[509070] Add an extension point to provide custom layout algorithms

A new extension point
"org.eclipse.sirius.diagram.ui.customLayoutAlgorithmProvider" has been
created and should be use by custom layout algorithm providers to be
sure to be available in VSM editor.

Bug: 509070
Change-Id: Ic8c796f68808b42ced53fb8bd6cb930d2c3865f1
Signed-off-by: Pierre Guilet <pierre.guilet@obeo.fr>

16 files changed, 593 insertions, 125 deletions

diff --git a/plugins/org.eclipse.sirius.diagram.elk/plugin.xml b/plugins/org.eclipse.sirius.diagram.elk/plugin.xml
index 523c6fff2b..05984629a6 100644
--- a/plugins/org.eclipse.sirius.diagram.elk/plugin.xml
+++ b/plugins/org.eclipse.sirius.diagram.elk/plugin.xml
@@ -16,4 +16,10 @@
        </Priority>
     </editpolicyProvider>
  </extension>
+  <extension
+        point="org.eclipse.sirius.diagram.ui.customLayoutAlgorithmProvider">
+     <customLayoutProvider
+           class="org.eclipse.sirius.diagram.elk.ELKAlgorithmProvider">
+     </customLayoutProvider>
+  </extension>
 </plugin>
diff --git a/plugins/org.eclipse.sirius.diagram.elk/src/org/eclipse/sirius/diagram/elk/DiagramElkPlugin.java b/plugins/org.eclipse.sirius.diagram.elk/src/org/eclipse/sirius/diagram/elk/DiagramElkPlugin.java
index 7c9ee89132..8c5b9d28a1 100644
--- a/plugins/org.eclipse.sirius.diagram.elk/src/org/eclipse/sirius/diagram/elk/DiagramElkPlugin.java
+++ b/plugins/org.eclipse.sirius.diagram.elk/src/org/eclipse/sirius/diagram/elk/DiagramElkPlugin.java
@@ -10,21 +10,6 @@
  *******************************************************************************/
 package org.eclipse.sirius.diagram.elk;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
-
-import org.eclipse.elk.core.data.LayoutAlgorithmData;
-import org.eclipse.elk.core.data.LayoutMetaDataService;
-import org.eclipse.elk.core.data.LayoutOptionData;
-import org.eclipse.elk.core.data.LayoutOptionData.Target;
-import org.eclipse.elk.core.data.LayoutOptionData.Type;
-import org.eclipse.elk.core.data.LayoutOptionData.Visibility;
-import org.eclipse.elk.core.options.CoreOptions;
-import org.eclipse.sirius.diagram.description.LayoutOption;
-import org.eclipse.sirius.diagram.ui.api.layout.EnumChoice;
-import org.eclipse.sirius.diagram.ui.api.layout.LayoutOptionFactory;
-import org.eclipse.sirius.diagram.ui.provider.DiagramUIPlugin;
 import org.eclipse.ui.plugin.AbstractUIPlugin;
 import org.osgi.framework.BundleContext;
 
@@ -45,62 +30,6 @@ public class DiagramElkPlugin extends AbstractUIPlugin {
     public void start(BundleContext context) throws Exception {
         super.start(context);
         plugin = this;
-
-        // we fill the Sirius layout algorithm registry with all ELK algorithms.
-        Collection<LayoutAlgorithmData> algorithmData = LayoutMetaDataService.getInstance().getAlgorithmData();
-        for (LayoutAlgorithmData layoutAlgorithmData : algorithmData) {
-
-            List<LayoutOptionData> optionDatas = LayoutMetaDataService.getInstance().getOptionData(layoutAlgorithmData, Target.PARENTS);
-            List<LayoutOption> layoutOptions = new ArrayList<>();
-            LayoutOptionFactory layoutOptionFactory = new LayoutOptionFactory();
-            for (LayoutOptionData layoutOptionData : optionDatas) {
-                if (!CoreOptions.ALGORITHM.getId().equals(layoutOptionData.getId()) && !layoutOptionData.getVisibility().equals(Visibility.HIDDEN)) {
-                    switch (layoutOptionData.getType()) {
-                    case STRING:
-                        layoutOptions.add(layoutOptionFactory.createStringOption((String) layoutOptionData.getDefault(), layoutOptionData.getId(), layoutOptionData.getDescription(),
-                                layoutOptionData.getName()));
-                        break;
-                    case BOOLEAN:
-                        layoutOptions.add(layoutOptionFactory.createBooleanOption((Boolean) layoutOptionData.getDefault(), layoutOptionData.getId(), layoutOptionData.getDescription(),
-                                layoutOptionData.getName()));
-                        break;
-                    case INT:
-                        layoutOptions.add(layoutOptionFactory.createIntegerOption((Integer) layoutOptionData.getDefault(), layoutOptionData.getId(), layoutOptionData.getDescription(),
-                                layoutOptionData.getName()));
-                        break;
-                    case DOUBLE:
-                        layoutOptions.add(layoutOptionFactory.createDoubleOption((Double) layoutOptionData.getDefault(), layoutOptionData.getId(), layoutOptionData.getDescription(),
-                                layoutOptionData.getName()));
-                        break;
-                    case ENUMSET:
-                    case ENUM:
-
-                        String[] choices = layoutOptionData.getChoices();
-                        List<EnumChoice> choicesList = new ArrayList<>();
-                        for (int i = 0; i < choices.length; i++) {
-                            String choiceId = choices[i];
-                            choicesList.add(new EnumChoice(choiceId, ""));
-
-                        }
-                        String defaultValue = null;
-                        Object defaultObject = layoutOptionData.getDefaultDefault();
-                        if (defaultObject instanceof Enum) {
-                            defaultValue = ((Enum<?>) defaultObject).name();
-                        }
-                        if (layoutOptionData.getType() == Type.ENUM) {
-                            layoutOptions.add(layoutOptionFactory.createEnumOption(choicesList, layoutOptionData.getId(), layoutOptionData.getDescription(), layoutOptionData.getName(), defaultValue));
-                        } else {
-                            layoutOptions.add(layoutOptionFactory.createEnumSetOption(choicesList, layoutOptionData.getId(), layoutOptionData.getDescription(), layoutOptionData.getName()));
-                        }
-
-                        break;
-                    default:
-                        break;
-                    }
-                }
-            }
-            DiagramUIPlugin.getPlugin().addLayoutProvider(layoutAlgorithmData.getId(), layoutAlgorithmData.getName(), () -> new ELKLayoutNodeProvider(), layoutOptions);
-        }
     }
 
