src/com/googlecode/lanterna/screen/TabBehaviour.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.screen;
  20
  21 /**
  22  * What to do about the tab character when putting on a {@code Screen}. Since tabs are a bit special, their meaning
  23  * depends on which column the cursor is in when it's printed, we'll need to have some way to tell the Screen what to
  24  * do when encountering a tab character.
  25  *
  26  * @author martin
  27  */
  28 public enum TabBehaviour {
  29     /**
  30      * Tab characters are not replaced, this will probably have undefined and weird behaviour!
  31      */
  32     IGNORE(null, null),
  33     /**
  34      * Tab characters are replaced with a single blank space, no matter where the tab was placed.
  35      */
  36     CONVERT_TO_ONE_SPACE(1, null),
  37     /**
  38      * Tab characters are replaced with two blank spaces, no matter where the tab was placed.
  39      */
  40     CONVERT_TO_TWO_SPACES(2, null),
  41     /**
  42      * Tab characters are replaced with three blank spaces, no matter where the tab was placed.
  43      */
  44     CONVERT_TO_THREE_SPACES(3, null),
  45     /**
  46      * Tab characters are replaced with four blank spaces, no matter where the tab was placed.
  47      */
  48     CONVERT_TO_FOUR_SPACES(4, null),
  49     /**
  50      * Tab characters are replaced with eight blank spaces, no matter where the tab was placed.
  51      */
  52     CONVERT_TO_EIGHT_SPACES(8, null),
  53     /**
  54      * Tab characters are replaced with enough space characters to reach the next column index that is evenly divisible
  55      * by 4, simulating a normal tab character when placed inside a text document.
  56      */
  57     ALIGN_TO_COLUMN_4(null, 4),
  58     /**
  59      * Tab characters are replaced with enough space characters to reach the next column index that is evenly divisible
  60      * by 8, simulating a normal tab character when placed inside a text document.
  61      */
  62     ALIGN_TO_COLUMN_8(null, 8),
  63     ;
  64
  65     private final Integer replaceFactor;
  66     private final Integer alignFactor;
  67
  68     TabBehaviour(Integer replaceFactor, Integer alignFactor) {
  69         this.replaceFactor = replaceFactor;
  70         this.alignFactor = alignFactor;
  71     }
  72
  73     /**
  74      * Given a string, being placed on the screen at column X, returns the same string with all tab characters (\t)
  75      * replaced according to this TabBehaviour.
  76      * @param string String that is going to be put to the screen, potentially containing tab characters
  77      * @param columnIndex Column on the screen where the first character of the string is going to end up
  78      * @return The input string with all tab characters replaced with spaces, according to this TabBehaviour
  79      */
  80     public String replaceTabs(String string, int columnIndex) {
  81         int tabPosition = string.indexOf('\t');
  82         while(tabPosition != -1) {
  83             String tabReplacementHere = getTabReplacement(columnIndex + tabPosition);
  84             string = string.substring(0, tabPosition) + tabReplacementHere + string.substring(tabPosition + 1);
  85             tabPosition += tabReplacementHere.length();
  86             tabPosition = string.indexOf('\t', tabPosition);
  87         }
  88         return string;
  89     }
  90
  91     /**
  92      * Returns the String that can replace a tab at the specified position, according to this TabBehaviour.
  93      * @param columnIndex Column index of where the tab character is placed
  94      * @return String consisting of 1 or more space character
  95      */
  96     public String getTabReplacement(int columnIndex) {
  97         int replaceCount;
  98         StringBuilder replace = new StringBuilder();
  99         if(replaceFactor != null) {
 100             replaceCount = replaceFactor;
 101         }
 102         else if (alignFactor != null) {
 103             replaceCount = alignFactor - (columnIndex % alignFactor);
 104         }
 105         else {
 106             return "\t";
 107         }
 108         for(int i = 0; i < replaceCount; i++) {
 109             replace.append(" ");
 110         }
 111         return replace.toString();
 112     }
 113 }