[2239] Add the support for a frontend tool to rotate Fork and Join nodes

CHANGELOG.adoc

@@ -74,6 +74,7 @@ It leverages the selection dialog to either create an _occurrence timeslice/snap
 - https://github.com/eclipse-syson/syson/issues/2260[#2260] [diagrams] Add the _New Assume Constraint_ or _New Require Constraint_ edge tools to create _assume_ and _require_ graphical edges.
 - https://github.com/eclipse-syson/syson/issues/2113[#2113] [diagrams] Handle start/end/merge/decision... graphical nodes on Action Flow View diagram background
 - https://github.com/eclipse-syson/syson/issues/2303[#2303] [diagrams] Add support for list item inheritance in _states_ and _exhibit states_ compartments
+- https://github.com/eclipse-syson/syson/issues/2239[#2239] [diagrams] Add the support for a frontend tool to rotate `ForkNode` and `JoinNode` graphical nodes
 
 == v2026.5.0
 

backend/application/syson-application-configuration/src/main/java/org/eclipse/syson/application/nodes/services/ForkJoinNodePaletteToolProvider.java

@@ -0,0 +1,97 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.syson.application.nodes.services;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+
+import org.eclipse.sirius.components.collaborative.diagrams.DiagramContext;
+import org.eclipse.sirius.components.collaborative.diagrams.dto.ITool;
+import org.eclipse.sirius.components.collaborative.diagrams.dto.SingleClickOnDiagramElementTool;
+import org.eclipse.sirius.components.collaborative.diagrams.dto.ToolSection;
+import org.eclipse.sirius.components.core.api.IEditingContext;
+import org.eclipse.sirius.components.core.api.IObjectSearchService;
+import org.eclipse.sirius.components.diagrams.Node;
+import org.eclipse.sirius.components.diagrams.description.IDiagramElementDescription;
+import org.eclipse.sirius.components.view.emf.diagram.api.IPaletteToolsProvider;
+import org.eclipse.syson.sysml.ForkNode;
+import org.eclipse.syson.sysml.JoinNode;
+import org.springframework.stereotype.Service;
+
+/**
+ * Used to contribute the <em>Rotate</em> tool for {@link ForkNode} and {@link JoinNode} graphical nodes.
+ * <p>
+ *     This {@link IPaletteToolsProvider} only declare the tool.
+ *     The behavior is contributed in the frontend.
+ * </p>
+ *
+ * @author gcoutable
+ */
+@Service
+public class ForkJoinNodePaletteToolProvider implements IPaletteToolsProvider {
+
+    private static final String FORK_JOIN_NODE_ROTATE_TOOL_ID = "fork_join_node_rotate_tool";
+
+    private static final String FORK_JOIN_NODE_ROTATE_TOOL_LABEL = "Rotate";
+
+    private static final String FORK_JOIN_NODE_ROTATE_TOOL_SECTION_ID = "edit-section";
+
+    private static final String FORK_JOIN_NODE_ROTATE_TOOL_SECTION_LABEL = "Edit";
+
+    private final IObjectSearchService objectSearchService;
+
+    public ForkJoinNodePaletteToolProvider(IObjectSearchService objectSearchService) {
+        this.objectSearchService = Objects.requireNonNull(objectSearchService);
+    }
+
+    @Override
+    public List<ToolSection> createExtraToolSections(IEditingContext editingContext, DiagramContext diagramContext, Object diagramElementDescription, Object diagramElement) {
+        List<ITool> extraTool = new ArrayList<>();
+
+        var optionalTargetObjectId = this.getTargetObjectId(diagramElement);
+
+        if (optionalTargetObjectId.isPresent() && diagramElementDescription instanceof IDiagramElementDescription nodeDescription) {
+            var semanticObject = this.objectSearchService.getObject(editingContext, optionalTargetObjectId.get());
+            if (semanticObject.isPresent() && (semanticObject.get() instanceof ForkNode || semanticObject.get() instanceof JoinNode)) {
+                ITool tool = SingleClickOnDiagramElementTool.newSingleClickOnDiagramElementTool(FORK_JOIN_NODE_ROTATE_TOOL_ID)
+                        .label(FORK_JOIN_NODE_ROTATE_TOOL_LABEL)
+                        .targetDescriptions(List.of(nodeDescription))
+                        .iconURL(List.of())
+                        .keyBindings(List.of())
+                        .build();
+                extraTool.add(tool);
+            }
+        }
+
+        if (!extraTool.isEmpty()) {
+            return List.of(new ToolSection(FORK_JOIN_NODE_ROTATE_TOOL_SECTION_ID, FORK_JOIN_NODE_ROTATE_TOOL_SECTION_LABEL, List.of(), extraTool));
+        } else {
+            return List.of();
+        }
+    }
+
+    private Optional<String> getTargetObjectId(Object diagramElement) {
+        Optional<String> result = Optional.empty();
+        if (diagramElement instanceof Node node) {
+            result = Optional.of(node.getTargetObjectId());
+        }
+        return result;
+    }
+
+    @Override
+    public List<ITool> createQuickAccessTools(IEditingContext editingContext, DiagramContext diagramContext, Object diagramElementDescription, Object diagramElement) {
+        return List.of();
+    }
+}

