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#include <private/qdrawhelper_p.h>

#include <private/qgl_p.h>

QT_BEGIN_NAMESPACE

static void QGL2GradientCache_free(void *ptr)

{

    delete reinterpret_cast<QGL2GradientCache *>(ptr);

}

Q_GLOBAL_STATIC_WITH_ARGS(QGLContextResource, qt_gradient_caches, (QGL2GradientCache_free))

QGL2GradientCache *QGL2GradientCache::cacheForContext(const QGLContext *context)

{

    QGL2GradientCache *p = reinterpret_cast<QGL2GradientCache *>(qt_gradient_caches()->value(context));

    if (!p) {

        QGLShareContextScope scope(context);

        p = new QGL2GradientCache;

        qt_gradient_caches()->insert(context, p);

    }

    return p;

}

void QGL2GradientCache::cleanCache() {

    QGLGradientColorTableHash::const_iterator it = cache.constBegin();

    for (; it != cache.constEnd(); ++it) {

        const CacheInfo &cache_info = it.value();

        glDeleteTextures(1, &cache_info.texId);

    }

    cache.clear();

}

GLuint QGL2GradientCache::getBuffer(const QGradient &gradient, qreal opacity)

{

    quint64 hash_val = 0;

    QGradientStops stops = gradient.stops();

    for (int i = 0; i < stops.size() && i <= 2; i++)

        hash_val += stops[i].second.rgba();

    QGLGradientColorTableHash::const_iterator it = cache.constFind(hash_val);

    if (it == cache.constEnd())

        return addCacheElement(hash_val, gradient, opacity);

    else {

        do {

            const CacheInfo &cache_info = it.value();

            if (cache_info.stops == stops && cache_info.opacity == opacity && cache_info.interpolationMode == gradient.interpolationMode()) {

                return cache_info.texId;

            }

            ++it;

        } while (it != cache.constEnd() && it.key() == hash_val);

        // an exact match for these stops and opacity was not found, create new cache

        return addCacheElement(hash_val, gradient, opacity);

    }

}

GLuint QGL2GradientCache::addCacheElement(quint64 hash_val, const QGradient &gradient, qreal opacity)

{

    if (cache.size() == maxCacheSize()) {

        int elem_to_remove = qrand() % maxCacheSize();

        quint64 key = cache.keys()[elem_to_remove];

        // need to call glDeleteTextures on each removed cache entry:

        QGLGradientColorTableHash::const_iterator it = cache.constFind(key);

        do {

            glDeleteTextures(1, &it.value().texId);

        } while (++it != cache.constEnd() && it.key() == key);

        cache.remove(key); // may remove more than 1, but OK

    }

    CacheInfo cache_entry(gradient.stops(), opacity, gradient.interpolationMode());

    uint buffer[1024];

    generateGradientColorTable(gradient, buffer, paletteSize(), opacity);

    glGenTextures(1, &cache_entry.texId);

    glBindTexture(GL_TEXTURE_2D, cache_entry.texId);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, paletteSize(), 1,

                    0, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

    return cache.insert(hash_val, cache_entry).value().texId;

}

// GL's expects pixels in RGBA (when using GL_RGBA), bin-endian (ABGR on x86).

// Qt always stores in ARGB reguardless of the byte-order the mancine uses.

static inline uint qtToGlColor(uint c)

{

    uint o;

#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN

    o = (c & 0xff00ff00)  // alpha & green already in the right place

        | ((c >> 16) & 0x000000ff) // red

        | ((c << 16) & 0x00ff0000); // blue

#else //Q_BIG_ENDIAN

    o = (c << 8)

        | ((c >> 24) & 0x000000ff);

#endif // Q_BYTE_ORDER

    return o;

}

//TODO: Let GL generate the texture using an FBO

void QGL2GradientCache::generateGradientColorTable(const QGradient& gradient, uint *colorTable, int size, qreal opacity) const

{

    int pos = 0;

    QGradientStops s = gradient.stops();

    QVector<uint> colors(s.size());

    for (int i = 0; i < s.size(); ++i)

        colors[i] = s[i].second.rgba(); // Qt LIES! It returns ARGB (on little-endian AND on big-endian)

    bool colorInterpolation = (gradient.interpolationMode() == QGradient::ColorInterpolation);

    uint alpha = qRound(opacity * 256);

    uint current_color = ARGB_COMBINE_ALPHA(colors[0], alpha);

    qreal incr = 1.0 / qreal(size);

    qreal fpos = 1.5 * incr;

    colorTable[pos++] = qtToGlColor(PREMUL(current_color));

    while (fpos <= s.first().first) {

        colorTable[pos] = colorTable[pos - 1];

        pos++;

        fpos += incr;

    }

    if (colorInterpolation)

        current_color = PREMUL(current_color);

    for (int i = 0; i < s.size() - 1; ++i) {

        qreal delta = 1/(s[i+1].first - s[i].first);

        uint next_color = ARGB_COMBINE_ALPHA(colors[i+1], alpha);

        if (colorInterpolation)

            next_color = PREMUL(next_color);

        while (fpos < s[i+1].first && pos < size) {

            int dist = int(256 * ((fpos - s[i].first) * delta));

            int idist = 256 - dist;

            if (colorInterpolation)

                colorTable[pos] = qtToGlColor(INTERPOLATE_PIXEL_256(current_color, idist, next_color, dist));

            else

                colorTable[pos] = qtToGlColor(PREMUL(INTERPOLATE_PIXEL_256(current_color, idist, next_color, dist)));

            ++pos;

            fpos += incr;

        }

        current_color = next_color;

    }

    Q_ASSERT(s.size() > 0);

    uint last_color = qtToGlColor(PREMUL(ARGB_COMBINE_ALPHA(colors[s.size() - 1], alpha)));

    for (;pos < size; ++pos)

        colorTable[pos] = last_color;

    // Make sure the last color stop is represented at the end of the table

    colorTable[size-1] = last_color;

}

QT_END_NAMESPACE