org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaTemplatesPage.java - jdt/eclipse.jdt.ui - Git at Google

 /*******************************************************************************
  * Copyright (c) 2007, 2011 Dakshinamurthy Karra, IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
  * which accompanies this distribution, and is available at
  * https://www.eclipse.org/legal/epl-2.0/
  *
  * SPDX-License-Identifier: EPL-2.0
  *
  * Contributors:
  *     Dakshinamurthy Karra (Jalian Systems) - Templates View - https://bugs.eclipse.org/bugs/show_bug.cgi?id=69581
  *******************************************************************************/
 package org.eclipse.jdt.internal.ui.javaeditor;

 import org.eclipse.swt.SWT;
 import org.eclipse.swt.graphics.Font;
 import org.eclipse.swt.graphics.Image;
 import org.eclipse.swt.layout.GridData;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Control;

 import org.eclipse.jface.preference.IPreferenceStore;
 import org.eclipse.jface.resource.JFaceResources;
 import org.eclipse.jface.window.Window;

 import org.eclipse.jface.text.BadLocationException;
 import org.eclipse.jface.text.Document;
 import org.eclipse.jface.text.IDocument;
 import org.eclipse.jface.text.ITextSelection;
 import org.eclipse.jface.text.ITextViewerExtension;
 import org.eclipse.jface.text.Position;
 import org.eclipse.jface.text.Region;
 import org.eclipse.jface.text.TextSelection;
 import org.eclipse.jface.text.TextUtilities;
 import org.eclipse.jface.text.source.ISourceViewer;
 import org.eclipse.jface.text.source.SourceViewer;
 import org.eclipse.jface.text.templates.ContextTypeRegistry;
 import org.eclipse.jface.text.templates.DocumentTemplateContext;
 import org.eclipse.jface.text.templates.Template;
 import org.eclipse.jface.text.templates.TemplateContextType;
 import org.eclipse.jface.text.templates.persistence.TemplateStore;

 import org.eclipse.ui.texteditor.templates.AbstractTemplatesPage;

 import org.eclipse.jdt.core.ICompilationUnit;
 import org.eclipse.jdt.core.IJavaElement;

 import org.eclipse.jdt.internal.corext.template.java.CompilationUnitContextType;
 import org.eclipse.jdt.internal.corext.template.java.JavaContext;
 import org.eclipse.jdt.internal.corext.template.java.JavaContextType;
 import org.eclipse.jdt.internal.corext.template.java.JavaDocContext;
 import org.eclipse.jdt.internal.corext.template.java.JavaDocContextType;
 import org.eclipse.jdt.internal.corext.template.java.SWTContextType;
 import org.eclipse.jdt.internal.corext.util.JavaModelUtil;

 import org.eclipse.jdt.ui.PreferenceConstants;
 import org.eclipse.jdt.ui.text.IJavaPartitions;
 import org.eclipse.jdt.ui.text.JavaTextTools;

 import org.eclipse.jdt.internal.ui.JavaPlugin;
 import org.eclipse.jdt.internal.ui.JavaPluginImages;
 import org.eclipse.jdt.internal.ui.preferences.EditTemplateDialog;
 import org.eclipse.jdt.internal.ui.preferences.JavaSourcePreviewerUpdater;
 import org.eclipse.jdt.internal.ui.text.SimpleJavaSourceViewerConfiguration;
 import org.eclipse.jdt.internal.ui.text.template.contentassist.TemplateProposal;
 import org.eclipse.jdt.internal.ui.text.template.preferences.TemplateVariableProcessor;


 /**
  * The templates page for the Java editor.
  *
  * @since 3.4
  */
 public class JavaTemplatesPage extends AbstractTemplatesPage {

 	private static final String PREFERENCE_PAGE_ID= "org.eclipse.jdt.ui.preferences.JavaTemplatePreferencePage"; //$NON-NLS-1$
 	private static final TemplateStore TEMPLATE_STORE= JavaPlugin.getDefault().getTemplateStore();
 	private static final IPreferenceStore PREFERENCE_STORE= JavaPlugin.getDefault().getPreferenceStore();
 	private static final ContextTypeRegistry TEMPLATE_CONTEXT_REGISTRY= JavaPlugin.getDefault().getTemplateContextRegistry();

 	private TemplateVariableProcessor fTemplateProcessor;
 	private JavaEditor fJavaEditor;

