ZyGraphSelectionObserver.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

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 com.google.security.zynamics.zylib.yfileswrap.gui.zygraph;

import com.google.security.zynamics.zylib.general.ListenerProvider;
import com.google.security.zynamics.zylib.gui.zygraph.IZyGraphSelectionListener;

import y.base.GraphEvent;
import y.view.Graph2D;
import y.view.Graph2DSelectionEvent;
import y.view.Selections;


public class ZyGraphSelectionObserver extends Selections.SelectionStateObserver {
  /**
   * List of listeners that are notified about selection events.
   */
  private final ListenerProvider<IZyGraphSelectionListener> m_selectionListeners =
      new ListenerProvider<IZyGraphSelectionListener>();

  private int sequenceCounter = 0;

  private boolean fireFlag = false;

  // In this class we're trying to cache a multi-selection event
  // to generate just a single graph selection event.
  //
  // Single-Selection events have the following form:
  //
  // 1. onGraphEvent comes with event.getType() == PreEvent
  // 2. onGraphEvent comes with event.getType() == PostEvent
  // 3. The actual events arrive at onGraph2DSelectionEvent
  //
  // Multi-Selection events work differently.
  //
  // 1. onGraphEvent comes with event.getType() == PreEvent
  // 2. onGraphEvent comes with event.getType() == PreEvent
  // 3. onGraphEvent comes with event.getType() == PostEvent
  // 4. The actual events arrive at onGraph2DSelectionEvent
  // 5. onGraphEvent comes with event.getType() == PostEvent
  //
  // We try to convert the multi-selection event into a single-
  // selection event by counting the events as they arrive.

  /**
   * Notifies all listeners about selection changes.
   */
  private void notifySelectionListeners() {
    for (final IZyGraphSelectionListener listener : m_selectionListeners) {
      // ESCA-JAVA0166: Catch Exception because we are calling a listener function
      try {
        listener.selectionChanged();
      } catch (final Exception exception) {
        exception.printStackTrace();
      }
    }
  }

  @Override
  protected void updateSelectionState(final Graph2D graph) {
    notifySelectionListeners();
  }

  /**
   * Adds a graph selection listener that is notified when the selection of the graph changes.
   * 
   * @param listener The listener to add.
   */
  public void addListener(final IZyGraphSelectionListener listener) {
    m_selectionListeners.addListener(listener);
  }

  @Override
  public void onGraph2DSelectionEvent(final Graph2DSelectionEvent e) {
    // Node: Animated layout could select bends. Bends should be ignored here.
    // Bend selection should not trigger any action of the listeners.
    if (e.isBendSelection() || e.isEdgeSelection()) {
      return;
    }

    // This function is called for each single event in an
    // event sequence.

    // In this function we fire the event if all event
    // sequences finished.
    if ((sequenceCounter == 0) && fireFlag) {
      updateSelectionState(e.getGraph2D());

      // We have to make sure that this event is only
      // sent once. When the next event sequence starts
      // this flag is reset.
      fireFlag = false;
    }
  }

  @Override
  public void onGraphEvent(final GraphEvent graphevent) {
    // This function receives only multi-selection events.

    if (graphevent.getType() == GraphEvent.PRE_EVENT) {
      // Count the started event sequences
      sequenceCounter++;
    } else if (graphevent.getType() == GraphEvent.POST_EVENT) {
      // Finish the counting of an event sequence

      sequenceCounter--;

      // If all event sequences finished, we can fire the event.
      if (sequenceCounter == 0) {
        updateSelectionState((Graph2D) graphevent.getGraph());

        // This flag makes sure to fire the event for single
        // selection events in onGraph2DSelectionEvent
        fireFlag = true;
      }
    }
  }

  /**
   * Removes a selection listener from the graph.
   * 
   * @param listener The listener to remove.
   */
  public void removeListener(final IZyGraphSelectionListener listener) {
    m_selectionListeners.removeListener(listener);
  }
}