+            }
+            if is_last {
+                x_axes.push(AxisHints::new_x().placement(VPlacement::Bottom));
+            }
+
+            let unit = majority_unit(&plot_group.signals).unwrap_or("empty");
+
+            let plot = Plot::new(("plot", plot_group.id))
+                .height(plot_height)
+                .include_x(full_min)
+                .include_x(full_max)
+                .allow_zoom(Vec2b { x: true, y: true })
+                .link_axis(link_group, Vec2b { x: true, y: false })
+                .link_cursor(link_group, Vec2b { x: true, y: false })
+                .legend(Legend::default())
+                .custom_x_axes(x_axes)
+                .custom_y_axes(vec![
+                    AxisHints::new_y().min_thickness(Y_AXIS_MIN_THICKNESS),
+                ]);
+
+            let response = plot.show(ui, |plot_ui| {
+                clamp_x_bounds(plot_ui, full_max, live, follow_prev_max);
+                if plot_group.signals.is_empty() {
+                    plot_ui.line(
+                        Line::new(
+                            format!("Plot {} [{}]", plot_index + 1, unit),
+                            PlotPoints::Owned(Vec::new()),
+                        ),
+                    );
+                    return plot_ui.pointer_coordinate().map(|c| c.x);
+                }
+
+                let bounds = plot_ui.plot_bounds();
+                let x_min = bounds.min()[0];
+                let x_max = bounds.max()[0];
+                let pixel_width = plot_ui.transform().frame().width() as usize;
+                let bucket_w = (x_max - x_min) / pixel_width.max(1) as f64;
+                let mut buf = Vec::new();
+                for (sig_index, sig) in plot_group.signals.iter().enumerate() {
+                    decimate(&sig.points, x_min, x_max, pixel_width.max(1), &mut buf);
+                    // When zoomed out, adjacent decimated points are bucket_w
+                    // apart, so don't split on anything smaller than that.
+                    let threshold = sig.gap_threshold.max(bucket_w * 1.5);
+                    let segments = split_at_gaps(std::mem::take(&mut buf), threshold);
+                    let color = color_for_index(sig_index);
+                    let name = line_label(sig, prev_cursor_x);
+                    for (i, seg) in segments.into_iter().enumerate() {
+                        // Only the first segment carries the name so the
+                        // legend shows a single entry per signal.
+                        let seg_name = if i == 0 { name.clone() } else { String::new() };
+                        plot_ui.line(
+                            Line::new(seg_name, PlotPoints::Owned(seg)).color(color),
+                        );
+                    }
+                }
+                plot_ui.pointer_coordinate().map(|c| c.x)
+            });
+            if let Some(x) = response.inner {
+                new_cursor_x = Some(x);
+            }
+        }
+
+        *cursor_x = new_cursor_x;
+    });
+}

svldplotter/src/plot_list.rs

@@ -0,0 +1,297 @@
+use std::cell::RefCell;
+
+use eframe::egui;
+use egui::ScrollArea;
+use egui_ltreeview::{
+    Action, DirPosition, DragAndDrop, NodeBuilder, TreeView, TreeViewBuilder,
+};
+
+use crate::signal::PlottedSignal;
+use crate::tree::{
+    decode_plot_node_id, plot_node_id, PLOT_FLAG, ROOT_NODE_ID, SIGNAL_FLAG,
+};
+
+/// Auto-placement cap. The user can manually drag more signals into a plot.
+pub const MAX_SIGNALS_PER_PLOT: usize = 5;
+
+pub struct PlotGroup {
+    pub id: u64,
+    pub signals: Vec<PlottedSignal>,
+}
+
+pub enum PlotListAction {
+    NewPlot,
+    Move(DragAndDrop<u64>),
+    RemovePlot(u64),
+    RemoveSignal(u64),
+}
+
+pub fn remove_plot(plots: &mut Vec<PlotGroup>, plot_id: u64) {
+    plots.retain(|p| p.id != plot_id);
+}
+
+/// Keep at most one empty plot; drop any further empties (keeps the
+/// first one encountered so the user's stable reference doesn't vanish).
+fn dedupe_empty(plots: &mut Vec<PlotGroup>) {
+    let mut seen_empty = false;
+    plots.retain(|p| {
+        if p.signals.is_empty() {
+            if seen_empty {
+                false
+            } else {
+                seen_empty = true;
+                true
+            }
+        } else {
+            true
+        }
+    });
+}
+
+/// Most common unit in the plot (first-wins on ties). Returns `None`
+/// when the plot is empty.
