code.vuplus.com Git - vuplus_webkit/blob - Source/WebCore/platform/graphics/StringTruncator.cpp

   1 /*
   2  * Copyright (C) 2005, 2006, 2007 Apple Inc.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * 1.  Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  * 2.  Redistributions in binary form must reproduce the above copyright
  11  *     notice, this list of conditions and the following disclaimer in the
  12  *     documentation and/or other materials provided with the distribution.
  13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  14  *     its contributors may be used to endorse or promote products derived
  15  *     from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include "config.h"
  30 #include "StringTruncator.h"
  31
  32 #include "Font.h"
  33 #include "TextBreakIterator.h"
  34 #include "TextRun.h"
  35 #include <wtf/Assertions.h>
  36 #include <wtf/Vector.h>
  37 #include <wtf/unicode/CharacterNames.h>
  38
  39 namespace WebCore {
  40
  41 #define STRING_BUFFER_SIZE 2048
  42
  43 typedef unsigned TruncationFunction(const String&, unsigned length, unsigned keepCount, UChar* buffer);
  44
  45 static inline int textBreakAtOrPreceding(TextBreakIterator* it, int offset)
  46 {
  47     if (isTextBreak(it, offset))
  48         return offset;
  49
  50     int result = textBreakPreceding(it, offset);
  51     return result == TextBreakDone ? 0 : result;
  52 }
  53
  54 static inline int boundedTextBreakFollowing(TextBreakIterator* it, int offset, int length)
  55 {
  56     int result = textBreakFollowing(it, offset);
  57     return result == TextBreakDone ? length : result;
  58 }
  59
  60 static unsigned centerTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer)
  61 {
  62     ASSERT(keepCount < length);
  63     ASSERT(keepCount < STRING_BUFFER_SIZE);
  64
  65     unsigned omitStart = (keepCount + 1) / 2;
  66     TextBreakIterator* it = characterBreakIterator(string.characters(), length);
  67     unsigned omitEnd = boundedTextBreakFollowing(it, omitStart + (length - keepCount) - 1, length);
  68     omitStart = textBreakAtOrPreceding(it, omitStart);
  69
  70     unsigned truncatedLength = omitStart + 1 + (length - omitEnd);
  71     ASSERT(truncatedLength <= length);
  72
  73     memcpy(buffer, string.characters(), sizeof(UChar) * omitStart);
  74     buffer[omitStart] = horizontalEllipsis;
  75     memcpy(&buffer[omitStart + 1], &string.characters()[omitEnd], sizeof(UChar) * (length - omitEnd));
  76
  77     return truncatedLength;
  78 }
  79
  80 static unsigned rightTruncateToBuffer(const String& string, unsigned length, unsigned keepCount, UChar* buffer)
  81 {
  82     ASSERT(keepCount < length);
  83     ASSERT(keepCount < STRING_BUFFER_SIZE);
  84
  85     TextBreakIterator* it = characterBreakIterator(string.characters(), length);
  86     unsigned keepLength = textBreakAtOrPreceding(it, keepCount);
  87     unsigned truncatedLength = keepLength + 1;
  88
  89     memcpy(buffer, string.characters(), sizeof(UChar) * keepLength);
  90     buffer[keepLength] = horizontalEllipsis;
  91
  92     return truncatedLength;
  93 }
  94
  95 static float stringWidth(const Font& renderer, const UChar* characters, unsigned length, bool disableRoundingHacks)
  96 {
  97     TextRun run(characters, length);
  98     if (disableRoundingHacks)
  99         run.disableRoundingHacks();
 100     return renderer.width(run);
 101 }
 102
 103 static String truncateString(const String& string, float maxWidth, const Font& font, TruncationFunction truncateToBuffer, bool disableRoundingHacks)
 104 {
 105     if (string.isEmpty())
 106         return string;
 107
 108     ASSERT(maxWidth >= 0);
 109
 110     float currentEllipsisWidth = stringWidth(font, &horizontalEllipsis, 1, disableRoundingHacks);
