src/third_party/WebKit/Source/platform/fonts/WidthIterator.cpp

   1 /*
   2  * Copyright (C) 2003, 2006, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
   3  * Copyright (C) 2008 Holger Hans Peter Freyther
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Library General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Library General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Library General Public License
  16  * along with this library; see the file COPYING.LIB.  If not, write to
  17  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  18  * Boston, MA 02110-1301, USA.
  19  *
  20  */
  21
  22 #include "config.h"
  23 #include "platform/fonts/WidthIterator.h"
  24
  25 #include "platform/fonts/Character.h"
  26 #include "platform/fonts/FontPlatformFeatures.h"
  27 #include "platform/fonts/GlyphBuffer.h"
  28 #include "platform/fonts/Latin1TextIterator.h"
  29 #include "platform/fonts/SimpleFontData.h"
  30 #include "platform/text/SurrogatePairAwareTextIterator.h"
  31 #include "wtf/MathExtras.h"
  32
  33 using namespace WTF;
  34 using namespace Unicode;
  35 using namespace std;
  36
  37 namespace WebCore {
  38
  39 WidthIterator::WidthIterator(const Font* font, const TextRun& run, HashSet<const SimpleFontData*>* fallbackFonts, bool accountForGlyphBounds, bool forTextEmphasis)
  40     : m_font(font)
  41     , m_run(run)
  42     , m_currentCharacter(0)
  43     , m_runWidthSoFar(0)
  44     , m_isAfterExpansion(!run.allowsLeadingExpansion())
  45     , m_finalRoundingWidth(0)
  46     , m_typesettingFeatures(font->fontDescription().typesettingFeatures())
  47     , m_fallbackFonts(fallbackFonts)
  48     , m_accountForGlyphBounds(accountForGlyphBounds)
  49     , m_maxGlyphBoundingBoxY(numeric_limits<float>::min())
  50     , m_minGlyphBoundingBoxY(numeric_limits<float>::max())
  51     , m_firstGlyphOverflow(0)
  52     , m_lastGlyphOverflow(0)
  53     , m_forTextEmphasis(forTextEmphasis)
  54 {
  55     // If the padding is non-zero, count the number of spaces in the run
  56     // and divide that by the padding for per space addition.
  57     m_expansion = m_run.expansion();
  58     if (!m_expansion)
  59         m_expansionPerOpportunity = 0;
  60     else {
  61         bool isAfterExpansion = m_isAfterExpansion;
  62         unsigned expansionOpportunityCount = m_run.is8Bit() ? Character::expansionOpportunityCount(m_run.characters8(), m_run.length(), m_run.direction(), isAfterExpansion) : Character::expansionOpportunityCount(m_run.characters16(), m_run.length(), m_run.direction(), isAfterExpansion);
  63         if (isAfterExpansion && !m_run.allowsTrailingExpansion())
  64             expansionOpportunityCount--;
  65
  66         if (!expansionOpportunityCount)
  67             m_expansionPerOpportunity = 0;
  68         else
  69             m_expansionPerOpportunity = m_expansion / expansionOpportunityCount;
  70     }
  71 }
  72
  73 GlyphData WidthIterator::glyphDataForCharacter(UChar32 character, bool mirror, int currentCharacter, unsigned& advanceLength)
  74 {
  75     ASSERT(m_font);
  76
  77 #if ENABLE(SVG_FONTS)
  78     if (TextRun::RenderingContext* renderingContext = m_run.renderingContext())
  79         return renderingContext->glyphDataForCharacter(*m_font, m_run, *this, character, mirror, currentCharacter, advanceLength);
  80 #endif
  81
  82     return m_font->glyphDataForCharacter(character, mirror);
  83 }
  84
  85 struct OriginalAdvancesForCharacterTreatedAsSpace {
  86 public:
  87     OriginalAdvancesForCharacterTreatedAsSpace(bool isSpace, float advanceBefore, float advanceAt)
  88         : characterIsSpace(isSpace)
  89         , advanceBeforeCharacter(advanceBefore)
  90         , advanceAtCharacter(advanceAt)
  91     {
  92     }
  93
  94     bool characterIsSpace;
  95     float advanceBeforeCharacter;
