/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id$ */
package org.apache.fop.text.linebreak;
/**
* This class is meant for supporting the Unicode line breaking algorithm.
* See: <a href="http://unicode.org/reports/tr14/">UTR 14</a>
*
*/
public class LineBreakStatus {
/** Constant indicating a Direct Break */
public static final byte DIRECT_BREAK = LineBreakUtils.DIRECT_BREAK;
/** Constant indicating an Indirect Break */
public static final byte INDIRECT_BREAK = LineBreakUtils.INDIRECT_BREAK;
/** Constant indicating a Combining Indirect Break */
public static final byte COMBINING_INDIRECT_BREAK = LineBreakUtils.COMBINING_INDIRECT_BREAK;
/** Constant indicating a Combining Prohibited Break */
public static final byte COMBINING_PROHIBITED_BREAK = LineBreakUtils.COMBINING_PROHIBITED_BREAK;
/** Constant indicating a Prohibited Break */
public static final byte PROHIBITED_BREAK = LineBreakUtils.PROHIBITED_BREAK;
/** Constant indicating a Explicit Break */
public static final byte EXPLICIT_BREAK = LineBreakUtils.EXPLICIT_BREAK;
private byte leftClass;
private boolean hadSpace;
/**
* Resets the class to the same state as if new LineBreakStatus() had just been called.
*/
public LineBreakStatus() {
reset();
}
/**
* Reset the status.
* This method will reset the status to the initial state. It is meant
* for recycling objects.
*/
public void reset() {
leftClass = -1;
hadSpace = false;
}
/**
* Check whether a line break may happen according to the rules described in
* the <a href="http://unicode.org/reports/tr14/#Algorithm">Unicode Line Breaking
* Algorithm</a>. The function returns the line breaking status of the point
* <em>before</em> the given character.
* The algorithm is the table-driven algorithm, as described in
* <a href="http://unicode.org/reports/tr14/#PairBasedImplementation">
* Unicode Technical Report #14</a>.
* The pair table is taken from {@link LineBreakUtils}.
*
* TODO: Better handling for AI, SA, SG and XX line break classes.
*
* @param c the character to check
* @return the break action to be taken
* one of: {@link #DIRECT_BREAK},
* {@link #INDIRECT_BREAK},
* {@link #COMBINING_INDIRECT_BREAK},
* {@link #COMBINING_PROHIBITED_BREAK},
* {@link #PROHIBITED_BREAK},
* {@link #EXPLICIT_BREAK}
*/
public byte nextChar(char c) {
byte currentClass = LineBreakUtils.getLineBreakProperty(c);
/* Initial conversions */
switch (currentClass) {
case 0: // Unassigned codepoint: same treatment as AI
case LineBreakUtils.LINE_BREAK_PROPERTY_AI:
case LineBreakUtils.LINE_BREAK_PROPERTY_SG:
case LineBreakUtils.LINE_BREAK_PROPERTY_XX:
// LB 1: Resolve AI, ... SG and XX into other line breaking classes
// depending on criteria outside the scope of this algorithm.
// In the absence of such criteria, it is recommended that
// classes AI, ... SG and XX be resolved to AL
currentClass = LineBreakUtils.LINE_BREAK_PROPERTY_AL;
break;
case LineBreakUtils.LINE_BREAK_PROPERTY_SA:
// LB 1: Resolve ... SA ... into other line breaking classes
// depending on criteria outside the scope of this algorithm.
// In the absence of such criteria, it is recommended that
// ... SA be resolved to AL, except that characters of
// class SA that have General_Category Mn or Mc be resolved to CM
switch (Character.getType(c)) {
case Character.COMBINING_SPACING_MARK: //General_Category "Mc"
case Character.NON_SPACING_MARK: //General_Category "Mn"
currentClass = LineBreakUtils.LINE_BREAK_PROPERTY_CM;
break;
default:
currentClass = LineBreakUtils.LINE_BREAK_PROPERTY_AL;
}
default:
//nop
}
/* Check 1: First character or initial character after a reset/mandatory break? */
switch (leftClass) {
case -1:
//first character or initial character after a reset()
leftClass = currentClass;
if (leftClass == LineBreakUtils.LINE_BREAK_PROPERTY_CM) {
// LB 10: Treat any remaining combining marks as AL
leftClass = LineBreakUtils.LINE_BREAK_PROPERTY_AL;
}
// LB 2: Never break at the start of text
return PROHIBITED_BREAK;
case LineBreakUtils.LINE_BREAK_PROPERTY_BK:
case LineBreakUtils.LINE_BREAK_PROPERTY_LF:
case LineBreakUtils.LINE_BREAK_PROPERTY_NL:
//first character after mandatory break
// LB 4: Always break after hard line breaks
// LB 5: Treat ... LF and NL has hard line breaks
reset();
leftClass = currentClass;
return EXPLICIT_BREAK;
case LineBreakUtils.LINE_BREAK_PROPERTY_CR:
//first character after a carriage return:
// LB 5: Treat CR followed by LF, as well as CR ... as hard line breaks
// If current is LF, then fall through to Check 2 (see below),
// and the hard break will be signaled for the character after LF (see above)
if (currentClass != LineBreakUtils.LINE_BREAK_PROPERTY_LF) {
reset();
leftClass = currentClass;
return EXPLICIT_BREAK;
}
default:
//nop
}
/* Check 2: current is a mandatory break or space? */
switch (currentClass) {
case LineBreakUtils.LINE_BREAK_PROPERTY_BK:
case LineBreakUtils.LINE_BREAK_PROPERTY_LF:
case LineBreakUtils.LINE_BREAK_PROPERTY_NL:
case LineBreakUtils.LINE_BREAK_PROPERTY_CR:
// LB 6: Do not break before a hard break
leftClass = currentClass;
return PROHIBITED_BREAK;
case LineBreakUtils.LINE_BREAK_PROPERTY_SP:
// LB 7: Do not break before spaces ...
// Zero-width spaces are in the pair-table (see below)
hadSpace = true;
return PROHIBITED_BREAK;
default:
//nop
}
/* Normal treatment, if the first two checks did not return */
boolean savedHadSpace = hadSpace;
hadSpace = false;
byte breakAction = LineBreakUtils.getLineBreakPairProperty(leftClass, currentClass);
switch (breakAction) {
case PROHIBITED_BREAK:
case DIRECT_BREAK:
leftClass = currentClass;
return breakAction;
case INDIRECT_BREAK:
leftClass = currentClass;
if (savedHadSpace) {
return INDIRECT_BREAK;
} else {
return PROHIBITED_BREAK;
}
case COMBINING_INDIRECT_BREAK:
if (savedHadSpace) {
leftClass = currentClass;
return COMBINING_INDIRECT_BREAK;
} else {
return PROHIBITED_BREAK;
}
case COMBINING_PROHIBITED_BREAK:
if (savedHadSpace) {
leftClass = currentClass;
}
return COMBINING_PROHIBITED_BREAK;
default:
assert false;
return breakAction;
}
}
/**
* for debugging only
*/
/*
public static void main(String args[]) {
LineBreakStatus lbs = new LineBreakStatus();
lbs.nextChar('\n');
lbs.nextChar('\n');
lbs.nextChar('x');
}
*/
}