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      1 /*
      2  * Copyright (C) Research In Motion Limited 2010. 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 #include "config.h"
     21 
     22 #include "core/rendering/svg/SVGTextLayoutEngineBaseline.h"
     23 
     24 #include "core/rendering/RenderObject.h"
     25 #include "core/rendering/style/SVGRenderStyle.h"
     26 #include "core/rendering/svg/SVGTextMetrics.h"
     27 #include "core/svg/SVGLengthContext.h"
     28 #include "platform/fonts/Font.h"
     29 #include "platform/text/UnicodeRange.h"
     30 
     31 namespace blink {
     32 
     33 SVGTextLayoutEngineBaseline::SVGTextLayoutEngineBaseline(const Font& font)
     34     : m_font(font)
     35 {
     36 }
     37 
     38 float SVGTextLayoutEngineBaseline::calculateBaselineShift(const SVGRenderStyle& style, SVGElement* contextElement) const
     39 {
     40     if (style.baselineShift() == BS_LENGTH) {
     41         RefPtr<SVGLength> baselineShiftValueLength = style.baselineShiftValue();
     42         if (baselineShiftValueLength->unitType() == LengthTypePercentage)
     43             return baselineShiftValueLength->valueAsPercentage() * m_font.fontDescription().computedPixelSize();
     44 
     45         SVGLengthContext lengthContext(contextElement);
     46         return baselineShiftValueLength->value(lengthContext);
     47     }
     48 
     49     switch (style.baselineShift()) {
     50     case BS_BASELINE:
     51         return 0;
     52     case BS_SUB:
     53         return -m_font.fontMetrics().floatHeight() / 2;
     54     case BS_SUPER:
     55         return m_font.fontMetrics().floatHeight() / 2;
     56     default:
     57         ASSERT_NOT_REACHED();
     58         return 0;
     59     }
     60 }
     61 
     62 EAlignmentBaseline SVGTextLayoutEngineBaseline::dominantBaselineToAlignmentBaseline(bool isVerticalText, const RenderObject* textRenderer) const
     63 {
     64     ASSERT(textRenderer);
     65     ASSERT(textRenderer->style());
     66     ASSERT(textRenderer->parent());
     67     ASSERT(textRenderer->parent()->style());
     68 
     69     const SVGRenderStyle& style = textRenderer->style()->svgStyle();
     70 
     71     EDominantBaseline baseline = style.dominantBaseline();
     72     if (baseline == DB_AUTO) {
     73         if (isVerticalText)
     74             baseline = DB_CENTRAL;
     75         else
     76             baseline = DB_ALPHABETIC;
     77     }
     78 
     79     switch (baseline) {
     80     case DB_USE_SCRIPT:
     81         // FIXME: The dominant-baseline and the baseline-table components are set by determining the predominant script of the character data content.
     82         return AB_ALPHABETIC;
     83     case DB_NO_CHANGE:
     84         return dominantBaselineToAlignmentBaseline(isVerticalText, textRenderer->parent());
     85     case DB_RESET_SIZE:
     86         return dominantBaselineToAlignmentBaseline(isVerticalText, textRenderer->parent());
     87     case DB_IDEOGRAPHIC:
     88         return AB_IDEOGRAPHIC;
     89     case DB_ALPHABETIC:
     90         return AB_ALPHABETIC;
     91     case DB_HANGING:
     92         return AB_HANGING;
     93     case DB_MATHEMATICAL:
     94         return AB_MATHEMATICAL;
     95     case DB_CENTRAL:
     96         return AB_CENTRAL;
     97     case DB_MIDDLE:
     98         return AB_MIDDLE;
     99     case DB_TEXT_AFTER_EDGE:
    100         return AB_TEXT_AFTER_EDGE;
    101     case DB_TEXT_BEFORE_EDGE:
    102         return AB_TEXT_BEFORE_EDGE;
    103     default:
    104         ASSERT_NOT_REACHED();
    105         return AB_AUTO;
    106     }
    107 }
    108 
    109 float SVGTextLayoutEngineBaseline::calculateAlignmentBaselineShift(bool isVerticalText, const RenderObject* textRenderer) const
    110 {
    111     ASSERT(textRenderer);
    112     ASSERT(textRenderer->style());
    113     ASSERT(textRenderer->parent());
    114 
    115     const RenderObject* textRendererParent = textRenderer->parent();
    116     ASSERT(textRendererParent);
    117 
    118     EAlignmentBaseline baseline = textRenderer->style()->svgStyle().alignmentBaseline();
    119     if (baseline == AB_AUTO || baseline == AB_BASELINE) {
    120         baseline = dominantBaselineToAlignmentBaseline(isVerticalText, textRendererParent);
    121         ASSERT(baseline != AB_AUTO && baseline != AB_BASELINE);
    122     }
    123 
    124     const FontMetrics& fontMetrics = m_font.fontMetrics();
    125 
    126     // Note: http://wiki.apache.org/xmlgraphics-fop/LineLayout/AlignmentHandling
