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      1 /*
      2  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
      3  * Copyright (C) 2007 Alp Toker <alp (at) atoker.com>
      4  * Copyright (C) 2013 Google Inc. All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     16  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     18  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     19  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     20  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     22  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     23  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     25  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 #include "config.h"
     29 #include "platform/graphics/Gradient.h"
     30 
     31 #include "platform/geometry/FloatRect.h"
     32 #include "platform/graphics/Color.h"
     33 #include "platform/graphics/GraphicsContext.h"
     34 #include "platform/graphics/skia/SkiaUtils.h"
     35 #include "third_party/skia/include/core/SkColorShader.h"
     36 #include "third_party/skia/include/core/SkShader.h"
     37 #include "third_party/skia/include/effects/SkGradientShader.h"
     38 
     39 namespace WebCore {
     40 
     41 Gradient::Gradient(const FloatPoint& p0, const FloatPoint& p1)
     42     : m_radial(false)
     43     , m_p0(p0)
     44     , m_p1(p1)
     45     , m_r0(0)
     46     , m_r1(0)
     47     , m_aspectRatio(1)
     48     , m_stopsSorted(false)
     49     , m_spreadMethod(SpreadMethodPad)
     50     , m_drawInPMColorSpace(false)
     51 {
     52 }
     53 
     54 Gradient::Gradient(const FloatPoint& p0, float r0, const FloatPoint& p1, float r1, float aspectRatio)
     55     : m_radial(true)
     56     , m_p0(p0)
     57     , m_p1(p1)
     58     , m_r0(r0)
     59     , m_r1(r1)
     60     , m_aspectRatio(aspectRatio)
     61     , m_stopsSorted(false)
     62     , m_spreadMethod(SpreadMethodPad)
     63     , m_drawInPMColorSpace(false)
     64 {
     65 }
     66 
     67 Gradient::~Gradient()
     68 {
     69 }
     70 
     71 void Gradient::addColorStop(float value, const Color& color)
     72 {
     73     float r;
     74     float g;
     75     float b;
     76     float a;
     77     color.getRGBA(r, g, b, a);
     78     m_stops.append(ColorStop(value, r, g, b, a));
     79 
     80     m_stopsSorted = false;
     81     m_gradient.clear();
     82 }
     83 
     84 void Gradient::addColorStop(const Gradient::ColorStop& stop)
     85 {
     86     m_stops.append(stop);
     87 
     88     m_stopsSorted = false;
     89     m_gradient.clear();
     90 }
     91 
     92 static inline bool compareStops(const Gradient::ColorStop& a, const Gradient::ColorStop& b)
     93 {
     94     return a.stop < b.stop;
     95 }
     96 
     97 void Gradient::sortStopsIfNecessary()
     98 {
     99     if (m_stopsSorted)
    100         return;
    101 
    102     m_stopsSorted = true;
    103 
    104     if (!m_stops.size())
    105         return;
    106 
    107     std::stable_sort(m_stops.begin(), m_stops.end(), compareStops);
    108 }
    109 
    110 bool Gradient::hasAlpha() const
    111 {
    112     for (size_t i = 0; i < m_stops.size(); i++) {
    113         if (m_stops[i].alpha < 1)
    114             return true;
    115     }
    116 
    117     return false;
    118 }
    119 
    120 void Gradient::setSpreadMethod(GradientSpreadMethod spreadMethod)
    121 {
    122     // FIXME: Should it become necessary, allow calls to this method after m_gradient has been set.
    123     ASSERT(!m_gradient);
    124 
    125     if (m_spreadMethod == spreadMethod)
    126         return;
    127 
    128     m_spreadMethod = spreadMethod;
    129 }
    130 
    131 void Gradient::setDrawsInPMColorSpace(bool drawInPMColorSpace)
    132 {
    133     if (drawInPMColorSpace == m_drawInPMColorSpace)
    134         return;
    135 
    136     m_drawInPMColorSpace = drawInPMColorSpace;
    137     m_gradient.clear();
    138 }
    139 
    140 void Gradient::setGradientSpaceTransform(const AffineTransform& gradientSpaceTransformation)
    141 {
    142     if (m_gradientSpaceTransformation == gradientSpaceTransformation)
    143         return;
    144 
    145     m_gradientSpaceTransformation = gradientSpaceTransformation;
    146     if (m_gradient)
    147         m_gradient->setLocalMatrix(affineTransformToSkMatrix(m_gradientSpaceTransformation));
    148 }
    149 
    150 static inline U8CPU F2B(float x)
    151 {
    152     return static_cast<int>(x * 255);
    153 }
    154 
    155 static SkColor makeSkColor(float a, float r, float g, float b)
    156 {
    157     return SkColorSetARGB(F2B(a), F2B(r), F2B(g), F2B(b));
    158 }
    159 
    160 // Determine the total number of stops needed, including pseudo-stops at the
    161 // ends as necessary.
    162 static size_t totalStopsNeeded(const Gradient::ColorStop* stopData, size_t count)
    163 {
    164     // N.B.: The tests in this function should kept in sync with the ones in
    165     // fillStops(), or badness happens.
    166     const Gradient::ColorStop* stop = stopData;
    167     size_t countUsed = count;
    168     if (count < 1 || stop->stop > 0.0)
    169         countUsed++;
    170     stop += count - 1;
    171     if (count < 1 || stop->stop < 1.0)
    172         countUsed++;
    173     return countUsed;
    174 }
    175 
    176 // Collect sorted stop position and color information into the pos and colors
    177 // buffers, ensuring stops at both 0.0 and 1.0. The buffers must be large
    178 // enough to hold information for all stops, including the new endpoints if
    179 // stops at 0.0 and 1.0 aren't already included.
