[896] Allow to make specific changes before and after the layout

Bug: eclipse-sirius#896
Change-Id: Ia06fcedcef118aff35741f57e2847d9e1aa53862
Signed-off-by: Axel RICHARD <axel.richard@obeo.fr>

CHANGELOG.adoc

@@ -39,6 +39,7 @@ Currently it is not possible to compute different values for width and height.
 - https://github.com/eclipse-sirius/sirius-components/issues/134[#134] [workbench] The internal API of the workbench is now ready to accept features leveraging a multi-selection
 - [form] Add a tooltip to always make the full label available
 - [core] Customize the Spring `ObjectMapper` instead of creating a brand new one from scratch in our `ObjectMapperConfiguration`
+- https://github.com/eclipse-sirius/sirius-components/issues/896[#896] [diagram] Allow to make specific changes before and after the layout
 
 === Bug fixes
 

backend/sirius-web-diagrams-layout/src/main/java/org/eclipse/sirius/web/diagrams/layout/ISiriusWebLayoutConfigurator.java

@@ -14,7 +14,10 @@
 
 import org.eclipse.elk.core.util.IGraphElementVisitor;
 import org.eclipse.elk.graph.ElkGraphElement;
+import org.eclipse.elk.graph.ElkNode;
 import org.eclipse.elk.graph.properties.IPropertyHolder;
+import org.eclipse.sirius.web.core.api.IEditingContext;
+import org.eclipse.sirius.web.diagrams.Diagram;
 
 /**
  * Interface that can configure layout options based on the {@code id} and {@code type} attributes of diagram elements.
@@ -30,4 +33,8 @@ public interface ISiriusWebLayoutConfigurator extends IGraphElementVisitor {
 
     IPropertyHolder configureByElementClass(Class<? extends ElkGraphElement> elementClass);
 
+    ElkNode applyBeforeLayout(ElkNode elkDiagram, IEditingContext editingContext, Diagram diagram);
+
+    ElkNode applyAfterLayout(ElkNode elkDiagram, IEditingContext editingContext, Diagram diagram);
+
 }

backend/sirius-web-diagrams-layout/src/main/java/org/eclipse/sirius/web/diagrams/layout/LayoutConfiguratorRegistry.java

@@ -27,6 +27,8 @@
 import org.eclipse.elk.core.options.SizeConstraint;
 import org.eclipse.elk.core.options.SizeOptions;
 import org.eclipse.elk.graph.ElkEdge;
+import org.eclipse.elk.graph.ElkNode;
+import org.eclipse.sirius.web.core.api.IEditingContext;
 import org.eclipse.sirius.web.diagrams.Diagram;
 import org.eclipse.sirius.web.diagrams.NodeType;
 import org.eclipse.sirius.web.diagrams.description.DiagramDescription;
@@ -122,4 +124,25 @@ public ISiriusWebLayoutConfigurator getLayoutConfigurator(Diagram diagram, Diagr
         }
         return this.getDefaultLayoutConfigurator();
     }
+
+    public ElkNode applyBeforeLayout(ElkNode elkDiagram, IEditingContext editingContext, Diagram diagram, DiagramDescription diagramDescription) {
+        for (var customLayoutProvider : this.customLayoutProviders) {
+            var customLayout = customLayoutProvider.getLayoutConfigurator(diagram, diagramDescription);
+            if (customLayout.isPresent()) {
+                return customLayout.get().applyBeforeLayout(elkDiagram, editingContext, diagram);
+            }
+        }
+        return elkDiagram;
+    }
+
+    public ElkNode applyAfterLayout(ElkNode elkDiagram, IEditingContext editingContext, Diagram diagram, DiagramDescription diagramDescription) {
+        for (var customLayoutProvider : this.customLayoutProviders) {
+            var customLayout = customLayoutProvider.getLayoutConfigurator(diagram, diagramDescription);
+            if (customLayout.isPresent()) {
+                return customLayout.get().applyAfterLayout(elkDiagram, editingContext, diagram);
+            }
+        }
+        return elkDiagram;
+    }
+
 }

backend/sirius-web-diagrams-layout/src/main/java/org/eclipse/sirius/web/diagrams/layout/LayoutService.java