+pub fn majority_unit(signals: &[PlottedSignal]) -> Option<&str> {
+    let mut counts: Vec<(&str, usize)> = Vec::new();
+    for sig in signals {
+        if let Some(c) = counts.iter_mut().find(|(u, _)| *u == sig.unit.as_str()) {
+            c.1 += 1;
+        } else {
+            counts.push((sig.unit.as_str(), 1));
+        }
+    }
+    counts.into_iter().max_by_key(|(_, c)| *c).map(|(u, _)| u)
+}
+
+pub fn contains_signal(plots: &[PlotGroup], signal_id: u64) -> bool {
+    plots
+        .iter()
+        .any(|p| p.signals.iter().any(|s| s.id == signal_id))
+}
+
+pub fn remove_signal(plots: &mut Vec<PlotGroup>, signal_id: u64) {
+    for plot in plots.iter_mut() {
+        if let Some(pos) = plot.signals.iter().position(|s| s.id == signal_id) {
+            plot.signals.remove(pos);
+            break;
+        }
+    }
+    dedupe_empty(plots);
+}
+
+/// Place `sig` into the first plot whose majority unit matches and that
+/// is under the cap; otherwise append a new plot at the end.
+pub fn add_signal_auto(
+    plots: &mut Vec<PlotGroup>,
+    next_plot_id: &mut u64,
+    sig: PlottedSignal,
+) {
+    let unit = sig.unit.as_str();
+    // Prefer an existing empty plot, then a unit-matching plot under cap.
+    let slot = plots
+        .iter()
+        .position(|p| p.signals.is_empty())
+        .or_else(|| {
+            plots.iter().position(|p| {
+                p.signals.len() < MAX_SIGNALS_PER_PLOT
+                    && majority_unit(&p.signals) == Some(unit)
+            })
+        });
+    if let Some(i) = slot {
+        plots[i].signals.push(sig);
+    } else {
+        plots.push(PlotGroup {
+            id: *next_plot_id,
+            signals: vec![sig],
+        });
+        *next_plot_id += 1;
+    }
+}
+
+pub fn new_plot(plots: &mut Vec<PlotGroup>, next_plot_id: &mut u64) {
+    if plots.iter().any(|p| p.signals.is_empty()) {
+        return;
+    }
+    plots.push(PlotGroup {
+        id: *next_plot_id,
+        signals: Vec::new(),
+    });
+    *next_plot_id += 1;
+}
+
+pub fn show_plot_list(
+    ui: &mut egui::Ui,
+    plots: &[PlotGroup],
+) -> Vec<PlotListAction> {
+    let events: RefCell<Vec<PlotListAction>> = RefCell::new(Vec::new());
+    if ui.button("+ New plot").clicked() {
+        events.borrow_mut().push(PlotListAction::NewPlot);
+    }
+    ScrollArea::both()
+        .scroll([true, true])
+        .scroll_bar_visibility(egui::scroll_area::ScrollBarVisibility::VisibleWhenNeeded)
+        .show(ui, |ui| {
+            let (_resp, actions) =
+                TreeView::<u64>::new(ui.make_persistent_id("PlotsTree"))
+                    .show(ui, |builder: &mut TreeViewBuilder<'_, u64>| {
+                        // Implicit root so the library can produce
+                        // Before/After positions for top-level plots.
