P2: true multi-axis overlay + gauge view

gui/widgets.py:
- MultiAxisPlot -- overlay with one Y axis PER UNIT (psi/V/rpm/C/%), linked
  ViewBoxes on X, so mixed-scale signals are readable at true values
  (base left axis + up to 4 right axes).
- SinglePlot -- one shared axis for the Normalize (% of range) mode.
- ArcGauge -- 270deg arc gauge with peak tick + numeric readout, own dark bg.
- GaugeGrid -- scrollable grid of gauges.

gui/main.py:
- Graph page is now a multi-axis/single-axis sub-stack; Normalize toggles
  between true multi-axis (raw) and single-axis (%). curves map key->color;
  plot ops route to the active graph widget.
- Gauge View menu enabled (3rd center page); gauges update on tick with peak.
- Theme applies to both plot widgets; profile switch clears graphs/gauges.

Fix: ArcGauge QPen built via setCapStyle (the QPen(...cap=...) kwarg segfaults
PySide6). Validated headless: driving preset -> 6 unit groups across 5 axes,
gauge view renders, normalize round-trips, profile-switch clears cleanly.
obdcore + diagnostics tests still pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs

README.md

@@ -73,21 +73,31 @@ python obd_reader.py COM5 --crank --dash-log crank.csv   # + record a CSV
 under the line), that's the high-pressure oil bleed-off — STC fitting / oil-rail
 O-rings. On exit it prints the peak and a verdict. `q` quits, `r` resets.
 
-## Graphical app (preview — P1)
+## Graphical app (preview)
 
-A cross-platform desktop GUI (PySide6 + pyqtgraph) is in progress. P1 = PID
+A cross-platform desktop GUI (PySide6 + pyqtgraph). Vehicle-agnostic — all PIDs,
-browser + live overlay plot; see [ARCHITECTURE.md](ARCHITECTURE.md) for the
+scaling, DTCs, and presets come from the JSON profiles in `profiles/`.
-roadmap (cranking/driving/diagnostics perspectives, record/playback, etc.).
 
 ```
 pip install -r requirements-gui.txt
 python run_gui.py        # tick "Mock" + Connect to explore with no adapter
 ```
 
-![P1 GUI](docs/gui-p1-preview.png)
+Features so far:
+- **PID browser** (left) grouped by system, live values, confidence badges
+- **Graph view** with **true multi-axis** overlay — one Y scale per unit (psi/V/rpm/…),
+  or a Normalize (% of range) mode
+- **Gauge view** — arc gauges with peak-hold, one per signal
+- **Table view** — value + min/max + confidence
+- **Diagnostics** — read/clear DTCs (guarded), no-start codes flagged
+- **Profile menu** — switch/import/edit vehicles; **File menu** — record/replay/export captures
 
-The whole app runs against simulated data (`MockLink`) so it can be developed
+![Multi-axis graph](docs/gui-p2-multiaxis.png)
-on any machine and only needs the truck for real captures.
+![Gauge view](docs/gui-p2-gauges.png)
+
+The whole app runs against simulated data (`MockLink`), so it can be developed
+on any machine and only needs the vehicle for real captures. See
+[ARCHITECTURE.md](ARCHITECTURE.md) for the roadmap.
 
 ---
 

gui/main.py

@@ -18,6 +18,7 @@ import pyqtgraph as pg
 from obdcore import (list_profiles, profiles_dir, save_profile, load_profile,
                      export_csv, replay_csv, TimeSeriesStore)
 from .controller import Controller
+from .widgets import MultiAxisPlot, SinglePlot, GaugeGrid
 
 PLOT_WINDOW_S = 60.0
 REFRESH_MS = 100
@@ -86,8 +87,8 @@ class MainWindow(QtWidgets.QMainWindow):
         self.view_table = self._act(viewm, "Table View", lambda: self._set_view(1),
                                     checkable=True)
         self.view_graph.setChecked(True)
-        gauges = self._act(viewm, "Gauge View  (P2)", lambda: None, checkable=True)
+        self.view_gauge = self._act(viewm, "Gauge View", lambda: self._set_view(2),
-        gauges.setEnabled(False)
+                                    checkable=True)
         viewm.addSeparator()
         self.show_pids = self._act(viewm, "Show PID Panel", self._toggle_pid_dock,
                                    checkable=True)
@@ -352,32 +353,43 @@ class MainWindow(QtWidgets.QMainWindow):
     def _build_center(self):
         self.stack = QtWidgets.QStackedWidget()
 
