path: root/src/share/classes/java/awt/event/MouseWheelEvent.java

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package java.awt.event;

import java.awt.Component;

import java.lang.annotation.Native;

/**
 * An event which indicates that the mouse wheel was rotated in a component.
 * <P>
 * A wheel mouse is a mouse which has a wheel in place of the middle button.
 * This wheel can be rotated towards or away from the user.  Mouse wheels are
 * most often used for scrolling, though other uses are possible.
 * <P>
 * A MouseWheelEvent object is passed to every <code>MouseWheelListener</code>
 * object which registered to receive the "interesting" mouse events using the
 * component's <code>addMouseWheelListener</code> method.  Each such listener
 * object gets a <code>MouseEvent</code> containing the mouse event.
 * <P>
 * Due to the mouse wheel's special relationship to scrolling Components,
 * MouseWheelEvents are delivered somewhat differently than other MouseEvents.
 * This is because while other MouseEvents usually affect a change on
 * the Component directly under the mouse
 * cursor (for instance, when clicking a button), MouseWheelEvents often have
 * an effect away from the mouse cursor (moving the wheel while
 * over a Component inside a ScrollPane should scroll one of the
 * Scrollbars on the ScrollPane).
 * <P>
 * MouseWheelEvents start delivery from the Component underneath the
 * mouse cursor.  If MouseWheelEvents are not enabled on the
 * Component, the event is delivered to the first ancestor
 * Container with MouseWheelEvents enabled.  This will usually be
 * a ScrollPane with wheel scrolling enabled.  The source
 * Component and x,y coordinates will be relative to the event's
 * final destination (the ScrollPane).  This allows a complex
 * GUI to be installed without modification into a ScrollPane, and
 * for all MouseWheelEvents to be delivered to the ScrollPane for
 * scrolling.
 * <P>
 * Some AWT Components are implemented using native widgets which
 * display their own scrollbars and handle their own scrolling.
 * The particular Components for which this is true will vary from
 * platform to platform.  When the mouse wheel is
 * moved over one of these Components, the event is delivered straight to
 * the native widget, and not propagated to ancestors.
 * <P>
 * Platforms offer customization of the amount of scrolling that
 * should take place when the mouse wheel is moved.  The two most
 * common settings are to scroll a certain number of "units"
 * (commonly lines of text in a text-based component) or an entire "block"
 * (similar to page-up/page-down).  The MouseWheelEvent offers
 * methods for conforming to the underlying platform settings.  These
 * platform settings can be changed at any time by the user.  MouseWheelEvents
 * reflect the most recent settings.
 * <P>
 * The <code>MouseWheelEvent</code> class includes methods for
 * getting the number of "clicks" by which the mouse wheel is rotated.
 * The {@link #getWheelRotation} method returns the integer number
 * of "clicks" corresponding to the number of notches by which the wheel was
 * rotated. In addition to this method, the <code>MouseWheelEvent</code>
 * class provides the {@link #getPreciseWheelRotation} method which returns
 * a double number of "clicks" in case a partial rotation occurred.
 * The {@link #getPreciseWheelRotation} method is useful if a mouse supports
 * a high-resolution wheel, such as a freely rotating wheel with no
 * notches. Applications can benefit by using this method to process
 * mouse wheel events more precisely, and thus, making visual perception
 * smoother.
 * <P>
 * Some devices (e.g. high-precision touchpads) may report scrolling deltas
 * in absolute values rather than in fractions of a "click". This data is
 * available via the {@link #getScrollingDelta} method and can be used,
 * for example, to implement pixel-perfect scrolling (which cannot be
 * implemented via the {@link #getPreciseWheelRotation} method, as fractions
 * of scrolling "units" cannot be reliably translated to pixel-precise deltas).
 *
 * @author Brent Christian
 * @see MouseWheelListener
 * @see java.awt.ScrollPane
 * @see java.awt.ScrollPane#setWheelScrollingEnabled(boolean)
 * @see javax.swing.JScrollPane
 * @see javax.swing.JScrollPane#setWheelScrollingEnabled(boolean)
 * @since 1.4
 */

public class MouseWheelEvent extends MouseEvent {

    /**
     * Constant representing scrolling by "units" (like scrolling with the
     * arrow keys)
     *
     * @see #getScrollType
     */
    @Native public static final int WHEEL_UNIT_SCROLL = 0;