     @Override
diff --git a/plugins/org.eclipse.sirius.diagram.elk/src/org/eclipse/sirius/diagram/elk/ELKAlgorithmProvider.java b/plugins/org.eclipse.sirius.diagram.elk/src/org/eclipse/sirius/diagram/elk/ELKAlgorithmProvider.java
new file mode 100644
index 0000000000..3e3b9aebee
--- /dev/null
+++ b/plugins/org.eclipse.sirius.diagram.elk/src/org/eclipse/sirius/diagram/elk/ELKAlgorithmProvider.java
@@ -0,0 +1,104 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Obeo
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+/**
+* 
+*/
+package org.eclipse.sirius.diagram.elk;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.eclipse.elk.core.data.LayoutAlgorithmData;
+import org.eclipse.elk.core.data.LayoutMetaDataService;
+import org.eclipse.elk.core.data.LayoutOptionData;
+import org.eclipse.elk.core.data.LayoutOptionData.Target;
+import org.eclipse.elk.core.data.LayoutOptionData.Type;
+import org.eclipse.elk.core.data.LayoutOptionData.Visibility;
+import org.eclipse.elk.core.options.CoreOptions;
+import org.eclipse.sirius.diagram.description.LayoutOption;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithm;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithmProvider;
+import org.eclipse.sirius.diagram.ui.api.layout.EnumChoice;
+import org.eclipse.sirius.diagram.ui.api.layout.LayoutOptionFactory;
+
+/**
+ * @author <a href=mailto:pierre.guilet@obeo.fr>Pierre Guilet</a>
+ *
+ */
+public class ELKAlgorithmProvider implements CustomLayoutAlgorithmProvider {
+
+    @Override
+    public List<CustomLayoutAlgorithm> getCustomLayoutAlgorithms() {
+        List<CustomLayoutAlgorithm> layoutAlgorithms = new ArrayList<>();
+        // we fill the Sirius layout algorithm registry with all ELK algorithms.
+        Collection<LayoutAlgorithmData> algorithmData = LayoutMetaDataService.getInstance().getAlgorithmData();
+        for (LayoutAlgorithmData layoutAlgorithmData : algorithmData) {
+
+            List<LayoutOptionData> optionDatas = LayoutMetaDataService.getInstance().getOptionData(layoutAlgorithmData, Target.PARENTS);
+            Map<String, LayoutOption> layoutOptions = new HashMap<>();
+            LayoutOptionFactory layoutOptionFactory = new LayoutOptionFactory();
+            for (LayoutOptionData layoutOptionData : optionDatas) {
+                if (!CoreOptions.ALGORITHM.getId().equals(layoutOptionData.getId()) && !layoutOptionData.getVisibility().equals(Visibility.HIDDEN)) {
+                    switch (layoutOptionData.getType()) {
+                    case STRING:
+                        layoutOptions.put(layoutOptionData.getId(), layoutOptionFactory.createStringOption((String) layoutOptionData.getDefault(), layoutOptionData.getId(),
+                                layoutOptionData.getDescription(), layoutOptionData.getName()));
+                        break;
+                    case BOOLEAN:
+                        layoutOptions.put(layoutOptionData.getId(), layoutOptionFactory.createBooleanOption((Boolean) layoutOptionData.getDefault(), layoutOptionData.getId(),
+                                layoutOptionData.getDescription(), layoutOptionData.getName()));
+                        break;
+                    case INT:
+                        layoutOptions.put(layoutOptionData.getId(), layoutOptionFactory.createIntegerOption((Integer) layoutOptionData.getDefault(), layoutOptionData.getId(),
+                                layoutOptionData.getDescription(), layoutOptionData.getName()));
+                        break;
+                    case DOUBLE:
+                        layoutOptions.put(layoutOptionData.getId(), layoutOptionFactory.createDoubleOption((Double) layoutOptionData.getDefault(), layoutOptionData.getId(),
+                                layoutOptionData.getDescription(), layoutOptionData.getName()));
+                        break;
+                    case ENUMSET:
+                    case ENUM:
+
+                        String[] choices = layoutOptionData.getChoices();
+                        List<EnumChoice> choicesList = new ArrayList<>();
+                        for (int i = 0; i < choices.length; i++) {
+                            String choiceId = choices[i];
+                            choicesList.add(new EnumChoice(choiceId, ""));
+
+                        }
+                        String defaultValue = null;
+                        Object defaultObject = layoutOptionData.getDefaultDefault();
+                        if (defaultObject instanceof Enum) {
+                            defaultValue = ((Enum<?>) defaultObject).name();
+                        }
+                        if (layoutOptionData.getType() == Type.ENUM) {
+                            layoutOptions.put(layoutOptionData.getId(),
+                                    layoutOptionFactory.createEnumOption(choicesList, layoutOptionData.getId(), layoutOptionData.getDescription(), layoutOptionData.getName(), defaultValue));
+                        } else {
+                            layoutOptions.put(layoutOptionData.getId(),
+                                    layoutOptionFactory.createEnumSetOption(choicesList, layoutOptionData.getId(), layoutOptionData.getDescription(), layoutOptionData.getName()));
+                        }
+
+                        break;
+                    default:
+                        break;
+                    }
+                }
+            }
+            layoutAlgorithms.add(new CustomLayoutAlgorithm(layoutAlgorithmData.getId(), layoutAlgorithmData.getName(), () -> new ELKLayoutNodeProvider(), layoutOptions));
+        }
+        return layoutAlgorithms;
+    }
+
+}
diff --git a/plugins/org.eclipse.sirius.diagram.ui/plugin.properties b/plugins/org.eclipse.sirius.diagram.ui/plugin.properties
index b913fcb756..ea641e6f85 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/plugin.properties
+++ b/plugins/org.eclipse.sirius.diagram.ui/plugin.properties
@@ -92,6 +92,7 @@ extension-point.styleConfigurationProvider..name = org.eclipse.sirius.diagram.ui
 extension-point.viewOrderingProvider.name = org.eclipse.sirius.diagram.ui.viewOrderingProvider
 extension-point.tabbarContributor.name = Tabbar Contributor Extension
 extension.diagramProblems.name = Sirius diagram editor Plugin problems
+extension-point.customLayoutAlgorithmProvider.name = org.eclipse.sirius.diagram.ui.api.layout.customLayoutAlgorithmProvider
 menu.find.label = Find
 menu.showHide.label = Show/Hide
 