-        # graph page
+        # graph page: a sub-stack of multi-axis (raw) and single-axis (normalized)
         gpage = QtWidgets.QWidget(); gl = QtWidgets.QVBoxLayout(gpage)
         gl.setContentsMargins(4, 4, 4, 4)
         bar = QtWidgets.QHBoxLayout()
         self.norm_chk = QtWidgets.QCheckBox("Normalize (% of range)")
-        self.norm_chk.toggled.connect(lambda v: self.norm_act.setChecked(v))
+        self.norm_chk.toggled.connect(self._set_normalize)
-        bar.addWidget(self.norm_chk); bar.addStretch(1)
+        bar.addWidget(self.norm_chk)
+        bar.addWidget(QtWidgets.QLabel("  (off = true multi-axis, one Y scale per unit)"))
+        bar.addStretch(1)
         bar.addWidget(QtWidgets.QLabel(f"window: {int(PLOT_WINDOW_S)}s"))
         gl.addLayout(bar)
-        self.plot = pg.PlotWidget()
+        self.multi = MultiAxisPlot()
-        self.plot.addLegend(offset=(10, 10))
+        self.single = SinglePlot()
-        self.plot.showGrid(x=True, y=True, alpha=0.25)
+        self.graph_stack = QtWidgets.QStackedWidget()
-        self.plot.setLabel("bottom", "time", units="s")
+        self.graph_stack.addWidget(self.multi)      # index 0 = multi-axis
-        gl.addWidget(self.plot)
+        self.graph_stack.addWidget(self.single)     # index 1 = normalized
-        self.stack.addWidget(gpage)
+        gl.addWidget(self.graph_stack)
+        self.stack.addWidget(gpage)                 # center index 0 = graph
 
-        # table page
+        # table page (center index 1)
         self.table = QtWidgets.QTableWidget(0, 6)
         self.table.setHorizontalHeaderLabels(["Signal", "Value", "Unit", "Min", "Max", "Conf"])
         self.table.horizontalHeader().setStretchLastSection(True)
         self.table.setEditTriggers(QtWidgets.QAbstractItemView.NoEditTriggers)
         self.stack.addWidget(self.table)
 
+        # gauge page (center index 2)
+        self.gauges = GaugeGrid()
+        self.stack.addWidget(self.gauges)
+
         self.setCentralWidget(self.stack)
         self._apply_theme()
 
+    def _graph(self):
+        """The active graph widget (multi-axis unless Normalize is on)."""
+        return self.single if self.norm_chk.isChecked() else self.multi
+
     def _build_statusbar(self):
         self.status = self.statusBar()
         self.status.showMessage("Not connected.  Pick a port (or Mock) and Connect.")
@@ -404,6 +416,7 @@ class MainWindow(QtWidgets.QMainWindow):
             QtWidgets.QMessageBox.critical(self, "Profile load failed", str(e))
             return
         self.curves.clear(); self._color_i = 0
+        self.multi.clear(); self.single.clear(); self.gauges.rebuild([])
         self._rebuild_for_profile()
         self._rebuild_profile_menu()
         self.status.showMessage(f"Loaded profile: {self.ctl.profile.name}")
@@ -538,25 +551,42 @@ class MainWindow(QtWidgets.QMainWindow):
     def _add_curve(self, key):
         p = self.ctl.reg.get(key)
         color = CURVE_COLORS[self._color_i % len(CURVE_COLORS)]; self._color_i += 1
-        self.curves[key] = self.plot.plot([], [], name=f"{p.name} ({p.unit})",
+        self.curves[key] = color                     # curves maps key -> color
-                                          pen=pg.mkPen(color=color, width=2))
+        self._graph().add_curve(key, f"{p.name} ({p.unit})", p.unit, color)
+        self._refresh_gauges()
 
