libjava/java/awt/event/MouseWheelEvent.java

   1 /* MouseWheelEvent.java -- a mouse wheel event
   2    Copyright (C) 2002 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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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.Component;
  42 import java.awt.Point;
  43
  44 /**
  45  * This event is generated for a mouse wheel rotation. The wheel (the middle
  46  * mouse button on most modern mice) can be rotated towards or away from the
  47  * user, and is ofteh used for scrolling.
  48  *
  49  * <p>Because of the special use for scrolling components, MouseWheelEvents
  50  * often affect a different component than the one located at the point of
  51  * the event. If the component under the mouse cursor does not accept wheel
  52  * events, the event is passed to the first ancestor container which does. This
  53  * is often a ScrollPane, which knows how to scroll. If an AWT component is
  54  * built from a native widget that knows how to use mouse wheel events, that
  55  * component will consume the event.
  56  *
  57  * <p>The two most common scroll types are "units" (lines at a time) or
  58  * "blocks" (pages at a time). The initial setting is taken from the platform,
  59  * although the user can adjust the setting at any time.
  60  *
  61  * @author Eric Blake <ebb9@email.byu.edu>
  62  * @see MouseWheelListener
  63  * @see ScrollPane
  64  * @see ScrollPane#setWheelScrollingEnabled(boolean)
  65  * @see JScrollPane
  66  * @see JScrollPane#setWheelScrollingEnabled(boolean)
  67  * @since 1.4
  68  * @status updated to 1.4
  69  */
  70 public class MouseWheelEvent extends MouseEvent
  71 {
  72   /**
  73    * Compatible with JDK 1.4+.
  74    */
  75   private static final long serialVersionUID = 6459879390515399677L;
  76
  77   /**
  78    * Indicates scrolling by units (lines).
  79    *
  80    * @see #getScrollType()
  81    */
  82   public static final int WHEEL_UNIT_SCROLL = 0;
  83
  84   /**
  85    * Indicates scrolling by blocks (pages).
  86    *
  87    * @see #getScrollType()
  88    */
  89   public static final int WHEEL_BLOCK_SCROLL = 1;
  90
  91   /**
  92    * Indicates what scroll type should take place. This should be limited
  93    * to {@link #WHEEL_UNIT_SCROLL} and {@link #WHEEL_BLOCK_SCROLL}.
  94    *
  95    * @serial the scroll type
  96    */
  97   private final int scrollType;
  98
  99   /**
 100    * Indicates the scroll amount. This is only meaningful if scrollType is
 101    * WHEEL_UNIT_SCROLL.
 102    *
 103    * @serial the number of lines to scroll
 104    */
 105   private final int scrollAmount;
 106
 107   /**
 108    * Indicates how far the mouse wheel was rotated.
 109    *
 110    * @serial the rotation amount
 111    */
 112   private final int wheelRotation;
 113
 114   /**
 115    * Initializes a new instance of <code>MouseWheelEvent</code> with the
 116    * specified information. Note that an invalid id leads to unspecified
 117    * results.
 118    *
 119    * @param source the source of the event
 120    * @param id the event id
 121    * @param when the timestamp of when the event occurred
 122    * @param modifiers any modifier bits for this event
 123    * @param x the X coordinate of the mouse point
 124    * @param y the Y coordinate of the mouse point
 125    * @param clickCount the number of mouse clicks for this event
 126    * @param popupTrigger true if this event triggers a popup menu
 127    * @param scrollType one of {@link #WHEEL_UNIT_SCROLL},
 128    *        {@link #WHEEL_BLOCK_SCROLL}
 129    * @param scrollAmount the number of units to scroll, ignored for block type
 130    * @param wheelRotation the number of rotation "clicks"
 131    * @throws IllegalArgumentException if source is null
 132    * @see MouseEvent#MouseEvent(Component, int, long, int, int, int, int,
 133    *      boolean)
 134    */
 135   public MouseWheelEvent(Component source, int id, long when, int modifiers,
 136                          int x, int y, int clickCount, boolean popupTrigger,
 137                          int scrollType, int scrollAmount, int wheelRotation)
 138   {
 139     super(source, id, when, modifiers, x, y, clickCount, popupTrigger);
 140     this.scrollType = scrollType;
 141     this.scrollAmount = scrollAmount;
 142     this.wheelRotation = wheelRotation;
 143   }
 144
 145   /**
 146    * This method returns the scrolling pattern this event requests. Legal
 147    * values are WHEEL_UNIT_SCROLL and WHEEL_BLOCK_SCROLL.
