src/com/googlecode/lanterna/TerminalTextUtils.java

   1 /*
   2  * This file is part of lanterna (http://code.google.com/p/lanterna/).
   3  *
   4  * lanterna is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  *
  17  * Copyright (C) 2010-2015 Martin
  18  */
  19 package com.googlecode.lanterna;
  20
  21 import java.util.ArrayList;
  22 import java.util.Arrays;
  23 import java.util.LinkedList;
  24 import java.util.List;
  25
  26 /**
  27  * This class contains a number of utility methods for analyzing characters and strings in a terminal context. The main
  28  * purpose is to make it easier to work with text that may or may not contain double-width text characters, such as CJK
  29  * (Chinese, Japanese, Korean) and other special symbols. This class assumes those are all double-width and in case the
  30  * terminal (-emulator) chooses to draw them (somehow) as single-column then all the calculations in this class will be
  31  * wrong. It seems safe to assume what this class considers double-width really is taking up two columns though.
  32  *
  33  * @author Martin
  34  */
  35 public class TerminalTextUtils {
  36     private TerminalTextUtils() {
  37     }
  38
  39     /**
  40      * Given a character, is this character considered to be a CJK character?
  41      * Shamelessly stolen from
  42      * <a href="http://stackoverflow.com/questions/1499804/how-can-i-detect-japanese-text-in-a-java-string">StackOverflow</a>
  43      * where it was contributed by user Rakesh N
  44      * @param c Character to test
  45      * @return {@code true} if the character is a CJK character
  46      *
  47      */
  48     public static boolean isCharCJK(final char c) {
  49         Character.UnicodeBlock unicodeBlock = Character.UnicodeBlock.of(c);
  50         return (unicodeBlock == Character.UnicodeBlock.HIRAGANA)
  51                 || (unicodeBlock == Character.UnicodeBlock.KATAKANA)
  52                 || (unicodeBlock == Character.UnicodeBlock.KATAKANA_PHONETIC_EXTENSIONS)
  53                 || (unicodeBlock == Character.UnicodeBlock.HANGUL_COMPATIBILITY_JAMO)
  54                 || (unicodeBlock == Character.UnicodeBlock.HANGUL_JAMO)
  55                 || (unicodeBlock == Character.UnicodeBlock.HANGUL_SYLLABLES)
  56                 || (unicodeBlock == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS)
  57                 || (unicodeBlock == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A)
  58                 || (unicodeBlock == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_B)
  59                 || (unicodeBlock == Character.UnicodeBlock.CJK_COMPATIBILITY_FORMS)
  60                 || (unicodeBlock == Character.UnicodeBlock.CJK_COMPATIBILITY_IDEOGRAPHS)
  61                 || (unicodeBlock == Character.UnicodeBlock.CJK_RADICALS_SUPPLEMENT)
  62                 || (unicodeBlock == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION)
  63                 || (unicodeBlock == Character.UnicodeBlock.ENCLOSED_CJK_LETTERS_AND_MONTHS)
  64                 || (unicodeBlock == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS && c < 0xFF61);    //The magic number here is the separating index between full-width and half-width
  65     }
  66
  67     /**
  68      * Checks if a character is expected to be taking up two columns if printed to a terminal. This will generally be
  69      * {@code true} for CJK (Chinese, Japanese and Korean) characters.
  70      * @param c Character to test if it's double-width when printed to a terminal
  71      * @return {@code true} if this character is expected to be taking up two columns when printed to the terminal,
  72      * otherwise {@code false}
  73      */
  74     public static boolean isCharDoubleWidth(final char c) {
  75         return isCharCJK(c);
  76     }
  77
  78     /**
  79      * @deprecated Call {@code getColumnWidth(s)} instead
  80      */
  81     @Deprecated
  82     public static int getTrueWidth(String s) {
  83         return getColumnWidth(s);
  84     }
  85
  86     /**
  87      * Given a string, returns how many columns this string would need to occupy in a terminal, taking into account that
  88      * CJK characters takes up two columns.