 	/**
 	 * Create a new AbstractTemplatesPage for the JavaEditor
 	 *
 	 * @param javaEditor the java editor
 	 */
 	public JavaTemplatesPage(JavaEditor javaEditor) {
 		super(javaEditor, javaEditor.getViewer());
 		fJavaEditor= javaEditor;
 		fTemplateProcessor= new TemplateVariableProcessor();
 	}

 	/*
 	 * @see org.eclipse.ui.texteditor.templates.AbstractTemplatesPage#insertTemplate(org.eclipse.jface.text.templates.Template, org.eclipse.jface.text.IDocument)
 	 */
 	@Override
 	protected void insertTemplate(Template template, IDocument document) {
 		if (!fJavaEditor.validateEditorInputState())
 			return;

 		ISourceViewer contextViewer= fJavaEditor.getViewer();
 		ITextSelection textSelection= (ITextSelection) contextViewer.getSelectionProvider().getSelection();
 		if (!isValidTemplate(document, template, textSelection.getOffset(), textSelection.getLength()))
 			return;
 		beginCompoundChange(contextViewer);
 		/*
 		 * The Editor checks whether a completion for a word exists before it allows for the template to be
 		 * applied. We pickup the current text at the selection position and replace it with the first char
 		 * of the template name for this to succeed.
 		 * Another advantage by this method is that the template replaces the selected text provided the
 		 * selection by itself is not used in the template pattern.
 		 */
 		String savedText;
 		try {
 			savedText= document.get(textSelection.getOffset(), textSelection.getLength());
 			if (savedText.length() == 0) {
 				String prefix= getIdentifierPart(document, template, textSelection.getOffset(), textSelection.getLength());
 				if (prefix.length() > 0 && !template.getName().startsWith(prefix.toString())) {
 					return;
 				}
 				if (prefix.length() > 0) {
 					contextViewer.setSelectedRange(textSelection.getOffset() - prefix.length(), prefix.length());
 					textSelection= (ITextSelection) contextViewer.getSelectionProvider().getSelection();
 				}
 			}
 			document.replace(textSelection.getOffset(), textSelection.getLength(), template.getName().substring(0, 1));
 		} catch (BadLocationException e) {
 			endCompoundChange(contextViewer);
 			return;
 		}
 		Position position= new Position(textSelection.getOffset() + 1, 0);
 		Region region= new Region(textSelection.getOffset() + 1, 0);
 		contextViewer.getSelectionProvider().setSelection(new TextSelection(textSelection.getOffset(), 1));
 		ICompilationUnit compilationUnit= (ICompilationUnit) EditorUtility.getEditorInputJavaElement(fJavaEditor, true);

 		TemplateContextType type= getContextTypeRegistry().getContextType(template.getContextTypeId());
 		DocumentTemplateContext context= ((CompilationUnitContextType) type).createContext(document, position, compilationUnit);
 		context.setVariable("selection", savedText); //$NON-NLS-1$
 		if (context.getKey().length() == 0) {
 			try {
 				document.replace(textSelection.getOffset(), 1, savedText);
 			} catch (BadLocationException e) {
 				endCompoundChange(contextViewer);
 				return;
 			}
 		}
 		TemplateProposal proposal= new TemplateProposal(template, context, region, null);
 		fJavaEditor.getSite().getPage().activate(fJavaEditor);
 		proposal.apply(fJavaEditor.getViewer(), ' ', 0, region.getOffset());
 		endCompoundChange(contextViewer);
 	}

 	@Override
 	protected ContextTypeRegistry getContextTypeRegistry() {
 		return TEMPLATE_CONTEXT_REGISTRY;
 	}

 	@Override
 	protected IPreferenceStore getTemplatePreferenceStore() {
 		return PREFERENCE_STORE;
 	}

 	@Override
 	public TemplateStore getTemplateStore() {
 		return TEMPLATE_STORE;
 	}