  96     float advanceAtCharacter;
  97 };
  98
  99 typedef Vector<pair<int, OriginalAdvancesForCharacterTreatedAsSpace>, 64> CharactersTreatedAsSpace;
 100
 101 static inline float applyFontTransforms(GlyphBuffer* glyphBuffer, unsigned& lastGlyphCount, TypesettingFeatures typesettingFeatures, CharactersTreatedAsSpace& charactersTreatedAsSpace)
 102 {
 103     ASSERT(typesettingFeatures & (Kerning | Ligatures));
 104
 105     if (!glyphBuffer)
 106         return 0;
 107
 108     unsigned glyphBufferSize = glyphBuffer->size();
 109     if (glyphBuffer->size() <= lastGlyphCount + 1)
 110         return 0;
 111
 112     FloatSize* advances = glyphBuffer->advances(0);
 113     float widthDifference = 0;
 114     for (unsigned i = lastGlyphCount; i < glyphBufferSize; ++i)
 115         widthDifference -= advances[i].width();
 116
 117     for (size_t i = 0; i < charactersTreatedAsSpace.size(); ++i) {
 118         int spaceOffset = charactersTreatedAsSpace[i].first;
 119         const OriginalAdvancesForCharacterTreatedAsSpace& originalAdvances = charactersTreatedAsSpace[i].second;
 120         if (spaceOffset && !originalAdvances.characterIsSpace)
 121             glyphBuffer->advances(spaceOffset - 1)->setWidth(originalAdvances.advanceBeforeCharacter);
 122         glyphBuffer->advances(spaceOffset)->setWidth(originalAdvances.advanceAtCharacter);
 123     }
 124     charactersTreatedAsSpace.clear();
 125
 126     for (unsigned i = lastGlyphCount; i < glyphBufferSize; ++i)
 127         widthDifference += advances[i].width();
 128
 129     lastGlyphCount = glyphBufferSize;
 130     return widthDifference;
 131 }
 132
 133 template <typename TextIterator>
 134 inline unsigned WidthIterator::advanceInternal(TextIterator& textIterator, GlyphBuffer* glyphBuffer)
 135 {
 136     bool rtl = m_run.rtl();
 137     bool hasExtraSpacing = (m_font->fontDescription().letterSpacing() || m_font->fontDescription().wordSpacing() || m_expansion) && !m_run.spacingDisabled();
 138
 139     float widthSinceLastRounding = m_runWidthSoFar;
 140     m_runWidthSoFar = floorf(m_runWidthSoFar);
 141     widthSinceLastRounding -= m_runWidthSoFar;
 142
 143     float lastRoundingWidth = m_finalRoundingWidth;
 144     FloatRect bounds;
 145
 146     const SimpleFontData* primaryFont = m_font->primaryFont();
 147     const SimpleFontData* lastFontData = primaryFont;
 148     unsigned lastGlyphCount = glyphBuffer ? glyphBuffer->size() : 0;
 149
 150     UChar32 character = 0;
 151     unsigned clusterLength = 0;
 152     CharactersTreatedAsSpace charactersTreatedAsSpace;
 153     while (textIterator.consume(character, clusterLength)) {
 154         unsigned advanceLength = clusterLength;
 155         const GlyphData& glyphData = glyphDataForCharacter(character, rtl, textIterator.currentCharacter(), advanceLength);
 156         Glyph glyph = glyphData.glyph;
 157         const SimpleFontData* fontData = glyphData.fontData;
 158
 159         ASSERT(fontData);
 160
 161         // Now that we have a glyph and font data, get its width.
 162         float width;
 163         if (character == '\t' && m_run.allowTabs())
 164             width = m_font->tabWidth(*fontData, m_run.tabSize(), m_run.xPos() + m_runWidthSoFar + widthSinceLastRounding);
 165         else {
 166             width = fontData->widthForGlyph(glyph);
 167
 168             // SVG uses horizontalGlyphStretch(), when textLength is used to stretch/squeeze text.
 169             width *= m_run.horizontalGlyphStretch();
 170
 171             // We special case spaces in two ways when applying word rounding.
 172             // First, we round spaces to an adjusted width in all fonts.
 173             // Second, in fixed-pitch fonts we ensure that all characters that
 174             // match the width of the space character have the same width as the space character.