 111
 112     UChar stringBuffer[STRING_BUFFER_SIZE];
 113     unsigned truncatedLength;
 114     unsigned keepCount;
 115     unsigned length = string.length();
 116
 117     if (length > STRING_BUFFER_SIZE) {
 118         keepCount = STRING_BUFFER_SIZE - 1; // need 1 character for the ellipsis
 119         truncatedLength = centerTruncateToBuffer(string, length, keepCount, stringBuffer);
 120     } else {
 121         keepCount = length;
 122         memcpy(stringBuffer, string.characters(), sizeof(UChar) * length);
 123         truncatedLength = length;
 124     }
 125
 126     float width = stringWidth(font, stringBuffer, truncatedLength, disableRoundingHacks);
 127     if (width <= maxWidth)
 128         return string;
 129
 130     unsigned keepCountForLargestKnownToFit = 0;
 131     float widthForLargestKnownToFit = currentEllipsisWidth;
 132
 133     unsigned keepCountForSmallestKnownToNotFit = keepCount;
 134     float widthForSmallestKnownToNotFit = width;
 135
 136     if (currentEllipsisWidth >= maxWidth) {
 137         keepCountForLargestKnownToFit = 1;
 138         keepCountForSmallestKnownToNotFit = 2;
 139     }
 140
 141     while (keepCountForLargestKnownToFit + 1 < keepCountForSmallestKnownToNotFit) {
 142         ASSERT(widthForLargestKnownToFit <= maxWidth);
 143         ASSERT(widthForSmallestKnownToNotFit > maxWidth);
 144
 145         float ratio = (keepCountForSmallestKnownToNotFit - keepCountForLargestKnownToFit)
 146             / (widthForSmallestKnownToNotFit - widthForLargestKnownToFit);
 147         keepCount = static_cast<unsigned>(maxWidth * ratio);
 148
 149         if (keepCount <= keepCountForLargestKnownToFit) {
 150             keepCount = keepCountForLargestKnownToFit + 1;
 151         } else if (keepCount >= keepCountForSmallestKnownToNotFit) {
 152             keepCount = keepCountForSmallestKnownToNotFit - 1;
 153         }
 154
 155         ASSERT(keepCount < length);
 156         ASSERT(keepCount > 0);
 157         ASSERT(keepCount < keepCountForSmallestKnownToNotFit);
 158         ASSERT(keepCount > keepCountForLargestKnownToFit);
 159
 160         truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer);
 161
 162         width = stringWidth(font, stringBuffer, truncatedLength, disableRoundingHacks);
 163         if (width <= maxWidth) {
 164             keepCountForLargestKnownToFit = keepCount;
 165             widthForLargestKnownToFit = width;
 166         } else {
 167             keepCountForSmallestKnownToNotFit = keepCount;
 168             widthForSmallestKnownToNotFit = width;
 169         }
 170     }
 171
 172     if (keepCountForLargestKnownToFit == 0) {
 173         keepCountForLargestKnownToFit = 1;
 174     }
 175
 176     if (keepCount != keepCountForLargestKnownToFit) {
 177         keepCount = keepCountForLargestKnownToFit;
 178         truncatedLength = truncateToBuffer(string, length, keepCount, stringBuffer);
 179     }
 180
 181     return String(stringBuffer, truncatedLength);
 182 }
 183
 184 String StringTruncator::centerTruncate(const String& string, float maxWidth, const Font& font, EnableRoundingHacksOrNot enableRoundingHacks)
 185 {
 186     return truncateString(string, maxWidth, font, centerTruncateToBuffer, !enableRoundingHacks);
 187 }
 188
 189 String StringTruncator::rightTruncate(const String& string, float maxWidth, const Font& font, EnableRoundingHacksOrNot enableRoundingHacks)
 190 {
 191     return truncateString(string, maxWidth, font, rightTruncateToBuffer, !enableRoundingHacks);
 192 }
 193
 194 float StringTruncator::width(const String& string, const Font& font, EnableRoundingHacksOrNot enableRoundingHacks)
 195 {
 196     return stringWidth(font, string.characters(), string.length(), !enableRoundingHacks);
 197 }
 198
 199 } // namespace WebCore