@@ -1029,6 +1030,8 @@ PinnedElementsHandler_notMovableMsg = Pinned elements can not move
 PinnedElementsHandler_remainOverlapsMsg = solvable but unsolved overlaps remain
 PinnedElementsHandler_unknownDirection = Unknown direction
 PinnedElementsSelectionCommand_dialogMessage = Pinned diagram elements are checked.
+LayoutAlgorithmProviderRegistry_classInitialization=The PageProvider class ''{0}'' could not be initialized.
+LayoutAlgorithmProviderRegistry_badClassType=The class ''{0}'' provided by the extension to extension point ''org.eclipse.sirius.ui.editor.airdEditoPageProvider'' is not an instance of ''org.eclipse.sirius.ui.editor.api.pages.PageProvider'' 
 PopupMenuContribution_storeMouseLocationCmdLabel = Store mouse location
 RefreshDiagramAction_cancelled = Cancelled
 RefreshDiagramAction_error = Error
diff --git a/plugins/org.eclipse.sirius.diagram.ui/plugin.xml b/plugins/org.eclipse.sirius.diagram.ui/plugin.xml
index 1bd4ab6af8..08a947814a 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/plugin.xml
+++ b/plugins/org.eclipse.sirius.diagram.ui/plugin.xml
@@ -20,6 +20,7 @@
    <extension-point id="formatDataManager" name="%extension-point.formatDataManager.name" schema="schema/formatDataManager.exsd"/>
    <extension-point id="imageSelector" name="%extension-point.imageSelector.name" schema="schema/imageSelector.exsd"/>
    <extension-point id="tabbarContributor" name="%extension-point.tabbarContributor.name" schema="schema/tabbarContributor.exsd"/>
+   <extension-point id="customLayoutAlgorithmProvider" name="%extension-point.customLayoutAlgorithmProvider.name" schema="schema/customLayoutAlgorithmProvider.exsd"/>
 
    <extension point="org.eclipse.ui.elementFactories">
      <factory
diff --git a/plugins/org.eclipse.sirius.diagram.ui/schema/customLayoutAlgorithmProvider.exsd b/plugins/org.eclipse.sirius.diagram.ui/schema/customLayoutAlgorithmProvider.exsd
new file mode 100644
index 0000000000..f8c5bc9238
--- /dev/null
+++ b/plugins/org.eclipse.sirius.diagram.ui/schema/customLayoutAlgorithmProvider.exsd
@@ -0,0 +1,97 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<!-- Schema file written by PDE -->
+<schema targetNamespace="org.eclipse.sirius.diagram.ui" xmlns="http://www.w3.org/2001/XMLSchema">
+<annotation>
+      <appInfo>
+         <meta.schema plugin="org.eclipse.sirius.diagram.ui" id="customLayoutAlgorithmProvider" name="%extension-point.customLayoutAlgorithmProvider.name"/>
+      </appInfo>
+      <documentation>
+         This extension allows to provide custom layout algorithms by registering a layout algorithm provider. These algorithms are made visible in Sirius VSM editor so that the specifier can specify one of these to be used by the arrange all action of a Sirius diagram editor for a particular diagram kind.
+      </documentation>
+   </annotation>
+
+   <element name="extension">
+      <annotation>
+         <appInfo>
+            <meta.element />
+         </appInfo>
+      </annotation>
+      <complexType>
+         <sequence>
+            <element ref="customLayoutProvider"/>
+         </sequence>
+         <attribute name="point" type="string" use="required">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="id" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="name" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+               <appInfo>
+                  <meta.attribute translatable="true"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <element name="customLayoutProvider">
+      <annotation>
+         <documentation>
+            A layout provider that will be usable by Sirius specifiers.
+
+It allows them to define the provided layout algorithm as the algorithm to use when doing an arrange all in a Sirius diagram editor.
+         </documentation>
+      </annotation>
+      <complexType>
+         <attribute name="class" type="string" use="required">
+            <annotation>
+               <documentation>
+                  The layout algorithm provider class .
+               </documentation>
+               <appInfo>
+                  <meta.attribute kind="java" basedOn=":org.eclipse.sirius.diagram.ui.api.layout.CustomAlgorithmProvider"/>
+               </appInfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <annotation>
+      <appInfo>
+         <meta.section type="since"/>
+      </appInfo>
+      <documentation>
+         6.0.0
+      </documentation>
+   </annotation>
+
+
+
+
+   <annotation>
+      <appInfo>
+         <meta.section type="copyright"/>
+      </appInfo>
+      <documentation>
+         Copyright (c) 2018 Obeo&lt;br&gt;
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License v1.0
+which accompanies this distribution, and is available at
+&lt;a href=&quot;http://www.eclipse.org/legal/epl-v10.html&quot;&gt;http://www.eclipse.org/legal/epl-v10.html&lt;/a&gt;
+      </documentation>
+   </annotation>
+
+</schema>
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/CustomLayoutConfigurationItemProviderSpec.java b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/CustomLayoutConfigurationItemProviderSpec.java
index c587485034..1fb5302a44 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/CustomLayoutConfigurationItemProviderSpec.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/CustomLayoutConfigurationItemProviderSpec.java
@@ -19,7 +19,7 @@ import org.eclipse.sirius.diagram.description.CustomLayoutConfiguration;
 import org.eclipse.sirius.diagram.description.EnumOption;
 import org.eclipse.sirius.diagram.description.LayoutOption;
 import org.eclipse.sirius.diagram.description.provider.CustomLayoutConfigurationItemProvider;
-import org.eclipse.sirius.diagram.ui.internal.layout.GenericLayoutProviderSupplier;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithm;
 import org.eclipse.sirius.diagram.ui.provider.DiagramUIPlugin;
 