 	/*
 	 * @see org.eclipse.ui.texteditor.templates.TextEditorTemplatesPage#isValidTemplate(org.eclipse.jface.text.templates.Template, int, int)
 	 */
 	@Override
 	protected boolean isValidTemplate(IDocument document, Template template, int offset, int length) {
 		String[] contextIds= getContextTypeIds(document, offset);
 		for (int i= 0; i < contextIds.length; i++) {
 			if (contextIds[i].equals(template.getContextTypeId())) {
 				DocumentTemplateContext context= getContext(document, template, offset, length);
 				return context.canEvaluate(template) || isTemplateAllowed(context, template);
 			}
 		}
 		return false;
 	}

 	@Override
 	protected SourceViewer createPatternViewer(Composite parent) {
 		IDocument document= new Document();
 		JavaTextTools tools= JavaPlugin.getDefault().getJavaTextTools();
 		tools.setupJavaDocumentPartitioner(document, IJavaPartitions.JAVA_PARTITIONING);
 		IPreferenceStore store= JavaPlugin.getDefault().getCombinedPreferenceStore();
 		JavaSourceViewer viewer= new JavaSourceViewer(parent, null, null, false, SWT.V_SCROLL | SWT.H_SCROLL, store);
 		SimpleJavaSourceViewerConfiguration configuration= new SimpleJavaSourceViewerConfiguration(tools.getColorManager(), store, null, IJavaPartitions.JAVA_PARTITIONING, false);
 		viewer.configure(configuration);
 		viewer.setEditable(false);
 		viewer.setDocument(document);

 		Font font= JFaceResources.getFont(PreferenceConstants.EDITOR_TEXT_FONT);
 		viewer.getTextWidget().setFont(font);
 		new JavaSourcePreviewerUpdater(viewer, configuration, store);

 		Control control= viewer.getControl();
 		GridData data= new GridData(GridData.HORIZONTAL_ALIGN_FILL | GridData.FILL_VERTICAL);
 		control.setLayoutData(data);

 		viewer.setEditable(false);
 		return viewer;
 	}

 	@Override
 	protected Image getImage(Template template) {
 		String contextId= template.getContextTypeId();
 		if (SWTContextType.ID_ALL.equals(contextId) || SWTContextType.ID_STATEMENTS.equals(contextId) || SWTContextType.ID_MEMBERS.equals(contextId))
 			return JavaPluginImages.get(JavaPluginImages.IMG_OBJS_SWT_TEMPLATE);
 		return JavaPluginImages.get(JavaPluginImages.IMG_OBJS_TEMPLATE);
 	}

 	/*
 	 * @see org.eclipse.ui.texteditor.templates.TextEditorTemplatesPage#editTemplate(org.eclipse.jface.text.templates.Template, boolean, boolean)
 	 */
 	@Override
 	protected Template editTemplate(Template template, boolean edit, boolean isNameModifiable) {
 		EditTemplateDialog dialog= new EditTemplateDialog(getSite().getShell(), template, edit, isNameModifiable, getContextTypeRegistry());
 		if (dialog.open() == Window.OK)
 			return dialog.getTemplate();
 		return null;
 	}

 	/*
 	 * @see org.eclipse.ui.texteditor.templates.TextEditorTemplatesPage#updatePatternViewer(org.eclipse.jface.text.templates.Template)
 	 */
 	@Override
 	protected void updatePatternViewer(Template template) {
 		if (template == null) {
 			getPatternViewer().getDocument().set(""); //$NON-NLS-1$
 			return ;
 		}
 		String contextId= template.getContextTypeId();
 		TemplateContextType type= getContextTypeRegistry().getContextType(contextId);
 		fTemplateProcessor.setContextType(type);

 		IDocument doc= getPatternViewer().getDocument();

 		String start= null;
 		if ("javadoc".equals(contextId)) { //$NON-NLS-1$
 			start= "/**" + doc.getLegalLineDelimiters()[0]; //$NON-NLS-1$
 		} else
 			start= ""; //$NON-NLS-1$

 		doc.set(start + template.getPattern());
 		int startLen= start.length();
 		getPatternViewer().setDocument(doc, startLen, doc.getLength() - startLen);
 	}

 	@Override
 	protected String getPreferencePageId() {
 		return PREFERENCE_PAGE_ID;
 	}