     def _remove_curve(self, key):
-        c = self.curves.pop(key, None)
+        if self.curves.pop(key, None) is None:
-        if c is not None:
+            return
-            self.plot.removeItem(c)
+        self.multi.remove_curve(key)
-            leg = self.plot.plotItem.legend
+        self.single.remove_curve(key)
-            if leg:
+        self._refresh_gauges()
-                try:
+
-                    leg.removeItem(c)
+    def _set_normalize(self, on):
-                except Exception:
+        """Swap between true multi-axis (raw) and single-axis (% of range)."""
-                    pass
+        self.norm_act.setChecked(on)
+        self.multi.clear(); self.single.clear()
+        self.graph_stack.setCurrentIndex(1 if on else 0)
+        active = self._graph()
+        for key, color in self.curves.items():
+            p = self.ctl.reg.get(key)
+            active.add_curve(key, f"{p.name} ({p.unit})", p.unit, color)
+        self._apply_theme()
+        self._redraw_curves(static=not self.ctl.connected)
+
+    def _refresh_gauges(self):
+        specs = []
+        for key, color in self.curves.items():
+            p = self.ctl.reg.get(key)
+            specs.append((key, p.name, p.unit, p.vmin, p.vmax, color))
+        self.gauges.rebuild(specs)
 
     # ---------- view ----------
     def _set_view(self, idx):
         self.stack.setCurrentIndex(idx)
         self.view_graph.setChecked(idx == 0)
         self.view_table.setChecked(idx == 1)
+        self.view_gauge.setChecked(idx == 2)
 
     def _toggle_pid_dock(self):
         self.pid_dock.setVisible(self.show_pids.isChecked())
@@ -569,10 +599,9 @@ class MainWindow(QtWidgets.QMainWindow):
         self._apply_theme()
 
     def _apply_theme(self):
-        bg, fg = THEMES[self._theme]
+        bg, _fg = THEMES[self._theme]
-        self.plot.setBackground(bg)
+        self.multi.set_background(bg)
-        self.plot.getAxis("bottom").setPen(fg); self.plot.getAxis("left").setPen(fg)
+        self.single.set_background(bg)
-        self.plot.getAxis("bottom").setTextPen(fg); self.plot.getAxis("left").setTextPen(fg)
 
     def _populate_table_rows(self):
         pids = self.ctl.reg.all()
@@ -661,7 +690,8 @@ class MainWindow(QtWidgets.QMainWindow):
         else:
             since = (self.ctl.t0 or 0) + max(0.0, self.ctl.now() - PLOT_WINDOW_S)
         normalize = self.norm_chk.isChecked()
-        for key, curve in self.curves.items():
+        active = self._graph()
+        for key in self.curves:
             p = self.ctl.reg.get(key)
             xs, ys = [], []
             for t, v in self.ctl.store.channel(key).series(since=since):
@@ -672,8 +702,9 @@ class MainWindow(QtWidgets.QMainWindow):
                     ys.append((v - p.vmin) / (p.vmax - p.vmin) * 100.0)
                 else:
                     ys.append(v)
-            curve.setData(xs, ys)
+            active.set_data(key, xs, ys)
-        self.plot.setLabel("left", "% of range" if normalize else "value")
+        if normalize:
+            self.single.set_y_label("% of range")
 
     def _tick(self):
         if not self.ctl.connected:
@@ -691,6 +722,11 @@ class MainWindow(QtWidgets.QMainWindow):
                 self.table.item(r, 3).setText("--" if lo is None else f"{lo:g}")
                 self.table.item(r, 4).setText("--" if hi is None else f"{hi:g}")
         self.tree.blockSignals(False)
+        if self.stack.currentIndex() == 2:           # gauge view
+            for key in self.curves:
+                lo, hi = self.ctl.store.minmax(key)
+                self.gauges.set_value(key, self.ctl.store.latest(key), peak=hi)
+        else:
             self._redraw_curves()
 
     def closeEvent(self, ev):

