org.waveprotocol.wave.client.common.util.OffsetPosition.java Source code

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Here is the source code for org.waveprotocol.wave.client.common.util.OffsetPosition.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.waveprotocol.wave.client.common.util;

import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.Window;

/**
 * Represents an x, y position relative to an offsetParent.
 *
 * If offsetParent is null, then interpret left and top as absolute positions on
 * the browser.
 *
 */
public final class OffsetPosition {
    public final int left;
    public final int top;
    public final Element offsetParent;

    public OffsetPosition(int left, int top, Element offsetParent) {
        this.left = left;
        this.top = top;
        this.offsetParent = offsetParent;
    }

    /**
     * Create a offset position base on the event's client X, Y. The return offset
     * position is relative to the Document body coordinate.
     *
     * @param event
     */
    public OffsetPosition(Event event) {
        // convert the event's client coordinate system, which is client area base, to the
        // body position coordinate system.

        this.left = event.getClientX() + Window.getScrollLeft() - Document.get().getBodyOffsetLeft();
        this.top = event.getClientY() + Window.getScrollTop() - Document.get().getBodyOffsetTop();

        this.offsetParent = null;
    }

    /**
     * Gets the position of target relative to a specified element.
     * @param target
     * @param relative
     */
    public static OffsetPosition getRelativePosition(OffsetPosition target, Element relative) {
        int parentLeft = 0;
        int parentTop = 0;
        if (target.offsetParent != null) {
            parentLeft = target.offsetParent.getAbsoluteLeft();
            parentTop = target.offsetParent.getAbsoluteTop();
        }
        int left = parentLeft + target.left - relative.getAbsoluteLeft();
        int top = parentTop + target.top - relative.getAbsoluteTop();
        return new OffsetPosition(left, top, relative);
    }
}