feat: support mixed signal axis groups

Add a transactional axis organizer for shared and separate signal plots.
Persist group assignments by object UUID and restore them across selections.
Synchronize compatible X axes and share layouts with detached plot views.
Preserve unique object UUIDs across creation, duplication, and HDF5 reloads.
Add French translations, release notes, and unit, Python, and E2E coverage.

Closes #16

Author: PierreRaybaut

CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
 
 ## [Unreleased]
 
+### Added in Unreleased
+
+- **Mixed signal axis groups**: selected signals may now be organized so related curves share one axis while other curves remain on separate vertical or horizontal axes. Compatible X axes stay synchronized, and each selection's organization is restored locally when the same workspace objects are selected again.
+
 ## [0.7.0] - 2026-08-03
 
 ### Added in 0.7.0

src/App.tsx

@@ -68,6 +68,7 @@ import { MultiImagePlot, MULTI_IMAGE_LIMIT } from "./components/MultiImagePlot";
 import {
   bundleSignalResults,
   normalizeSignalLayoutMode,
+  type SignalAxisGroup,
   type SignalLayoutMode,
   type SignalResultBundle,
 } from "./components/signalPlotLayout";
@@ -79,9 +80,11 @@ import {
   LazyProfileDefinitionDialog as ProfileDefinitionDialog,
   LazyRoiGridDialog as RoiGridDialog,
   LazySeparateViewDialog as SeparateViewDialog,
+  LazySignalAxisGroupsDialog as SignalAxisGroupsDialog,
   LazySignalPlot as SignalPlot,
 } from "./components/lazyPlotComponents";
 import { useSelectionView } from "./hooks/useSelectionView";
+import { useSignalAxisGroups } from "./hooks/useSignalAxisGroups";
 import { DataSetDialog } from "./components/DataSetDialog";
 import type { ProfileFeatureId } from "./components/ProfileDefinitionDialog";
 import { OperandPicker } from "./components/OperandPicker";
@@ -677,6 +680,33 @@ export default function App() {
   /** Other signals selected alongside ``currentId`` and rendered according
    *  to the persisted multi-signal layout preference. */
   const [extraSignals, setExtraSignals] = useState<SignalData[]>([]);
+  const selectedSignalData = useMemo(
+    () => (data ? [data, ...extraSignals] : []),
+    [data, extraSignals],
+  );
+  const { groups: signalAxisGroups, applyGroups: applySignalAxisGroups } =
+    useSignalAxisGroups(selectedSignalData);
+  const [signalAxisGroupsDialogOpen, setSignalAxisGroupsDialogOpen] =
+    useState(false);
+  const openSignalAxisGroupsDialog = useCallback(
+    () => setSignalAxisGroupsDialogOpen(true),
+    [],
+  );
+  const closeSignalAxisGroupsDialog = useCallback(
+    () => setSignalAxisGroupsDialogOpen(false),
+    [],
+  );
+  const handleApplySignalAxisGroups = useCallback(
+    (
+      groups: SignalAxisGroup[],
+      layoutMode: Exclude<SignalLayoutMode, "overlay">,
+    ) => {
+      applySignalAxisGroups(groups);
+      setSignalLayoutMode(layoutMode);
+      setSignalAxisGroupsDialogOpen(false);
+    },
+    [applySignalAxisGroups, setSignalLayoutMode],
+  );
   const [imageData, setImageData] = useState<ImageData | null>(null);
   const [extraImages, setExtraImages] = useState<ImageData[]>([]);
   /** Multi-image view mode: ``false`` = thumbnail grid (default),
@@ -3985,6 +4015,9 @@ export default function App() {
         signalLayoutMode,
         signalLayoutAvailable: treeKind === "signal",
         onSetSignalLayoutMode: setSignalLayoutMode,
+        signalAxisGroupsAvailable:
+          treeKind === "signal" && selectedSignalData.length > 1,
+        onOrganizeSignalAxes: openSignalAxisGroupsDialog,
         onOpenSeparateView: openSeparateView,
         hasSelection: selectedIds.length > 0 || currentId !== null,
         notebookFloating,
@@ -4120,6 +4153,8 @@ export default function App() {
       toggleGraphicalTitles,
       signalLayoutMode,
       setSignalLayoutMode,
+      selectedSignalData.length,
+      openSignalAxisGroupsDialog,
       openSeparateView,
       aiPanelVisible,
       toggleAIPanel,
@@ -4496,6 +4531,8 @@ export default function App() {
                   extraResults={extraResults}
                   layoutMode={signalLayoutMode}
                   onLayoutModeChange={setSignalLayoutMode}
+                  axisGroups={signalAxisGroups}
+                  onEditAxisGroups={openSignalAxisGroupsDialog}
                 />
               </Suspense>
             )}
@@ -4999,11 +5036,28 @@ export default function App() {
                   showGraphicalTitles={showGraphicalTitles}
                   signalLayoutMode={signalLayoutMode}
                   onSignalLayoutModeChange={setSignalLayoutMode}
+                  signalAxisGroups={signalAxisGroups}
+                  onEditSignalAxisGroups={openSignalAxisGroupsDialog}
                   onClose={closeSeparateView}
                 />
               </Suspense>
             );
           })()}
+        {signalAxisGroupsDialogOpen && selectedSignalData.length > 1 && (
+          <Suspense fallback={null}>
+            <SignalAxisGroupsDialog
+              key={selectedSignalData
+                .map((signal) => `${signal.uuid ?? ""}:${signal.id}`)
+                .sort()
+                .join("|")}
+              signals={selectedSignalData}
+              groups={signalAxisGroups}
+              layoutMode={signalLayoutMode}
+              onApply={handleApplySignalAxisGroups}
+              onCancel={closeSignalAxisGroupsDialog}
+            />
+          </Suspense>
+        )}
         <DialogBridge />
         {contextMenu && (
           <ContextMenu