 /**
@@ -49,10 +49,10 @@ public class CustomLayoutConfigurationItemProviderSpec extends CustomLayoutConfi
 
     @Override
     protected void collectNewChildDescriptors(Collection<Object> newChildDescriptors, Object object) {
-        Map<String, GenericLayoutProviderSupplier> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutProviderRegistry();
+        Map<String, CustomLayoutAlgorithm> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutAlgorithms();
         CustomLayoutConfiguration layout = (CustomLayoutConfiguration) object;
 
-        GenericLayoutProviderSupplier genericLayoutProviderSupplier = layoutProviderRegistry.get(layout.getId());
+        CustomLayoutAlgorithm genericLayoutProviderSupplier = layoutProviderRegistry.get(layout.getId());
         Map<String, LayoutOption> layoutOptions = genericLayoutProviderSupplier.getLayoutOptions();
         for (LayoutOption layoutOption : layoutOptions.values()) {
             LayoutOption copy = EcoreUtil.copy(layoutOption);
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumLayoutOptionItemProviderSpec.java b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumLayoutOptionItemProviderSpec.java
index eec6e228f6..db0e6b0eb9 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumLayoutOptionItemProviderSpec.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumLayoutOptionItemProviderSpec.java
@@ -21,7 +21,7 @@ import org.eclipse.sirius.diagram.description.EnumLayoutOption;
 import org.eclipse.sirius.diagram.description.EnumLayoutValue;
 import org.eclipse.sirius.diagram.description.LayoutOption;
 import org.eclipse.sirius.diagram.description.provider.EnumLayoutOptionItemProvider;
-import org.eclipse.sirius.diagram.ui.internal.layout.GenericLayoutProviderSupplier;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithm;
 import org.eclipse.sirius.diagram.ui.provider.DiagramUIPlugin;
 
 /**
@@ -51,10 +51,10 @@ public class EnumLayoutOptionItemProviderSpec extends EnumLayoutOptionItemProvid
 
     @Override
     protected void collectNewChildDescriptors(Collection<Object> newChildDescriptors, Object object) {
-        Map<String, GenericLayoutProviderSupplier> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutProviderRegistry();
+        Map<String, CustomLayoutAlgorithm> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutAlgorithms();
         EnumLayoutOption layoutOption = (EnumLayoutOption) object;
         CustomLayoutConfiguration layout = (CustomLayoutConfiguration) layoutOption.eContainer();
-        GenericLayoutProviderSupplier genericLayoutProviderSupplier = layoutProviderRegistry.get(layout.getId());
+        CustomLayoutAlgorithm genericLayoutProviderSupplier = layoutProviderRegistry.get(layout.getId());
         Map<String, LayoutOption> layoutOptions = genericLayoutProviderSupplier.getLayoutOptions();
         EnumLayoutOption layoutOptionTemplate = (EnumLayoutOption) layoutOptions.get(layoutOption.getId());
         EList<EnumLayoutValue> choices = layoutOptionTemplate.getChoices();
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumSetLayoutOptionItemProviderSpec.java b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumSetLayoutOptionItemProviderSpec.java
index 93a05916d0..4b34a289c7 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumSetLayoutOptionItemProviderSpec.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-diag/org/eclipse/sirius/diagram/internal/description/provider/EnumSetLayoutOptionItemProviderSpec.java
@@ -22,7 +22,7 @@ import org.eclipse.sirius.diagram.description.EnumLayoutValue;
 import org.eclipse.sirius.diagram.description.EnumSetLayoutOption;
 import org.eclipse.sirius.diagram.description.LayoutOption;
 import org.eclipse.sirius.diagram.description.provider.EnumSetLayoutOptionItemProvider;
-import org.eclipse.sirius.diagram.ui.internal.layout.GenericLayoutProviderSupplier;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithm;
 import org.eclipse.sirius.diagram.ui.provider.DiagramUIPlugin;
 
 /**
@@ -52,10 +52,10 @@ public class EnumSetLayoutOptionItemProviderSpec extends EnumSetLayoutOptionItem
 
     @Override
     protected void collectNewChildDescriptors(Collection<Object> newChildDescriptors, Object object) {
-        Map<String, GenericLayoutProviderSupplier> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutProviderRegistry();
+        Map<String, CustomLayoutAlgorithm> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutAlgorithms();
         EnumSetLayoutOption layoutOption = (EnumSetLayoutOption) object;
         CustomLayoutConfiguration layout = (CustomLayoutConfiguration) layoutOption.eContainer();
-        GenericLayoutProviderSupplier genericLayoutProviderSupplier = layoutProviderRegistry.get(layout.getId());
+        CustomLayoutAlgorithm genericLayoutProviderSupplier = layoutProviderRegistry.get(layout.getId());
         Map<String, LayoutOption> layoutOptions = genericLayoutProviderSupplier.getLayoutOptions();
         EnumSetLayoutOption layoutOptionTemplate = (EnumSetLayoutOption) layoutOptions.get(layoutOption.getId());
         EList<EnumLayoutValue> choices = layoutOptionTemplate.getChoices();
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/description/provider/DiagramDescriptionItemProvider.java b/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/description/provider/DiagramDescriptionItemProvider.java
index c1999d0dde..38054f3c42 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/description/provider/DiagramDescriptionItemProvider.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/description/provider/DiagramDescriptionItemProvider.java
@@ -35,7 +35,7 @@ import org.eclipse.sirius.diagram.description.Layer;
 import org.eclipse.sirius.diagram.description.concern.ConcernFactory;
 import org.eclipse.sirius.diagram.description.concern.ConcernSet;
 import org.eclipse.sirius.diagram.description.filter.FilterFactory;
-import org.eclipse.sirius.diagram.ui.internal.layout.GenericLayoutProviderSupplier;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithm;
 import org.eclipse.sirius.diagram.ui.provider.DiagramUIPlugin;
 import org.eclipse.sirius.diagram.ui.provider.Messages;
 import org.eclipse.sirius.viewpoint.description.DescriptionPackage;
@@ -655,9 +655,9 @@ public class DiagramDescriptionItemProvider extends DragAndDropTargetDescription
      *            the child descriptor collection where to add new child descriptors.
      */
     private void addAllCustomLayoutChildDescriptors(Collection<Object> newChildDescriptors) {
-        Map<String, GenericLayoutProviderSupplier> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutProviderRegistry();
-        Set<Entry<String, GenericLayoutProviderSupplier>> layoutProviders = layoutProviderRegistry.entrySet();
-        for (Entry<String, GenericLayoutProviderSupplier> layoutProviderEntry : layoutProviders) {
+        Map<String, CustomLayoutAlgorithm> layoutProviderRegistry = DiagramUIPlugin.getPlugin().getLayoutAlgorithms();
+        Set<Entry<String, CustomLayoutAlgorithm>> layoutProviders = layoutProviderRegistry.entrySet();
+        for (Entry<String, CustomLayoutAlgorithm> layoutProviderEntry : layoutProviders) {
             CustomLayoutConfiguration customConfiguration = DescriptionFactory.eINSTANCE.createCustomLayoutConfiguration();
             customConfiguration.setId(layoutProviderEntry.getKey());
             customConfiguration.setLabel(layoutProviderEntry.getValue().getLabel());
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/ui/provider/DiagramUIPlugin.java b/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/ui/provider/DiagramUIPlugin.java
index 6b3cfd7138..7db23aca22 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/ui/provider/DiagramUIPlugin.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src-gen/org/eclipse/sirius/diagram/ui/provider/DiagramUIPlugin.java
@@ -18,10 +18,13 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.function.Supplier;
 
