[960] Display possible 'subject' Usages in a tree instead of a list

In the 'General View' diagram, the creation tool for SubjectParameter
now shows possible candidate Usages in a tree instead of a flat list.

Bug: #960
Signed-off-by: Florent Latombe <florent.latombe@obeo.fr>

Author: flatombe

CHANGELOG.adoc

@@ -17,6 +17,7 @@
 - https://github.com/eclipse-syson/syson/issues/1061[#1061] [general-view] Add ellipsis on `Packages` label, to provide visual feedback on name overflow.
 - https://github.com/eclipse-syson/syson/issues/1007[#1007] Improve direct edit on Feature elements to be able to set the `isDefault` and `isInitial` properties
 - https://github.com/eclipse-syson/syson/issues/1033[#1033] [explorer] Make it possible to create a diagram representation directly under a `root Namespace` element
+- https://github.com/eclipse-syson/syson/issues/960[#960] [general-view] In the selection dialog of the `subject` creation tool, display possible `Usage` candidates in a tree instead of a list.
 
 === New features
 

backend/views/syson-diagram-common-view/src/main/java/org/eclipse/syson/diagram/common/view/services/ViewToolService.java

@@ -1227,6 +1227,29 @@ public List<? extends Object> getStakeholderSelectionDialogChildren(Object selec
         return this.getChildrenWithInstancesOf(selectionDialogTreeElement, SysmlPackage.eINSTANCE.getPartUsage());
     }
 
+    /**
+     * Provides the root elements in the tree of the selection dialog for the SubjectParameter creation tool.
+     *
+     * @param editingContext
+     *            the (non-{@code null}) {@link IEditingContext}.
+     * @return the (non-{@code null}) {@link List} of all {@link Resource} that contain at least one {@link Type}.
+     */
+    public List<Resource> getSubjectSelectionDialogElements(IEditingContext editingContext) {
+        return this.getAllResourcesWithInstancesOf(editingContext, SysmlPackage.eINSTANCE.getUsage());
+    }
+
+    /**
+     * Provides the children of element in the tree of the selection dialog for the SubjectParameter creation tool.
+     *
+     * @param selectionDialogTreeElement
+     *            a (non-{@code null}) selection dialog tree element.
+     * @return the (non-{@code null}) {@link List} of all children that contain (possibly indirectly) or are
+     *         {@link Usage}.
+     */
+    public List<? extends Object> getSubjectSelectionDialogChildren(Object selectionDialogTreeElement) {
+        return this.getChildrenWithInstancesOf(selectionDialogTreeElement, SysmlPackage.eINSTANCE.getUsage());
+    }
+
     /**
      * Provides the root elements in the tree of the selection dialog for the ActorParameter creation tool.
      *

backend/views/syson-diagram-common-view/src/main/java/org/eclipse/syson/diagram/common/view/tools/SubjectCompartmentNodeToolProvider.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2024 Obeo.
+ * Copyright (c) 2024, 2025 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
@@ -12,12 +12,8 @@
  *******************************************************************************/
 package org.eclipse.syson.diagram.common.view.tools;
 
-import java.util.List;
-
 import org.eclipse.sirius.components.view.diagram.SelectionDialogDescription;
-import org.eclipse.syson.sysml.SysmlPackage;
 import org.eclipse.syson.util.AQLUtils;
-import org.eclipse.syson.util.SysMLMetamodelHelper;
 
 /**
  * Node tool provider for Subject compartment in the element that need such compartment.
@@ -33,13 +29,14 @@ protected String getServiceCallExpression() {
 
     @Override
     protected SelectionDialogDescription getSelectionDialogDescription() {
-        String domainType = SysMLMetamodelHelper.buildQualifiedName(SysmlPackage.eINSTANCE.getType());
         var selectionDialogTree = this.diagramBuilderHelper.newSelectionDialogTreeDescription()
-                .elementsExpression(AQLUtils.getSelfServiceCallExpression("getAllReachable", List.of(domainType, "false")))
+                .elementsExpression(AQLUtils.getServiceCallExpression("editingContext", "getSubjectSelectionDialogElements"))
+                .childrenExpression(AQLUtils.getSelfServiceCallExpression("getSubjectSelectionDialogChildren"))
+                .isSelectableExpression("aql:self.oclIsKindOf(sysml::Usage)")
                 .build();
         return this.diagramBuilderHelper.newSelectionDialogDescription()
                 .selectionDialogTreeDescription(selectionDialogTree)
-                .selectionMessage("Select an existing Type as subject:")
+                .selectionMessage("Select an existing Usage as subject:")
                 .build();
     }
 

doc/content/modules/user-manual/assets/images/release-notes-gv-subject-creation-selection-dialog-tree.png

@@ -18,6 +18,10 @@ image::release-notes-package-name-ellipsis-overflow.png[Package name overflow wi
 
 image::release-notes-create-diagram-on-root-namespace-element.png[Create diagram on root namespace element, width=50%, height=50%]
 
+- In the `General View` diagram, the subject creation tool displays available `Usages` in a tree instead of a list.
+
+image::release-notes-gv-subject-creation-selection-dialog-tree.png['subject creation tool selection dialog tree' compartment, width=50%, height=50%]
+
 == Dependency update
 
 == Technical details