 	/**
 	 * Undomanager - end compound change
 	 *
 	 * @param viewer the viewer
 	 */
 	private void endCompoundChange(ISourceViewer viewer) {
 		if (viewer instanceof ITextViewerExtension)
 			((ITextViewerExtension) viewer).getRewriteTarget().endCompoundChange();
 	}

 	/**
 	 * Undomanager - begin a compound change
 	 *
 	 * @param viewer the viewer
 	 */
 	private void beginCompoundChange(ISourceViewer viewer) {
 		if (viewer instanceof ITextViewerExtension)
 			((ITextViewerExtension) viewer).getRewriteTarget().beginCompoundChange();
 	}

 	/**
 	 * Check whether the template is allowed eventhough the context can't evaluate it. This is
 	 * needed because the Dropping of a template is more lenient than ctl-space invoked code assist.
 	 *
 	 * @param context the template context
 	 * @param template the template
 	 * @return true if the template is allowed
 	 */
 	private boolean isTemplateAllowed(DocumentTemplateContext context, Template template) {
 		int offset;
 		try {
 			if (template.getContextTypeId().equals(JavaDocContextType.ID)) {
 				return (offset= context.getCompletionOffset()) > 0 && Character.isWhitespace(context.getDocument().getChar(offset - 1));
 			} else {
 				return ((offset= context.getCompletionOffset()) > 0 && !isTemplateNamePart(context.getDocument().getChar(offset - 1)));
 			}
 		} catch (BadLocationException e) {
 		}
 		return false;
 	}

 	/**
 	 * Checks whether the character is a valid character in Java template names
 	 *
 	 * @param ch the character
 	 * @return <code>true</code> if the character is part of a template name
 	 */
 	private boolean isTemplateNamePart(char ch) {
 		return !Character.isWhitespace(ch) && ch != '(' && ch != ')' && ch != '{' && ch != '}' && ch != ';';
 	}

 	/**
 	 * Get context
 	 *
 	 * @param document the document
 	 * @param template the template
 	 * @param offset the offset
 	 * @param length the length
 	 * @return the context
 	 */
 	private DocumentTemplateContext getContext(IDocument document, Template template, final int offset, int length) {
 		DocumentTemplateContext context;
 		if (template.getContextTypeId().equals(JavaDocContextType.ID)) {
 			context= new JavaDocContext(getContextTypeRegistry().getContextType(template.getContextTypeId()), document, new Position(offset, length), (ICompilationUnit) EditorUtility
 					.getEditorInputJavaElement(fJavaEditor, true));
 		} else {
 			context= new JavaContext(getContextTypeRegistry().getContextType(template.getContextTypeId()), document, new Position(offset, length), (ICompilationUnit) EditorUtility.getEditorInputJavaElement(
 					fJavaEditor, true));
 		}
 		return context;
 	}

 	/**
 	 * Get the active contexts for the given position in the document.
 	 * <p>
 	 * FIXME: should trigger code assist to get the context.
 	 * </p>
 	 *
 	 * @param document the document
 	 * @param offset the offset
 	 * @return an array of valid context id
 	 */
 	@Override
 	protected String[] getContextTypeIds(IDocument document, int offset) {
 		try {
 			String partition= TextUtilities.getContentType(document, IJavaPartitions.JAVA_PARTITIONING, offset, true);
 			String[] ids= new String[] { JavaContextType.ID_ALL, JavaContextType.ID_MEMBERS, JavaContextType.ID_STATEMENTS, SWTContextType.ID_ALL, SWTContextType.ID_STATEMENTS, SWTContextType.ID_MEMBERS};
 			if (partition.equals(IJavaPartitions.JAVA_DOC))
 				ids= new String[] { JavaDocContextType.ID };
 			IJavaElement elem= EditorUtility.getEditorInputJavaElement(fJavaEditor, true);
 			if (elem != null && JavaModelUtil.MODULE_INFO_JAVA.equals(elem.getElementName())) {
 				ids= new String[] { JavaContextType.ID_MODULE };
 			}
 			return ids;
 		} catch (BadLocationException e) {
 			return new String[0];
 		}
 	}