+import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IPath;
+import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Path;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.core.runtime.Status;
 import org.eclipse.draw2d.geometry.Dimension;
 import org.eclipse.emf.common.EMFPlugin;
 import org.eclipse.emf.common.notify.AdapterFactory;
@@ -44,16 +47,15 @@ import org.eclipse.jface.viewers.DecorationOverlayIcon;
 import org.eclipse.jface.viewers.IDecoration;
 import org.eclipse.jface.viewers.ILabelProvider;
 import org.eclipse.sirius.common.ui.tools.internal.preference.DynamicConfigurationHelper;
-import org.eclipse.sirius.diagram.description.LayoutOption;
 import org.eclipse.sirius.diagram.description.concern.provider.ConcernItemProviderAdapterFactory;
 import org.eclipse.sirius.diagram.description.filter.provider.FilterItemProviderAdapterFactory;
 import org.eclipse.sirius.diagram.provider.DiagramItemProviderAdapterFactory;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithm;
 import org.eclipse.sirius.diagram.ui.business.internal.image.ImageSelectorDescriptorRegistryListener;
 import org.eclipse.sirius.diagram.ui.business.internal.image.refresh.WorkspaceImageFigureRefresher;
-import org.eclipse.sirius.diagram.ui.internal.layout.GenericLayoutProviderSupplier;
+import org.eclipse.sirius.diagram.ui.internal.layout.CustomLayoutAlgorithmProviderRegistry;
 import org.eclipse.sirius.diagram.ui.internal.refresh.listeners.WorkspaceFileResourceChangeListener;
 import org.eclipse.sirius.diagram.ui.tools.api.decoration.SiriusDecorationProviderRegistry;
-import org.eclipse.sirius.diagram.ui.tools.api.layout.provider.DefaultLayoutProvider;
 import org.eclipse.sirius.diagram.ui.tools.api.preferences.SiriusDiagramUiPreferencesKeys;
 import org.eclipse.sirius.diagram.ui.tools.internal.decoration.DescribedDecorationDescriptorProvider;
 import org.eclipse.sirius.diagram.ui.tools.internal.decoration.EditModeDecorationDescriptorProvider;
@@ -160,7 +162,12 @@ public final class DiagramUIPlugin extends EMFPlugin {
          * A registry containing all layout providers that can be specified directly in the VSM. A layout provider
          * provides a layout algorithm that can be used when doing an arrange all on a Sirius diagram.
          */
-        private Map<String, GenericLayoutProviderSupplier> layoutProviderRegistry;
+        private Map<String, CustomLayoutAlgorithm> layoutAlgorithmsRegistry;
+
+        /**
+         * A registry updating the {@link Implementation#layoutAlgorithmsRegistry} from extension point declarations.
+         */
+        private CustomLayoutAlgorithmProviderRegistry layoutAlgorithmProviderRegistry;
 
         /**
          * Creates an instance. <!-- begin-user-doc --> <!-- end-user-doc -->
@@ -176,42 +183,54 @@ public final class DiagramUIPlugin extends EMFPlugin {
         }
 
         /**
-         * Add a new layout provider to the registry.
+         * Add a new custom layout algorithm to the registry.
          *
-         * @param providerId
-         *            the id of the layout provider to register.
-         * @param providerLabel
-         *            the label of the layout provider to register.
-         * @param layoutSupplier
-         *            the {@link DefaultLayoutProvider} instances supplier.
-         * @param layoutOptions
-         */
-        public void addLayoutProvider(String providerId, String providerLabel, Supplier<DefaultLayoutProvider> layoutSupplier, List<LayoutOption> layoutOptions) {
-            Map<String, LayoutOption> optionsMap = new HashMap<String, LayoutOption>();
-            for (LayoutOption layoutOption : layoutOptions) {
-                optionsMap.put(layoutOption.getId(), layoutOption);
-            }
-            layoutProviderRegistry.put(providerId, new GenericLayoutProviderSupplier(providerLabel, layoutSupplier, optionsMap));
+         * @param customLayoutAlgorithm
+         *            the layout algorithm to add.
+         */
+        public void addLayoutAlgorithm(CustomLayoutAlgorithm customLayoutAlgorithm) {
+            layoutAlgorithmsRegistry.put(customLayoutAlgorithm.getId(), customLayoutAlgorithm);
         }
 
         /**
-         * Remove the layout provider identified by the given id from the registry.
+         * Remove the layout algorithm identified by the given id from the registry.
          *
          * @param layoutProviderId
-         *            the id of the layout provider to remove from the registry.
-         * @return the layout provider removed if such element exists.
+         *            the id of the layout algorithm to remove from the registry.
+         * @return the layout algorithm removed if such element exists.
          */
-        public GenericLayoutProviderSupplier removeLayoutProvider(String layoutProviderId) {
-            return layoutProviderRegistry.remove(layoutProviderId);
+        public CustomLayoutAlgorithm removeLayoutAlgorithm(String layoutProviderId) {
+            return layoutAlgorithmsRegistry.remove(layoutProviderId);
         }
 