backend/views/syson-diagram-common-view/src/main/java/org/eclipse/syson/diagram/common/view/nodes/ForkActionNodeDescriptionProvider.java

@@ -49,7 +49,7 @@ protected String getRemoveToolLabel() {
 
     @Override
     protected UserResizableDirection isNodeResizable() {
-        return UserResizableDirection.HORIZONTAL;
+        return UserResizableDirection.BOTH;
     }
 
     @Override

doc/content/modules/user-manual/pages/release-notes/2026.7.0.adoc

@@ -47,6 +47,9 @@ image::release-notes-assume-and-require-edge-tools.png[list available edge tools
 Users should use the dedicated tools to edit expressions instead, as they ensure only valid expressions (with all names resolving) are accepted.
 ** Add support for list item inheritance in _states_ and _exhibit states_ compartments.
 ** Add support for creating _Start_, _Done_, _Decision_, _Fork_, _Join_, and _Merge_ actions directly on the background of an `Action Flow View` diagram if its root element is an `ActionUsage` or `ActionDefinition`.
+** Add the support for a tool to rotate `ForkNode` and `JoinNode` graphical nodes.
++
+image::release-notes-rotate-fork-join-graphical-nodes.png[For both fork nodes and two join nodes, display one horizontal and one vertical graphical node. Also display the palette with the rotate tool, width=60%,height=60%]
 
 * In the _Explorer_ view:
 

frontend/syson-components/src/extensions/registry/SysONExtensionRegistry.tsx

@@ -65,6 +65,7 @@ import { NewSysMLExpressionMenuContribution } from '../expressions/NewSysMLExpre
 import { InsertTextualSysMLMenuContribution } from '../InsertTextualSysMLv2MenuContribution';
 import { SysONNavigationBarMenuIcon } from '../navigationBarMenu/SysONNavigationBarMenuIcon';
 import { PublishProjectSysMLContentsAsLibraryCommand } from '../omnibox/PublishProjectSysMLContentsAsLibraryCommand';
+import { RotateNodeToolOverriddenContribution } from '../rotateNodeTool/RotateNodeToolOverriddenContribution';
 import { SysONDiagramPanelMenu } from '../SysONDiagramPanelMenu';
 
 const sysONExtensionRegistry: ExtensionRegistry = new ExtensionRegistry();
@@ -272,6 +273,12 @@ const diagramPaletteToolOverriddenContributions: PaletteToolOverriddenContributi
     },
     component: DeleteExpressionDiagramToolOverriddenContribution,
   },
+  {
+    canHandle: (tool: GQLTool) => {
+      return tool.id === 'fork_join_node_rotate_tool';
+    },
+    component: RotateNodeToolOverriddenContribution,
+  },
 ];
 
 sysONExtensionRegistry.putData<PaletteToolOverriddenContributionProps[]>(paletteToolOverrideExtensionPoint, {

frontend/syson-components/src/extensions/rotateNodeTool/RotateNodeToolOverriddenContribution.tsx