gui/widgets.py

@@ -0,0 +1,245 @@
+"""Custom widgets for the ford-obd GUI: a unit-grouped multi-axis plot, a
+simple single-axis plot, and an arc gauge / gauge grid.
+
+All three plot/gauge containers share a small interface so the main window can
+swap between them:  add_curve(key,name,unit,color) / set_data(key,xs,ys) /
+remove_curve(key) / clear().
+"""
+import math
+
+from PySide6 import QtCore, QtGui, QtWidgets
+import pyqtgraph as pg
+
+MAX_EXTRA_AXES = 4          # base left axis + up to 4 right axes (5 units shown)
+
+
+class SinglePlot(QtWidgets.QWidget):
+    """One shared Y axis. Used for the Normalize (% of range) mode."""
+
+    def __init__(self):
+        super().__init__()
+        lay = QtWidgets.QVBoxLayout(self)
+        lay.setContentsMargins(0, 0, 0, 0)
+        self.pw = pg.PlotWidget()
+        self.pw.addLegend(offset=(10, 10))
+        self.pw.showGrid(x=True, y=True, alpha=0.25)
+        self.pw.setLabel("bottom", "time", units="s")
+        lay.addWidget(self.pw)
+        self._curves = {}
+
+    def set_y_label(self, text):
+        self.pw.setLabel("left", text)
+
+    def add_curve(self, key, name, unit, color):
+        self._curves[key] = self.pw.plot([], [], name=name, pen=pg.mkPen(color, width=2))
+
+    def set_data(self, key, xs, ys):
+        c = self._curves.get(key)
+        if c is not None:
+            c.setData(xs, ys)
+
+    def remove_curve(self, key):
+        c = self._curves.pop(key, None)
+        if c is not None:
+            self.pw.removeItem(c)
+            leg = self.pw.plotItem.legend
+            if leg:
+                try:
+                    leg.removeItem(c)
+                except Exception:
+                    pass
+
+    def clear(self):
+        for key in list(self._curves):
+            self.remove_curve(key)
+
+    def set_background(self, bg):
+        self.pw.setBackground(bg)
+
+
+class MultiAxisPlot(QtWidgets.QWidget):
+    """Overlay with one Y axis PER UNIT (psi / V / rpm / C / %), so mixed-scale
+    signals are all readable at their true values. Curves are grouped by unit;
+    each extra unit gets its own right-hand axis + linked ViewBox."""
+
+    def __init__(self):
+        super().__init__()
+        lay = QtWidgets.QVBoxLayout(self)
+        lay.setContentsMargins(0, 0, 0, 0)
+        self.glw = pg.GraphicsLayoutWidget()
+        lay.addWidget(self.glw)
+        self.p = self.glw.addPlot()
+        self.p.showGrid(x=True, y=True, alpha=0.2)
+        self.p.setLabel("bottom", "time", units="s")
+        self.legend = self.p.addLegend(offset=(10, 10))
+        self.base_vb = self.p.vb
+        self._units = {}        # unit -> {vb, ax, base}
+        self._curves = {}       # key -> {curve, unit}
+        self._next_col = 3
+        self.base_vb.sigResized.connect(self._sync)
+
+    def _ensure_unit(self, unit):
+        e = self._units.get(unit)
+        if e is not None:
+            return e
+        if not self._units:                         # first unit -> base left axis
+            self.p.setLabel("left", unit)
+            e = {"vb": self.base_vb, "ax": self.p.getAxis("left"), "base": True}
+        elif len(self._units) - 1 < MAX_EXTRA_AXES:  # add a right axis
+            vb = pg.ViewBox()
+            ax = pg.AxisItem("right")
+            self.p.layout.addItem(ax, 2, self._next_col)
+            self._next_col += 1
+            self.p.scene().addItem(vb)
+            ax.linkToView(vb)
+            vb.setXLink(self.p)
+            ax.setLabel(unit)
+            e = {"vb": vb, "ax": ax, "base": False}
+            self._sync()
+        else:                                        # out of axes -> reuse base
+            e = self._units[next(iter(self._units))]
+        self._units[unit] = e
+        return e
+
+    def add_curve(self, key, name, unit, color):
+        e = self._ensure_unit(unit)
+        curve = pg.PlotCurveItem(pen=pg.mkPen(color, width=2), name=name)
+        e["vb"].addItem(curve)
+        self.legend.addItem(curve, name)
+        self._curves[key] = {"curve": curve, "unit": unit}
+
+    def set_data(self, key, xs, ys):
+        c = self._curves.get(key)
+        if c is not None:
+            c["curve"].setData(xs, ys)
+
+    def remove_curve(self, key):
+        c = self._curves.pop(key, None)
+        if not c:
+            return
+        e = self._units.get(c["unit"])
+        if e:
+            e["vb"].removeItem(c["curve"])
+        try:
+            self.legend.removeItem(c["curve"])
+        except Exception:
+            pass