         /**
          * Returns the unmodifiable registry containing all layout providers that can be specified directly in the VSM.
          *
-         * @return an unmodifiable map of layout providers suppliers associated to their ids.
+         * @return an unmodifiable map of CustomLayoutAlgorithm associated to their id.
+         */
+        public Map<String, CustomLayoutAlgorithm> getLayoutAlgorithms() {
+            return Collections.unmodifiableMap(layoutAlgorithmsRegistry);
+        }
+
+        /**
+         * Logs an error in the error log.
+         * 
+         * @param message
+         *            the message to log (optional).
+         * @param e
+         *            the exception (optional).
          */
-        public Map<String, GenericLayoutProviderSupplier> getLayoutProviderRegistry() {
-            return Collections.unmodifiableMap(layoutProviderRegistry);
+        public void error(final String message, final Exception e) {
+            String msgToDisplay = message;
+            if (message == null && e != null) {
+                msgToDisplay = e.getMessage();
+            }
+            if (e instanceof CoreException) {
+                this.getLog().log(((CoreException) e).getStatus());
+            } else {
+                final IStatus status = new Status(IStatus.ERROR, this.getBundle().getSymbolicName(), msgToDisplay, e);
+                this.getLog().log(status);
+            }
         }
 
         /**
@@ -239,7 +258,10 @@ public final class DiagramUIPlugin extends EMFPlugin {
             layoutDataManagerRegistryListener = new LayoutDataManagerRegistryListener();
             layoutDataManagerRegistryListener.init();
 
-            layoutProviderRegistry = new HashMap<String, GenericLayoutProviderSupplier>();
+            layoutAlgorithmsRegistry = new HashMap<String, CustomLayoutAlgorithm>();
+
+            layoutAlgorithmProviderRegistry = new CustomLayoutAlgorithmProviderRegistry(layoutAlgorithmsRegistry);
+            Platform.getExtensionRegistry().addListener(layoutAlgorithmProviderRegistry, CustomLayoutAlgorithmProviderRegistry.LAYOUT_ALGORITHM_PROVIDER_EXTENSION_POINT_ID);
 
             registerCoreDecorationProviders();
         }
@@ -272,7 +294,7 @@ public final class DiagramUIPlugin extends EMFPlugin {
                 // can occur when using CDO (if the view is
                 // closed when transactions have been closed)
             }
-            layoutProviderRegistry = null;
+            layoutAlgorithmsRegistry = null;
             formatDataManagerRegistryListener.dispose();
             formatDataManagerRegistryListener = null;
 
