CompareModelsAction.java

/**
 * <copyright>
 * 
 * Copyright (c) 2010-2016  Thales Global Services S.A.S.
 * 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:
 *    Thales Global Services S.A.S. - initial API and implementation
 * 
 * </copyright>
 */
package org.eclipse.emf.diffmerge.ui.setup;

import java.util.Collections;
import java.util.List;

import org.eclipse.compare.CompareUI;
import org.eclipse.emf.diffmerge.ui.EMFDiffMergeUIPlugin;
import org.eclipse.jface.action.IAction;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.IObjectActionDelegate;
import org.eclipse.ui.IWorkbenchPart;


/**
 * The default action for calling the EMF Diff/Merge UI.
 * @author Olivier Constant
 */
public class CompareModelsAction implements IObjectActionDelegate {
  // In 3.6, Eclipse Compare terminates a comparison process immediately if the selected resources
  // are identical, even though they are only similar root entry points for fragmented models
  // containing differences in non-root resources.
  
  /** The user selection (initially null) */
  private IStructuredSelection _selection;
  
  /** The current shell (initially null) */
  private Shell _shell;
  
  
  /**
   * Constructor
   */
  public CompareModelsAction() {
    _selection = null;
    _shell = null;
  }
  
  /**
   * Return the current selection
   * @return a non-null, potentially empty, unmodifiable list
   */
  @SuppressWarnings("unchecked")
  protected List<Object> getSelection() {
    List<Object> result;
    if (_selection == null)
      result = Collections.emptyList();
    else
      result = Collections.unmodifiableList(_selection.toList());
    return result;
  }
  
  /**
   * Return the current shell
   * @return a potentially null shell
   */
  protected Shell getShell() {
    return _shell;
  }
  
  /**
   * Return whether this action is applicable given the current selection
   */
  protected boolean isApplicable() {
    List<Object> allSelected = getSelection();
    int size = allSelected.size();
    if (size != 2 && size != 3)
      return false;
    ComparisonSetupManager manager = EMFDiffMergeUIPlugin.getDefault().getSetupManager();
    for (Object selected : allSelected) {
      if (!manager.isValidEntrypoint(selected))
        return false;
    }
    return true;
  }
  
  /**
   * @see org.eclipse.ui.IActionDelegate#run(org.eclipse.jface.action.IAction)
   */
  public void run(IAction action_p) {
    List<Object> allSelected = getSelection();
    int size = allSelected.size();
    if (size == 2 || size == 3) {
      ComparisonSetupManager manager = EMFDiffMergeUIPlugin.getDefault().getSetupManager();
      EMFDiffMergeEditorInput editorInput =
          manager.createEditorInputWithUI(getShell(),
              allSelected.get(0), allSelected.get(1), size == 3? allSelected.get(2): null);
      if (editorInput != null)
        CompareUI.openCompareEditor(editorInput);
    }
  }
  
  /**
   * @see org.eclipse.ui.IActionDelegate#selectionChanged(org.eclipse.jface.action.IAction, org.eclipse.jface.viewers.ISelection)
   */
  public void selectionChanged(IAction action_p, ISelection selection_p) {
    if (selection_p instanceof IStructuredSelection)
      _selection = (IStructuredSelection)selection_p;
    else
      _selection = null;
    if (action_p != null)
      action_p.setEnabled(isApplicable());
  }
  
  /**
   * @see org.eclipse.ui.IObjectActionDelegate#setActivePart(org.eclipse.jface.action.IAction, org.eclipse.ui.IWorkbenchPart)
   */
  public void setActivePart(IAction action_p, IWorkbenchPart targetPart_p) {
    if (targetPart_p != null && targetPart_p.getSite() != null)
      _shell = targetPart_p.getSite().getShell();
  }
  
}