+
+    def clear(self):
+        for key in list(self._curves):
+            self.remove_curve(key)
+
+    def set_y_label(self, _text):
+        pass                                         # multi-axis labels itself per unit
+
+    def set_background(self, bg):
+        self.glw.setBackground(bg)
+
+    def _sync(self):
+        rect = self.base_vb.sceneBoundingRect()
+        for e in self._units.values():
+            if not e["base"]:
+                e["vb"].setGeometry(rect)
+                e["vb"].linkedViewChanged(self.base_vb, e["vb"].XAxis)
+
+
+class ArcGauge(QtWidgets.QWidget):
+    """A 270-degree arc gauge for a single signal: filled arc to the current
+    value, peak tick, big numeric readout, name + unit."""
+
+    def __init__(self, name, unit, vmin, vmax, accent="#3cb44b"):
+        super().__init__()
+        self.name = name
+        self.unit = unit
+        self.vmin = float(vmin)
+        self.vmax = float(vmax) if vmax != vmin else float(vmin) + 1.0
+        self.accent = QtGui.QColor(accent)
+        self.value = None
+        self.peak = None
+        self.setMinimumSize(150, 130)
+
+    def set_value(self, v, peak=None):
+        self.value = v
+        self.peak = peak
+        self.update()
+
+    def _frac(self, v):
+        return max(0.0, min(1.0, (v - self.vmin) / (self.vmax - self.vmin)))
+
+    def paintEvent(self, _ev):
+        p = QtGui.QPainter(self)
+        p.setRenderHint(QtGui.QPainter.Antialiasing)
+        w, h = self.width(), self.height()
+        p.fillRect(self.rect(), QtGui.QColor("#141414"))   # own dark bg (theme-proof)
+        m = 14
+        side = min(w, h - 18)
+        rect = QtCore.QRectF((w - side) / 2 + m / 2, m / 2, side - m, side - m)
+        start, span = 225 * 16, -270 * 16            # 270deg sweep, top-open down
+
+        def arc_pen(color, width):
+            pen = QtGui.QPen(QtGui.QColor(color), width)
+            pen.setCapStyle(QtCore.Qt.RoundCap)
+            return pen
+
+        p.setPen(arc_pen("#333", 9))
+        p.drawArc(rect, start, span)
+
+        if self.value is not None:
+            frac = self._frac(self.value)
+            p.setPen(arc_pen(self.accent, 9))
+            p.drawArc(rect, start, int(span * frac))
+            if self.peak is not None and self.peak != self.value:
+                pf = self._frac(self.peak)
+                ang = (225 - 270 * pf)
+                p.setPen(QtGui.QPen(QtGui.QColor("#e6c84b"), 2))
+                cx, cy = rect.center().x(), rect.center().y()
+                r1, r2 = side / 2 - m - 9, side / 2 - m + 2
+                a = math.radians(ang)
+                p.drawLine(QtCore.QPointF(cx + r1 * math.cos(a), cy - r1 * math.sin(a)),
+                           QtCore.QPointF(cx + r2 * math.cos(a), cy - r2 * math.sin(a)))
+
+        p.setPen(QtGui.QColor("#eee"))
+        f = p.font(); f.setPointSize(15); f.setBold(True); p.setFont(f)
+        val = "--" if self.value is None else f"{self.value:g}"
+        p.drawText(rect, QtCore.Qt.AlignCenter, val)
+        f.setPointSize(8); f.setBold(False); p.setFont(f)
+        p.setPen(QtGui.QColor("#999"))
+        p.drawText(QtCore.QRectF(0, h - 16, w, 14), QtCore.Qt.AlignCenter,
+                   f"{self.name}  ({self.unit})" if self.unit else self.name)
+        p.end()
+
+
+class GaugeGrid(QtWidgets.QScrollArea):
+    """Scrollable grid of ArcGauges, one per signal."""
+
+    def __init__(self):
+        super().__init__()
+        self.setWidgetResizable(True)
+        self.setStyleSheet("QScrollArea, QWidget { background: #111; }")
+        self._inner = QtWidgets.QWidget()
+        self._grid = QtWidgets.QGridLayout(self._inner)
+        self._grid.setSpacing(8)
+        self.setWidget(self._inner)
+        self._gauges = {}
+        self._cols = 4
+
+    def rebuild(self, specs):
+        """specs: list of (key, name, unit, vmin, vmax, accent)."""
+        while self._grid.count():
+            item = self._grid.takeAt(0)
+            wdg = item.widget()
+            if wdg:
+                wdg.deleteLater()
+        self._gauges = {}
+        for i, (key, name, unit, vmin, vmax, accent) in enumerate(specs):
+            g = ArcGauge(name, unit, vmin, vmax, accent)
+            self._gauges[key] = g
+            self._grid.addWidget(g, i // self._cols, i % self._cols)
+
+    def keys(self):
+        return set(self._gauges)
+
+    def set_value(self, key, v, peak=None):
+        g = self._gauges.get(key)
+        if g is not None:
+            g.set_value(v, peak)