third_party/WebKit/Source/core/rendering/RenderCombineText.cpp

   1 /*
   2  * Copyright (C) 2011 Apple Inc. All rights reserved.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Library General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library 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 GNU
  12  * Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public License
  15  * along with this library; see the file COPYING.LIB.  If not, write to
  16  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17  * Boston, MA 02110-1301, USA.
  18  *
  19  */
  20
  21 #include "config.h"
  22 #include "core/rendering/RenderCombineText.h"
  23
  24 #include "core/layout/TextRunConstructor.h"
  25 #include "platform/graphics/GraphicsContext.h"
  26
  27 namespace blink {
  28
  29 const float textCombineMargin = 1.1f; // Allow em + 10% margin
  30
  31 RenderCombineText::RenderCombineText(Node* node, PassRefPtr<StringImpl> string)
  32     : RenderText(node, string)
  33     , m_combinedTextWidth(0)
  34     , m_scaleX(1.0f)
  35     , m_isCombined(false)
  36     , m_needsFontUpdate(false)
  37 {
  38 }
  39
  40 void RenderCombineText::styleDidChange(StyleDifference diff, const LayoutStyle* oldStyle)
  41 {
  42     setStyleInternal(LayoutStyle::clone(styleRef()));
  43     RenderText::styleDidChange(diff, oldStyle);
  44
  45     updateIsCombined();
  46 }
  47
  48 void RenderCombineText::setTextInternal(PassRefPtr<StringImpl> text)
  49 {
  50     RenderText::setTextInternal(text);
  51
  52     updateIsCombined();
  53 }
  54
  55 float RenderCombineText::width(unsigned from, unsigned length, const Font& font, float xPosition, TextDirection direction, HashSet<const SimpleFontData*>* fallbackFonts, GlyphOverflow* glyphOverflow) const
  56 {
  57     if (!length)
  58         return 0;
  59
  60     if (hasEmptyText())
  61         return 0;
  62
  63     if (m_isCombined)
  64         return font.fontDescription().computedSize();
  65
  66     return RenderText::width(from, length, font, xPosition, direction, fallbackFonts, glyphOverflow);
  67 }
  68
  69 void scaleHorizontallyAndTranslate(GraphicsContext& context, float scaleX, float centerX, float offsetX, float offsetY)
  70 {
  71     context.concatCTM(AffineTransform(scaleX, 0, 0, 1, centerX * (1.0f - scaleX) + offsetX * scaleX, offsetY));
  72 }
  73
  74 void RenderCombineText::transformToInlineCoordinates(GraphicsContext& context, const FloatRect& boxRect) const
  75 {
  76     ASSERT(!m_needsFontUpdate);
  77     ASSERT(m_isCombined);
  78     if (m_scaleX >= 1.0f) {
  79         // Fast path, more than 90% of cases
  80         ASSERT(m_scaleX == 1.0f);
  81         context.concatCTM(AffineTransform::translation(offsetXNoScale(boxRect), offsetY()));
  82         return;
  83     }
  84     ASSERT(m_scaleX > 0.0f);
  85     const float centerX = boxRect.x() + boxRect.width() / 2;
  86     scaleHorizontallyAndTranslate(context, m_scaleX, centerX, offsetX(boxRect), offsetY());
  87 }
  88
  89 void RenderCombineText::transformLayoutRect(FloatRect& boxRect) const
  90 {
  91     ASSERT(!m_needsFontUpdate);
  92     ASSERT(m_isCombined);
  93     boxRect.move(offsetXNoScale(boxRect), offsetY());
  94 }
  95
  96 void RenderCombineText::updateIsCombined()
  97 {
  98     // CSS3 spec says text-combine works only in vertical writing mode.
  99     m_isCombined = !style()->isHorizontalWritingMode()
 100         // Nothing to combine.
 101         && !hasEmptyText();
 102
 103     if (m_isCombined)
 104         m_needsFontUpdate = true;
 105 }
 106
 107 void RenderCombineText::updateFont()
 108 {
 109     if (!m_needsFontUpdate)
 110         return;
 111
 112     m_needsFontUpdate = false;
 113
 114     if (!m_isCombined)
 115         return;
 116
 117     TextRun run = constructTextRun(this, originalFont(), this, styleRef(), style()->direction());
 118     FontDescription description = originalFont().fontDescription();
 119     float emWidth = description.computedSize();
 120     if (!(style()->textDecorationsInEffect() & (TextDecorationUnderline | TextDecorationOverline)))
 121         emWidth *= textCombineMargin;
 122
 123     description.setOrientation(Horizontal); // We are going to draw combined text horizontally.
 124     m_combinedTextWidth = originalFont().width(run);
 125
 126     FontSelector* fontSelector = style()->font().fontSelector();
 127
 128     bool shouldUpdateFont = style()->setFontDescription(description); // Need to change font orientation to horizontal.
 129
 130     if (m_combinedTextWidth <= emWidth) {
 131         m_scaleX = 1.0f;
 132     } else {
 133         // Need to try compressed glyphs.
 134         static const FontWidthVariant widthVariants[] = { HalfWidth, ThirdWidth, QuarterWidth };
 135         for (size_t i = 0 ; i < WTF_ARRAY_LENGTH(widthVariants) ; ++i) {
 136             description.setWidthVariant(widthVariants[i]);
 137             Font compressedFont = Font(description);
 138             compressedFont.update(fontSelector);
 139             float runWidth = compressedFont.width(run);
 140             if (runWidth <= emWidth) {
 141                 m_combinedTextWidth = runWidth;
 142
 143                 // Replace my font with the new one.
 144                 shouldUpdateFont = style()->setFontDescription(description);
 145                 break;
 146             }
 147         }
 148
 149         // If width > ~1em, shrink to fit within ~1em, otherwise render without scaling (no expansion)
 150         // http://dev.w3.org/csswg/css-writing-modes-3/#text-combine-compression
 151         if (m_combinedTextWidth > emWidth) {
 152             m_scaleX = emWidth / m_combinedTextWidth;
 153             m_combinedTextWidth = emWidth;
 154         } else {
 155             m_scaleX = 1.0f;
 156         }
 157     }
 158
 159     if (shouldUpdateFont)
 160         style()->font().update(fontSelector);
 161 }
 162
 163 } // namespace blink