1/* 2 * Copyright (c) 2000, 2013, 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 */ 25package javax.swing.text; 26 27import java.awt.Shape; 28 29/** 30 * <code>NavigationFilter</code> can be used to restrict where the cursor can 31 * be positioned. When the default cursor positioning actions attempt to 32 * reposition the cursor they will call into the 33 * <code>NavigationFilter</code>, assuming 34 * the <code>JTextComponent</code> has a non-null 35 * <code>NavigationFilter</code> set. In this manner 36 * the <code>NavigationFilter</code> can effectively restrict where the 37 * cursor can be positioned. Similarly <code>DefaultCaret</code> will call 38 * into the <code>NavigationFilter</code> when the user is changing the 39 * selection to further restrict where the cursor can be positioned. 40 * <p> 41 * Subclasses can conditionally call into supers implementation to restrict 42 * where the cursor can be placed, or call directly into the 43 * <code>FilterBypass</code>. 44 * 45 * @see javax.swing.text.Caret 46 * @see javax.swing.text.DefaultCaret 47 * @see javax.swing.text.View 48 * 49 * @since 1.4 50 */ 51public class NavigationFilter { 52 /** 53 * Invoked prior to the Caret setting the dot. The default implementation 54 * calls directly into the <code>FilterBypass</code> with the passed 55 * in arguments. Subclasses may wish to conditionally 56 * call super with a different location, or invoke the necessary method 57 * on the <code>FilterBypass</code> 58 * 59 * @param fb FilterBypass that can be used to mutate caret position 60 * @param dot the position >= 0 61 * @param bias Bias to place the dot at 62 */ 63 public void setDot(FilterBypass fb, int dot, Position.Bias bias) { 64 fb.setDot(dot, bias); 65 } 66 67 /** 68 * Invoked prior to the Caret moving the dot. The default implementation 69 * calls directly into the <code>FilterBypass</code> with the passed 70 * in arguments. Subclasses may wish to conditionally 71 * call super with a different location, or invoke the necessary 72 * methods on the <code>FilterBypass</code>. 73 * 74 * @param fb FilterBypass that can be used to mutate caret position 75 * @param dot the position >= 0 76 * @param bias Bias for new location 77 */ 78 public void moveDot(FilterBypass fb, int dot, Position.Bias bias) { 79 fb.moveDot(dot, bias); 80 } 81 82 /** 83 * Returns the next visual position to place the caret at from an 84 * existing position. The default implementation simply forwards the 85 * method to the root View. Subclasses may wish to further restrict the 86 * location based on additional criteria. 87 * 88 * @param text JTextComponent containing text 89 * @param pos Position used in determining next position 90 * @param bias Bias used in determining next position 91 * @param direction the direction from the current position that can 92 * be thought of as the arrow keys typically found on a keyboard. 93 * This will be one of the following values: 94 * <ul> 95 * <li>SwingConstants.WEST 96 * <li>SwingConstants.EAST 97 * <li>SwingConstants.NORTH 98 * <li>SwingConstants.SOUTH 99 * </ul> 100 * @param biasRet Used to return resulting Bias of next position 101 * @return the location within the model that best represents the next 102 * location visual position 103 * @exception BadLocationException for a bad location within a document model 104 * @exception IllegalArgumentException if <code>direction</code> 105 * doesn't have one of the legal values above 106 */ 107 public int getNextVisualPositionFrom(JTextComponent text, int pos, 108 Position.Bias bias, int direction, 109 Position.Bias[] biasRet) 110 throws BadLocationException { 111 return text.getUI().getNextVisualPositionFrom(text, pos, bias, 112 direction, biasRet); 113 } 114 115 116 /** 117 * Used as a way to circumvent calling back into the caret to 118 * position the cursor. Caret implementations that wish to support 119 * a NavigationFilter must provide an implementation that will 120 * not callback into the NavigationFilter. 121 * @since 1.4 122 */ 123 public abstract static class FilterBypass { 124 /** 125 * Returns the Caret that is changing. 126 * 127 * @return Caret that is changing 128 */ 129 public abstract Caret getCaret(); 130 131 /** 132 * Sets the caret location, bypassing the NavigationFilter. 133 * 134 * @param dot the position >= 0 135 * @param bias Bias to place the dot at 136 */ 137 public abstract void setDot(int dot, Position.Bias bias); 138 139 /** 140 * Moves the caret location, bypassing the NavigationFilter. 141 * 142 * @param dot the position >= 0 143 * @param bias Bias for new location 144 */ 145 public abstract void moveDot(int dot, Position.Bias bias); 146 } 147} 148