src/actions/registry.ts

@@ -458,6 +458,10 @@ export interface ViewActionCallbacks {
   signalLayoutAvailable: boolean;
   /** Select and persist the multi-signal plot arrangement. */
   onSetSignalLayoutMode: (mode: SignalLayoutMode) => void;
+  /** Whether more than one signal is available for axis grouping. */
+  signalAxisGroupsAvailable: boolean;
+  /** Open the selected-signal axis grouping editor. */
+  onOrganizeSignalAxes: () => void;
   /** Open the current selection in a full-screen popout dialog. */
   onOpenSeparateView: () => void;
   /** True when the active panel has at least one object selected
@@ -548,6 +552,15 @@ export function buildViewActions(cb: ViewActionCallbacks): ActionDescriptor[] {
         if (cb.signalLayoutMode !== mode) cb.onSetSignalLayoutMode(mode);
       },
     })),
+    {
+      id: "view.signal_axes.organize",
+      label: t("Organize axes…"),
+      menuPath: "View/Signal plot layout/Organize axes…",
+      beginGroup: true,
+      enabled: (state) =>
+        state.status === "ready" && !state.busy && cb.signalAxisGroupsAvailable,
+      run: cb.onOrganizeSignalAxes,
+    },
     {
       id: "view.notebook_floating",
       label: `${notebookPrefix}${t("Detach Notebooks panel")}`,

src/components/SeparateViewDialog.tsx

@@ -16,7 +16,11 @@
 import { useEffect } from "react";
 import { ImagePlot } from "./ImagePlot";
 import { SignalPlot } from "./SignalPlot";
-import type { SignalLayoutMode, SignalResultBundle } from "./signalPlotLayout";
+import type {
+  SignalAxisGroup,
+  SignalLayoutMode,
+  SignalResultBundle,
+} from "./signalPlotLayout";
 import type {
   ImageData,
   PlotlyAnnotations,
@@ -53,6 +57,8 @@ interface Props {
   showGraphicalTitles: boolean;
   signalLayoutMode: SignalLayoutMode;
   onSignalLayoutModeChange: (mode: SignalLayoutMode) => void;
+  signalAxisGroups: readonly SignalAxisGroup[];
+  onEditSignalAxisGroups: () => void;
   onClose: () => void;
 }
 
@@ -62,6 +68,8 @@ export function SeparateViewDialog({
   showGraphicalTitles,
   signalLayoutMode,
   onSignalLayoutModeChange,
+  signalAxisGroups,
+  onEditSignalAxisGroups,
   onClose,
 }: Props) {
   // Close on Escape — same convention as the existing ConfirmDialog.
@@ -117,6 +125,8 @@ export function SeparateViewDialog({
               extraResults={content.extraResults}
               layoutMode={signalLayoutMode}
               onLayoutModeChange={onSignalLayoutModeChange}
+              axisGroups={signalAxisGroups}
+              onEditAxisGroups={onEditSignalAxisGroups}
             />
           ) : (
             <ImagePlot