libjava/classpath/java/awt/event/MouseWheelEvent.java

   1 /* MouseWheelEvent.java -- a mouse wheel event
   2    Copyright (C) 2002, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.awt.event;
  40
  41 import java.awt.Adjustable;
  42 import java.awt.Component;
  43 import java.awt.Rectangle;
  44 import java.awt.ScrollPane;
  45
  46 import javax.swing.JScrollPane;
  47 import javax.swing.Scrollable;
  48
  49 /**
  50  * This event is generated for a mouse wheel rotation. The wheel (the middle
  51  * mouse button on most modern mice) can be rotated towards or away from the
  52  * user, and is often used for scrolling.
  53  *
  54  * <p>Because of the special use for scrolling components, MouseWheelEvents
  55  * often affect a different component than the one located at the point of
  56  * the event. If the component under the mouse cursor does not accept wheel
  57  * events, the event is passed to the first ancestor container which does. This
  58  * is often a ScrollPane, which knows how to scroll. If an AWT component is
  59  * built from a native widget that knows how to use mouse wheel events, that
  60  * component will consume the event.
  61  *
  62  * <p>The two most common scroll types are "units" (lines at a time) or
  63  * "blocks" (pages at a time). The initial setting is taken from the platform,
  64  * although the user can adjust the setting at any time.
  65  *
  66  * @author Eric Blake (ebb9@email.byu.edu)
  67  * @see MouseWheelListener
  68  * @see ScrollPane
  69  * @see ScrollPane#setWheelScrollingEnabled(boolean)
  70  * @see JScrollPane
  71  * @see JScrollPane#setWheelScrollingEnabled(boolean)
  72  * @since 1.4
  73  * @status updated to 1.4
  74  */
  75 public class MouseWheelEvent extends MouseEvent
  76 {
  77   /**
  78    * Compatible with JDK 1.4+.
  79    */
  80   private static final long serialVersionUID = 6459879390515399677L;
  81
  82   /**
  83    * Indicates scrolling by units (lines).
  84    *
  85    * @see #getScrollType()
  86    */
  87   public static final int WHEEL_UNIT_SCROLL = 0;
  88
  89   /**
  90    * Indicates scrolling by blocks (pages).
  91    *
  92    * @see #getScrollType()
  93    */
  94   public static final int WHEEL_BLOCK_SCROLL = 1;
  95
  96   /**
  97    * Indicates what scroll type should take place. This should be limited
  98    * to {@link #WHEEL_UNIT_SCROLL} and {@link #WHEEL_BLOCK_SCROLL}.
  99    *
 100    * @serial the scroll type
 101    */
 102   private final int scrollType;
 103
 104   /**
 105    * Indicates the scroll amount. This is only meaningful if scrollType is
 106    * WHEEL_UNIT_SCROLL.
 107    *
 108    * @serial the number of lines to scroll
 109    */
 110   private final int scrollAmount;
 111
 112   /**
 113    * Indicates how far the mouse wheel was rotated.
 114    *
 115    * @serial the rotation amount
 116    */
 117   private final int wheelRotation;
 118
 119   /**
 120    * Initializes a new instance of <code>MouseWheelEvent</code> with the
 121    * specified information. Note that an invalid id leads to unspecified
 122    * results.