 175             if (m_run.applyWordRounding() && width == fontData->spaceWidth() && (fontData->pitch() == FixedPitch || glyph == fontData->spaceGlyph()))
 176                 width = fontData->adjustedSpaceWidth();
 177         }
 178
 179         if (fontData != lastFontData && width) {
 180             if (shouldApplyFontTransforms())
 181                 m_runWidthSoFar += applyFontTransforms(glyphBuffer, lastGlyphCount, m_typesettingFeatures, charactersTreatedAsSpace);
 182
 183             lastFontData = fontData;
 184             if (m_fallbackFonts && fontData != primaryFont) {
 185                 // FIXME: This does a little extra work that could be avoided if
 186                 // glyphDataForCharacter() returned whether it chose to use a small caps font.
 187                 if (m_font->fontDescription().variant() == FontVariantNormal || character == toUpper(character))
 188                     m_fallbackFonts->add(fontData);
 189                 else {
 190                     ASSERT(m_font->fontDescription().variant() == FontVariantSmallCaps);
 191                     const GlyphData& uppercaseGlyphData = m_font->glyphDataForCharacter(toUpper(character), rtl);
 192                     if (uppercaseGlyphData.fontData != primaryFont)
 193                         m_fallbackFonts->add(uppercaseGlyphData.fontData);
 194                 }
 195             }
 196         }
 197
 198         if (hasExtraSpacing) {
 199             // Account for letter-spacing.
 200             if (width && m_font->fontDescription().letterSpacing())
 201                 width += m_font->fontDescription().letterSpacing();
 202
 203             static bool expandAroundIdeographs = FontPlatformFeatures::canExpandAroundIdeographsInComplexText();
 204             bool treatAsSpace = Character::treatAsSpace(character);
 205             if (treatAsSpace || (expandAroundIdeographs && Character::isCJKIdeographOrSymbol(character))) {
 206                 // Distribute the run's total expansion evenly over all expansion opportunities in the run.
 207                 if (m_expansion) {
 208                     float previousExpansion = m_expansion;
 209                     if (!treatAsSpace && !m_isAfterExpansion) {
 210                         // Take the expansion opportunity before this ideograph.
 211                         m_expansion -= m_expansionPerOpportunity;
 212                         float expansionAtThisOpportunity = !m_run.applyWordRounding() ? m_expansionPerOpportunity : roundf(previousExpansion) - roundf(m_expansion);
 213                         m_runWidthSoFar += expansionAtThisOpportunity;
 214                         if (glyphBuffer) {
 215                             if (glyphBuffer->isEmpty()) {
 216                                 if (m_forTextEmphasis)
 217                                     glyphBuffer->add(fontData->zeroWidthSpaceGlyph(), fontData, m_expansionPerOpportunity);
 218                                 else
 219                                     glyphBuffer->add(fontData->spaceGlyph(), fontData, expansionAtThisOpportunity);
 220                             } else
 221                                 glyphBuffer->expandLastAdvance(expansionAtThisOpportunity);
 222                         }
 223                         previousExpansion = m_expansion;
 224                     }
 225                     if (m_run.allowsTrailingExpansion() || (m_run.ltr() && textIterator.currentCharacter() + advanceLength < static_cast<size_t>(m_run.length()))
 226                         || (m_run.rtl() && textIterator.currentCharacter())) {
 227                         m_expansion -= m_expansionPerOpportunity;
 228                         width += !m_run.applyWordRounding() ? m_expansionPerOpportunity : roundf(previousExpansion) - roundf(m_expansion);
 229                         m_isAfterExpansion = true;
 230                     }
 231                 } else
 232                     m_isAfterExpansion = false;
 233
 234                 // Account for word spacing.
 235                 // We apply additional space between "words" by adding width to the space character.
 236                 if (treatAsSpace && (character != '\t' || !m_run.allowTabs()) && (textIterator.currentCharacter() || character == noBreakSpace) && m_font->fontDescription().wordSpacing())
 237                     width += m_font->fontDescription().wordSpacing();
 238             } else
 239                 m_isAfterExpansion = false;
 240         }
 241
 242         if (shouldApplyFontTransforms() && glyphBuffer && Character::treatAsSpace(character)) {
 243             charactersTreatedAsSpace.append(make_pair(glyphBuffer->size(),
 244                 OriginalAdvancesForCharacterTreatedAsSpace(character == ' ',
 245                     glyphBuffer->size() ? glyphBuffer->advanceAt(glyphBuffer->size() - 1).width() : 0,
 246                     width)));
 247         }
 248
 249         if (m_accountForGlyphBounds) {
 250             bounds = fontData->boundsForGlyph(glyph);
 251             if (!textIterator.currentCharacter())
 252                 m_firstGlyphOverflow = max<float>(0, -bounds.x());
 253         }
 254
 255         if (m_forTextEmphasis && !Character::canReceiveTextEmphasis(character))
 256             glyph = 0;
 257
 258         // Advance past the character we just dealt with.
