com.ikon.frontend.client.panel.left.ExtendedScrollPanel.java Source code

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Here is the source code for com.ikon.frontend.client.panel.left.ExtendedScrollPanel.java

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/**
 *  openkm, Open Document Management System (http://www.openkm.com)
 *  Copyright (c) 2006-2013  Paco Avila & Josep Llort
 *
 *  No bytes were intentionally harmed during the development of this application.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package com.ikon.frontend.client.panel.left;

import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.ui.ScrollPanel;

public class ExtendedScrollPanel extends ScrollPanel {

    /*
     HOW IT RUNS EXTENDEDSCROLL DESCRIPTION
         
     [getAbsoluteLeft() , getAbsoluteTop()]
     ^
     |
     x--------------------------x-> [getAbsoluteLeft()+getOffsetWidth() , getAbsoluteTop()]
     |         ^   timer       |
     |         |   fired      | (timer fired while is on this zone )
     |         |            |                     
     |--------------------------x   <- MARGIN_AUTO_SCROLL_POS (Zone on auto scroll up while drag & drop       
     |                     |
     |                     |
     |                     |
     |                     |
     |                     |                     
     |                     |                     
     |                     |
     |                     |
     |                     |
     |                     |
     |--------------------------x   <- MARGIN_AUTO_SCROLL_POS (Zone on auto scroll downwhile drag & drop
     |         ^   timer      |                     
     |         |   fired      |   
     |         |            |
     x--------------------------x-> [getAbsoluteLeft()+getOffsetHeight() , getAbsoluteLeft() + getOffsetWidth()]
          
     ^
     |
     [getAbsoluteLeft() , getAbsoluteTop() + getOffsetHeight()]
        
     */

    private final int MARGIN_AUTO_SCROLL_POS = 30; // Sets 30px from top widget and 30px from bottom to start autoscroll during drag  and drop
    private final int SCROLL_ACCELERATION = 20; // Acceleration factor to top / down scroll during drag and drop
    private final int TIMER_SPEED = 100;

    private Timer timer = null;

    /* (non-Javadoc)
     * @see com.google.gwt.user.client.ui.UIObject#getAbsoluteTop()
     */
    public int getAbsoluteTop() {
        // Must be make a correction on getAbsoluteTop when the scroll is enabled the real absolute top is
        // super absoluteTop value + actual scroll position
        return super.getAbsoluteTop() + getVerticalScrollPosition();
    }

    /**
     * Evaluate if x,y position is on scroll square widget
     * 
     * @param x position
     * @param y position
     * @return
     */
    private boolean isOverlap(int x, int y) {
        boolean xOverlap = getAbsoluteLeft() <= x && (getAbsoluteLeft() + getOffsetWidth()) >= x;
        boolean yOverlap = getAbsoluteTop() <= y && (getAbsoluteTop() + getOffsetHeight()) >= y;

        return (xOverlap && yOverlap);
    }

    /**
     * ScrollDown
     * 
     *  * Scrolls down with SCROLL_ACCELERATION factor
     */
    private void ScrollDown() {
        this.setVerticalScrollPosition(getVerticalScrollPosition() + SCROLL_ACCELERATION);
    }

    /**
     * ScrollUp
     * 
     * Scrolls up with SCROLL_ACCELERATION factor
     */
    private void ScrollUp() {
        this.setVerticalScrollPosition(getVerticalScrollPosition() - SCROLL_ACCELERATION);
    }

    /**
     * isAutoScrollUp
     * 
     * Determines is x,y position is on auto scroll up square
     * 
     * @param x position
     * @param y position
     * @return
     */
    private boolean isAutoScrollUp(int x, int y) {
        boolean xOverlap = getAbsoluteLeft() <= x && (getAbsoluteLeft() + getOffsetWidth()) >= x;
        boolean yOverlap = getAbsoluteTop() <= y && (getAbsoluteTop() + MARGIN_AUTO_SCROLL_POS) >= y;

        return (xOverlap && yOverlap);
    }

    /**
     * isAutoScrollDown
     * 
     * Determines is x,y position is on auto scroll down square
     * 
     * @param x position
     * @param y position
     * @return
     */
    private boolean isAutoScrollDown(int x, int y) {
        boolean xOverlap = getAbsoluteLeft() <= x && (getAbsoluteLeft() + getOffsetWidth()) >= x;
        boolean yOverlap = (getAbsoluteTop() + getOffsetHeight() - MARGIN_AUTO_SCROLL_POS) <= y
                && (getAbsoluteTop() + getOffsetHeight()) >= y;

        return (xOverlap && yOverlap);
    }

    /**
     * ScrollOnDragDrop
     * 
     * @param x position
     * @param y position
     */
    public void ScrollOnDragDrop(int x, int y) {
        if (isOverlap(x, y)) {
            if (isAutoScrollUp(x, y)) {
                if (timer == null) {
                    timer = new Timer() {
                        public void run() {
                            ScrollUp();
                        }
                    };
                    timer.scheduleRepeating(TIMER_SPEED);
                }
            } else if (isAutoScrollDown(x, y)) {
                if (timer == null) {
                    timer = new Timer() {
                        public void run() {
                            ScrollDown();
                        }
                    };
                    timer.scheduleRepeating(TIMER_SPEED);
                }
            } else {
                destroyTimer();
            }
        } else {
            destroyTimer();
        }
    }

    /**
     * destroyTimer
     * 
     * Removes the scroll up / down timer
     */
    public void destroyTimer() {
        if (timer != null) {
            timer.cancel();
            timer = null;
        }
    }

}