1 /* 2 * Copyright (C) 2014 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; 18 19 import android.annotation.NonNull; 20 import android.text.Primitive.PrimitiveType; 21 import android.text.StaticLayout.LineBreaks; 22 23 import java.util.ArrayList; 24 import java.util.List; 25 26 import static android.text.Primitive.PrimitiveType.PENALTY_INFINITY; 27 28 // Based on the native implementation of GreedyLineBreaker in 29 // frameworks/base/core/jni/android_text_StaticLayout.cpp revision b808260 30 public class GreedyLineBreaker extends LineBreaker { 31 32 public GreedyLineBreaker(@NonNull List<Primitive> primitives, @NonNull LineWidth lineWidth, 33 @NonNull TabStops tabStops) { 34 super(primitives, lineWidth, tabStops); 35 } 36 37 @Override 38 public void computeBreaks(@NonNull LineBreaks lineBreaks) { 39 BreakInfo breakInfo = new BreakInfo(); 40 int lineNum = 0; 41 float width = 0, printedWidth = 0; 42 boolean breakFound = false, goodBreakFound = false; 43 int breakIndex = 0, goodBreakIndex = 0; 44 float breakWidth = 0, goodBreakWidth = 0; 45 int firstTabIndex = Integer.MAX_VALUE; 46 47 float maxWidth = mLineWidth.getLineWidth(lineNum); 48 49 int numPrimitives = mPrimitives.size(); 50 // greedily fit as many characters as possible on each line 51 // loop over all primitives, and choose the best break point 52 // (if possible, a break point without splitting a word) 53 // after going over the maximum length 54 for (int i = 0; i < numPrimitives; i++) { 55 Primitive p = mPrimitives.get(i); 56 57 // update the current line width 58 if (p.type == PrimitiveType.BOX || p.type == PrimitiveType.GLUE) { 59 width += p.width; 60 if (p.type == PrimitiveType.BOX) { 61 printedWidth = width; 62 } 63 } else if (p.type == PrimitiveType.VARIABLE) { 64 width = mTabStops.width(width); 65 // keep track of first tab character in the region we are examining 66 // so we can determine whether or not a line contains a tab 67 firstTabIndex = Math.min(firstTabIndex, i); 68 } 69 70 // find the best break point for the characters examined so far 71 if (printedWidth > maxWidth) { 72 //noinspection StatementWithEmptyBody 73 if (breakFound || goodBreakFound) { 74 if (goodBreakFound) { 75 // a true line break opportunity existed in the characters examined so far, 76 // so there is no need to split a word 77 i = goodBreakIndex; // no +1 because of i++ 78 lineNum++; 79 maxWidth = mLineWidth.getLineWidth(lineNum); 80 breakInfo.mBreaksList.add(mPrimitives.get(goodBreakIndex).location); 81 breakInfo.mWidthsList.add(goodBreakWidth); 82 breakInfo.mFlagsList.add(firstTabIndex < goodBreakIndex); 83 firstTabIndex = Integer.MAX_VALUE; 84 } else { 85 // must split a word because there is no other option 86 i = breakIndex; // no +1 because of i++ 87 lineNum++; 88 maxWidth = mLineWidth.getLineWidth(lineNum); 89 breakInfo.mBreaksList.add(mPrimitives.get(breakIndex).location); 90 breakInfo.mWidthsList.add(breakWidth); 91 breakInfo.mFlagsList.add(firstTabIndex < breakIndex); 92 firstTabIndex = Integer.MAX_VALUE; 93 } 94 printedWidth = width = 0; 95 goodBreakFound = breakFound = false; 96 goodBreakWidth = breakWidth = 0; 97 continue; 98 } else { 99 // no choice, keep going... must make progress by putting at least one 100 // character on a line, even if part of that character is cut off -- 101 // there is no other option 102 } 103 } 104 105 // update possible break points 106 if (p.type == PrimitiveType.PENALTY && 107 p.penalty < PENALTY_INFINITY) { 108 // this does not handle penalties with width 109 110 // handle forced line break 111 if (p.penalty == -PENALTY_INFINITY) { 112 lineNum++; 113 maxWidth = mLineWidth.getLineWidth(lineNum); 114 breakInfo.mBreaksList.add(p.location); 115 breakInfo.mWidthsList.add(printedWidth); 116 breakInfo.mFlagsList.add(firstTabIndex < i); 117 firstTabIndex = Integer.MAX_VALUE; 118 printedWidth = width = 0; 119 goodBreakFound = breakFound = false; 120 goodBreakWidth = breakWidth = 0; 121 continue; 122 } 123 if (i > breakIndex && (printedWidth <= maxWidth || !breakFound)) { 124 breakFound = true; 125 breakIndex = i; 126 breakWidth = printedWidth; 127 } 128 if (i > goodBreakIndex && printedWidth <= maxWidth) { 129 goodBreakFound = true; 130 goodBreakIndex = i; 131 goodBreakWidth = printedWidth; 132 } 133 } else if (p.type == PrimitiveType.WORD_BREAK) { 134 // only do this if necessary -- we don't want to break words 135 // when possible, but sometimes it is unavoidable 136 if (i > breakIndex && (printedWidth <= maxWidth || !breakFound)) { 137 breakFound = true; 138 breakIndex = i; 139 breakWidth = printedWidth; 140 } 141 } 142 } 143 144 if (breakFound || goodBreakFound) { 145 // output last break if there are more characters to output 146 if (goodBreakFound) { 147 breakInfo.mBreaksList.add(mPrimitives.get(goodBreakIndex).location); 148 breakInfo.mWidthsList.add(goodBreakWidth); 149 breakInfo.mFlagsList.add(firstTabIndex < goodBreakIndex); 150 } else { 151 breakInfo.mBreaksList.add(mPrimitives.get(breakIndex).location); 152 breakInfo.mWidthsList.add(breakWidth); 153 breakInfo.mFlagsList.add(firstTabIndex < breakIndex); 154 } 155 } 156 breakInfo.copyTo(lineBreaks); 157 } 158 159 private static class BreakInfo { 160 List<Integer> mBreaksList = new ArrayList<Integer>(); 161 List<Float> mWidthsList = new ArrayList<Float>(); 162 List<Boolean> mFlagsList = new ArrayList<Boolean>(); 163 164 public void copyTo(LineBreaks lineBreaks) { 165 if (lineBreaks.breaks.length != mBreaksList.size()) { 166 lineBreaks.breaks = new int[mBreaksList.size()]; 167 lineBreaks.widths = new float[mWidthsList.size()]; 168 lineBreaks.flags = new int[mFlagsList.size()]; 169 } 170 171 int i = 0; 172 for (int b : mBreaksList) { 173 lineBreaks.breaks[i] = b; 174 i++; 175 } 176 i = 0; 177 for (float b : mWidthsList) { 178 lineBreaks.widths[i] = b; 179 i++; 180 } 181 i = 0; 182 for (boolean b : mFlagsList) { 183 lineBreaks.flags[i] = b ? TAB_MASK : 0; 184 i++; 185 } 186 187 mBreaksList = null; 188 mWidthsList = null; 189 mFlagsList = null; 190 } 191 } 192 } 193