@@ -284,6 +306,9 @@ public final class DiagramUIPlugin extends EMFPlugin {
 
             imageSelectorDescriptorRegistryListener.dispose();
             imageSelectorDescriptorRegistryListener = null;
+
+            layoutAlgorithmProviderRegistry = null;
+            layoutAlgorithmsRegistry = null;
             /*
              * Disposing the images
              */
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/api/layout/CustomLayoutAlgorithm.java b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/api/layout/CustomLayoutAlgorithm.java
new file mode 100644
index 0000000000..0c14be079f
--- /dev/null
+++ b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/api/layout/CustomLayoutAlgorithm.java
@@ -0,0 +1,105 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Obeo
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.sirius.diagram.ui.api.layout;
+
+import java.util.Map;
+import java.util.function.Supplier;
+
+import org.eclipse.sirius.diagram.description.LayoutOption;
+import org.eclipse.sirius.diagram.ui.tools.api.layout.provider.DefaultLayoutProvider;
+
+/**
+ * A component providing all needed information to provide a custom layout algorithm that can be used to layout Sirius
+ * diagrams.
+ * 
+ * @author <a href="mailto:pierre.guilet@obeo.fr">Pierre Guilet</a>
+ *
+ */
+public class CustomLayoutAlgorithm {
+
+    /**
+     * The algorithm's id.
+     */
+    private String id;
+
+    /**
+     * The algorithm's label that should be used in UI to present it.
+     */
+    private String label;
+
+    /**
+     * A supplier of {@link DefaultLayoutProvider} that contains the layout algorithm.
+     */
+    private Supplier<DefaultLayoutProvider> layoutSupplier;
+
+    /**
+     * The options allowing to configure the layout algorithm behavior indexed by their name. Use the factory
+     * {@link LayoutOptionFactory} to create it.
+     */
+    private Map<String, LayoutOption> layoutOptions;
+
+    /**
+     * Initialize the custom layout algorithm with given information.
+     * 
+     * @param id
+     *            the algorithm's id.
+     * @param label
+     *            the algorithm's label that should be used in UI to present it.
+     * @param layoutSupplier
+     *            a supplier of {@link DefaultLayoutProvider} that contains the layout algorithm.
+     * @param layoutOptions
+     *            the options allowing to configure the layout algorithm behavior. Use the factory
+     *            {@link LayoutOptionFactory} to create it.
+     */
+    public CustomLayoutAlgorithm(String id, String label, Supplier<DefaultLayoutProvider> layoutSupplier, Map<String, LayoutOption> layoutOptions) {
+        super();
+        this.id = id;
+        this.label = label;
+        this.layoutSupplier = layoutSupplier;
+        this.layoutOptions = layoutOptions;
+    }
+
+    /**
+     * Returns the algorithm's id.
+     * 
+     * @return the algorithm's id.
+     */
+    public String getId() {
+        return id;
+    }
+
+    /**
+     * Returns the algorithm's label that should be used in UI to present it.
+     * 
+     * @return the algorithm's label that should be used in UI to present it.
+     */
+    public String getLabel() {
+        return label;
+    }
+
+    /**
+     * Returns the options allowing to configure the layout algorithm behavior indexed by their names.
+     * 
+     * @return the options allowing to configure the layout algorithm behavior indexed by their names.
+     */
+    public Map<String, LayoutOption> getLayoutOptions() {
+        return layoutOptions;
+    }
+
+    /**
+     * Returns an instance of {@link DefaultLayoutProvider} that contains the layout algorithm.
+     * 
+     * @return an instance of {@link DefaultLayoutProvider} that contains the layout algorithm.
+     */
+    public DefaultLayoutProvider getLayoutAlgorithmInstance() {
+        return layoutSupplier.get();
+    }
+}
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/api/layout/CustomLayoutAlgorithmProvider.java b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/api/layout/CustomLayoutAlgorithmProvider.java
new file mode 100644
index 0000000000..6ff3b72bb0
--- /dev/null
+++ b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/api/layout/CustomLayoutAlgorithmProvider.java
@@ -0,0 +1,31 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Obeo
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.sirius.diagram.ui.api.layout;
+
+import java.util.List;
+
+/**
+ * The purpose of this component is to provide custom layout algorithms to Sirius that can be used by VSM specifiers.
+ * The specifiers will then be able to select the custom layout algorithms to use when arranging a Sirius diagram.
+ * 
+ * @author <a href="mailto:pierre.guilet@obeo.fr">Pierre Guilet</a>
+ *
+ */
+public interface CustomLayoutAlgorithmProvider {
+
+    /**
+     * Returns the custom layout algorithms that should be available to VSM specifiers to specify the kind of layouting
+     * that will be done when arranging a particular diagram kind.
+     * 
+     * @return the custom layout algorithms.
+     */
+    List<CustomLayoutAlgorithm> getCustomLayoutAlgorithms();
+}
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/internal/layout/CustomLayoutAlgorithmProviderRegistry.java b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/internal/layout/CustomLayoutAlgorithmProviderRegistry.java
new file mode 100644
index 0000000000..f9b8b9d84a
--- /dev/null
+++ b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/internal/layout/CustomLayoutAlgorithmProviderRegistry.java
@@ -0,0 +1,148 @@
+/*******************************************************************************
+ * Copyright (c) 2018 Obeo
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.sirius.diagram.ui.internal.layout;
+
+import java.text.MessageFormat;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.IConfigurationElement;
+import org.eclipse.core.runtime.IExtension;
+import org.eclipse.core.runtime.IExtensionPoint;
+import org.eclipse.core.runtime.IExtensionRegistry;
+import org.eclipse.core.runtime.IRegistryEventListener;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithm;
+import org.eclipse.sirius.diagram.ui.api.layout.CustomLayoutAlgorithmProvider;
+import org.eclipse.sirius.diagram.ui.provider.DiagramUIPlugin;
+import org.eclipse.sirius.diagram.ui.provider.Messages;
+
+/**
+ * This registry dynamically update providers in the given custom layout algorithm registry when plugins providing some
+ * are activated/deactivated.
+ * 
+ * @author <a href="mailto:pierre.guilet@obeo.fr">Pierre Guilet</a>
+ *
+ */
+public class CustomLayoutAlgorithmProviderRegistry implements IRegistryEventListener {
+    /**
+     * Custom layout algorithm provider extension point's id.
+     */
+    public static final String LAYOUT_ALGORITHM_PROVIDER_EXTENSION_POINT_ID = "org.eclipse.sirius.diagram.ui.customLayoutAlgorithmProvider"; //$NON-NLS-1$
+
+    /**
+     * Page provider element's name.
+     */
+    private static final String LAYOUT_ALGORITHM_PROVIDER_ELEMENT_NAME = "customLayoutProvider"; //$NON-NLS-1$
+
+    /**
+     * Page provider's class attribute's name.
+     */
+    private static final String LAYOUT_ALGORITHM_PROVIDER_CLASS_ATTRIBUTE_NAME = "class"; //$NON-NLS-1$
+
+    /**
+     * A map of {@link IExtension} currently provided by plugins to the {@link CustomLayoutAlgorithmProvider} they
+     * provide.
+     */
+    private Map<IExtension, CustomLayoutAlgorithmProvider> extensionToLayoutAlgorithmProvider;
+
+    /**
+     * A registry containing all layout providers that can be specified directly in the VSM. A layout provider provides
+     * a layout algorithm that can be used when doing an arrange all on a Sirius diagram.
+     */
+    private Map<String, CustomLayoutAlgorithm> layoutProviderRegistry;
+
+    /**
+     * Initialize this registry with a {@link PageProviderRegistry}.
+     * 
+     * @param thePageRegistry
+     *            the page registry providing pages from registered {@link CustomLayoutAlgorithmProvider}.
+     */
+    public CustomLayoutAlgorithmProviderRegistry(Map<String, CustomLayoutAlgorithm> layoutProviderRegistry) {
+        this.layoutProviderRegistry = layoutProviderRegistry;
+        extensionToLayoutAlgorithmProvider = new HashMap<>();
+        final IExtensionRegistry registry = Platform.getExtensionRegistry();
+
+        for (IExtension extension : registry.getExtensionPoint(LAYOUT_ALGORITHM_PROVIDER_EXTENSION_POINT_ID).getExtensions()) {
+            parseExtension(extension);
+        }
+    }
+
+    @Override
+    public void added(IExtension[] extensions) {
+        for (IExtension extension : extensions) {
+            parseExtension(extension);
+        }
+    }
+
+    /**
+     * Parse extension. If the extension corresponds to the extension point identified by
+     * {@link CustomLayoutAlgorithmProviderRegistry#LAYOUT_ALGORITHM_PROVIDER_EXTENSION_POINT_ID}, then all
+     * {@link CustomLayoutAlgorithmProvider} it provides are registered to the layout provider registry instance.
+     * 
+     * @param extension
+     *            the extension to parse.
+     */
+    private void parseExtension(IExtension extension) {
+        CustomLayoutAlgorithmProvider layoutAlgorithmProvider = extensionToLayoutAlgorithmProvider.get(extension);
+        if (layoutAlgorithmProvider == null) {
+
+            IConfigurationElement[] configurationElements = extension.getConfigurationElements();
+            for (IConfigurationElement configurationElement : configurationElements) {
+                if (LAYOUT_ALGORITHM_PROVIDER_ELEMENT_NAME.equals(configurationElement.getName())) {
+                    try {
+                        Object newInstance = configurationElement.createExecutableExtension(LAYOUT_ALGORITHM_PROVIDER_CLASS_ATTRIBUTE_NAME);
+                        if (CustomLayoutAlgorithmProvider.class.isAssignableFrom(newInstance.getClass())) {
+                            CustomLayoutAlgorithmProvider CustomAlgorithmProvider = (CustomLayoutAlgorithmProvider) newInstance;
+                            List<CustomLayoutAlgorithm> customLayoutAlgorithms = CustomAlgorithmProvider.getCustomLayoutAlgorithms();
+                            for (CustomLayoutAlgorithm customLayoutAlgorithm : customLayoutAlgorithms) {
+                                layoutProviderRegistry.put(customLayoutAlgorithm.getId(), customLayoutAlgorithm);
+                            }
+                        } else {
+                            DiagramUIPlugin.getPlugin().error(MessageFormat.format(Messages.LayoutAlgorithmProviderRegistry_badClassType, newInstance.getClass().getName()), null);
+                        }
+                    } catch (CoreException e) {
+                        DiagramUIPlugin.getPlugin().error(MessageFormat.format(Messages.LayoutAlgorithmProviderRegistry_classInitialization, configurationElement.getName()), e);
+                    }
+                }
+            }
+        }
+    }
+
+    @Override
+    public void removed(IExtension[] extensions) {
+        for (IExtension extension : extensions) {
+            CustomLayoutAlgorithmProvider layoutAlgorithmProvider = extensionToLayoutAlgorithmProvider.get(extension);
+
+            if (layoutAlgorithmProvider != null) {
+                List<CustomLayoutAlgorithm> customLayoutAlgorithms = layoutAlgorithmProvider.getCustomLayoutAlgorithms();
+                for (CustomLayoutAlgorithm customLayoutAlgorithm : customLayoutAlgorithms) {
+                    layoutProviderRegistry.remove(customLayoutAlgorithm.getId());
+                }
+            }
+            extensionToLayoutAlgorithmProvider.remove(extension);
+        }
+
+    }
+
+    @Override
+    public void added(IExtensionPoint[] extensionPoints) {
+
+    }
+
+    @Override
+    public void removed(IExtensionPoint[] extensionPoints) {
+
+    }
+
+}
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/internal/layout/GenericLayoutProvider.java b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/internal/layout/GenericLayoutProvider.java
index fe543cdf35..fd2b5293e5 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/internal/layout/GenericLayoutProvider.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/internal/layout/GenericLayoutProvider.java
@@ -10,8 +10,6 @@
  *******************************************************************************/
 package org.eclipse.sirius.diagram.ui.internal.layout;
 
