1 /* 2 * Copyright (C) 2022 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.text.method; 18 19 import android.annotation.IntDef; 20 21 import java.lang.annotation.Retention; 22 import java.lang.annotation.RetentionPolicy; 23 24 /** 25 * The interface for the index mapping information of a transformed text returned by 26 * {@link TransformationMethod}. This class is mainly used to support the 27 * {@link TransformationMethod} that alters the text length. 28 * @hide 29 */ 30 @android.ravenwood.annotation.RavenwoodKeepWholeClass 31 public interface OffsetMapping { 32 /** 33 * The mapping strategy for a character offset. 34 * 35 * @see #originalToTransformed(int, int) 36 * @see #transformedToOriginal(int, int) 37 */ 38 int MAP_STRATEGY_CHARACTER = 0; 39 40 /** 41 * The mapping strategy for a cursor position. 42 * 43 * @see #originalToTransformed(int, int) 44 * @see #transformedToOriginal(int, int) 45 */ 46 int MAP_STRATEGY_CURSOR = 1; 47 48 @IntDef(prefix = { "MAP_STRATEGY" }, value = { 49 MAP_STRATEGY_CHARACTER, 50 MAP_STRATEGY_CURSOR 51 }) 52 @Retention(RetentionPolicy.SOURCE) 53 @interface MapStrategy {} 54 55 /** 56 * Map an offset at original text to the offset at transformed text. <br/> 57 * 58 * This function must be a monotonically non-decreasing function. In other words, if the offset 59 * advances at the original text, the offset at the transformed text must advance or stay there. 60 * <br/> 61 * 62 * Depending on the mapping strategy, a same offset can be mapped differently. For example, 63 * <pre> 64 * Original: ABCDE 65 * Transformed: ABCXDE ('X' is introduced due to the transformation.) 66 * </pre> 67 * Let's check the offset 3, which is the offset of the character 'D'. 68 * If we want to map the character offset 3, it should be mapped to index 4. 69 * If we want to map the cursor offset 3 (the offset of the character before which the cursor is 70 * placed), it's unclear if the mapped cursor is before 'X' or after 'X'. 71 * This depends on how the transformed text reacts an insertion at offset 3 in the original 72 * text. Assume character 'V' is insert at offset 3 in the original text, and the original text 73 * become "ABCVDE". The transformed text can be: 74 * <pre> 75 * 1) "ABCVXDE" 76 * or 77 * 2) "ABCXVDE" 78 * </pre> 79 * In the first case, the offset 3 should be mapped to 3 (before 'X'). And in the second case, 80 * the offset should be mapped to 4 (after 'X').<br/> 81 * 82 * In some cases, a character offset at the original text doesn't have a proper corresponding 83 * offset at the transformed text. For example: 84 * <pre> 85 * Original: ABCDE 86 * Transformed: ABDE ('C' is deleted due to the transformation.) 87 * </pre> 88 * The character offset 2 can be mapped either to offset 2 or 3, but neither is meaningful. For 89 * convenience, it MUST map to the next offset (offset 3 in this case), or the 90 * transformedText.length() if there is no valid character to map. 91 * This is mandatory when the map strategy is {@link #MAP_STRATEGY_CHARACTER}, but doesn't 92 * apply for other map strategies. 93 * 94 * @param offset the offset at the original text. It's normally equal to or less than the 95 * originalText.length(). When {@link #MAP_STRATEGY_CHARACTER} is passed, it must 96 * be less than originalText.length(). For convenience, it's also allowed to be 97 * negative, which represents an invalid offset. When the given offset is 98 * negative, this method should return it as it is. 99 * @param strategy the mapping strategy. Depending on its value, the same offset can be mapped 100 * differently. 101 * @return the mapped offset at the transformed text, must be equal to or less than the 102 * transformedText.length(). 103 * 104 * @see #transformedToOriginal(int, int) 105 */ originalToTransformed(int offset, @MapStrategy int strategy)106 int originalToTransformed(int offset, @MapStrategy int strategy); 107 108 /** 109 * Map an offset at transformed text to the offset at original text. This is the reverse method 110 * of {@link #originalToTransformed(int, int)}. <br/> 111 * This function must be a monotonically non-decreasing function. In other words, if the offset 112 * advances at the original text, the offset at the transformed text must advance or stay there. 113 * <br/> 114 * Similar to the {@link #originalToTransformed(int, int)} if a character offset doesn't have a 115 * corresponding offset at the transformed text, it MUST return the value as the previous 116 * offset. This is mandatory when the map strategy is {@link #MAP_STRATEGY_CHARACTER}, 117 * but doesn't apply for other map strategies. 118 * 119 * @param offset the offset at the transformed text. It's normally equal to or less than the 120 * transformedText.length(). When {@link #MAP_STRATEGY_CHARACTER} is passed, it 121 * must be less than transformedText.length(). For convenience, it's also allowed 122 * to be negative, which represents an invalid offset. When the given offset is 123 * negative, this method should return it as it is. 124 * @param strategy the mapping strategy. Depending on its value, the same offset can be mapped 125 * differently. 126 * @return the mapped offset at the original text, must be equal to or less than the 127 * original.length(). 128 * 129 * @see #originalToTransformed(int, int) 130 */ transformedToOriginal(int offset, @MapStrategy int strategy)131 int transformedToOriginal(int offset, @MapStrategy int strategy); 132 133 /** 134 * Map a text update in the original text to an update the transformed text. 135 * This method used to determine how the transformed text is updated in response to an 136 * update in the original text. It is always called before the original text being changed. 137 * 138 * The main usage of this method is to update text layout incrementally. So it should report 139 * the range where text needs to be laid out again. 140 * 141 * @param textUpdate the {@link TextUpdate} object containing the text update information on 142 * the original text. The transformed text update information will also be 143 * stored at this object. 144 */ originalToTransformed(TextUpdate textUpdate)145 void originalToTransformed(TextUpdate textUpdate); 146 147 /** 148 * The class that stores the text update information that from index <code>where</code>, 149 * <code>after</code> characters will replace the old text that has length <code>before</code>. 150 */ 151 class TextUpdate { 152 /** The start index of the text update range, inclusive */ 153 public int where; 154 /** The length of the replaced old text. */ 155 public int before; 156 /** The length of the new text that replaces the old text. */ 157 public int after; 158 159 /** 160 * Creates a {@link TextUpdate} object. 161 * @param where the start index of the text update range. 162 * @param before the length of the replaced old text. 163 * @param after the length of the new text that replaces the old text. 164 */ TextUpdate(int where, int before, int after)165 public TextUpdate(int where, int before, int after) { 166 this.where = where; 167 this.before = before; 168 this.after = after; 169 } 170 } 171 } 172