 148    *
 149    * @return the scroll type
 150    * @see Adjustable#getUnitIncrement()
 151    * @see Adjustable#getBlockIncrement()
 152    * @see Scrollable#getScrollableUnitIncrement(Rectangle, int, int)
 153    * @see Scrollable#getScrollableBlockIncrement(Rectangle, int, int)
 154    */
 155   public int getScrollType()
 156   {
 157     return scrollType;
 158   }
 159
 160   /**
 161    * Returns the number of units to scroll in response to this event. This
 162    * only makes sense when the scroll type is WHEEL_UNIT_SCROLL.
 163    *
 164    * @return the number of scroll units, if defined
 165    * @see #getScrollType()
 166    */
 167   public int getScrollAmount()
 168   {
 169     return scrollAmount;
 170   }
 171
 172   /**
 173    * Gets the number of "clicks" the wheel was rotated. Negative values move
 174    * up (away) from the user, positive values move down (towards) the user.
 175    *
 176    * @return the number of rotation clicks
 177    */
 178   public int getWheelRotation()
 179   {
 180     return wheelRotation;
 181   }
 182
 183   /**
 184    * This is a convenience method which aids in a common listener for scrolling
 185    * a scrollpane (although this is already built into ScrollPane and
 186    * JScrollPane). This method only makes sense when getScrollType() returns
 187    * WHEEL_UNIT_SCROLL.
 188    *
 189    * <p>This accounts for direction of scroll and amount of wheel movement, as
 190    * interpreted by the platform settings.
 191    *
 192    * @return the number of units to scroll
 193    * @see #getScrollType()
 194    * @see #getScrollAmount()
 195    * @see MouseWheelListener
 196    * @see Adjustable
 197    * @see Adjustable#getUnitIncrement()
 198    * @see Scrollable
 199    * @see Scrollable#getScrollableUnitIncrement(Rectangle, int, int)
 200    * @see ScrollPane
 201    * @see ScrollPane#setWheelScrollingEnabled(boolean)
 202    * @see JScrollPane
 203    * @see JScrollPane#setWheelScrollingEnabled(boolean)
 204    */
 205   public int getUnitsToScroll()
 206   {
 207     return wheelRotation * scrollAmount;
 208   }
 209
 210   /**
 211    * Returns a string identifying this event. For mouse wheel events, this
 212    * is <code>super.paramString() + ",scrollType=WHEEL_" +
 213    * (getScrollType() == WHEEL_UNIT_SCROLL ? "UNIT" : "BLOCK")
 214    * + "_SCROLL,scrollAmount=" + getScrollAmount() + ",wheelRotation="
 215    * + getWheelRotation()</code>.
 216    *
 217    * @return a string identifying this event
 218    */
 219   public String paramString()
 220   {
 221     return super.paramString() + ",scrollType="
 222       + (scrollType == WHEEL_UNIT_SCROLL ? "WHEEL_UNIT_SCROLL"
 223          : scrollType == WHEEL_BLOCK_SCROLL ? "WHEEL_BLOCK_SCROLL"
 224          : "unknown scroll type")
 225       + ",scrollAmount=" + scrollAmount + ",wheelRotation=" + wheelRotation;
 226   }
 227 } // class MouseWheelEvent