 	/**
 	 * Get the Java identifier terminated at the given offset
 	 *
 	 * @param document the document
 	 * @param template the template
 	 * @param offset the offset
 	 * @param length the length
 	 * @return the identifier part the Java identifier
 	 */
 	private String getIdentifierPart(IDocument document, Template template, int offset, int length) {
 		return getContext(document, template, offset, length).getKey();
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2007, 2011 Dakshinamurthy Karra, IBM Corporation and others.
	*
	* This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License 2.0
	* which accompanies this distribution, and is available at
	* https://www.eclipse.org/legal/epl-2.0/
	*
	* SPDX-License-Identifier: EPL-2.0
	*
	* Contributors:
	* Dakshinamurthy Karra (Jalian Systems) - Templates View - https://bugs.eclipse.org/bugs/show_bug.cgi?id=69581
	*******************************************************************************/
	package org.eclipse.jdt.internal.ui.javaeditor;

	import org.eclipse.swt.SWT;
	import org.eclipse.swt.graphics.Font;
	import org.eclipse.swt.graphics.Image;
	import org.eclipse.swt.layout.GridData;
	import org.eclipse.swt.widgets.Composite;
	import org.eclipse.swt.widgets.Control;

	import org.eclipse.jface.preference.IPreferenceStore;
	import org.eclipse.jface.resource.JFaceResources;
	import org.eclipse.jface.window.Window;

	import org.eclipse.jface.text.BadLocationException;
	import org.eclipse.jface.text.Document;
	import org.eclipse.jface.text.IDocument;
	import org.eclipse.jface.text.ITextSelection;
	import org.eclipse.jface.text.ITextViewerExtension;
	import org.eclipse.jface.text.Position;
	import org.eclipse.jface.text.Region;
	import org.eclipse.jface.text.TextSelection;
	import org.eclipse.jface.text.TextUtilities;
	import org.eclipse.jface.text.source.ISourceViewer;
	import org.eclipse.jface.text.source.SourceViewer;
	import org.eclipse.jface.text.templates.ContextTypeRegistry;
	import org.eclipse.jface.text.templates.DocumentTemplateContext;
	import org.eclipse.jface.text.templates.Template;
	import org.eclipse.jface.text.templates.TemplateContextType;
	import org.eclipse.jface.text.templates.persistence.TemplateStore;

	import org.eclipse.ui.texteditor.templates.AbstractTemplatesPage;

	import org.eclipse.jdt.core.ICompilationUnit;
	import org.eclipse.jdt.core.IJavaElement;

	import org.eclipse.jdt.internal.corext.template.java.CompilationUnitContextType;
	import org.eclipse.jdt.internal.corext.template.java.JavaContext;
	import org.eclipse.jdt.internal.corext.template.java.JavaContextType;
	import org.eclipse.jdt.internal.corext.template.java.JavaDocContext;
	import org.eclipse.jdt.internal.corext.template.java.JavaDocContextType;
	import org.eclipse.jdt.internal.corext.template.java.SWTContextType;
	import org.eclipse.jdt.internal.corext.util.JavaModelUtil;

	import org.eclipse.jdt.ui.PreferenceConstants;
	import org.eclipse.jdt.ui.text.IJavaPartitions;
	import org.eclipse.jdt.ui.text.JavaTextTools;

	import org.eclipse.jdt.internal.ui.JavaPlugin;
	import org.eclipse.jdt.internal.ui.JavaPluginImages;
	import org.eclipse.jdt.internal.ui.preferences.EditTemplateDialog;
	import org.eclipse.jdt.internal.ui.preferences.JavaSourcePreviewerUpdater;
	import org.eclipse.jdt.internal.ui.text.SimpleJavaSourceViewerConfiguration;
	import org.eclipse.jdt.internal.ui.text.template.contentassist.TemplateProposal;
	import org.eclipse.jdt.internal.ui.text.template.preferences.TemplateVariableProcessor;