 123    *
 124    * @param source the source of the event
 125    * @param id the event id
 126    * @param when the timestamp of when the event occurred
 127    * @param modifiers any modifier bits for this event
 128    * @param x the X coordinate of the mouse point
 129    * @param y the Y coordinate of the mouse point
 130    * @param clickCount the number of mouse clicks for this event
 131    * @param popupTrigger true if this event triggers a popup menu
 132    * @param scrollType one of {@link #WHEEL_UNIT_SCROLL},
 133    *        {@link #WHEEL_BLOCK_SCROLL}
 134    * @param scrollAmount the number of units to scroll, ignored for block type
 135    * @param wheelRotation the number of rotation "clicks"
 136    * @throws IllegalArgumentException if source is null
 137    * @see MouseEvent#MouseEvent(Component, int, long, int, int, int, int,
 138    *      boolean)
 139    */
 140   public MouseWheelEvent(Component source, int id, long when, int modifiers,
 141                          int x, int y, int clickCount, boolean popupTrigger,
 142                          int scrollType, int scrollAmount, int wheelRotation)
 143   {
 144     super(source, id, when, modifiers, x, y, clickCount, popupTrigger);
 145     this.scrollType = scrollType;
 146     this.scrollAmount = scrollAmount;
 147     this.wheelRotation = wheelRotation;
 148   }
 149
 150   /**
 151    * This method returns the scrolling pattern this event requests. Legal
 152    * values are {@link #WHEEL_UNIT_SCROLL} and {@link #WHEEL_BLOCK_SCROLL}.
 153    *
 154    * @return the scroll type
 155    * @see Adjustable#getUnitIncrement()
 156    * @see Adjustable#getBlockIncrement()
 157    * @see Scrollable#getScrollableUnitIncrement(Rectangle, int, int)
 158    * @see Scrollable#getScrollableBlockIncrement(Rectangle, int, int)
 159    */
 160   public int getScrollType()
 161   {
 162     return scrollType;
 163   }
 164
 165   /**
 166    * Returns the number of units to scroll in response to this event. This
 167    * only makes sense when the scroll type is WHEEL_UNIT_SCROLL.
 168    *
 169    * @return the number of scroll units, if defined
 170    * @see #getScrollType()
 171    */
 172   public int getScrollAmount()
 173   {
 174     return scrollAmount;
 175   }
 176
 177   /**
 178    * Gets the number of "clicks" the wheel was rotated. Negative values move
 179    * up (away) from the user, positive values move down (towards) the user.
 180    *
 181    * @return the number of rotation clicks
 182    */
 183   public int getWheelRotation()
 184   {
 185     return wheelRotation;
 186   }
 187
 188   /**
 189    * This is a convenience method which aids in a common listener for scrolling
 190    * a scrollpane (although this is already built into ScrollPane and
 191    * JScrollPane). This method only makes sense when getScrollType() returns
 192    * WHEEL_UNIT_SCROLL.
 193    *
 194    * <p>This accounts for direction of scroll and amount of wheel movement, as
 195    * interpreted by the platform settings.
 196    *
 197    * @return the number of units to scroll
 198    * @see #getScrollType()
 199    * @see #getScrollAmount()
 200    * @see MouseWheelListener
 201    * @see Adjustable
 202    * @see Adjustable#getUnitIncrement()
 203    * @see Scrollable
 204    * @see Scrollable#getScrollableUnitIncrement(Rectangle, int, int)
 205    * @see ScrollPane
 206    * @see ScrollPane#setWheelScrollingEnabled(boolean)
 207    * @see JScrollPane
 208    * @see JScrollPane#setWheelScrollingEnabled(boolean)
 209    */
 210   public int getUnitsToScroll()
 211   {
 212     return wheelRotation * scrollAmount;
 213   }
 214
 215   /**
 216    * Returns a string identifying this event. For mouse wheel events, this
 217    * is <code>super.paramString() + ",scrollType=WHEEL_" +
 218    * (getScrollType() == WHEEL_UNIT_SCROLL ? "UNIT" : "BLOCK")
 219    * + "_SCROLL,scrollAmount=" + getScrollAmount() + ",wheelRotation="
 220    * + getWheelRotation()</code>.
 221    *
 222    * @return a string identifying this event
 223    */
 224   public String paramString()
 225   {
 226     return super.paramString() + ",scrollType="
 227       + (scrollType == WHEEL_UNIT_SCROLL ? "WHEEL_UNIT_SCROLL"
 228          : scrollType == WHEEL_BLOCK_SCROLL ? "WHEEL_BLOCK_SCROLL"
 229          : "unknown scroll type")
 230       + ",scrollAmount=" + scrollAmount + ",wheelRotation=" + wheelRotation;
 231   }
 232 } // class MouseWheelEvent