    /**
     * Constant representing scrolling by a "block" (like scrolling
     * with page-up, page-down keys)
     *
     * @see #getScrollType
     */
    @Native public static final int WHEEL_BLOCK_SCROLL = 1;

    /**
     * Indicates what sort of scrolling should take place in response to this
     * event, based on platform settings.  Legal values are:
     * <ul>
     * <li> WHEEL_UNIT_SCROLL
     * <li> WHEEL_BLOCK_SCROLL
     * </ul>
     *
     * @see #getScrollType
     */
    int scrollType;

    /**
     * Only valid for scrollType WHEEL_UNIT_SCROLL.
     * Indicates number of units that should be scrolled per
     * click of mouse wheel rotation, based on platform settings.
     *
     * @see #getScrollAmount
     * @see #getScrollType
     */
    int scrollAmount;

    /**
     * Indicates how far the mouse wheel was rotated.
     *
     * @see #getWheelRotation
     */
    int wheelRotation;

    /**
     * Indicates how far the mouse wheel was rotated.
     *
     * @see #getPreciseWheelRotation
     */
    double preciseWheelRotation;

    /**
     * Contains scrolling delta as an absolute value (if available).
     *
     * @see #getScrollingDelta
     */
    double scrollingDelta;

    /*
     * serialVersionUID
     */

    private static final long serialVersionUID = -991214153494842848L;

    /**
     * Constructs a <code>MouseWheelEvent</code> object with the
     * specified source component, type, modifiers, coordinates,
     * scroll type, scroll amount, and wheel rotation.
     * <p>Absolute coordinates xAbs and yAbs are set to source's location on screen plus
     * relative coordinates x and y. xAbs and yAbs are set to zero if the source is not showing.
     * <p>Note that passing in an invalid <code>id</code> results in
     * unspecified behavior. This method throws an
     * <code>IllegalArgumentException</code> if <code>source</code>
     * is <code>null</code>.
     *
     * @param source         the <code>Component</code> that originated
     *                       the event
     * @param id             the integer that identifies the event
     * @param when           a long that gives the time the event occurred
     * @param modifiers      the modifier keys down during event
     *                       (shift, ctrl, alt, meta)
     * @param x              the horizontal x coordinate for the mouse location
     * @param y              the vertical y coordinate for the mouse location
     * @param clickCount     the number of mouse clicks associated with event
     * @param popupTrigger   a boolean, true if this event is a trigger for a
     *                       popup-menu
     * @param scrollType     the type of scrolling which should take place in
     *                       response to this event;  valid values are
     *                       <code>WHEEL_UNIT_SCROLL</code> and
     *                       <code>WHEEL_BLOCK_SCROLL</code>
     * @param  scrollAmount  for scrollType <code>WHEEL_UNIT_SCROLL</code>,
     *                       the number of units to be scrolled
     * @param wheelRotation  the integer number of "clicks" by which the mouse
     *                       wheel was rotated
     *
     * @throws IllegalArgumentException if <code>source</code> is null
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, boolean)
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, int, int, boolean, int)
     */
    public MouseWheelEvent (Component source, int id, long when, int modifiers,
                      int x, int y, int clickCount, boolean popupTrigger,
                      int scrollType, int scrollAmount, int wheelRotation) {

        this(source, id, when, modifiers, x, y, 0, 0, clickCount,
             popupTrigger, scrollType, scrollAmount, wheelRotation);
    }