    180 static void fillStops(const Gradient::ColorStop* stopData,
    181     size_t count, SkScalar* pos, SkColor* colors)
    182 {
    183     const Gradient::ColorStop* stop = stopData;
    184     size_t start = 0;
    185     if (count < 1) {
    186         // A gradient with no stops must be transparent black.
    187         pos[0] = WebCoreFloatToSkScalar(0.0);
    188         colors[0] = makeSkColor(0.0, 0.0, 0.0, 0.0);
    189         start = 1;
    190     } else if (stop->stop > 0.0) {
    191         // Copy the first stop to 0.0. The first stop position may have a slight
    192         // rounding error, but we don't care in this float comparison, since
    193         // 0.0 comes through cleanly and people aren't likely to want a gradient
    194         // with a stop at (0 + epsilon).
    195         pos[0] = WebCoreFloatToSkScalar(0.0);
    196         colors[0] = makeSkColor(stop->alpha, stop->red, stop->green, stop->blue);
    197         start = 1;
    198     }
    199 
    200     for (size_t i = start; i < start + count; i++) {
    201         pos[i] = WebCoreFloatToSkScalar(stop->stop);
    202         colors[i] = makeSkColor(stop->alpha, stop->red, stop->green, stop->blue);
    203         ++stop;
    204     }
    205 
    206     // Copy the last stop to 1.0 if needed. See comment above about this float
    207     // comparison.
    208     if (count < 1 || (--stop)->stop < 1.0) {
    209         pos[start + count] = WebCoreFloatToSkScalar(1.0);
    210         colors[start + count] = colors[start + count - 1];
    211     }
    212 }
    213 
    214 SkShader* Gradient::shader()
    215 {
    216     if (m_gradient)
    217         return m_gradient.get();
    218 
    219     sortStopsIfNecessary();
    220     ASSERT(m_stopsSorted);
    221 
    222     size_t countUsed = totalStopsNeeded(m_stops.data(), m_stops.size());
    223     ASSERT(countUsed >= 2);
    224     ASSERT(countUsed >= m_stops.size());
    225 
    226     // FIXME: Why is all this manual pointer math needed?!
    227     SkAutoMalloc storage(countUsed * (sizeof(SkColor) + sizeof(SkScalar)));
    228     SkColor* colors = (SkColor*)storage.get();
    229     SkScalar* pos = (SkScalar*)(colors + countUsed);
    230 
    231     fillStops(m_stops.data(), m_stops.size(), pos, colors);
    232 
    233     SkShader::TileMode tile = SkShader::kClamp_TileMode;
    234     switch (m_spreadMethod) {
    235     case SpreadMethodReflect:
    236         tile = SkShader::kMirror_TileMode;
    237         break;
    238     case SpreadMethodRepeat:
    239         tile = SkShader::kRepeat_TileMode;
    240         break;
    241     case SpreadMethodPad:
    242         tile = SkShader::kClamp_TileMode;
    243         break;
    244     }
    245 
    246     uint32_t shouldDrawInPMColorSpace = m_drawInPMColorSpace ? SkGradientShader::kInterpolateColorsInPremul_Flag : 0;
    247     if (m_radial) {
    248         // Since the two-point radial gradient is slower than the plain radial,
    249         // only use it if we have to.
    250         if (m_p0 == m_p1 && m_r0 <= 0.0f) {
    251             m_gradient = adoptRef(SkGradientShader::CreateRadial(m_p1, m_r1, colors, pos, static_cast<int>(countUsed), tile, 0, shouldDrawInPMColorSpace));
    252         } else {
    253             // The radii we give to Skia must be positive. If we're given a
    254             // negative radius, ask for zero instead.
    255             SkScalar radius0 = m_r0 >= 0.0f ? WebCoreFloatToSkScalar(m_r0) : 0;
    256             SkScalar radius1 = m_r1 >= 0.0f ? WebCoreFloatToSkScalar(m_r1) : 0;
    257             m_gradient = adoptRef(SkGradientShader::CreateTwoPointConical(m_p0, radius0, m_p1, radius1, colors, pos, static_cast<int>(countUsed), tile, 0, shouldDrawInPMColorSpace));
    258         }
    259 
    260         if (aspectRatio() != 1) {
    261             // CSS3 elliptical gradients: apply the elliptical scaling at the
    262             // gradient center point.
    263             m_gradientSpaceTransformation.translate(m_p0.x(), m_p0.y());
    264             m_gradientSpaceTransformation.scale(1, 1 / aspectRatio());
    265             m_gradientSpaceTransformation.translate(-m_p0.x(), -m_p0.y());
    266             ASSERT(m_p0 == m_p1);
    267         }
    268     } else {
    269         SkPoint pts[2] = { m_p0, m_p1 };
    270         m_gradient = adoptRef(SkGradientShader::CreateLinear(pts, colors, pos, static_cast<int>(countUsed), tile, 0, shouldDrawInPMColorSpace));
    271     }
    272 
    273     if (!m_gradient) {
    274         // use last color, since our "geometry" was degenerate (e.g. radius==0)
    275         m_gradient = adoptRef(new SkColorShader(colors[countUsed - 1]));
    276     } else {
    277         m_gradient->setLocalMatrix(affineTransformToSkMatrix(m_gradientSpaceTransformation));
    278     }
    279     return m_gradient.get();
    280 }
    281 
    282 } //namespace
    283