[lang][ui] Add "Correct indentation" menu item.

In order to avoid the anoying behavior of the Ctrl+I shortcut (type a
tab character), a "Correct indentation" command is created and binded to
Ctrl+I. This command formats the selected code.

Signed-off-by: Stéphane Galland <galland@arakhne.org>

main/coreplugins/io.sarl.lang.ui/plugin.xml

@@ -615,7 +615,9 @@
 	</extension>
 
 
-	<!-- The following elements are added by hand for the SARL project. -->
+	<!-- *******************************************************
+		 The following elements are added by hand for the SARL project.
+	     ******************************************************* -->
 
    <extension
          point="org.eclipse.ui.contexts">
@@ -665,4 +667,37 @@
 
    <extension-point id="extraGenerators" name="%extraGenerators" schema="schema/extraGenerators.exsd"/>
 
+ 	<!-- Correct indentation feature within the SARL editor -->
+   <extension point="org.eclipse.ui.commands">
+      <command
+            id="io.sarl.lang.ui.editor.correctIndentation"
+            name="Correct indentation">
+      </command>
+   </extension>
+   <extension point="org.eclipse.ui.handlers">
+      <handler
+            class="io.sarl.lang.ui.SARLExecutableExtensionFactory:io.sarl.lang.ui.editor.CorrectIndentationHandler"
+            commandId="io.sarl.lang.ui.editor.correctIndentation">
+      </handler>
+   </extension>
+   <extension point="org.eclipse.ui.menus">
+      <menuContribution allPopups="true" locationURI="popup:xtext.ui.SourceMenu?after=org.eclipse.xtext.ui.FormatAction">
+         <command commandId="io.sarl.lang.ui.editor.correctIndentation"
+                  label="Correct indentation"
+                  style="push">
+               <visibleWhen checkEnabled="false">
+                  <reference
+                        definitionId="isActiveEditorAnInstanceOfXtextEditor">
+                  </reference>
+               </visibleWhen>
+         </command>
+      </menuContribution>
+   </extension>
+   <extension point="org.eclipse.ui.bindings">
+    <key sequence="M1+I"
+      contextId="org.eclipse.xtext.ui.XtextEditorScope"
+      commandId="io.sarl.lang.ui.editor.correctIndentation"
+      schemeId="org.eclipse.ui.defaultAcceleratorConfiguration"/>
+   </extension>
+
  </plugin>

main/coreplugins/io.sarl.lang.ui/src/io/sarl/lang/ui/editor/CorrectIndentationHandler.java

@@ -0,0 +1,65 @@
+/*
+ * $Id$
+ *
+ * SARL is an general-purpose agent programming language.
+ * More details on http://www.sarl.io
+ *
+ * Copyright (C) 2014-2018 the original authors or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.sarl.lang.ui.editor;
+
+import javax.inject.Inject;
+
+import com.google.inject.Provider;
+import org.eclipse.core.commands.AbstractHandler;
+import org.eclipse.core.commands.ExecutionEvent;
+import org.eclipse.core.commands.ExecutionException;
+import org.eclipse.jface.text.IRegion;
+import org.eclipse.jface.text.ITextSelection;
+import org.eclipse.jface.text.Region;
+import org.eclipse.xtext.ui.editor.XtextEditor;
+import org.eclipse.xtext.ui.editor.formatting2.ContentFormatter;
+import org.eclipse.xtext.ui.editor.model.IXtextDocument;
+import org.eclipse.xtext.ui.editor.utils.EditorUtils;
+
+/**
+ * Handler for correct the indentation within a SARL code.
+ *
+ * @author $Author: sgalland$
+ * @version $FullVersion$
+ * @mavengroupid $GroupId$
+ * @mavenartifactid $ArtifactId$
+ * @since 0.7
+ */
+public class CorrectIndentationHandler extends AbstractHandler {
+
+	@Inject
+	private Provider<ContentFormatter> formatterProvider;
+
+	@Override
+	public Object execute(ExecutionEvent event) throws ExecutionException {
+		final XtextEditor activeXtextEditor = EditorUtils.getActiveXtextEditor(event);
+		if (activeXtextEditor == null) {
+			return null;
+		}
+		final IXtextDocument doc = activeXtextEditor.getDocument();
+		final ITextSelection selection = (ITextSelection) activeXtextEditor.getSelectionProvider().getSelection();
+		final IRegion region = new Region(selection.getOffset(), selection.getLength());
+		this.formatterProvider.get().format(doc, region);
+		return null;
+	}
+
+}