@@ -0,0 +1,46 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+import { DiagramContext, DiagramContextValue } from '@eclipse-sirius/sirius-components-diagrams';
+import { PaletteToolContributionComponentProps } from '@eclipse-sirius/sirius-components-palette';
+import Rotate90DegreesCwIcon from '@mui/icons-material/Rotate90DegreesCw';
+import ListItemButton from '@mui/material/ListItemButton';
+import ListItemIcon from '@mui/material/ListItemIcon';
+import ListItemText from '@mui/material/ListItemText';
+import { Fragment, useContext } from 'react';
+import { useRotateNode } from './useRotateNode';
+
+export const RotateNodeToolOverriddenContribution = ({
+  representationElementIds,
+}: PaletteToolContributionComponentProps) => {
+  const { readOnly } = useContext<DiagramContextValue>(DiagramContext);
+  const { rotate } = useRotateNode();
+
+  return (
+    <Fragment key="overridden_tool_node-rotate-contribution">
+      <ListItemButton
+        onClick={() => rotate(representationElementIds)}
+        data-testid="overridden_tool_node-rotate"
+        disabled={readOnly}
+        sx={{ paddingTop: 0, paddingBottom: 0 }}>
+        <ListItemIcon
+          sx={{ minWidth: 0, marginRight: (theme) => theme.spacing(2), color: (theme) => theme.palette.text.primary }}>
+          <Rotate90DegreesCwIcon fontSize="small" />
+        </ListItemIcon>
+        <ListItemText
+          primary={'Rotate'}
+          sx={{ '& .MuiListItemText-primary': { whiteSpace: 'nowrap', overflow: 'hidden', textOverflow: 'ellipsis' } }}
+        />
+      </ListItemButton>
+    </Fragment>
+  );
+};

frontend/syson-components/src/extensions/rotateNodeTool/useRotateNode.ts

@@ -0,0 +1,93 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+
+import { EdgeData, NodeData, useLayout, useSynchronizeLayoutData } from '@eclipse-sirius/sirius-components-diagrams';
+import { Edge, Node, useReactFlow } from '@xyflow/react';
+import { UseRotateNodeValue } from './useRotateNode.types';
+
+export const useRotateNode = (): UseRotateNodeValue => {
+  const { getNodes, getEdges, setNodes, setEdges } = useReactFlow<Node<NodeData>, Edge<EdgeData>>();
+  const { synchronizeLayoutData } = useSynchronizeLayoutData();
+  const { layout } = useLayout();
+
+  const rotate = (representationElementIds: string[]) => {
+    const updatedNodes: Node<NodeData>[] = getNodes().map((node) => {
+      if (representationElementIds.length > 0 && node.id === representationElementIds[0]) {
+        const cx = node.position.x + (node.width ?? 0) / 2;
+        const cy = node.position.y + (node.height ?? 0) / 2;
+
+        const newWidth = node.height ?? 0;
+        const newHeight = node.width ?? 0;
+
+        const newX = cx - newWidth / 2;
+        const newY = cy - newHeight / 2;
+        return {
+          ...node,
+          position: { x: newX, y: newY },
+          width: newWidth,
+          height: newHeight,
+          data: { ...node.data, resizedByUser: true, connectionHandles: [] },
+        };
+      }
+      return node;
+    });
+
+    const updatedEdges: Edge<EdgeData>[] = getEdges().map((edge) => {
+      if (
+        ((representationElementIds.length > 0 && edge.source === representationElementIds[0]) ||
+          edge.target === representationElementIds[0]) &&
+        edge.data
+      ) {
+        return {
+          ...edge,
+          data: {
+            ...edge.data,
+            bendingPoints: null,
+          },
+        };
+      }
+      return edge;
+    });
+
+    const diagramToLayout = {
+      nodes: updatedNodes,
+      edges: updatedEdges,
+    };
+
+    layout(diagramToLayout, diagramToLayout, null, 'UNDEFINED', (laidOutDiagram) => {
+      const updatedNodesAfterLayout = updatedNodes.map((node) => {
+        if (representationElementIds.find((nodeId) => nodeId === node.id)) {
+          return laidOutDiagram.nodes.find((laidOutNode) => laidOutNode.id === node.id) ?? node;
+        }
+        return node;
+      });
+
+      const updatedEdgesAfterLayout = updatedEdges.map((edge) => {
+        if (representationElementIds.find((nodeId) => nodeId === edge.source || nodeId === edge.target)) {
+          return laidOutDiagram.edges.find((laidOutEdge) => laidOutEdge.id === edge.id) ?? edge;
+        }
+        return edge;
+      });
+
+      setNodes(updatedNodesAfterLayout);
+      setEdges(updatedEdgesAfterLayout);
+      const finalDiagram = {
+        nodes: updatedNodesAfterLayout,
+        edges: updatedEdgesAfterLayout,
+      };
+      synchronizeLayoutData(crypto.randomUUID(), 'layout', finalDiagram, 'UNCHANGED');
+    });
+  };
+
+  return { rotate };
+};