    /**
     * Constructs a <code>MouseWheelEvent</code> object with the
     * specified source component, type, modifiers, coordinates,
     * absolute coordinates, scroll type, scroll amount, and wheel rotation.
     * <p>Note that passing in an invalid <code>id</code> results in
     * unspecified behavior. This method throws an
     * <code>IllegalArgumentException</code> if <code>source</code>
     * is <code>null</code>.<p>
     * Even if inconsistent values for relative and absolute coordinates are
     * passed to the constructor, the MouseWheelEvent instance is still
     * created and no exception is thrown.
     *
     * @param source         the <code>Component</code> that originated
     *                       the event
     * @param id             the integer that identifies the event
     * @param when           a long that gives the time the event occurred
     * @param modifiers      the modifier keys down during event
     *                       (shift, ctrl, alt, meta)
     * @param x              the horizontal x coordinate for the mouse location
     * @param y              the vertical y coordinate for the mouse location
     * @param xAbs           the absolute horizontal x coordinate for the mouse location
     * @param yAbs           the absolute vertical y coordinate for the mouse location
     * @param clickCount     the number of mouse clicks associated with event
     * @param popupTrigger   a boolean, true if this event is a trigger for a
     *                       popup-menu
     * @param scrollType     the type of scrolling which should take place in
     *                       response to this event;  valid values are
     *                       <code>WHEEL_UNIT_SCROLL</code> and
     *                       <code>WHEEL_BLOCK_SCROLL</code>
     * @param  scrollAmount  for scrollType <code>WHEEL_UNIT_SCROLL</code>,
     *                       the number of units to be scrolled
     * @param wheelRotation  the integer number of "clicks" by which the mouse
     *                       wheel was rotated
     *
     * @throws IllegalArgumentException if <code>source</code> is null
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, boolean)
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, int, int, boolean, int)
     * @since 1.6
     */
    public MouseWheelEvent (Component source, int id, long when, int modifiers,
                            int x, int y, int xAbs, int yAbs, int clickCount, boolean popupTrigger,
                            int scrollType, int scrollAmount, int wheelRotation) {

        this(source, id, when, modifiers, x, y, xAbs, yAbs, clickCount, popupTrigger,
             scrollType, scrollAmount, wheelRotation, wheelRotation);

    }


    /**
     * Constructs a <code>MouseWheelEvent</code> object with the specified
     * source component, type, modifiers, coordinates, absolute coordinates,
     * scroll type, scroll amount, and wheel rotation.
     * <p>Note that passing in an invalid <code>id</code> parameter results
     * in unspecified behavior. This method throws an
     * <code>IllegalArgumentException</code> if <code>source</code> equals
     * <code>null</code>.
     * <p>Even if inconsistent values for relative and absolute coordinates
     * are passed to the constructor, a <code>MouseWheelEvent</code> instance
     * is still created and no exception is thrown.
     *
     * @param source         the <code>Component</code> that originated the event
     * @param id             the integer value that identifies the event
     * @param when           a long value that gives the time when the event occurred
     * @param modifiers      the modifier keys down during event
     *                       (shift, ctrl, alt, meta)
     * @param x              the horizontal <code>x</code> coordinate for the
     *                       mouse location
     * @param y              the vertical <code>y</code> coordinate for the
     *                       mouse location
     * @param xAbs           the absolute horizontal <code>x</code> coordinate for
     *                       the mouse location
     * @param yAbs           the absolute vertical <code>y</code> coordinate for
     *                       the mouse location
     * @param clickCount     the number of mouse clicks associated with the event
     * @param popupTrigger   a boolean value, <code>true</code> if this event is a trigger
     *                       for a popup-menu
     * @param scrollType     the type of scrolling which should take place in
     *                       response to this event;  valid values are
     *                       <code>WHEEL_UNIT_SCROLL</code> and
     *                       <code>WHEEL_BLOCK_SCROLL</code>
     * @param  scrollAmount  for scrollType <code>WHEEL_UNIT_SCROLL</code>,
     *                       the number of units to be scrolled
     * @param wheelRotation  the integer number of "clicks" by which the mouse wheel
     *                       was rotated
     * @param preciseWheelRotation the double number of "clicks" by which the mouse wheel
     *                       was rotated
     *
     * @throws IllegalArgumentException if <code>source</code> is null
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, boolean)
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, int, int, boolean, int)
     * @since 1.7
     */
    public MouseWheelEvent (Component source, int id, long when, int modifiers,
                            int x, int y, int xAbs, int yAbs, int clickCount, boolean popupTrigger,
                            int scrollType, int scrollAmount, int wheelRotation, double preciseWheelRotation) {

        this(source, id, when, modifiers, x, y, xAbs, yAbs, clickCount, popupTrigger,
             scrollType, scrollAmount, wheelRotation, preciseWheelRotation, 0);
    }

