root/Source/core/rendering/break_lines.cpp

DEFINITIONS

1. isBreakableSpace
2. shouldBreakAfter
3. needsLineBreakIterator
4. nextBreakablePosition
5. nextBreakablePositionIgnoringNBSP

/*
 * Copyright (C) 2005, 2007, 2010 Apple Inc. All rights reserved.
 * Copyright (C) 2011 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "core/rendering/break_lines.h"

#include "platform/text/TextBreakIterator.h"
#include "wtf/ASCIICType.h"
#include "wtf/StdLibExtras.h"
#include "wtf/unicode/CharacterNames.h"

namespace WebCore {

template<bool treatNoBreakSpaceAsBreak>
static inline bool isBreakableSpace(UChar ch)
{
    switch (ch) {
    case ' ':
    case '\n':
    case '\t':
        return true;
    case noBreakSpace:
        return treatNoBreakSpaceAsBreak;
    default:
        return false;
    }
}

static const UChar asciiLineBreakTableFirstChar = '!';
static const UChar asciiLineBreakTableLastChar = 127;

// Pack 8 bits into one byte
#define B(a, b, c, d, e, f, g, h) \
    ((a) | ((b) << 1) | ((c) << 2) | ((d) << 3) | ((e) << 4) | ((f) << 5) | ((g) << 6) | ((h) << 7))

// Line breaking table row for each digit (0-9)
#define DI { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }

// Line breaking table row for ascii letters (a-z A-Z)
#define AL { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }

#define F 0xFF

// Line breaking table for printable ASCII characters. Line breaking opportunities in this table are as below:
// - before opening punctuations such as '(', '<', '[', '{' after certain characters (compatible with Firefox 3.6);
// - after '-' and '?' (backward-compatible, and compatible with Internet Explorer).
// Please refer to <https://bugs.webkit.org/show_bug.cgi?id=37698> for line breaking matrixes of different browsers
// and the ICU standard.
static const unsigned char asciiLineBreakTable[][(asciiLineBreakTableLastChar - asciiLineBreakTableFirstChar) / 8 + 1] = {
    //  !  "  #  $  %  &  '  (     )  *  +  ,  -  .  /  0  1-8   9  :  ;  <  =  >  ?  @     A-X      Y  Z  [  \  ]  ^  _  `     a-x      y  z  {  |  }  ~  DEL
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // !
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // "
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // #
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // $
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // %
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // &
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // '
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // (
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // )
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // *
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // +
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // ,
    { B(1, 1, 1, 1, 1, 1, 1, 1), B(1, 1, 1, 1, 1, 0, 1, 0), 0, B(0, 1, 1, 1, 1, 1, 1, 1), F, F, F, B(1, 1, 1, 1, 1, 1, 1, 1), F, F, F, B(1, 1, 1, 1, 1, 1, 1, 1) }, // - Note: breaking before '0'-'9' is handled hard-coded in shouldBreakAfter().
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // .
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // /
    DI,  DI,  DI,  DI,  DI,  DI,  DI,  DI,  DI,  DI, // 0-9
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // :
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // ;
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // <
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // =
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // >
    { B(0, 0, 1, 1, 1, 1, 0, 1), B(0, 1, 1, 0, 1, 0, 0, 1), F, B(1, 0, 0, 1, 1, 1, 0, 1), F, F, F, B(1, 1, 1, 1, 0, 1, 1, 1), F, F, F, B(1, 1, 1, 1, 0, 1, 1, 0) }, // ?
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // @
    AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL, // A-Z
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // [
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // '\'
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // ]
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // ^
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // _
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // `
    AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL,  AL, // a-z
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // {
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // |
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // }
    { B(0, 0, 0, 0, 0, 0, 0, 1), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 1, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 1, 0, 0, 0, 0, 0) }, // ~
    { B(0, 0, 0, 0, 0, 0, 0, 0), B(0, 0, 0, 0, 0, 0, 0, 0), 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0), 0, 0, 0, B(0, 0, 0, 0, 0, 0, 0, 0) }, // DEL
};

