1 /*
   2  * Copyright (c) 2011, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javafx.scene.layout;
  27 
  28 import com.sun.javafx.scene.layout.PaneHelper;
  29 import javafx.beans.DefaultProperty;
  30 import javafx.collections.ObservableList;
  31 import javafx.scene.Node;
  32 
  33 /**
  34  * Base class for layout panes which need to expose the children list as public
  35  * so that users of the subclass can freely add/remove children.
  36  * <p>
  37  * This class may be used directly in cases where absolute positioning of children
  38  * is required since it does not perform layout beyond resizing resizable children
  39  * to their preferred sizes. It is the application's responsibility to position the
  40  * children since the pane leaves the positions alone during layout.
  41  * For example:
  42  * <pre>{@code
  43  *     Pane canvas = new Pane();
  44  *     canvas.setStyle("-fx-background-color: black;");
  45  *     canvas.setPrefSize(200,200);
  46  *     Circle circle = new Circle(50,Color.BLUE);
  47  *     circle.relocate(20, 20);
  48  *     Rectangle rectangle = new Rectangle(100,100,Color.RED);
  49  *     rectangle.relocate(70,70);
  50  *     canvas.getChildren().addAll(circle,rectangle);
  51  * }</pre>
  52  * <p>
  53  * Note: if an application needs children to be kept aligned within a parent (centered,
  54  * positioned at top-left, etc), it should use a {@link javafx.scene.layout.StackPane StackPane}
  55  * instead.</p>
  56  *
  57  * <p>
  58  * Pane resizes each managed child regardless of the child's visible property value;
  59  * unmanaged children are ignored for all layout calculations.</p>
  60  *
  61  * <h3>Resizable Range</h3>
  62  *
  63  * <p>
  64  * A pane's parent will resize the pane within the pane's resizable range
  65  * during layout.   By default the pane computes this range based on its content
  66  * as outlined in the table below:
  67  * </p>
  68  *
  69  * <table border="1">
  70  * <caption>Pane Resize Table</caption>
  71  * <tr><td></td><th scope="col">width</th><th scope="col">height</th></tr>
  72  * <tr><th scope="row">minimum</th>
  73  * <td>left plus right insets.</td>
  74  * <td>top plus bottom insets.</td></tr>
  75  * <tr><th scope="row">preferred</th>
  76  * <td>width required to encompass each child at its current x location and preferred width.</td>
  77  * <td>height required to encompass each child at its current y location and preferred height.</td></tr>
  78  * <tr><th scope="row">maximum</th>
  79  * <td>Double.MAX_VALUE</td><td>Double.MAX_VALUE</td></tr>
  80  * </table>
  81  * <p>
  82  * A pane's unbounded maximum width and height are an indication to the parent that
  83  * it may be resized beyond its preferred size to fill whatever space is assigned to it.
  84  * <p>
  85  * Pane provides properties for setting the size range directly.  These
  86  * properties default to the sentinel value Region.USE_COMPUTED_SIZE, however the
  87  * application may set them to other values as needed:
  88  * <pre><code>
  89  *     <b>pane.setPrefSize(500,400);</b>
  90  * </code></pre>
  91  * Applications may restore the computed values by setting these properties back
  92  * to Region.USE_COMPUTED_SIZE.
  93  * <p>
  94  * Pane does not clip its content by default, so it is possible that childrens'
  95  * bounds may extend outside its own bounds, either if children are positioned
  96  * at negative coordinates or the pane is resized smaller than its preferred size.</p>
  97  *
  98  * @since JavaFX 2.0
  99  */
 100 @DefaultProperty("children")
 101 public class Pane extends Region {
 102     static {
 103         PaneHelper.setPaneAccessor(new PaneHelper.PaneAccessor() {
 104         });
 105     }
 106 
 107     static void setConstraint(Node node, Object key, Object value) {
 108         if (value == null) {
 109             node.getProperties().remove(key);
 110         } else {
 111             node.getProperties().put(key, value);
 112         }
 113         if (node.getParent() != null) {
 114             node.getParent().requestLayout();
 115         }
 116     }
 117 
 118     static Object getConstraint(Node node, Object key) {
 119         if (node.hasProperties()) {
 120             Object value = node.getProperties().get(key);
 121             if (value != null) {
 122                 return value;
 123             }
 124         }
 125         return null;
 126     }
 127 
 128     {
 129         // To initialize the class helper at the begining each constructor of this class
 130         PaneHelper.initHelper(this);
 131     }
 132     /**
 133      * Creates a Pane layout.
 134      */
 135     public Pane() {
 136         super();
 137     }
 138 
 139     /**
 140      * Creates a Pane layout.
 141      * @param children The initial set of children for this pane.
 142      * @since JavaFX 8.0
 143      */
 144     public Pane(Node... children) {
 145         super();
 146         getChildren().addAll(children);
 147     }
 148 
 149     /**
 150      *
 151      * @return modifiable list of children.
 152      */
 153     @Override public ObservableList<Node> getChildren() {
 154         return super.getChildren();
 155     }
 156 
 157 }
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