  89      * @param s String to check length
  90      * @return Number of actual terminal columns the string would occupy
  91      */
  92     public static int getColumnWidth(String s) {
  93         return getColumnIndex(s, s.length());
  94     }
  95
  96     /**
  97      * Given a string and a character index inside that string, find out what the column index of that character would
  98      * be if printed in a terminal. If the string only contains non-CJK characters then the returned value will be same
  99      * as {@code stringCharacterIndex}, but if there are CJK characters the value will be different due to CJK
 100      * characters taking up two columns in width. If the character at the index in the string is a CJK character itself,
 101      * the returned value will be the index of the left-side of character.
 102      * @param s String to translate the index from
 103      * @param stringCharacterIndex Index within the string to get the terminal column index of
 104      * @return Index of the character inside the String at {@code stringCharacterIndex} when it has been writted to a
 105      * terminal
 106      * @throws StringIndexOutOfBoundsException if the index given is outside the String length or negative
 107      */
 108     public static int getColumnIndex(String s, int stringCharacterIndex) throws StringIndexOutOfBoundsException {
 109         int index = 0;
 110         for(int i = 0; i < stringCharacterIndex; i++) {
 111             if(isCharCJK(s.charAt(i))) {
 112                 index++;
 113             }
 114             index++;
 115         }
 116         return index;
 117     }
 118
 119     /**
 120      * This method does the reverse of getColumnIndex, given a String and imagining it has been printed out to the
 121      * top-left corner of a terminal, in the column specified by {@code columnIndex}, what is the index of that
 122      * character in the string. If the string contains no CJK characters, this will always be the same as
 123      * {@code columnIndex}. If the index specified is the right column of a CJK character, the index is the same as if
 124      * the column was the left column. So calling {@code getStringCharacterIndex("英", 0)} and
 125      * {@code getStringCharacterIndex("英", 1)} will both return 0.
 126      * @param s String to translate the index to
 127      * @param columnIndex Column index of the string written to a terminal
 128      * @return The index in the string of the character in terminal column {@code columnIndex}
 129      */
 130     public static int getStringCharacterIndex(String s, int columnIndex) {
 131         int index = 0;
 132         int counter = 0;
 133         while(counter < columnIndex) {
 134             if(isCharCJK(s.charAt(index++))) {
 135                 counter++;
 136                 if(counter == columnIndex) {
 137                     return index - 1;
 138                 }
 139             }
 140             counter++;
 141         }
 142         return index;
 143     }
 144
 145     /**
 146      * Given a string that may or may not contain CJK characters, returns the substring which will fit inside
 147      * <code>availableColumnSpace</code> columns. This method does not handle special cases like tab or new-line.
 148      * <p>
 149      * Calling this method is the same as calling {@code fitString(string, 0, availableColumnSpace)}.
 150      * @param string The string to fit inside the availableColumnSpace
 151      * @param availableColumnSpace Number of columns to fit the string inside
 152      * @return The whole or part of the input string which will fit inside the supplied availableColumnSpace
 153      */
 154     public static String fitString(String string, int availableColumnSpace) {
 155         return fitString(string, 0, availableColumnSpace);
 156     }
 157
 158     /**
 159      * Given a string that may or may not contain CJK characters, returns the substring which will fit inside
 160      * <code>availableColumnSpace</code> columns. This method does not handle special cases like tab or new-line.
 161      * <p>
 162      * This overload has a {@code fromColumn} parameter that specified where inside the string to start fitting. Please
 163      * notice that {@code fromColumn} is not a character index inside the string, but a column index as if the string
 164      * has been printed from the left-most side of the terminal. So if the string is "日本語", fromColumn set to 1 will
 165      * not starting counting from the second character ("本") in the string but from the CJK filler character belonging
 166      * to "日". If you want to count from a particular character index inside the string, please pass in a substring
 167      * and use fromColumn set to 0.
 168      * @param string The string to fit inside the availableColumnSpace
 169      * @param fromColumn From what column of the input string to start fitting (see description above!)
