comiit

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

@@ -21,8 +21,10 @@ 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_signal;
-use crate::tree::{build_tree, decode_signal_node_id, show_dbc_tree, MsgNode};
+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();
@@ -203,13 +205,11 @@ impl MyEguiApp {
         // 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((msg_id, sig_idx)) = decode_signal_node_id(sig.id) {
-                    if let Some(new_sig) = compute_signal(&data, msg_id, sig_idx, sig.id) {
+                if let Some(new_sig) = resolve_signal(&data, sig.id) {
                     *sig = new_sig;
                 }
             }
         }
-        }
         self.data = Some(data);
     }
 
@@ -276,37 +276,56 @@ impl MyEguiApp {
         self.tree = build_tree(&dbc, data);
         for plot in &mut self.plots {
             for sig in &mut plot.signals {
-                if let Some((msg_id, sig_idx)) = decode_signal_node_id(sig.id) {
-                    if let Some(new_sig) = compute_signal(data, msg_id, sig_idx, sig.id) {
+                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);
+                }
+            }
+        }
     }
 
-    fn handle_dbc_toggles(&mut self, toggles: Vec<u64>) {
-        for id in toggles {
+    /// 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);
-            } else if let Some((msg_id, sig_idx)) = decode_signal_node_id(id) {
-                // 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.
+            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 {
-                    continue;
+            return;
         };
-                if let Some(sig) = compute_signal(data, msg_id, sig_idx, id) {
+        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 {
@@ -419,7 +438,7 @@ impl eframe::App for MyEguiApp {
                         }
                     })
                     .inner;
-                self.handle_dbc_toggles(toggles);
+                self.handle_signal_actions(toggles);
                 self.handle_plot_actions(plot_actions);
                 for action in files_actions {
                     match action {

svldplotter/src/signal.rs

@@ -1,6 +1,8 @@
 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,
@@ -49,6 +51,52 @@ pub fn compute_signal(
     })
 }
 
+/// 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;

svldplotter/src/tree.rs

@@ -1,7 +1,9 @@
+use std::cell::RefCell;
+
 use can_dbc::Dbc;
 use eframe::egui;
 use egui::ScrollArea;
-use egui_ltreeview::{Action, TreeView, TreeViewBuilder};
+use egui_ltreeview::{Action, NodeBuilder, TreeView, TreeViewBuilder};
 use fuzzy_matcher::FuzzyMatcher;
 use fuzzy_matcher::skim::SkimMatcherV2;
 use libsvld::DecodeResult;
@@ -20,11 +22,33 @@ pub struct MsgNode {
 // 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)
 }
@@ -79,13 +103,14 @@ pub fn build_tree(dbc: &Dbc, data: &DecodeResult) -> Vec<MsgNode> {
         .collect()
 }
 
-/// Render the DBC tree and return the signal IDs the user clicked to toggle.
+/// 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<u64> {
-    let mut toggles = Vec::new();
+) -> Vec<SignalAction> {
+    let events: RefCell<Vec<SignalAction>> = RefCell::new(Vec::new());
     ui.add(
         egui::TextEdit::singleline(filter)
             .hint_text("Filter messages/signals")
@@ -119,7 +144,21 @@ pub fn show_dbc_tree(
                             }
                             builder.dir(msg.id, msg.label.as_str());
                             for sig in matching {
-                                builder.leaf(sig.id, sig.name.as_str());
+                                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();
                         }
@@ -128,11 +167,11 @@ pub fn show_dbc_tree(
                 if let Action::SetSelected(ids) = action {
                     for id in ids {
                         if id & SIGNAL_FLAG != 0 {
-                            toggles.push(id);
+                            events.borrow_mut().push(SignalAction::Toggle(id));
                         }
                     }
                 }
             }
         });
-    toggles
+    events.into_inner()
 }