+                        builder.dir(ROOT_NODE_ID, "Plots");
+                        for (i, plot) in plots.iter().enumerate() {
+                            let unit = majority_unit(&plot.signals).unwrap_or("empty");
+                            let label = format!("Plot {} [{}]", i + 1, unit);
+                            let plot_id = plot.id;
+                            let node = NodeBuilder::dir(plot_node_id(plot.id))
+                                .label(label)
+                                .activatable(true)
+                                .context_menu(|ui| {
+                                    if ui.button("Remove plot").clicked() {
+                                        events
+                                            .borrow_mut()
+                                            .push(PlotListAction::RemovePlot(plot_id));
+                                        ui.close();
+                                    }
+                                });
+                            builder.node(node);
+                            for sig in &plot.signals {
+                                let sig_id = sig.id;
+                                let node = NodeBuilder::leaf(sig.id)
+                                    .label(sig.label.as_str())
+                                    .context_menu(|ui| {
+                                        if ui.button("Remove signal").clicked() {
+                                            events.borrow_mut().push(
+                                                PlotListAction::RemoveSignal(sig_id),
+                                            );
+                                            ui.close();
+                                        }
+                                    });
+                                builder.node(node);
+                            }
+                            builder.close_dir();
+                        }
+                        builder.close_dir();
+                    });
+            for action in actions {
+                match action {
+                    Action::Move(dd) => {
+                        events.borrow_mut().push(PlotListAction::Move(dd));
+                    }
+                    Action::Activate(act) => {
+                        for id in act.selected {
+                            if id & SIGNAL_FLAG != 0 {
+                                events
+                                    .borrow_mut()
+                                    .push(PlotListAction::RemoveSignal(id));
+                            } else if let Some(plot_id) = decode_plot_node_id(id) {
+                                events
+                                    .borrow_mut()
+                                    .push(PlotListAction::RemovePlot(plot_id));
+                            }
+                        }
+                    }
+                    _ => {}
+                }
+            }
+        });
+    events.into_inner()
+}
+
+/// Apply a drag-and-drop move to the plot list.
+///
+/// Sources are either signal leaves (move signal between/within plots) or
+/// plot dirs (reorder plots). Mixed sources are handled item-by-item.
+pub fn apply_move(plots: &mut Vec<PlotGroup>, dd: DragAndDrop<u64>) {
+    for source in dd.source {
+        if source & SIGNAL_FLAG != 0 {
+            apply_signal_move(plots, source, dd.target, &dd.position);
+        } else if source & PLOT_FLAG != 0 {
+            apply_plot_move(plots, source & !PLOT_FLAG, dd.target, &dd.position);
+        }
+    }
+    dedupe_empty(plots);
+}
+
+fn apply_signal_move(
+    plots: &mut Vec<PlotGroup>,
+    signal_id: u64,
+    target: u64,
+    position: &DirPosition<u64>,
+) {
+    // Resolve the target plot. If dropped on the root or somewhere we
+    // can't interpret, leave the signal where it is.
+    let target_plot_id = if let Some(pid) = decode_plot_node_id(target) {
+        pid
+    } else {
+        return;
+    };
+
+    // Detach from its current plot.
+    let detached = plots.iter_mut().find_map(|p| {
+        p.signals
+            .iter()
+            .position(|s| s.id == signal_id)
+            .map(|pos| p.signals.remove(pos))
+    });
+    let Some(sig) = detached else {
+        return;
+    };
+
+    let Some(target_plot) = plots.iter_mut().find(|p| p.id == target_plot_id) else {
+        return;
+    };
+    let insert_at = match position {
+        DirPosition::First => 0,
+        DirPosition::Last => target_plot.signals.len(),
+        DirPosition::Before(sibling) => target_plot
+            .signals
+            .iter()
+            .position(|s| s.id == *sibling)
+            .unwrap_or(target_plot.signals.len()),
+        DirPosition::After(sibling) => target_plot
+            .signals
+            .iter()
+            .position(|s| s.id == *sibling)
+            .map(|i| i + 1)
+            .unwrap_or(target_plot.signals.len()),
+    };
+    target_plot.signals.insert(insert_at, sig);
+}
+
+fn apply_plot_move(
+    plots: &mut Vec<PlotGroup>,
+    plot_id: u64,
+    target: u64,
+    position: &DirPosition<u64>,
+) {
+    // Only reordering at the root level is supported. Dropping a plot
+    // onto another plot is treated as "place after that plot".
