WebCore/html/CanvasGradient.cpp

/*
 * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
 * Copyright (C) 2007 Alp Toker <alp@atoker.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#include "config.h"
#include "CanvasGradient.h"

#include "CSSParser.h"

#if PLATFORM(CG)
#include <ApplicationServices/ApplicationServices.h>
#elif PLATFORM(QT)
#include <QGradient>
#elif PLATFORM(CAIRO)
#include <cairo.h>
#endif

namespace WebCore {

CanvasGradient::CanvasGradient(const FloatPoint& p0, const FloatPoint& p1)
    : m_radial(false), m_p0(p0), m_p1(p1), m_stopsSorted(false), m_lastStop(0)
#if PLATFORM(CG)
    , m_shading(0)
#elif PLATFORM(QT)
    , m_shading(0)
#elif PLATFORM(CAIRO)
    , m_shading(0)
#endif
{
}

CanvasGradient::CanvasGradient(const FloatPoint& p0, float r0, const FloatPoint& p1, float r1)
    : m_radial(true), m_p0(p0), m_p1(p1), m_r0(r0), m_r1(r1), m_stopsSorted(false), m_lastStop(0)
#if PLATFORM(CG)
    , m_shading(0)
#elif PLATFORM(QT)
    , m_shading(0)
#elif PLATFORM(CAIRO)
    , m_shading(0)
#endif
{
}

CanvasGradient::~CanvasGradient()
{
#if PLATFORM(CG)
    CGShadingRelease(m_shading);
#elif PLATFORM(QT)
    delete m_shading;
#elif PLATFORM(CAIRO)
    cairo_pattern_destroy(m_shading);
#endif
}

void CanvasGradient::addColorStop(float value, const String& color)
{
    RGBA32 rgba = 0; // default is transparant black
    CSSParser::parseColor(rgba, color);
    m_stops.append(ColorStop(value,
        ((rgba >> 16) & 0xFF) / 255.0f,
        ((rgba >> 8) & 0xFF) / 255.0f,
        (rgba & 0xFF) / 255.0f,
        ((rgba >> 24) & 0xFF) / 255.0f));

    m_stopsSorted = false;

#if PLATFORM(CG)
    CGShadingRelease(m_shading);
    m_shading = 0;
#elif PLATFORM(QT)
    delete m_shading;
    m_shading = 0;
#elif PLATFORM(CAIRO)
    cairo_pattern_destroy(m_shading);
    m_shading = 0;
#endif
}

#if PLATFORM(CG)

static void gradientCallback(void* info, const CGFloat* in, CGFloat* out)
{
    float r, g, b, a;
    static_cast<CanvasGradient*>(info)->getColor(*in, &r, &g, &b, &a);
    out[0] = r;
    out[1] = g;
    out[2] = b;
    out[3] = a;
}

CGShadingRef CanvasGradient::platformShading()
{
    if (m_shading)
        return m_shading;

    const CGFloat intervalRanges[2] = { 0, 1 };
    const CGFloat colorComponentRanges[4 * 2] = { 0, 1, 0, 1, 0, 1, 0, 1 };
    const CGFunctionCallbacks gradientCallbacks = { 0, gradientCallback, 0 };
    CGFunctionRef colorFunction = CGFunctionCreate(this, 1, intervalRanges, 4, colorComponentRanges, &gradientCallbacks);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    if (m_radial)
        m_shading = CGShadingCreateRadial(colorSpace, m_p0, m_r0, m_p1, m_r1, colorFunction, true, true);
    else
        m_shading = CGShadingCreateAxial(colorSpace, m_p0, m_p1, colorFunction, true, true);

    CGColorSpaceRelease(colorSpace);
    CGFunctionRelease(colorFunction);

    return m_shading;
}

#elif PLATFORM(QT)

