com.google.gwt.event.dom.client.MouseWheelEvent.java Source code

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Here is the source code for com.google.gwt.event.dom.client.MouseWheelEvent.java

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/*
 * Copyright 2008 Google Inc.
 * 
 * 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.gwt.event.dom.client;

/**
 * Represents a native mouse wheel event.
 */
public class MouseWheelEvent extends MouseEvent<MouseWheelHandler> {

    /**
     * Event type for mouse wheel events. Represents the meta-data associated with
     * this event.
     */
    private static final Type<MouseWheelHandler> TYPE = new Type<MouseWheelHandler>("mousewheel",
            new MouseWheelEvent());

    static {
        /**
         * Hidden type used to ensure DOMMouseScroll gets registered in the type map.
         * This is the special name used on Mozilla browsers for what everyone else
         * calls 'mousewheel'.
         */
        new Type<MouseWheelHandler>("DOMMouseScroll", new MouseWheelEvent());
    }

    /**
     * Gets the event type associated with mouse wheel events.
     * 
     * @return the handler type
     */
    public static Type<MouseWheelHandler> getType() {
        return TYPE;
    }

    /**
     * Protected constructor, use
     * {@link DomEvent#fireNativeEvent(com.google.gwt.dom.client.NativeEvent, com.google.gwt.event.shared.HasHandlers)}
     * to fire mouse wheel events.
     */
    protected MouseWheelEvent() {
    }

    @Override
    public final Type<MouseWheelHandler> getAssociatedType() {
        return TYPE;
    }

    /**
     * Get the change in the mouse wheel position along the Y-axis; positive if
     * the mouse wheel is moving north (toward the top of the screen) or negative
     * if the mouse wheel is moving south (toward the bottom of the screen).
     * 
     * Note that delta values are not normalized across browsers or OSes.
     * 
     * @return the delta of the mouse wheel along the y axis
     */
    public int getDeltaY() {
        return getNativeEvent().getMouseWheelVelocityY();
    }

    /**
     * Convenience method that returns <code>true</code> if {@link #getDeltaY()}
     * is a negative value (ie, the velocity is directed toward the top of the
     * screen).
     * 
     * @return true if the velocity is directed toward the top of the screen
     */
    public boolean isNorth() {
        return getDeltaY() < 0;
    }

    /**
     * Convenience method that returns <code>true</code> if {@link #getDeltaY()}
     * is a positive value (ie, the velocity is directed toward the bottom of the
     * screen).
     * 
     * @return true if the velocity is directed toward the bottom of the screen
     */
    public boolean isSouth() {
        return getDeltaY() > 0;
    }

    @Override
    protected void dispatch(MouseWheelHandler handler) {
        handler.onMouseWheel(this);
    }
}