1 /**
2 * This file Copyright (c) 2014-2018 Magnolia International
3 * Ltd. (http://www.magnolia-cms.com). All rights reserved.
4 *
5 *
6 * This file is dual-licensed under both the Magnolia
7 * Network Agreement and the GNU General Public License.
8 * You may elect to use one or the other of these licenses.
9 *
10 * This file is distributed in the hope that it will be
11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
12 * implied warranty of MERCHANTABILITY or FITNESS FOR A
13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
14 * Redistribution, except as permitted by whichever of the GPL
15 * or MNA you select, is prohibited.
16 *
17 * 1. For the GPL license (GPL), you can redistribute and/or
18 * modify this file under the terms of the GNU General
19 * Public License, Version 3, as published by the Free Software
20 * Foundation. You should have received a copy of the GNU
21 * General Public License, Version 3 along with this program;
22 * if not, write to the Free Software Foundation, Inc., 51
23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
24 *
25 * 2. For the Magnolia Network Agreement (MNA), this file
26 * and the accompanying materials are made available under the
27 * terms of the MNA which accompanies this distribution, and
28 * is available at http://www.magnolia-cms.com/mna.html
29 *
30 * Any modifications to this file must keep this entire header
31 * intact.
32 *
33 */
34 package info.magnolia.ui.vaadin.gwt.client.editor.jsni.scroll;
35
36 import info.magnolia.ui.vaadin.gwt.client.jquerywrapper.JQueryWrapper;
37
38 import com.google.gwt.dom.client.Element;
39 import com.google.gwt.dom.client.Style;
40
41 /**
42 * Tracks the initial offset top position of an element and is capable of restoring it later. This is used to prevent the
43 * selected component or area to move out of sight, when the control-bars appear.
44 */
45 public class ElementScrollPositionPreserver {
46
47 private final Element element;
48 private final int currentOffsetTop;
49 private final int initialScrollTop;
50
51 public ElementScrollPositionPreserver(Element element) {
52 this.element = element;
53 currentOffsetTop = getOffsetTop();
54 JQueryWrapper parent = getScrollParent(element);
55 initialScrollTop = parent.getScrollTop();
56 }
57
58 public void restorePosition() {
59 int newBarTop = getOffsetTop();
60 int delta = newBarTop - currentOffsetTop;
61 JQueryWrapper parent = getScrollParent(element);
62 if (parent.getScrollTop() + delta <= newBarTop) {
63 parent.setScrollTop(initialScrollTop + delta);
64 }
65 }
66
67 private int getOffsetTop() {
68 final Style style = element.getStyle();
69 final String displayValue = style.getDisplay();
70
71 style.clearDisplay();
72 int offsetTop = element.getOffsetTop();
73 if ("none".equalsIgnoreCase(displayValue)) {
74 offsetTop -= element.getOffsetHeight();
75 }
76 style.setProperty("display", displayValue);
77 return offsetTop;
78 }
79
80 /**
81 * Locates the nearest scrollable parent. If there's none - returns body element.
82 * Almost verbatim copy of JQuery UI getScrollParent() function.
83 * @see <a href="http://api.jqueryui.com/scrollParent/">getScrollParent()</a>
84 */
85 private native JQueryWrapper getScrollParent(Element e) /*-{
86 var jq = $wnd.$(e);
87 jq.scrollParent = function( includeHidden ) {
88 var position = this.css( "position" ),
89 excludeStaticParent = position === "absolute",
90 overflowRegex = includeHidden ? /(auto|scroll|hidden)/ : /(auto|scroll)/,
91 scrollParent = this.parents().filter( function() {
92 var parent = $wnd.$( this );
93 if ( excludeStaticParent && parent.css( "position" ) === "static" ) {
94 return false;
95 }
96 return overflowRegex.test( parent.css( "overflow" ) + parent.css( "overflow-y" ) + parent.css( "overflow-x" ) );
97 }).eq( 0 );
98 return position === "fixed" || !scrollParent.length ? $wnd.$( this[ 0 ].ownerDocument || document) : scrollParent;
99 };
100 return jq.scrollParent(false);
101 }-*/;
102 }