    127     switch (baseline) {
    128     case AB_BEFORE_EDGE:
    129     case AB_TEXT_BEFORE_EDGE:
    130         return fontMetrics.floatAscent();
    131     case AB_MIDDLE:
    132         return fontMetrics.xHeight() / 2;
    133     case AB_CENTRAL:
    134         return (fontMetrics.floatAscent() - fontMetrics.floatDescent()) / 2;
    135     case AB_AFTER_EDGE:
    136     case AB_TEXT_AFTER_EDGE:
    137     case AB_IDEOGRAPHIC:
    138         return -fontMetrics.floatDescent();
    139     case AB_ALPHABETIC:
    140         return 0;
    141     case AB_HANGING:
    142         return fontMetrics.floatAscent() * 8 / 10.f;
    143     case AB_MATHEMATICAL:
    144         return fontMetrics.floatAscent() / 2;
    145     case AB_BASELINE:
    146     default:
    147         ASSERT_NOT_REACHED();
    148         return 0;
    149     }
    150 }
    151 
    152 float SVGTextLayoutEngineBaseline::calculateGlyphOrientationAngle(bool isVerticalText, const SVGRenderStyle& style, const UChar& character) const
    153 {
    154     switch (isVerticalText ? style.glyphOrientationVertical() : style.glyphOrientationHorizontal()) {
    155     case GO_AUTO: {
    156         // Spec: Fullwidth ideographic and fullwidth Latin text will be set with a glyph-orientation of 0-degrees.
    157         // Text which is not fullwidth will be set with a glyph-orientation of 90-degrees.
    158         unsigned unicodeRange = findCharUnicodeRange(character);
    159         if (unicodeRange == cRangeSetLatin || unicodeRange == cRangeArabic)
    160             return 90;
    161 
    162         return 0;
    163     }
    164     case GO_90DEG:
    165         return 90;
    166     case GO_180DEG:
    167         return 180;
    168     case GO_270DEG:
    169         return 270;
    170     case GO_0DEG:
    171     default:
    172         return 0;
    173     }
    174 }
    175 
    176 static inline bool glyphOrientationIsMultiplyOf180Degrees(float orientationAngle)
    177 {
    178     return !fabsf(fmodf(orientationAngle, 180));
    179 }
    180 
    181 float SVGTextLayoutEngineBaseline::calculateGlyphAdvanceAndOrientation(bool isVerticalText, const SVGTextMetrics& metrics, float angle, float& xOrientationShift, float& yOrientationShift) const
    182 {
    183     bool orientationIsMultiplyOf180Degrees = glyphOrientationIsMultiplyOf180Degrees(angle);
    184 
    185     // The function is based on spec requirements:
    186     //
    187     // Spec: If the 'glyph-orientation-horizontal' results in an orientation angle that is not a multiple of
    188     // of 180 degrees, then the current text position is incremented according to the vertical metrics of the glyph.
    189     //
    190     // Spec: If if the 'glyph-orientation-vertical' results in an orientation angle that is not a multiple of
    191     // 180 degrees, then the current text position is incremented according to the horizontal metrics of the glyph.
    192 
    193     const FontMetrics& fontMetrics = m_font.fontMetrics();
    194 
    195     // Vertical orientation handling.
    196     if (isVerticalText) {
    197         float ascentMinusDescent = fontMetrics.floatAscent() - fontMetrics.floatDescent();
    198         if (!angle) {
    199             xOrientationShift = (ascentMinusDescent - metrics.width()) / 2;
    200             yOrientationShift = fontMetrics.floatAscent();
    201         } else if (angle == 180)
    202             xOrientationShift = (ascentMinusDescent + metrics.width()) / 2;
    203         else if (angle == 270) {
    204             yOrientationShift = metrics.width();
    205             xOrientationShift = ascentMinusDescent;
    206         }
    207 
    208         // Vertical advance calculation.
    209         if (angle && !orientationIsMultiplyOf180Degrees)
    210             return metrics.width();
    211 
    212         return metrics.height();
    213     }
    214 
    215     // Horizontal orientation handling.
    216     if (angle == 90)
    217         yOrientationShift = -metrics.width();
    218     else if (angle == 180) {
    219         xOrientationShift = metrics.width();
    220         yOrientationShift = -fontMetrics.floatAscent();
    221     } else if (angle == 270)
    222         xOrientationShift = metrics.width();
    223 
    224     // Horizontal advance calculation.
    225     if (angle && !orientationIsMultiplyOf180Degrees)
    226         return metrics.height();
    227 
    228     return metrics.width();
    229 }
    230 
    231 }
    232