@@ -83,10 +83,16 @@ public Diagram layout(IEditingContext editingContext, Diagram diagram) {
         ELKConvertedDiagram convertedDiagram = this.elkDiagramConverter.convert(diagram);
 
         ElkNode elkDiagram = convertedDiagram.getElkDiagram();
-        var representationDescription = this.representationDescriptionSearchService.findById(editingContext, diagram.getDescriptionId());
+        var optionalRepresentationDescription = this.representationDescriptionSearchService.findById(editingContext, diagram.getDescriptionId());
         ISiriusWebLayoutConfigurator layoutConfigurator;
-        if (representationDescription.isPresent() && representationDescription.get() instanceof DiagramDescription) {
-            layoutConfigurator = this.layoutConfiguratorRegistry.getLayoutConfigurator(diagram, (DiagramDescription) representationDescription.get());
+        if (optionalRepresentationDescription.isPresent()) {
+            var representationDescription = optionalRepresentationDescription.get();
+            if (representationDescription instanceof DiagramDescription) {
+                elkDiagram = this.layoutConfiguratorRegistry.applyBeforeLayout(elkDiagram, editingContext, diagram, (DiagramDescription) representationDescription);
+                layoutConfigurator = this.layoutConfiguratorRegistry.getLayoutConfigurator(diagram, (DiagramDescription) representationDescription);
+            } else {
+                layoutConfigurator = this.layoutConfiguratorRegistry.getDefaultLayoutConfigurator();
+            }
         } else {
             layoutConfigurator = this.layoutConfiguratorRegistry.getDefaultLayoutConfigurator();
         }
@@ -95,6 +101,13 @@ public Diagram layout(IEditingContext editingContext, Diagram diagram) {
         IGraphLayoutEngine engine = new RecursiveGraphLayoutEngine();
         engine.layout(elkDiagram, new BasicProgressMonitor());
 
+        if (optionalRepresentationDescription.isPresent()) {
+            var representationDescription = optionalRepresentationDescription.get();
+            if (representationDescription instanceof DiagramDescription) {
+                elkDiagram = this.layoutConfiguratorRegistry.applyAfterLayout(elkDiagram, editingContext, diagram, (DiagramDescription) representationDescription);
+            }
+        }
+
         Map<String, ElkGraphElement> id2ElkGraphElements = convertedDiagram.getId2ElkGraphElements();
         Diagram layoutedDiagram = this.elkLayoutedDiagramProvider.getLayoutedDiagram(diagram, elkDiagram, id2ElkGraphElements);
 

backend/sirius-web-diagrams-layout/src/main/java/org/eclipse/sirius/web/diagrams/layout/SiriusWebLayoutConfigurator.java

@@ -17,8 +17,11 @@
 
 import org.eclipse.elk.core.LayoutConfigurator;
 import org.eclipse.elk.graph.ElkGraphElement;
+import org.eclipse.elk.graph.ElkNode;
 import org.eclipse.elk.graph.properties.IPropertyHolder;
 import org.eclipse.elk.graph.properties.MapPropertyHolder;
+import org.eclipse.sirius.web.core.api.IEditingContext;
+import org.eclipse.sirius.web.diagrams.Diagram;
 
 /**
  * Specialized {@link LayoutConfigurator} that can configure layout options based on the {@code id} and {@code type}
@@ -92,4 +95,14 @@ private SiriusWebLayoutConfigurator overrideWith(SiriusWebLayoutConfigurator lay
         return this;
     }
 
+    @Override
+    public ElkNode applyBeforeLayout(ElkNode elkDiagram, IEditingContext editingContext, Diagram diagram) {
+        return elkDiagram;
+    }
+
+    @Override
+    public ElkNode applyAfterLayout(ElkNode elkDiagram, IEditingContext editingContext, Diagram diagram) {
+        return elkDiagram;
+    }
+
 }