	/**
	* The templates page for the Java editor.
	*
	* @since 3.4
	*/
	public class JavaTemplatesPage extends AbstractTemplatesPage {

	private static final String PREFERENCE_PAGE_ID= "org.eclipse.jdt.ui.preferences.JavaTemplatePreferencePage"; //$NON-NLS-1$
	private static final TemplateStore TEMPLATE_STORE= JavaPlugin.getDefault().getTemplateStore();
	private static final IPreferenceStore PREFERENCE_STORE= JavaPlugin.getDefault().getPreferenceStore();
	private static final ContextTypeRegistry TEMPLATE_CONTEXT_REGISTRY= JavaPlugin.getDefault().getTemplateContextRegistry();

	private TemplateVariableProcessor fTemplateProcessor;
	private JavaEditor fJavaEditor;

	/**
	* Create a new AbstractTemplatesPage for the JavaEditor
	*
	* @param javaEditor the java editor
	*/
	public JavaTemplatesPage(JavaEditor javaEditor) {
	super(javaEditor, javaEditor.getViewer());
	fJavaEditor= javaEditor;
	fTemplateProcessor= new TemplateVariableProcessor();
	}

	/*
	* @see org.eclipse.ui.texteditor.templates.AbstractTemplatesPage#insertTemplate(org.eclipse.jface.text.templates.Template, org.eclipse.jface.text.IDocument)
	*/
	@Override
	protected void insertTemplate(Template template, IDocument document) {
	if (!fJavaEditor.validateEditorInputState())
	return;

	ISourceViewer contextViewer= fJavaEditor.getViewer();
	ITextSelection textSelection= (ITextSelection) contextViewer.getSelectionProvider().getSelection();
	if (!isValidTemplate(document, template, textSelection.getOffset(), textSelection.getLength()))
	return;
	beginCompoundChange(contextViewer);
	/*
	* The Editor checks whether a completion for a word exists before it allows for the template to be
	* applied. We pickup the current text at the selection position and replace it with the first char
	* of the template name for this to succeed.
	* Another advantage by this method is that the template replaces the selected text provided the
	* selection by itself is not used in the template pattern.
	*/
	String savedText;
	try {
	savedText= document.get(textSelection.getOffset(), textSelection.getLength());
	if (savedText.length() == 0) {
	String prefix= getIdentifierPart(document, template, textSelection.getOffset(), textSelection.getLength());
	if (prefix.length() > 0 && !template.getName().startsWith(prefix.toString())) {
	return;
	}
	if (prefix.length() > 0) {
	contextViewer.setSelectedRange(textSelection.getOffset() - prefix.length(), prefix.length());
	textSelection= (ITextSelection) contextViewer.getSelectionProvider().getSelection();
	}
	}
	document.replace(textSelection.getOffset(), textSelection.getLength(), template.getName().substring(0, 1));
	} catch (BadLocationException e) {
	endCompoundChange(contextViewer);
	return;
	}
	Position position= new Position(textSelection.getOffset() + 1, 0);
	Region region= new Region(textSelection.getOffset() + 1, 0);
	contextViewer.getSelectionProvider().setSelection(new TextSelection(textSelection.getOffset(), 1));
	ICompilationUnit compilationUnit= (ICompilationUnit) EditorUtility.getEditorInputJavaElement(fJavaEditor, true);

	TemplateContextType type= getContextTypeRegistry().getContextType(template.getContextTypeId());
	DocumentTemplateContext context= ((CompilationUnitContextType) type).createContext(document, position, compilationUnit);
	context.setVariable("selection", savedText); //$NON-NLS-1$
	if (context.getKey().length() == 0) {
	try {
	document.replace(textSelection.getOffset(), 1, savedText);
	} catch (BadLocationException e) {
	endCompoundChange(contextViewer);
	return;
	}
	}
	TemplateProposal proposal= new TemplateProposal(template, context, region, null);
	fJavaEditor.getSite().getPage().activate(fJavaEditor);
	proposal.apply(fJavaEditor.getViewer(), ' ', 0, region.getOffset());
	endCompoundChange(contextViewer);
	}

	@Override
	protected ContextTypeRegistry getContextTypeRegistry() {
	return TEMPLATE_CONTEXT_REGISTRY;
	}

	@Override
	protected IPreferenceStore getTemplatePreferenceStore() {
	return PREFERENCE_STORE;
	}