+    let from = match plots.iter().position(|p| p.id == plot_id) {
+        Some(i) => i,
+        None => return,
+    };
+    let plot = plots.remove(from);
+
+    let to = if target == ROOT_NODE_ID {
+        match position {
+            DirPosition::First => 0,
+            DirPosition::Last => plots.len(),
+            DirPosition::Before(sibling) => decode_plot_node_id(*sibling)
+                .and_then(|pid| plots.iter().position(|p| p.id == pid))
+                .unwrap_or(plots.len()),
+            DirPosition::After(sibling) => decode_plot_node_id(*sibling)
+                .and_then(|pid| plots.iter().position(|p| p.id == pid))
+                .map(|i| i + 1)
+                .unwrap_or(plots.len()),
+        }
+    } else if let Some(target_plot_id) = decode_plot_node_id(target) {
+        plots
+            .iter()
+            .position(|p| p.id == target_plot_id)
+            .map(|i| i + 1)
+            .unwrap_or(plots.len())
+    } else {
+        plots.len()
+    };
+
+    let to = to.min(plots.len());
+    plots.insert(to, plot);
+}

svldplotter/src/signal.rs

@@ -0,0 +1,166 @@
+use egui_plot::PlotPoint;
+use libsvld::DecodeResult;
+
+use crate::tree::{decode_signal_node_id, is_delay_node_id};
+
+pub struct PlottedSignal {
+    pub id: u64,
+    pub label: String,
+    pub unit: String,
+    pub points: Vec<PlotPoint>,
+    pub gap_threshold: f64,
+}
+
+/// A jump in x larger than this is treated as a hole in the data and the
+/// line is broken rather than bridged. Based on the median sample interval.
+fn compute_gap_threshold(points: &[PlotPoint]) -> f64 {
+    if points.len() < 2 {
+        return f64::INFINITY;
+    }
+    let mut deltas: Vec<f64> =
+        points.windows(2).map(|w| w[1].x - w[0].x).collect();
+    deltas.sort_by(|a, b| a.total_cmp(b));
+    let median = deltas[deltas.len() / 2];
+    (median * 10.0).max(f64::MIN_POSITIVE)
+}
+
+pub fn compute_signal(
+    data: &DecodeResult,
+    msg_id: u32,
+    sig_idx: usize,
+    id: u64,
+) -> Option<PlottedSignal> {
+    let meta = data.metadata.get(&msg_id)?;
+    let sig = meta.signals.get(sig_idx)?;
+    let frames = data.data.get(&msg_id)?;
+    let mut points = Vec::with_capacity(frames.len());
+    for frame in frames {
+        let bytes = u64::from_le_bytes(frame.data);
+        points.push(PlotPoint {
+            x: frame.timestamp,
+            y: libsvld::motec::extract_signal(bytes, &sig.signal),
+        });
+    }
+    let gap_threshold = compute_gap_threshold(&points);
+    Some(PlottedSignal {
+        id,
+        label: sig.name.clone(),
+        unit: sig.unit.clone(),
+        points,
+        gap_threshold,
+    })
+}
+
+/// Build a signal whose value is the time delay between consecutive CAN
+/// frames of a message (Δt, in seconds), keyed off one of its signals.
+/// The first frame has no predecessor, so it produces no point. Plotted at
+/// the timestamp of the later frame.
+pub fn compute_delay_signal(
+    data: &DecodeResult,
+    msg_id: u32,
+    sig_idx: usize,
+    id: u64,
+) -> Option<PlottedSignal> {
+    let meta = data.metadata.get(&msg_id)?;
+    let sig = meta.signals.get(sig_idx)?;
+    let frames = data.data.get(&msg_id)?;
+    let mut points = Vec::with_capacity(frames.len().saturating_sub(1));
+    let mut prev: Option<f64> = None;
+    for frame in frames {
+        if let Some(p) = prev {
+            points.push(PlotPoint {
+                x: frame.timestamp,
+                y: frame.timestamp - p,
+            });
+        }
+        prev = Some(frame.timestamp);
+    }
+    let gap_threshold = compute_gap_threshold(&points);
+    Some(PlottedSignal {
+        id,
+        label: format!("{} Δt", sig.name),
+        unit: "s".to_string(),
+        points,
+        gap_threshold,
+    })
+}
+
+/// Resolve a plotted-signal node id against decoded data, dispatching to the
+/// value or frame-delay computation based on the id's flags. Used to (re)build
+/// a `PlottedSignal` whenever the underlying data changes (ASC switch, live).
+pub fn resolve_signal(data: &DecodeResult, id: u64) -> Option<PlottedSignal> {
+    let (msg_id, sig_idx) = decode_signal_node_id(id)?;
+    if is_delay_node_id(id) {
+        compute_delay_signal(data, msg_id, sig_idx, id)
+    } else {
+        compute_signal(data, msg_id, sig_idx, id)
+    }
+}
+
+pub fn nearest_y(points: &[PlotPoint], x: f64) -> Option<f64> {
+    if points.is_empty() {
+        return None;
+    }
+    let i = points.partition_point(|p| p.x < x);
+    let candidates = [
+        i.checked_sub(1).map(|j| &points[j]),
+        points.get(i),
+    ];
+    candidates
+        .into_iter()
+        .flatten()
+        .min_by(|a, b| (a.x - x).abs().total_cmp(&(b.x - x).abs()))
+        .map(|p| p.y)
+}
+
+// Min/max bucketing: for each horizontal pixel column in [x_min, x_max], emit
+// the min-y and max-y point so spikes survive decimation. Pushed in x order
+// (min/max swapped if needed) to keep the line monotonically increasing in x.