 259         textIterator.advance(advanceLength);
 260
 261         float oldWidth = width;
 262
 263         // Force characters that are used to determine word boundaries for the rounding hack
 264         // to be integer width, so following words will start on an integer boundary.
 265         if (m_run.applyWordRounding() && Character::isRoundingHackCharacter(character)) {
 266             width = ceilf(width);
 267
 268             // Since widthSinceLastRounding can lose precision if we include measurements for
 269             // preceding whitespace, we bypass it here.
 270             m_runWidthSoFar += width;
 271
 272             // Since this is a rounding hack character, we should have reset this sum on the previous
 273             // iteration.
 274             ASSERT(!widthSinceLastRounding);
 275         } else {
 276             // Check to see if the next character is a "rounding hack character", if so, adjust
 277             // width so that the total run width will be on an integer boundary.
 278             if ((m_run.applyWordRounding() && textIterator.currentCharacter() < m_run.length() && Character::isRoundingHackCharacter(*(textIterator.characters())))
 279                 || (m_run.applyRunRounding() && textIterator.currentCharacter() >= m_run.length())) {
 280                 float totalWidth = widthSinceLastRounding + width;
 281                 widthSinceLastRounding = ceilf(totalWidth);
 282                 width += widthSinceLastRounding - totalWidth;
 283                 m_runWidthSoFar += widthSinceLastRounding;
 284                 widthSinceLastRounding = 0;
 285             } else
 286                 widthSinceLastRounding += width;
 287         }
 288
 289         if (glyphBuffer)
 290             glyphBuffer->add(glyph, fontData, (rtl ? oldWidth + lastRoundingWidth : width));
 291
 292         lastRoundingWidth = width - oldWidth;
 293
 294         if (m_accountForGlyphBounds) {
 295             m_maxGlyphBoundingBoxY = max(m_maxGlyphBoundingBoxY, bounds.maxY());
 296             m_minGlyphBoundingBoxY = min(m_minGlyphBoundingBoxY, bounds.y());
 297             m_lastGlyphOverflow = max<float>(0, bounds.maxX() - width);
 298         }
 299     }
 300
 301     if (shouldApplyFontTransforms())
 302         m_runWidthSoFar += applyFontTransforms(glyphBuffer, lastGlyphCount, m_typesettingFeatures, charactersTreatedAsSpace);
 303
 304     unsigned consumedCharacters = textIterator.currentCharacter() - m_currentCharacter;
 305     m_currentCharacter = textIterator.currentCharacter();
 306     m_runWidthSoFar += widthSinceLastRounding;
 307     m_finalRoundingWidth = lastRoundingWidth;
 308     return consumedCharacters;
 309 }
 310
 311 unsigned WidthIterator::advance(int offset, GlyphBuffer* glyphBuffer)
 312 {
 313     int length = m_run.length();
 314
 315     if (offset > length)
 316         offset = length;
 317
 318     if (m_currentCharacter >= static_cast<unsigned>(offset))
 319         return 0;
 320
 321     if (m_run.is8Bit()) {
 322         Latin1TextIterator textIterator(m_run.data8(m_currentCharacter), m_currentCharacter, offset, length);
 323         return advanceInternal(textIterator, glyphBuffer);
 324     }
 325
 326     SurrogatePairAwareTextIterator textIterator(m_run.data16(m_currentCharacter), m_currentCharacter, offset, length);
 327     return advanceInternal(textIterator, glyphBuffer);
 328 }
 329
 330 bool WidthIterator::advanceOneCharacter(float& width, GlyphBuffer& glyphBuffer)
 331 {
 332     unsigned oldSize = glyphBuffer.size();
 333     advance(m_currentCharacter + 1, &glyphBuffer);
 334     float w = 0;
 335     for (unsigned i = oldSize; i < glyphBuffer.size(); ++i)
 336         w += glyphBuffer.advanceAt(i).width();
 337     width = w;
 338     return glyphBuffer.size() > oldSize;
 339 }
 340
 341 }