	@Override
	public TemplateStore getTemplateStore() {
	return TEMPLATE_STORE;
	}

	/*
	* @see org.eclipse.ui.texteditor.templates.TextEditorTemplatesPage#isValidTemplate(org.eclipse.jface.text.templates.Template, int, int)
	*/
	@Override
	protected boolean isValidTemplate(IDocument document, Template template, int offset, int length) {
	String[] contextIds= getContextTypeIds(document, offset);
	for (int i= 0; i < contextIds.length; i++) {
	if (contextIds[i].equals(template.getContextTypeId())) {
	DocumentTemplateContext context= getContext(document, template, offset, length);
	return context.canEvaluate(template) \|\| isTemplateAllowed(context, template);
	}
	}
	return false;
	}

	@Override
	protected SourceViewer createPatternViewer(Composite parent) {
	IDocument document= new Document();
	JavaTextTools tools= JavaPlugin.getDefault().getJavaTextTools();
	tools.setupJavaDocumentPartitioner(document, IJavaPartitions.JAVA_PARTITIONING);
	IPreferenceStore store= JavaPlugin.getDefault().getCombinedPreferenceStore();
	JavaSourceViewer viewer= new JavaSourceViewer(parent, null, null, false, SWT.V_SCROLL \| SWT.H_SCROLL, store);
	SimpleJavaSourceViewerConfiguration configuration= new SimpleJavaSourceViewerConfiguration(tools.getColorManager(), store, null, IJavaPartitions.JAVA_PARTITIONING, false);
	viewer.configure(configuration);
	viewer.setEditable(false);
	viewer.setDocument(document);

	Font font= JFaceResources.getFont(PreferenceConstants.EDITOR_TEXT_FONT);
	viewer.getTextWidget().setFont(font);
	new JavaSourcePreviewerUpdater(viewer, configuration, store);

	Control control= viewer.getControl();
	GridData data= new GridData(GridData.HORIZONTAL_ALIGN_FILL \| GridData.FILL_VERTICAL);
	control.setLayoutData(data);

	viewer.setEditable(false);
	return viewer;
	}

	@Override
	protected Image getImage(Template template) {
	String contextId= template.getContextTypeId();
	if (SWTContextType.ID_ALL.equals(contextId) \|\| SWTContextType.ID_STATEMENTS.equals(contextId) \|\| SWTContextType.ID_MEMBERS.equals(contextId))
	return JavaPluginImages.get(JavaPluginImages.IMG_OBJS_SWT_TEMPLATE);
	return JavaPluginImages.get(JavaPluginImages.IMG_OBJS_TEMPLATE);
	}

	/*
	* @see org.eclipse.ui.texteditor.templates.TextEditorTemplatesPage#editTemplate(org.eclipse.jface.text.templates.Template, boolean, boolean)
	*/
	@Override
	protected Template editTemplate(Template template, boolean edit, boolean isNameModifiable) {
	EditTemplateDialog dialog= new EditTemplateDialog(getSite().getShell(), template, edit, isNameModifiable, getContextTypeRegistry());
	if (dialog.open() == Window.OK)
	return dialog.getTemplate();
	return null;
	}

	/*
	* @see org.eclipse.ui.texteditor.templates.TextEditorTemplatesPage#updatePatternViewer(org.eclipse.jface.text.templates.Template)
	*/
	@Override
	protected void updatePatternViewer(Template template) {
	if (template == null) {
	getPatternViewer().getDocument().set(""); //$NON-NLS-1$
	return ;
	}
	String contextId= template.getContextTypeId();
	TemplateContextType type= getContextTypeRegistry().getContextType(contextId);
	fTemplateProcessor.setContextType(type);

	IDocument doc= getPatternViewer().getDocument();

	String start= null;
	if ("javadoc".equals(contextId)) { //$NON-NLS-1$
	start= "/**" + doc.getLegalLineDelimiters()[0]; //$NON-NLS-1$
	} else
	start= ""; //$NON-NLS-1$

	doc.set(start + template.getPattern());
	int startLen= start.length();
	getPatternViewer().setDocument(doc, startLen, doc.getLength() - startLen);
	}

	@Override
	protected String getPreferencePageId() {
	return PREFERENCE_PAGE_ID;
	}