-import java.util.function.Supplier;
-
 import org.eclipse.emf.ecore.EObject;
 import org.eclipse.gmf.runtime.diagram.ui.editparts.IGraphicalEditPart;
 import org.eclipse.gmf.runtime.diagram.ui.services.layout.AbstractLayoutEditPartProvider;
@@ -36,10 +34,9 @@ public class GenericLayoutProvider implements LayoutProvider {
 
     @Override
     public AbstractLayoutEditPartProvider getLayoutNodeProvider(final IGraphicalEditPart container) {
-        Supplier<DefaultLayoutProvider> layoutProvider = getGenericLayoutProvider(container);
+        DefaultLayoutProvider layoutProvider = getGenericLayoutProvider(container);
         if (layoutProvider != null) {
-
-            return new ArrangeSelectionLayoutProvider(layoutProvider.get());
+            return new ArrangeSelectionLayoutProvider(layoutProvider);
         }
         return null;
     }
@@ -55,14 +52,14 @@ public class GenericLayoutProvider implements LayoutProvider {
     }
 
     /**
-     * Returns the generic layout provider associated to the description of the {@link DDiagram} related to the given
-     * part.
+     * Returns the {@link CustomLayoutConfiguration} associated to the description of the {@link DDiagram} related to
+     * the given part.
      * 
      * @param container
-     * @return the generic layout provider associated to the description of the {@link DDiagram} related to the given
-     *         part. Null if no such element exists.
+     * @return the {@link CustomLayoutConfiguration} associated to the description of the {@link DDiagram} related to
+     *         the given part. Null if no such element exists.
      */
-    private Supplier<DefaultLayoutProvider> getGenericLayoutProvider(final IGraphicalEditPart container) {
+    private CustomLayoutConfiguration getCustomLayoutConfiguration(final IGraphicalEditPart container) {
         final View view = container.getNotationView();
         final EObject modelElement = view.getElement();
         if (view instanceof Diagram && modelElement instanceof DDiagram) {
@@ -71,11 +68,27 @@ public class GenericLayoutProvider implements LayoutProvider {
             if (desc != null) {
                 final Layout layout = desc.getLayout();
                 if (layout instanceof CustomLayoutConfiguration) {
-                    return DiagramUIPlugin.getPlugin().getLayoutProviderRegistry().get(((CustomLayoutConfiguration) layout).getId()).getLayoutProviderSupplier();
+                    return (CustomLayoutConfiguration) layout;
                 }
             }
         }
         return null;
     }
 
+    /**
+     * Returns the generic layout provider associated to the description of the {@link DDiagram} related to the given
+     * part.
+     * 
+     * @param container
+     * @return the generic layout provider associated to the description of the {@link DDiagram} related to the given
+     *         part. Null if no such element exists.
+     */
+    private DefaultLayoutProvider getGenericLayoutProvider(final IGraphicalEditPart container) {
+        CustomLayoutConfiguration customLayoutConfiguration = getCustomLayoutConfiguration(container);
+        if (customLayoutConfiguration != null) {
+            return DiagramUIPlugin.getPlugin().getLayoutAlgorithms().get(customLayoutConfiguration.getId()).getLayoutAlgorithmInstance();
+        }
+        return null;
+    }
+
 }
diff --git a/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/provider/Messages.java b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/provider/Messages.java
index 226476793c..e7adbabe2b 100644
--- a/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/provider/Messages.java
+++ b/plugins/org.eclipse.sirius.diagram.ui/src/org/eclipse/sirius/diagram/ui/provider/Messages.java
@@ -1511,6 +1511,12 @@ public final class Messages {
     @TranslatableMessage
     public static String ResetToDefaultFiltersAction_tooltip;
 
+    @TranslatableMessage
+    public static String LayoutAlgorithmProviderRegistry_badClassType;
+
+    @TranslatableMessage
+    public static String LayoutAlgorithmProviderRegistry_classInitialization;
+
     // CHECKSTYLE:ON
 
     private Messages() {