org.eclipse.gmf.runtime.common.ui.services/src/org/eclipse/gmf/runtime/common/ui/services/elementselection/ElementSelectionComposite.java

/******************************************************************************
 * Copyright (c) 2005 IBM Corporation and others.
 * 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:
 *    IBM Corporation - initial API and implementation 
 ****************************************************************************/
package org.eclipse.gmf.runtime.common.ui.services.elementselection;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.eclipse.gmf.runtime.common.ui.services.internal.elementselection.ElementSelectionCompositeContentProvider;
import org.eclipse.gmf.runtime.common.ui.services.internal.elementselection.ElementSelectionCompositeLabelProvider;
import org.eclipse.jface.dialogs.Dialog;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.jface.viewers.ViewerSorter;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.ModifyEvent;
import org.eclipse.swt.events.ModifyListener;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.graphics.FontMetrics;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.Text;

/**
 * The element selection composite. The composite functional similar to the JDT
 * select type dialog. There is a filter field and a table containing a list of
 * elements to select from.
 * <p>
 * The element selection composite requires an IElementSelectionInput as input
 * for the element selection service.
 * <p>
 * Subclasses must override the {@link #isValidSelection}and
 * {@link #handleSelection(boolean)} to provide custom validation.
 * 
 * @author Anthony Hunter <a href="mailto:anthonyh@ca.ibm.com">
 *         anthonyh@ca.ibm.com </a>
 */
public abstract class ElementSelectionComposite {

	/**
	 * The title to display at the top of the element selection composite.
	 */
	private final String title;

	/**
	 * The elements that have been selected by the user.
	 */
	private final List selectedElements = new ArrayList();

	/**
	 * Text control to display the filter text.
	 */
	private Text filterText = null;

	/**
	 * The table viewer to display list of matching objects.
	 */
	private TableViewer tableViewer = null;

	/**
	 * The input for the element selection service.
	 */
	private IElementSelectionInput input;

	/**
	 * Constructs a new instance that will create the new composite.
	 * 
	 * @param title
	 *            the dialog title
	 * @param input
	 *            the element selection input.
	 */
	public ElementSelectionComposite(String title, IElementSelectionInput input) {

		super();
		this.title = title;
		this.input = input;
	}

	/**
	 * Determines if the selected elements are a valid selection.
	 * 
	 * @param currentSelectedElements
	 *            the selected list of Elements
	 * @return <code>true</code> if the selected elements are a valid
	 *         selection
	 */
	abstract protected boolean isValidSelection(List currentSelectedElements);

	/**
	 * Handle a selection change, where the validity of the new selection is
	 * encoded in <code>isValid</code>.
	 * 
	 * @param isValid
	 *            <code>true</code> if the new selection is valid,
	 *            <code>false</code> otherwise.
	 */
	public abstract void handleSelection(boolean isValid);

	/**
	 * Creates the composite.
	 * 
	 * @param parent
	 *            the parent composite
	 * @return the new composite
	 */
	public Composite createComposite(Composite parent) {

		Composite result = new Composite(parent, SWT.NONE);
		result.setLayout(new GridLayout());
		result.setLayoutData(new GridData(GridData.FILL_BOTH));

		// Add the selection title label
		Label label = new Label(result, SWT.NONE);
		label.setText(title);

		// Add the element selection text widget
		filterText = new Text(result, SWT.SINGLE | SWT.BORDER);
		filterText.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
		filterText.addModifyListener(new ModifyListener() {

			public void modifyText(ModifyEvent e) {
				handleFilterChange();
			}

		});

		// Add the table viewer
		int selectStyle = SWT.SINGLE;
		tableViewer = new TableViewer(result, selectStyle | SWT.H_SCROLL
			| SWT.V_SCROLL | SWT.BORDER);
		tableViewer.setUseHashlookup(true);

		Table table = tableViewer.getTable();
		GridData gridData = new GridData(GridData.FILL_BOTH);
		GC gc = new GC(result);
		gc.setFont(JFaceResources.getDefaultFont());
		FontMetrics fontMetrics = gc.getFontMetrics();
		gc.dispose();
		gridData.widthHint = Dialog
			.convertWidthInCharsToPixels(fontMetrics, 80);
		gridData.heightHint = table.getItemHeight() * 15;
		table.setLayoutData(gridData);

		table.addSelectionListener(new SelectionListener() {

			public void widgetSelected(SelectionEvent e) {
				handleSelectionChange();
			}

			public void widgetDefaultSelected(SelectionEvent e) {
				// method not implemented
			}
		});

		tableViewer
			.setLabelProvider(new ElementSelectionCompositeLabelProvider());
		tableViewer
			.setContentProvider(new ElementSelectionCompositeContentProvider(
				input));
		tableViewer.setSorter(new ViewerSorter());

		createCompositeAdditions(result);

		return result;
	}

	/**
	 * The method is provided so that clients can add additional fields to the
	 * bottom of the selection composite. For example, clients may want to a
	 * checkbox button to the bottom of the composite.
	 * 
	 * @param parent
	 *            the parent composite
	 */
	protected void createCompositeAdditions(Composite parent) {
		/* clients are expected to override this method */
	}

	/**
	 * Handles a filter change.
	 */
	private void handleFilterChange() {
		tableViewer.setInput(filterText.getText());
		Object element = tableViewer.getElementAt(0);
		if (element != null) {
			tableViewer.setSelection(new StructuredSelection(element), true);
		}
		handleSelectionChange();
	}

	/**
	 * Handles a selection change and validates the new selection.
	 */
	public void handleSelectionChange() {
		StructuredSelection selection = (StructuredSelection) tableViewer
			.getSelection();
		if (selection.size() == 0) {
			// nothing selected
			selectedElements.clear();
			handleSelection(false);
			return;
		}

		List selectionList = selection.toList();

		// get the current selected elements
		List currentSelectedElements = new ArrayList();
		for (Iterator iter = selectionList.iterator(); iter.hasNext();) {
			AbstractMatchingObject matchingObject = (AbstractMatchingObject) iter
				.next();
			currentSelectedElements.add(matchingObject);
		}

		// validate selection
		boolean isValidSelection = isValidSelection(currentSelectedElements);

		// store the selection
		selectedElements.clear();
		if (isValidSelection) {
			selectedElements.addAll(currentSelectedElements);
		}

		// update UI based on selection
		handleSelection(isValidSelection);

	}

	/**
	 * Gets the user selected elements.
	 * 
	 * @return the user selected elements
	 */
	public List getSelectedElements() {
		List result = new ArrayList();
		for (Iterator iter = selectedElements.iterator(); iter.hasNext();) {
			IMatchingObject matchingObject = (IMatchingObject) iter.next();
			IElementSelectionProvider provider = matchingObject.getProvider();
			Object object = provider.resolve(matchingObject);
			result.add(object);
		}
		return result;
	}
}