    /**
     * Constructs a <code>MouseWheelEvent</code> object with the specified
     * source component, type, modifiers, coordinates, absolute coordinates,
     * scroll type, scroll amount, wheel rotation and scrolling delta.
     * <p>Note that passing in an invalid <code>id</code> parameter results
     * in unspecified behavior. This method throws an
     * <code>IllegalArgumentException</code> if <code>source</code> equals
     * <code>null</code>.
     * <p>Even if inconsistent values for relative and absolute coordinates
     * are passed to the constructor, a <code>MouseWheelEvent</code> instance
     * is still created and no exception is thrown.
     *
     * @param source         the <code>Component</code> that originated the event
     * @param id             the integer value that identifies the event
     * @param when           a long value that gives the time when the event occurred
     * @param modifiers      the modifier keys down during event
     *                       (shift, ctrl, alt, meta)
     * @param x              the horizontal <code>x</code> coordinate for the
     *                       mouse location
     * @param y              the vertical <code>y</code> coordinate for the
     *                       mouse location
     * @param xAbs           the absolute horizontal <code>x</code> coordinate for
     *                       the mouse location
     * @param yAbs           the absolute vertical <code>y</code> coordinate for
     *                       the mouse location
     * @param clickCount     the number of mouse clicks associated with the event
     * @param popupTrigger   a boolean value, <code>true</code> if this event is a trigger
     *                       for a popup-menu
     * @param scrollType     the type of scrolling which should take place in
     *                       response to this event;  valid values are
     *                       <code>WHEEL_UNIT_SCROLL</code> and
     *                       <code>WHEEL_BLOCK_SCROLL</code>
     * @param  scrollAmount  for scrollType <code>WHEEL_UNIT_SCROLL</code>,
     *                       the number of units to be scrolled
     * @param wheelRotation  the integer number of "clicks" by which the mouse wheel
     *                       was rotated
     * @param preciseWheelRotation the double number of "clicks" by which the mouse wheel
     *                       was rotated
     * @param scrollingDelta the scrolling delta as an absolute value
     *
     * @throws IllegalArgumentException if <code>source</code> is null
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, boolean)
     * @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, int, int, boolean, int)
     * @deprecated This constructor is available only in JetBrains Runtime
     * @since 1.9
     */
    public MouseWheelEvent (Component source, int id, long when, int modifiers,
                            int x, int y, int xAbs, int yAbs, int clickCount, boolean popupTrigger,
                            int scrollType, int scrollAmount,
                            int wheelRotation, double preciseWheelRotation, double scrollingDelta) {

        super(source, id, when, modifiers, x, y, xAbs, yAbs, clickCount,
              popupTrigger, MouseEvent.NOBUTTON);

        this.scrollType = scrollType;
        this.scrollAmount = scrollAmount;
        this.wheelRotation = wheelRotation;
        this.preciseWheelRotation = preciseWheelRotation;
        this.scrollingDelta = scrollingDelta;
    }

    /**
     * Returns the type of scrolling that should take place in response to this
     * event.  This is determined by the native platform.  Legal values are:
     * <ul>
     * <li> MouseWheelEvent.WHEEL_UNIT_SCROLL
     * <li> MouseWheelEvent.WHEEL_BLOCK_SCROLL
     * </ul>
     *
     * @return either MouseWheelEvent.WHEEL_UNIT_SCROLL or
     *  MouseWheelEvent.WHEEL_BLOCK_SCROLL, depending on the configuration of
     *  the native platform.
     * @see java.awt.Adjustable#getUnitIncrement
     * @see java.awt.Adjustable#getBlockIncrement
     * @see javax.swing.Scrollable#getScrollableUnitIncrement
     * @see javax.swing.Scrollable#getScrollableBlockIncrement
     */
    public int getScrollType() {
        return scrollType;
    }

    /**
     * Returns the number of units that should be scrolled per
     * click of mouse wheel rotation.
     * Only valid if <code>getScrollType</code> returns
     * <code>MouseWheelEvent.WHEEL_UNIT_SCROLL</code>
     *
     * @return number of units to scroll, or an undefined value if
     *  <code>getScrollType</code> returns
     *  <code>MouseWheelEvent.WHEEL_BLOCK_SCROLL</code>
     * @see #getScrollType
     */
    public int getScrollAmount() {
        return scrollAmount;
    }

    /**
     * Returns the number of "clicks" the mouse wheel was rotated, as an integer.
     * A partial rotation may occur if the mouse supports a high-resolution wheel.
     * In this case, the method returns zero until a full "click" has been accumulated.
     *
     * @return negative values if the mouse wheel was rotated up/away from
     * the user, and positive values if the mouse wheel was rotated down/
     * towards the user
     * @see #getPreciseWheelRotation
     * @see #getScrollingDelta
     */
    public int getWheelRotation() {
        return wheelRotation;
    }

