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#include "gltexture.h"
#include <QImage>


QT_BEGIN_NAMESPACE
/*!
    \class GLTexture
    \brief The GLTexture class simplifies the use of OpenGL textures.
*/

// Copied from QGLWidget::convertToGLFormat
static QImage QGLWidget_convertToGLFormat(const QImage& img)
{
    QImage res = img.convertToFormat(QImage::Format_ARGB32);
    res = res.mirrored();

    if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
        // Qt has ARGB; OpenGL wants RGBA
        for (int i=0; i < res.height(); i++) {
            uint *p = (uint*)res.scanLine(i);
            uint *end = p + res.width();
            while (p < end) {
                *p = (*p << 8) | ((*p >> 24) & 0xFF);
                p++;
            }
        }
    }
    else {
        // Qt has ARGB; OpenGL wants ABGR (i.e. RGBA backwards)
        res = res.rgbSwapped();
    }
    return res;
}
class GLTexturePrivate
{
public:
    GLTexturePrivate(GLTexture *_q)
        : q(_q), texture(0), width(0), height(0), 
           horizWrap(GLTexture::Repeat), vertWrap(GLTexture::Repeat),
           minFilter(GLTexture::Linear), magFilter(GLTexture::Linear)
    {
    }

    GLTexture *q;
    GLuint texture;
    int width;
    int height;
    GLTexture::WrapMode horizWrap;
    GLTexture::WrapMode vertWrap;
    GLTexture::FilterMode minFilter;
    GLTexture::FilterMode magFilter;

    void genTexture();
};

void GLTexturePrivate::genTexture()
{
    if (texture)
        return;

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minFilter);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magFilter);
    q->setHorizontalWrap(horizWrap);
    q->setVerticalWrap(vertWrap);
}

GLTexture::GLTexture()
: d(new GLTexturePrivate(this))
{
}

GLTexture::GLTexture(const QString &file)
: d(new GLTexturePrivate(this))
{
    QImage img(file);
    if (!img.isNull())
        setImage(img);
}

GLTexture::GLTexture(const QImage &img)
: d(new GLTexturePrivate(this))
{
    setImage(img);
}

GLTexture::~GLTexture()
{
    if (d->texture)
        glDeleteTextures(1, &d->texture);
    delete d;
    d = 0;
}

bool GLTexture::isNull() const
{
    return d->texture == 0;
}

void GLTexture::clear()
{
    if (d->texture) {
        glDeleteTextures(1, &d->texture);
        d->texture = 0;
        d->width = 0;
        d->height = 0;
    }
}

static inline int npot(int size)
{    
    size--;
    size |= size >> 1;
    size |= size >> 2;
    size |= size >> 4;
    size |= size >> 8;
    size |= size >> 16;
    size++;
    return size;
}

/*!
    Set the texture to \a img.  If the texture has already been created (either
    by explicitly setting the size, or by previously setting an image), it will
    be destroyed and a new texture created with \a img's contents and size.
 */
void GLTexture::setImage(const QImage &img)
{
    if (img.isNull())
        return;

    d->genTexture();

    //QImage dataImage = img.scaled(npot(img.width()), npot(img.height()), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
    QImage dataImage = QGLWidget_convertToGLFormat(img);

    glBindTexture(GL_TEXTURE_2D, d->texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, dataImage.width(), 
                 dataImage.height(), 0, 
                 (dataImage.format() == QImage::Format_ARGB32)?GL_RGBA:GL_RGB, 
                 GL_UNSIGNED_BYTE, dataImage.bits());
    d->width = dataImage.width();
    d->height = dataImage.height();

#if 0
    glGenerateMipmap(GL_TEXTURE_2D);
    int e = glGetError();
    if (d->magFilter == Linear)
        setMagFilter(MipmapLinear);
    if (d->minFilter == Linear)
        setMinFilter((GLTexture::FilterMode)GL_LINEAR_MIPMAP_LINEAR);
#endif
}

void GLTexture::copyImage(const QImage &img, const QPoint &point, 
                          const QRect &srcRect)
{
    qFatal("Not implemented");
    Q_UNUSED(img);
    Q_UNUSED(point);
    Q_UNUSED(srcRect);
}

QSize GLTexture::size() const
{
    return QSize(d->width, d->height);
}

int GLTexture::width() const
{
    return d->width;
}

int GLTexture::height() const
{
    return d->height;
}

/*!
    Sets the \a size of the texture.  This will destroy the current contents of
    the texture.  If an image has been assigned, it will need to be reassigned
    using either setImage() or copyImage().

    If size is invalid (width or height is less than or equal to 0) the texture
    will be destroyed.  This is equivalent to calling clear().
*/
void GLTexture::setSize(const QSize &size)
{
    if (size.width() <= 0 || size.height() <= 0) {
        clear();
        return;
    }

    d->genTexture();
    glBindTexture(GL_TEXTURE_2D, d->texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, size.width(), size.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
    d->width = size.width();
    d->height = size.height();
}

GLTexture::WrapMode GLTexture::horizontalWrap() const
{
    return d->horizWrap;
}

GLTexture::WrapMode GLTexture::verticalWrap() const
{
    return d->vertWrap;
}

void GLTexture::setHorizontalWrap(WrapMode mode)
{
    d->horizWrap = mode; 
    if (d->texture) {
        GLint last;
        glGetIntegerv(GL_TEXTURE_BINDING_2D, &last);
        if (GLuint(last) != d->texture)
            glBindTexture(GL_TEXTURE_2D, d->texture);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, mode);
        if (GLuint(last) != d->texture)
            glBindTexture(GL_TEXTURE_2D, last);
    }
}

/*!
    Set the veritcal wrap mode to \a mode.
 */
void GLTexture::setVerticalWrap(WrapMode mode)
{
    d->vertWrap = mode; 
    if (d->texture) {
        GLint last;
        glGetIntegerv(GL_TEXTURE_BINDING_2D, &last);
        if (GLuint(last) != d->texture)
            glBindTexture(GL_TEXTURE_2D, d->texture);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, mode);
        if (GLuint(last) != d->texture)
            glBindTexture(GL_TEXTURE_2D, last);
    }
}

GLTexture::FilterMode GLTexture::minFilter() const
{
    return d->minFilter;
}

GLTexture::FilterMode GLTexture::magFilter() const
{
    return d->magFilter;
}

void GLTexture::setMinFilter(FilterMode f)
{
    if (d->minFilter == f)
       return;
    d->minFilter = f;
    if (d->texture) {
        glBindTexture(GL_TEXTURE_2D, d->texture);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, d->minFilter);
    }
}

void GLTexture::setMagFilter(FilterMode f)
{
    if (d->magFilter == f)
       return;
    d->magFilter = f;
    if (d->texture) {
        glBindTexture(GL_TEXTURE_2D, d->texture);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, d->magFilter);
    }
}

GLuint GLTexture::texture() const
{
    return d->texture;
}

QT_END_NAMESPACE