code: /*******************************************************************************
   * Copyright (c) 2000, 2008 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.omnetpp.common.swt.custom;
  
  import org.eclipse.swt.SWT;
  import org.eclipse.swt.dnd.DND;
  import org.eclipse.swt.dnd.DropTargetAdapter;
  import org.eclipse.swt.dnd.DropTargetEffect;
  import org.eclipse.swt.dnd.DropTargetEvent;
  import org.eclipse.swt.graphics.FontMetrics;
  import org.eclipse.swt.graphics.GC;
  import org.eclipse.swt.graphics.Point;
  import org.eclipse.swt.graphics.Rectangle;
  import org.eclipse.swt.widgets.Event;
  import org.eclipse.swt.widgets.Listener;
  
  /**
   * This adapter class provides a default drag under effect (eg. select and scroll)
   * when a drag occurs over a <code>StyledText</code>.
   *
   * <p>Classes that wish to provide their own drag under effect for a <code>StyledText</code>
   * can extend this class, override the <code>StyledTextDropTargetEffect.dragOver</code>
   * method and override any other applicable methods in <code>StyledTextDropTargetEffect</code> to
   * display their own drag under effect.</p>
   *
   * Subclasses that override any methods of this class should call the corresponding
   * <code>super</code> method to get the default drag under effect implementation.
   *
   * <p>The feedback value is either one of the FEEDBACK constants defined in
   * class <code>DND</code> which is applicable to instances of this class,
   * or it must be built by <em>bitwise OR</em>'ing together
   * (that is, using the <code>int</code> "|" operator) two or more
   * of those <code>DND</code> effect constants.
   * </p>
   * <p>
   * <dl>
   * <dt><b>Feedback:</b></dt>
   * <dd>FEEDBACK_SELECT, FEEDBACK_SCROLL</dd>
   * </dl>
   * </p>
   *
   * @see DropTargetAdapter
   * @see DropTargetEvent
   * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
   *
   * @since 3.3
   */
  public class StyledTextDropTargetEffect extends DropTargetEffect {
      static final int CARET_WIDTH = 2;
      static final int SCROLL_HYSTERESIS = 100; // milli seconds
      static final int SCROLL_TOLERANCE = 20; // pixels
  
      int currentOffset = -1;
      long scrollBeginTime;
      int scrollX = -1, scrollY = -1;
      Listener paintListener;
  
      /**
       * Creates a new <code>StyledTextDropTargetEffect</code> to handle the drag under effect on the specified
       * <code>StyledText</code>.
       *
       * @param styledText the <code>StyledText</code> over which the user positions the cursor to drop the data
       */
      public StyledTextDropTargetEffect(StyledText styledText) {
          super(styledText);
          paintListener = new Listener () {
              public void handleEvent (Event event) {
                  if (currentOffset != -1) {
                      StyledText text = (StyledText) getControl();
                      Point position = text.getLocationAtOffset(currentOffset);
                      int height = text.getLineHeight(currentOffset);
                      event.gc.setBackground(event.display.getSystemColor (SWT.COLOR_BLACK));
                      event.gc.fillRectangle(position.x, position.y, CARET_WIDTH, height);
                  }
              }
          };
      }
  
      /**
       * This implementation of <code>dragEnter</code> provides a default drag under effect
       * for the feedback specified in <code>event.feedback</code>.
       *
       * For additional information see <code>DropTargetAdapter.dragEnter</code>.
       *
       * Subclasses that override this method should call <code>super.dragEnter(event)</code>
       * to get the default drag under effect implementation.
       *
       * @param event  the information associated with the drag start event
       *
       * @see DropTargetAdapter
       * @see DropTargetEvent
       */
      public void dragEnter(DropTargetEvent event) {
          currentOffset = -1;
          scrollBeginTime = 0;
          scrollX = -1;
          scrollY = -1;
          getControl().removeListener(SWT.Paint, paintListener);
          getControl().addListener (SWT.Paint, paintListener);
      }
  
      /**
       * This implementation of <code>dragLeave</code> provides a default drag under effect
       * for the feedback specified in <code>event.feedback</code>.
       *
       * For additional information see <code>DropTargetAdapter.dragLeave</code>.
       *
       * Subclasses that override this method should call <code>super.dragLeave(event)</code>
       * to get the default drag under effect implementation.
       *
       * @param event  the information associated with the drag leave event
       *
       * @see DropTargetAdapter
       * @see DropTargetEvent
       */
      public void dragLeave(DropTargetEvent event) {
          StyledText text = (StyledText) getControl();
          if (currentOffset != -1) {
              refreshCaret(text, currentOffset, -1);
          }
          text.removeListener(SWT.Paint, paintListener);
          scrollBeginTime = 0;
          scrollX = -1;
          scrollY = -1;
      }
  