QGradient* CanvasGradient::platformShading()
{
    if (m_shading)
        return m_shading;

    if (m_radial)
        m_shading = new QRadialGradient(m_p0.x(), m_p0.y(), m_r0, m_p1.x(), m_p1.y());
    else m_shading = new QLinearGradient(m_p0.x(), m_p0.y(), m_p1.x(), m_p1.y());

    QColor stopColor;
    Vector<ColorStop>::iterator stopIterator = m_stops.begin();;
    while (stopIterator != m_stops.end()) {
        stopColor.setRgbF(stopIterator->red, stopIterator->green, stopIterator->blue, stopIterator->alpha);
        m_shading->setColorAt(stopIterator->stop, stopColor);
        ++stopIterator;
    }

    return m_shading;
}

#elif PLATFORM(CAIRO)

cairo_pattern_t* CanvasGradient::platformShading()
{
    if (m_shading)
        return m_shading;

    if (m_radial)
        m_shading = cairo_pattern_create_radial(m_p0.x(), m_p0.y(), m_r0, m_p1.x(), m_p1.y(), m_r1);
    else
        m_shading = cairo_pattern_create_linear(m_p0.x(), m_p0.y(), m_p1.x(), m_p1.y());

    Vector<ColorStop>::iterator stopIterator = m_stops.begin();
    while (stopIterator != m_stops.end()) {
        cairo_pattern_add_color_stop_rgba(m_shading, stopIterator->stop, stopIterator->red, stopIterator->green, stopIterator->blue, stopIterator->alpha);
        ++stopIterator;
    }

    return m_shading;
}

#endif

static inline bool compareStops(const CanvasGradient::ColorStop &a, const CanvasGradient::ColorStop &b)
{
    return a.stop < b.stop;
}

void CanvasGradient::getColor(float value, float* r, float* g, float* b, float* a)
{
    ASSERT(value >= 0);
    ASSERT(value <= 1);

    if (m_stops.isEmpty()) {
        *r = 0;
        *g = 0;
        *b = 0;
        *a = 0;
        return;
    }
    if (!m_stopsSorted) {
        if (m_stops.size())
            std::stable_sort(m_stops.begin(), m_stops.end(), compareStops);
        m_stopsSorted = true;
    }
    if (value <= 0 || value <= m_stops.first().stop) {
        *r = m_stops.first().red;
        *g = m_stops.first().green;
        *b = m_stops.first().blue;
        *a = m_stops.first().alpha;
        return;
    }
    if (value >= 1 || value >= m_stops.last().stop) {
        *r = m_stops.last().red;
        *g = m_stops.last().green;
        *b = m_stops.last().blue;
        *a = m_stops.last().alpha;
        return;
    }

    // Find stop before and stop after and interpolate.
    int stop = findStop(value);
    const ColorStop& lastStop = m_stops[stop];    
    const ColorStop& nextStop = m_stops[stop + 1];
    float stopFraction = (value - lastStop.stop) / (nextStop.stop - lastStop.stop);
    *r = lastStop.red + (nextStop.red - lastStop.red) * stopFraction;
    *g = lastStop.green + (nextStop.green - lastStop.green) * stopFraction;
    *b = lastStop.blue + (nextStop.blue - lastStop.blue) * stopFraction;
    *a = lastStop.alpha + (nextStop.alpha - lastStop.alpha) * stopFraction;
}

int CanvasGradient::findStop(float value) const
{
    ASSERT(value >= 0);
    ASSERT(value <= 1);
    ASSERT(m_stopsSorted);

    int numStops = m_stops.size();
    ASSERT(numStops >= 2);
    ASSERT(m_lastStop < numStops - 1);

    int i = m_lastStop;
    if (value < m_stops[i].stop)
        i = 1;
    else
        i = m_lastStop + 1;

    for (; i < numStops - 1; ++i)
        if (value < m_stops[i].stop)
            break;

    m_lastStop = i - 1;
    return m_lastStop;
}

} //namespace