/********************************************************************
 KWin - the KDE window manager
 This file is part of the KDE project.

Copyright (C) 2006-2007 Rivo Laks <rivolaks@hot.ee>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*********************************************************************/

#include "kwinglutils.h"

#ifdef KWIN_HAVE_OPENGL

#include "kwinglobals.h"
#include "kwineffects.h"

#include "kdebug.h"
#include <kstandarddirs.h>

#include <QPixmap>
#include <QImage>
#include <QHash>
#include <QFile>


#define DEBUG_GLRENDERTARGET 0

#define MAKE_GL_VERSION(major, minor, release)  ( ((major) << 16) | ((minor) << 8) | (release) )


namespace KWin
{
// Variables
// GL version, use MAKE_GL_VERSION() macro for comparing with a specific version
static int glVersion;
// GLX version, use MAKE_GL_VERSION() macro for comparing with a specific version
static int glXVersion;
// List of all supported GL and GLX extensions
static QStringList glExtensions;
static QStringList glxExtensions;

int glTextureUnitsCount;


// Functions
void initGLX()
    {
    // Get GLX version
    int major, minor;
    glXQueryVersion( display(), &major, &minor );
    glXVersion = MAKE_GL_VERSION( major, minor, 0 );
    // Get list of supported GLX extensions
    glxExtensions = QString((const char*)glXQueryExtensionsString(
        display(), DefaultScreen( display()))).split(' ');

    glxResolveFunctions();
    }

void initGL()
    {
    // Get OpenGL version
    QString glversionstring = QString((const char*)glGetString(GL_VERSION));
    QStringList glversioninfo = glversionstring.left(glversionstring.indexOf(' ')).split('.');
    glVersion = MAKE_GL_VERSION(glversioninfo[0].toInt(), glversioninfo[1].toInt(),
                                    glversioninfo.count() > 2 ? glversioninfo[2].toInt() : 0);
    // Get list of supported OpenGL extensions
    glExtensions = QString((const char*)glGetString(GL_EXTENSIONS)).split(' ');

    // handle OpenGL extensions functions
    glResolveFunctions();

    GLTexture::initStatic();
    GLShader::initStatic();
    GLRenderTarget::initStatic();
    GLVertexBuffer::initStatic();
    }

bool hasGLVersion(int major, int minor, int release)
    {
    return glVersion >= MAKE_GL_VERSION(major, minor, release);
    }

bool hasGLXVersion(int major, int minor, int release)
    {
    return glXVersion >= MAKE_GL_VERSION(major, minor, release);
    }

bool hasGLExtension(const QString& extension)
    {
    return glExtensions.contains(extension) || glxExtensions.contains(extension);
    }

static QString formatGLError( GLenum err )
    {
    switch ( err )
        {
        case GL_NO_ERROR:          return "GL_NO_ERROR";
        case GL_INVALID_ENUM:      return "GL_INVALID_ENUM";
        case GL_INVALID_VALUE:     return "GL_INVALID_VALUE";
        case GL_INVALID_OPERATION: return "GL_INVALID_OPERATION";
        case GL_STACK_OVERFLOW:    return "GL_STACK_OVERFLOW";
        case GL_STACK_UNDERFLOW:   return "GL_STACK_UNDERFLOW";
        case GL_OUT_OF_MEMORY:     return "GL_OUT_OF_MEMORY";
        default: return QString( "0x" ) + QString::number( err, 16 );
        }
    }

bool checkGLError( const char* txt )
    {
    GLenum err = glGetError();
    if( err != GL_NO_ERROR )
        {
        kWarning(1212) << "GL error (" << txt << "): " << formatGLError( err );
        return true;
        }
    return false;
    }

int nearestPowerOfTwo( int x )
    {
    // This method had been copied from Qt's nearest_gl_texture_size()
    int n = 0, last = 0;
    for (int s = 0; s < 32; ++s) {
        if (((x>>s) & 1) == 1) {
            ++n;
            last = s;
        }
    }
    if (n > 1)
        return 1 << (last+1);
    return 1 << last;
    }

void renderGLGeometry( int count, const float* vertices, const float* texture, const float* color,
    int dim, int stride )
    {
    return renderGLGeometry( infiniteRegion(), count, vertices, texture, color, dim, stride );
    }