+pub fn decimate(
+    points: &[PlotPoint],
+    x_min: f64,
+    x_max: f64,
+    buckets: usize,
+    out: &mut Vec<PlotPoint>,
+) {
+    out.clear();
+    if points.is_empty() || buckets == 0 || !(x_max > x_min) {
+        return;
+    }
+
+    let start = points.partition_point(|p| p.x < x_min).saturating_sub(1);
+    let end = (points.partition_point(|p| p.x <= x_max) + 1).min(points.len());
+    let visible = &points[start..end];
+
+    if visible.len() <= buckets * 2 {
+        out.extend_from_slice(visible);
+        return;
+    }
+
+    let bucket_w = (x_max - x_min) / buckets as f64;
+    let mut cursor = 0;
+    for bucket in 0..buckets {
+        let bucket_end_x = x_min + (bucket as f64 + 1.0) * bucket_w;
+        let bucket_start = cursor;
+        while cursor < visible.len() && visible[cursor].x < bucket_end_x {
+            cursor += 1;
+        }
+        if bucket_start == cursor {
+            continue;
+        }
+        let slice = &visible[bucket_start..cursor];
+        let mut min_p = slice[0];
+        let mut max_p = slice[0];
+        for p in &slice[1..] {
+            if p.y < min_p.y { min_p = *p; }
+            if p.y > max_p.y { max_p = *p; }
+        }
+        if min_p.x <= max_p.x {
+            out.push(min_p);
+            out.push(max_p);
+        } else {
+            out.push(max_p);
+            out.push(min_p);
+        }
+    }
+}

svldplotter/src/tree.rs

@@ -0,0 +1,177 @@
+use std::cell::RefCell;
+
+use can_dbc::Dbc;
+use eframe::egui;
+use egui::ScrollArea;
+use egui_ltreeview::{Action, NodeBuilder, TreeView, TreeViewBuilder};
+use fuzzy_matcher::FuzzyMatcher;
+use fuzzy_matcher::skim::SkimMatcherV2;
+use libsvld::DecodeResult;
+
+pub struct SigNode {
+    pub id: u64,
+    pub name: String,
+}
+
+pub struct MsgNode {
+    pub id: u64,
+    pub label: String,
+    pub signals: Vec<SigNode>,
+}
+
+// Node-id encoding shared across the two tree views.
+//   bit 63 set → signal leaf
+//   bit 62 set → plot directory (in the lower "plots" tree)
+//   bit 61 set → "frame delay" variant of a signal (keeps bit 63 set too, so
+//                it still behaves like a signal for selection / drag-and-drop)
+//   ROOT_NODE_ID → the implicit root of the lower tree
+pub const SIGNAL_FLAG: u64 = 1 << 63;
+pub const PLOT_FLAG: u64 = 1 << 62;
+pub const DELAY_FLAG: u64 = 1 << 61;
+pub const ROOT_NODE_ID: u64 = 1;
+
+/// User actions emitted by the DBC signal tree.
+pub enum SignalAction {
+    /// Toggle plotting of a signal's value (left-click).
+    Toggle(u64),
+    /// Toggle plotting of the inter-frame delay (Δt) for a signal's message
+    /// (right-click → context menu). The id is the plain signal node id.
+    PlotDelay(u64),
+}
+
+/// Derive the "frame delay" node id for a plain signal node id.
+pub fn delay_node_id(signal_id: u64) -> u64 {
+    signal_id | DELAY_FLAG
+}
+
+/// Whether a node id refers to the inter-frame delay variant of a signal.