	/**
	* Undomanager - end compound change
	*
	* @param viewer the viewer
	*/
	private void endCompoundChange(ISourceViewer viewer) {
	if (viewer instanceof ITextViewerExtension)
	((ITextViewerExtension) viewer).getRewriteTarget().endCompoundChange();
	}

	/**
	* Undomanager - begin a compound change
	*
	* @param viewer the viewer
	*/
	private void beginCompoundChange(ISourceViewer viewer) {
	if (viewer instanceof ITextViewerExtension)
	((ITextViewerExtension) viewer).getRewriteTarget().beginCompoundChange();
	}

	/**
	* Check whether the template is allowed eventhough the context can't evaluate it. This is
	* needed because the Dropping of a template is more lenient than ctl-space invoked code assist.
	*
	* @param context the template context
	* @param template the template
	* @return true if the template is allowed
	*/
	private boolean isTemplateAllowed(DocumentTemplateContext context, Template template) {
	int offset;
	try {
	if (template.getContextTypeId().equals(JavaDocContextType.ID)) {
	return (offset= context.getCompletionOffset()) > 0 && Character.isWhitespace(context.getDocument().getChar(offset - 1));
	} else {
	return ((offset= context.getCompletionOffset()) > 0 && !isTemplateNamePart(context.getDocument().getChar(offset - 1)));
	}
	} catch (BadLocationException e) {
	}
	return false;
	}

	/**
	* Checks whether the character is a valid character in Java template names
	*
	* @param ch the character
	* @return <code>true</code> if the character is part of a template name
	*/
	private boolean isTemplateNamePart(char ch) {
	return !Character.isWhitespace(ch) && ch != '(' && ch != ')' && ch != '{' && ch != '}' && ch != ';';
	}

	/**
	* Get context
	*
	* @param document the document
	* @param template the template
	* @param offset the offset
	* @param length the length
	* @return the context
	*/
	private DocumentTemplateContext getContext(IDocument document, Template template, final int offset, int length) {
	DocumentTemplateContext context;
	if (template.getContextTypeId().equals(JavaDocContextType.ID)) {
	context= new JavaDocContext(getContextTypeRegistry().getContextType(template.getContextTypeId()), document, new Position(offset, length), (ICompilationUnit) EditorUtility
	.getEditorInputJavaElement(fJavaEditor, true));
	} else {
	context= new JavaContext(getContextTypeRegistry().getContextType(template.getContextTypeId()), document, new Position(offset, length), (ICompilationUnit) EditorUtility.getEditorInputJavaElement(
	fJavaEditor, true));
	}
	return context;
	}

	/**
	* Get the active contexts for the given position in the document.
	* <p>
	* FIXME: should trigger code assist to get the context.
	* </p>
	*
	* @param document the document
	* @param offset the offset
	* @return an array of valid context id
	*/
	@Override
	protected String[] getContextTypeIds(IDocument document, int offset) {
	try {
	String partition= TextUtilities.getContentType(document, IJavaPartitions.JAVA_PARTITIONING, offset, true);
	String[] ids= new String[] { JavaContextType.ID_ALL, JavaContextType.ID_MEMBERS, JavaContextType.ID_STATEMENTS, SWTContextType.ID_ALL, SWTContextType.ID_STATEMENTS, SWTContextType.ID_MEMBERS};
	if (partition.equals(IJavaPartitions.JAVA_DOC))
	ids= new String[] { JavaDocContextType.ID };
	IJavaElement elem= EditorUtility.getEditorInputJavaElement(fJavaEditor, true);
	if (elem != null && JavaModelUtil.MODULE_INFO_JAVA.equals(elem.getElementName())) {
	ids= new String[] { JavaContextType.ID_MODULE };
	}
	return ids;
	} catch (BadLocationException e) {
	return new String[0];
	}
	}

	/**
	* Get the Java identifier terminated at the given offset
	*
	* @param document the document
	* @param template the template
	* @param offset the offset
	* @param length the length
	* @return the identifier part the Java identifier
	*/
	private String getIdentifierPart(IDocument document, Template template, int offset, int length) {
	return getContext(document, template, offset, length).getKey();
	}
	}