      /**
       * This implementation of <code>dragOver</code> provides a default drag under effect
       * for the feedback specified in <code>event.feedback</code>.
       *
       * For additional information see <code>DropTargetAdapter.dragOver</code>.
       *
       * Subclasses that override this method should call <code>super.dragOver(event)</code>
       * to get the default drag under effect implementation.
       *
       * @param event  the information associated with the drag over event
       *
       * @see DropTargetAdapter
       * @see DropTargetEvent
       * @see DND#FEEDBACK_SELECT
       * @see DND#FEEDBACK_SCROLL
       */
      public void dragOver(DropTargetEvent event) {
          int effect = event.feedback;
          StyledText text = (StyledText) getControl();
  
          Point pt = text.getDisplay().map(null, text, event.x, event.y);
          if ((effect & DND.FEEDBACK_SCROLL) == 0) {
              scrollBeginTime = 0;
              scrollX = scrollY = -1;
          } else {
              if (text.getCharCount() == 0) {
                  scrollBeginTime = 0;
                  scrollX = scrollY = -1;
              } else {
                  if (scrollX != -1 && scrollY != -1 && scrollBeginTime != 0 &&
                      (pt.x >= scrollX && pt.x <= (scrollX + SCROLL_TOLERANCE) ||
                       pt.y >= scrollY && pt.y <= (scrollY + SCROLL_TOLERANCE))) {
                      if (System.currentTimeMillis() >= scrollBeginTime) {
                          Rectangle area = text.getClientArea();
                          GC gc = new GC(text);
                          FontMetrics fm = gc.getFontMetrics();
                          gc.dispose();
                          int charWidth = fm.getAverageCharWidth();
                          int scrollAmount = 10*charWidth;
                          if (pt.x < area.x + 3*charWidth) {
                              int leftPixel = text.getHorizontalPixel();
                              text.setHorizontalPixel(leftPixel - scrollAmount);
                          }
                          if (pt.x > area.width - 3*charWidth) {
                              int leftPixel = text.getHorizontalPixel();
                              text.setHorizontalPixel(leftPixel + scrollAmount);
                          }
                          int lineHeight = text.getLineHeight();
                          if (pt.y < area.y + lineHeight) {
                              int topPixel = text.getTopPixel();
                              text.setTopPixel(topPixel - lineHeight);
                          }
                          if (pt.y > area.height - lineHeight) {
                              int topPixel = text.getTopPixel();
                              text.setTopPixel(topPixel + lineHeight);
                          }
                          scrollBeginTime = 0;
                          scrollX = scrollY = -1;
                      }
                  } else {
                      scrollBeginTime = System.currentTimeMillis() + SCROLL_HYSTERESIS;
                      scrollX = pt.x;
                      scrollY = pt.y;
                  }
              }
          }
  
          if ((effect & DND.FEEDBACK_SELECT) != 0) {
              int[] trailing = new int [1];
              int newOffset = text.getOffsetAtPoint(pt.x, pt.y, trailing, false);
              newOffset += trailing [0];
              if (newOffset != currentOffset) {
                  refreshCaret(text, currentOffset, newOffset);
                  currentOffset = newOffset;
              }
          }
      }
  
      void refreshCaret(StyledText text, int oldOffset, int newOffset) {
          if (oldOffset != newOffset) {
              if (oldOffset != -1) {
                  Point oldPos = text.getLocationAtOffset(oldOffset);
                  int oldHeight = text.getLineHeight(oldOffset);
                  text.redraw (oldPos.x, oldPos.y, CARET_WIDTH, oldHeight, false);
              }
              if (newOffset != -1) {
                  Point newPos = text.getLocationAtOffset(newOffset);
                  int newHeight = text.getLineHeight(newOffset);
                  text.redraw (newPos.x, newPos.y, CARET_WIDTH, newHeight, false);
              }
          }
      }
  
      /**
       * This implementation of <code>dropAccept</code> provides a default drag under effect
       * for the feedback specified in <code>event.feedback</code>.
       *
       * For additional information see <code>DropTargetAdapter.dropAccept</code>.
       *
       * Subclasses that override this method should call <code>super.dropAccept(event)</code>
       * to get the default drag under effect implementation.
       *
       * @param event  the information associated with the drop accept event
       *
       * @see DropTargetAdapter
       * @see DropTargetEvent
       */
      public void dropAccept(DropTargetEvent event) {
          if (currentOffset != -1) {
              StyledText text = (StyledText) getControl();
              text.setSelection(currentOffset);
              currentOffset = -1;
          }
      }
  }
  