+pub fn is_delay_node_id(id: u64) -> bool {
+    id & DELAY_FLAG != 0
+}
+
+pub fn signal_node_id(msg_id: u32, sig_idx: usize) -> u64 {
+    SIGNAL_FLAG | ((msg_id as u64) << 16) | (sig_idx as u64)
+}
+
+pub fn decode_signal_node_id(id: u64) -> Option<(u32, usize)> {
+    if id & SIGNAL_FLAG == 0 {
+        return None;
+    }
+    let msg_id = ((id >> 16) & 0xFFFF_FFFF) as u32;
+    let sig_idx = (id & 0xFFFF) as usize;
+    Some((msg_id, sig_idx))
+}
+
+pub fn plot_node_id(plot_id: u64) -> u64 {
+    PLOT_FLAG | plot_id
+}
+
+pub fn decode_plot_node_id(id: u64) -> Option<u64> {
+    if id & SIGNAL_FLAG != 0 || id & PLOT_FLAG == 0 {
+        return None;
+    }
+    Some(id & !PLOT_FLAG)
+}
+
+pub fn build_tree(dbc: &Dbc, data: &DecodeResult) -> Vec<MsgNode> {
+    let mut msgs: Vec<&libsvld::motec::MessageMetadata> = data.metadata.values().collect();
+    msgs.sort_by_key(|m| m.id);
+    msgs.into_iter()
+        .map(|msg| {
+            let name = dbc
+                .messages
+                .iter()
+                .find(|x| x.id.raw() == msg.id)
+                .map(|x| x.name.as_str())
+                .unwrap_or("?");
+            let label = format!("0x{:X}  {}", msg.id, name);
+            let signals = msg
+                .signals
+                .iter()
+                .enumerate()
+                .map(|(sig_idx, signal)| SigNode {
+                    id: signal_node_id(msg.id, sig_idx),
+                    name: signal.name.clone(),
+                })
+                .collect();
+            MsgNode {
+                id: msg.id as u64,
+                label,
+                signals,
+            }
+        })
+        .collect()
+}
+
+/// Render the DBC tree and return the user's actions: left-clicking a signal
+/// toggles its value plot; right-clicking offers a "plot frame delay" entry.
+pub fn show_dbc_tree(
+    ui: &mut egui::Ui,
+    filter: &mut String,
+    tree: &[MsgNode],
+) -> Vec<SignalAction> {
+    let events: RefCell<Vec<SignalAction>> = RefCell::new(Vec::new());
+    ui.add(
+        egui::TextEdit::singleline(filter)
+            .hint_text("Filter messages/signals")
+            .desired_width(f32::INFINITY),
+    );
+    let needle = filter.trim();
+    let matcher = SkimMatcherV2::default().ignore_case();
+    ScrollArea::both()
+        .scroll([true, true])
+        .scroll_bar_visibility(egui::scroll_area::ScrollBarVisibility::VisibleWhenNeeded)
+        .show(ui, |ui| {
+            let (_resp, actions) =
+                TreeView::<u64>::new(ui.make_persistent_id("SignalsTree"))
+                    .allow_drag_and_drop(false)
+                    .show(ui, |builder: &mut TreeViewBuilder<'_, u64>| {
+                        for msg in tree {
+                            let msg_hit = needle.is_empty()
+                                || matcher.fuzzy_match(&msg.label, needle).is_some();
+                            let matching: Vec<&SigNode> = if msg_hit {
+                                msg.signals.iter().collect()
+                            } else {
+                                msg.signals
+                                    .iter()
+                                    .filter(|s| {
+                                        matcher.fuzzy_match(&s.name, needle).is_some()
+                                    })
+                                    .collect()
+                            };
+                            if !msg_hit && matching.is_empty() {
+                                continue;
+                            }
+                            builder.dir(msg.id, msg.label.as_str());
+                            for sig in matching {
+                                let sig_id = sig.id;
+                                let node = NodeBuilder::leaf(sig.id)
+                                    .label(sig.name.as_str())
+                                    .context_menu(|ui| {
+                                        if ui
+                                            .button("Plot frame delay (Δt)")
+                                            .clicked()
+                                        {
+                                            events.borrow_mut().push(
+                                                SignalAction::PlotDelay(sig_id),
+                                            );
+                                            ui.close();
+                                        }
+                                    });
+                                builder.node(node);
+                            }
+                            builder.close_dir();
+                        }
+                    });
+            for action in actions {
+                if let Action::SetSelected(ids) = action {
+                    for id in ids {
+                        if id & SIGNAL_FLAG != 0 {
+                            events.borrow_mut().push(SignalAction::Toggle(id));
+                        }
+                    }
+                }
+            }
+        });
+    events.into_inner()
+}