 170      * @param availableColumnSpace Number of columns to fit the string inside
 171      * @return The whole or part of the input string which will fit inside the supplied availableColumnSpace
 172      */
 173     public static String fitString(String string, int fromColumn, int availableColumnSpace) {
 174         if(availableColumnSpace <= 0) {
 175             return "";
 176         }
 177
 178         StringBuilder bob = new StringBuilder();
 179         int column = 0;
 180         int index = 0;
 181         while(index < string.length() && column < fromColumn) {
 182             char c = string.charAt(index++);
 183             column += TerminalTextUtils.isCharCJK(c) ? 2 : 1;
 184         }
 185         if(column > fromColumn) {
 186             bob.append(" ");
 187             availableColumnSpace--;
 188         }
 189
 190         while(availableColumnSpace > 0 && index < string.length()) {
 191             char c = string.charAt(index++);
 192             availableColumnSpace -= TerminalTextUtils.isCharCJK(c) ? 2 : 1;
 193             if(availableColumnSpace < 0) {
 194                 bob.append(' ');
 195             }
 196             else {
 197                 bob.append(c);
 198             }
 199         }
 200         return bob.toString();
 201     }
 202
 203     /**
 204      * This method will calculate word wrappings given a number of lines of text and how wide the text can be printed.
 205      * The result is a list of new rows where word-wrapping was applied.
 206      * @param maxWidth Maximum number of columns that can be used before word-wrapping is applied, if <= 0 then the
 207      *                 lines will be returned unchanged
 208      * @param lines Input text
 209      * @return The input text word-wrapped at {@code maxWidth}; this may contain more rows than the input text
 210      */
 211     public static List<String> getWordWrappedText(int maxWidth, String... lines) {
 212         //Bounds checking
 213         if(maxWidth <= 0) {
 214             return Arrays.asList(lines);
 215         }
 216
 217         List<String> result = new ArrayList<String>();
 218         LinkedList<String> linesToBeWrapped = new LinkedList<String>(Arrays.asList(lines));
 219         while(!linesToBeWrapped.isEmpty()) {
 220             String row = linesToBeWrapped.removeFirst();
 221             int rowWidth = getColumnWidth(row);
 222             if(rowWidth <= maxWidth) {
 223                 result.add(row);
 224             }
 225             else {
 226                 //Now search in reverse and find the first possible line-break
 227                 final int characterIndexMax = getStringCharacterIndex(row, maxWidth);
 228                 int characterIndex = characterIndexMax;
 229                 while(characterIndex >= 0 &&
 230                         !Character.isSpaceChar(row.charAt(characterIndex)) &&
 231                         !isCharCJK(row.charAt(characterIndex))) {
 232                     characterIndex--;
 233                 }
 234                 // right *after* a CJK is also a "nice" spot to break the line!
 235                 if (characterIndex >= 0 && characterIndex < characterIndexMax &&
 236                       isCharCJK(row.charAt(characterIndex))) {
 237                     characterIndex++; // with these conditions it fits!
 238                 }
 239
 240                 if(characterIndex < 0) {
 241                     //Failed! There was no 'nice' place to cut so just cut it at maxWidth
 242                     characterIndex = Math.max(characterIndexMax, 1); // at least 1 char
 243                     result.add(row.substring(0, characterIndex));
 244                     linesToBeWrapped.addFirst(row.substring(characterIndex));
 245                 }
 246                 else {
 247                     // characterIndex == 0 only happens, if either
 248                     //   - first char is CJK and maxWidth==1   or
 249                     //   - first char is whitespace
 250                     // either way: put it in row before break to prevent infinite loop.
 251                     characterIndex = Math.max( characterIndex, 1); // at least 1 char
 252
 253                     //Ok, split the row, add it to the result and continue processing the second half on a new line
 254                     result.add(row.substring(0, characterIndex));
 255                     while(characterIndex < row.length() &&
 256                           Character.isSpaceChar(row.charAt(characterIndex))) {
 257                         characterIndex++;
 258                     };
 259                     if (characterIndex < row.length()) { // only if rest contains non-whitespace
 260                         linesToBeWrapped.addFirst(row.substring(characterIndex));
 261                     }
 262                 }
 263             }
 264         }
 265         return result;
 266     }
 267 }