#undef B
#undef F
#undef DI
#undef AL

COMPILE_ASSERT(WTF_ARRAY_LENGTH(asciiLineBreakTable) == asciiLineBreakTableLastChar - asciiLineBreakTableFirstChar + 1, TestLineBreakTableConsistency);

static inline bool shouldBreakAfter(UChar lastCh, UChar ch, UChar nextCh)
{
    // Don't allow line breaking between '-' and a digit if the '-' may mean a minus sign in the context,
    // while allow breaking in 'ABCD-1234' and '1234-5678' which may be in long URLs.
    if (ch == '-' && isASCIIDigit(nextCh))
        return isASCIIAlphanumeric(lastCh);

    // If both ch and nextCh are ASCII characters, use a lookup table for enhanced speed and for compatibility
    // with other browsers (see comments for asciiLineBreakTable for details).
    if (ch >= asciiLineBreakTableFirstChar && ch <= asciiLineBreakTableLastChar
            && nextCh >= asciiLineBreakTableFirstChar && nextCh <= asciiLineBreakTableLastChar) {
        const unsigned char* tableRow = asciiLineBreakTable[ch - asciiLineBreakTableFirstChar];
        int nextChIndex = nextCh - asciiLineBreakTableFirstChar;
        return tableRow[nextChIndex / 8] & (1 << (nextChIndex % 8));
    }
    // Otherwise defer to the Unicode algorithm by returning false.
    return false;
}

template<bool treatNoBreakSpaceAsBreak>
inline bool needsLineBreakIterator(UChar ch)
{
    if (treatNoBreakSpaceAsBreak)
        return ch > asciiLineBreakTableLastChar;
    return ch > asciiLineBreakTableLastChar && ch != noBreakSpace;
}

template<typename CharacterType, bool treatNoBreakSpaceAsBreak>
static inline int nextBreakablePosition(LazyLineBreakIterator& lazyBreakIterator, const CharacterType* str, unsigned length, int pos)
{
    int len = static_cast<int>(length);
    int nextBreak = -1;

    CharacterType lastLastCh = pos > 1 ? str[pos - 2] : static_cast<CharacterType>(lazyBreakIterator.secondToLastCharacter());
    CharacterType lastCh = pos > 0 ? str[pos - 1] : static_cast<CharacterType>(lazyBreakIterator.lastCharacter());
    unsigned priorContextLength = lazyBreakIterator.priorContextLength();
    for (int i = pos; i < len; i++) {
        CharacterType ch = str[i];

        if (isBreakableSpace<treatNoBreakSpaceAsBreak>(ch) || shouldBreakAfter(lastLastCh, lastCh, ch))
            return i;

        if (needsLineBreakIterator<treatNoBreakSpaceAsBreak>(ch) || needsLineBreakIterator<treatNoBreakSpaceAsBreak>(lastCh)) {
            if (nextBreak < i) {
                // Don't break if positioned at start of primary context and there is no prior context.
                if (i || priorContextLength) {
                    TextBreakIterator* breakIterator = lazyBreakIterator.get(priorContextLength);
                    if (breakIterator) {
                        nextBreak = breakIterator->following(i - 1 + priorContextLength);
                        if (nextBreak >= 0) {
                            nextBreak -= priorContextLength;
                        }
                    }
                }
            }
            if (i == nextBreak && !isBreakableSpace<treatNoBreakSpaceAsBreak>(lastCh))
                return i;
        }

        lastLastCh = lastCh;
        lastCh = ch;
    }

    return len;
}

int nextBreakablePositionIgnoringNBSP(LazyLineBreakIterator& lazyBreakIterator, int pos)
{
    String string = lazyBreakIterator.string();
    if (string.is8Bit())
        return nextBreakablePosition<LChar, false>(lazyBreakIterator, string.characters8(), string.length(), pos);
    return nextBreakablePosition<UChar, false>(lazyBreakIterator, string.characters16(), string.length(), pos);
}

} // namespace WebCore