frontend/syson-components/src/extensions/rotateNodeTool/useRotateNode.types.ts

@@ -0,0 +1,16 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+
+export interface UseRotateNodeValue {
+  rotate: (representationElementIds: string[]) => void;
+}

integration-tests-playwright/playwright/e2e/rotate-node.spec.ts

@@ -0,0 +1,82 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Obeo.
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+import { expect, test } from '@playwright/test';
+import { PlaywrightExplorer } from '../helpers/PlaywrightExplorer';
+import { PlaywrightNode } from '../helpers/PlaywrightNode';
+import { PlaywrightProject } from '../helpers/PlaywrightProject';
+
+test.describe('diagram - general view', () => {
+  let projectId;
+  test.beforeEach(async ({ page, request }) => {
+    await page.addInitScript(() => {
+      // @ts-expect-error: we use a variable in the DOM to disable `fitView` functionality for Cypress tests.
+      window.document.DEACTIVATE_FIT_VIEW_FOR_CYPRESS_TESTS = true;
+    });
+    const project = await new PlaywrightProject(request).createSysMLV2Project('general');
+    projectId = project.projectId;
+
+    await page.goto(`/projects/${projectId}/edit`);
+    const playwrightExplorer = new PlaywrightExplorer(page);
+    await playwrightExplorer.uploadDocument('SysMLv2WithGeneralView.sysml');
+    await playwrightExplorer.expand('SysMLv2WithGeneralView.sysml');
+    await playwrightExplorer.expand('Package1');
+    await playwrightExplorer.createRepresentation('view1 [GeneralView]', 'General View', 'view1');
+
+    await page.getByTestId('arrange-all-main-button').click();
+
+    const partNode = new PlaywrightNode(page, 'part1', 'List');
+    await expect(partNode.nodeLocator).toBeAttached();
+
+    // Keep the diagram content visible without depending on Sirius Web's arrange-all toolbar controls.
+    await page.getByTestId('zoom-out').click();
+  });
+
+  test.afterEach(async ({ request }) => {
+    await new PlaywrightProject(request).deleteProject(projectId);
+  });
+
+  test('WHEN applying the rotate tool on a fork node, THEN the node is rotated', async ({ page, browserName }) => {
+    if (browserName === 'firefox') {
+      test.skip(); //The test fails inexplicably in Firefox.
+    }
+
+    // Create a new Action node
+    await page.getByTestId('rf__wrapper').click({ button: 'right', position: { x: 250, y: 250 } });
+    await expect(page.getByTestId('Palette')).toBeAttached();
+    await page.getByTestId('toolSection-Behavior').click();
+    await page.getByTestId('tool-New Action').click();
+    const playwrightActionNode = new PlaywrightNode(page, 'action1', 'List');
+    await expect(playwrightActionNode.nodeLocator).toBeAttached();
+
+    // Create a new Fork node in the Action node
+    await playwrightActionNode.openPalette();
+    await page.getByTestId('toolSection-Behavior').click();
+    await page.getByTestId('tool-New Fork').click();
+    const playwrightForkNode = new PlaywrightNode(page, 'forkNode1');
+    await expect(playwrightForkNode.nodeLocator).toBeAttached();
+    const {width, height} = await playwrightForkNode.getReactFlowSize();
+    const expectedRotatedWidth = height;
+    const expectedRotatedHeight = width;
+
+    // Apply the rotate tool on the Fork node
+    await playwrightForkNode.openPalette();
+    await page.getByTestId('toolSection-Edit').click();
+    await page.getByTestId('overridden_tool_node-rotate').click();
+    await playwrightForkNode.closePalette();
+    const rotatedSize = await playwrightForkNode.getReactFlowSize();
+
+    expect(rotatedSize.width).toBeCloseTo(expectedRotatedWidth, 0);
+    expect(rotatedSize.height).toBeCloseTo(expectedRotatedHeight, 0);
+  });
+
+});