    /**
     * Returns the number of "clicks" the mouse wheel was rotated, as a double.
     * A partial rotation may occur if the mouse supports a high-resolution wheel.
     * In this case, the return value will include a fractional "click".
     *
     * @return negative values if the mouse wheel was rotated up or away from
     * the user, and positive values if the mouse wheel was rotated down or
     * towards the user
     * @see #getWheelRotation
     * @see #getScrollingDelta
     * @since 1.7
     */
    public double getPreciseWheelRotation() {
        return preciseWheelRotation;
    }

    /**
     * Returns the scrolling delta as an absolute value.
     * Returns 0.0 when scrolling delta is available only as a number of "clicks" or
     * as a fraction of a "click".
     * <P>
     * The method returns natural numbers, however, for future extensibility,
     * the return type is declared as {@code double}.
     *
     * @return negative values for scrolling up, positive values for scrolling down
     * (natural numbers)
     * @see #getWheelRotation
     * @see #getPreciseWheelRotation
     * @since 1.8
     */
    public double getScrollingDelta() {
        return scrollingDelta;
    }

    /**
     * This is a convenience method to aid in the implementation of
     * the common-case MouseWheelListener - to scroll a ScrollPane or
     * JScrollPane by an amount which conforms to the platform settings.
     * (Note, however, that <code>ScrollPane</code> and
     * <code>JScrollPane</code> already have this functionality built in.)
     * <P>
     * This method returns the number of units to scroll when scroll type is
     * MouseWheelEvent.WHEEL_UNIT_SCROLL, and should only be called if
     * <code>getScrollType</code> returns MouseWheelEvent.WHEEL_UNIT_SCROLL.
     * <P>
     * Direction of scroll, amount of wheel movement,
     * and platform settings for wheel scrolling are all accounted for.
     * This method does not and cannot take into account value of the
     * Adjustable/Scrollable unit increment, as this will vary among
     * scrolling components.
     * <P>
     * A simplified example of how this method might be used in a
     * listener:
     * <pre>
     *  mouseWheelMoved(MouseWheelEvent event) {
     *      ScrollPane sp = getScrollPaneFromSomewhere();
     *      Adjustable adj = sp.getVAdjustable()
     *      if (MouseWheelEvent.getScrollType() == WHEEL_UNIT_SCROLL) {
     *          int totalScrollAmount =
     *              event.getUnitsToScroll() *
     *              adj.getUnitIncrement();
     *          adj.setValue(adj.getValue() + totalScrollAmount);
     *      }
     *  }
     * </pre>
     *
     * @return the number of units to scroll based on the direction and amount
     *  of mouse wheel rotation, and on the wheel scrolling settings of the
     *  native platform
     * @see #getScrollType
     * @see #getScrollAmount
     * @see MouseWheelListener
     * @see java.awt.Adjustable
     * @see java.awt.Adjustable#getUnitIncrement
     * @see javax.swing.Scrollable
     * @see javax.swing.Scrollable#getScrollableUnitIncrement
     * @see java.awt.ScrollPane
     * @see java.awt.ScrollPane#setWheelScrollingEnabled
     * @see javax.swing.JScrollPane
     * @see javax.swing.JScrollPane#setWheelScrollingEnabled
     */
    public int getUnitsToScroll() {
        return scrollAmount * wheelRotation;
    }

    /**
     * Returns a parameter string identifying this event.
     * This method is useful for event-logging and for debugging.
     *
     * @return a string identifying the event and its attributes
     */
    public String paramString() {
        String scrollTypeStr = null;

        if (getScrollType() == WHEEL_UNIT_SCROLL) {
            scrollTypeStr = "WHEEL_UNIT_SCROLL";
        }
        else if (getScrollType() == WHEEL_BLOCK_SCROLL) {
            scrollTypeStr = "WHEEL_BLOCK_SCROLL";
        }
        else {
            scrollTypeStr = "unknown scroll type";
        }
        return super.paramString()+",scrollType="+scrollTypeStr+
         ",scrollAmount="+getScrollAmount()+",wheelRotation="+
         getWheelRotation()+",preciseWheelRotation="+getPreciseWheelRotation()+
         ",scrollingDelta="+getScrollingDelta();
    }
}