void renderGLGeometry( const QRegion& region, int count,
    const float* vertices, const float* texture, const float* color,
    int dim, int stride )
    {
    // Using arrays only makes sense if we have larger number of vertices.
    //  Otherwise overhead of enabling/disabling them is too big.
    bool use_arrays = (count > 5);

    if( use_arrays )
        {
        glPushAttrib( GL_ENABLE_BIT );
        glPushClientAttrib( GL_CLIENT_VERTEX_ARRAY_BIT );
        // Enable arrays
        glEnableClientState( GL_VERTEX_ARRAY );
        glVertexPointer( dim, GL_FLOAT, stride, vertices );
        if( texture != NULL )
            {
            glEnableClientState( GL_TEXTURE_COORD_ARRAY );
            glTexCoordPointer( 2, GL_FLOAT, stride, texture );
            }
        if( color != NULL )
            {
            glEnableClientState( GL_COLOR_ARRAY );
            glColorPointer( 4, GL_FLOAT, stride, color );
            }
        }

    // Clip using scissoring
    PaintClipper pc( region );
    for( PaintClipper::Iterator iterator;
         !iterator.isDone();
         iterator.next())
        {
        if( use_arrays )
            glDrawArrays( GL_QUADS, 0, count );
        else
            renderGLGeometryImmediate( count, vertices, texture, color, dim, stride );
        }

    if( use_arrays )
        {
        glPopClientAttrib();
        glPopAttrib();
        }
    }

void renderGLGeometryImmediate( int count, const float* vertices, const float* texture, const float* color,
      int dim, int stride )
{
    // Find out correct glVertex*fv function according to dim parameter.
    void ( *glVertexFunc )( const float* ) = glVertex2fv;
    if( dim == 3 )
        glVertexFunc = glVertex3fv;
    else if( dim == 4 )
        glVertexFunc = glVertex4fv;

    // These are number of _floats_ per item, not _bytes_ per item as opengl uses.
    int vsize, tsize, csize;
    vsize = tsize = csize = stride / sizeof(float);
    if( !stride )
        {
        // 0 means that arrays are tightly packed. This gives us different
        //  strides for different arrays
        vsize = dim;
        tsize = 2;
        csize = 4;
        }

    glBegin( GL_QUADS );
    // This sucks. But makes it faster.
    if( texture && color )
        {
        for( int i = 0; i < count; i++ )
            {
            glTexCoord2fv( texture + i*tsize );
            glColor4fv( color + i*csize );
            glVertexFunc( vertices + i*vsize );
            }
        }
    else if( texture )
        {
        for( int i = 0; i < count; i++ )
            {
            glTexCoord2fv( texture + i*tsize );
            glVertexFunc( vertices + i*vsize );
            }
        }
    else if( color )
        {
        for( int i = 0; i < count; i++ )
            {
            glColor4fv( color + i*csize );
            glVertexFunc( vertices + i*vsize );
            }
        }
    else
        {
        for( int i = 0; i < count; i++ )
            glVertexFunc( vertices + i*vsize );
        }
    glEnd();
}

void addQuadVertices(QVector<float>& verts, float x1, float y1, float x2, float y2)
{
    verts << x1 << y1;
    verts << x1 << y2;
    verts << x2 << y2;
    verts << x2 << y1;
}

//****************************************
// GLTexture
//****************************************

bool GLTexture::mNPOTTextureSupported = false;
bool GLTexture::mFramebufferObjectSupported = false;
bool GLTexture::mSaturationSupported = false;

GLTexture::GLTexture()
    {
    init();
    }

GLTexture::GLTexture( const QImage& image, GLenum target )
    {
    init();
    load( image, target );
    }

GLTexture::GLTexture( const QPixmap& pixmap, GLenum target )
    {
    init();
    load( pixmap, target );
    }

GLTexture::GLTexture( const QString& fileName )
    {
    init();
    load( fileName );
    }

GLTexture::GLTexture( int width, int height )
    {
    init();

    if( NPOTTextureSupported() || ( isPowerOfTwo( width ) && isPowerOfTwo( height )))
        {
        mTarget = GL_TEXTURE_2D;
        mScale.setWidth( 1.0 / width);
        mScale.setHeight( 1.0 / height);
        mSize = QSize( width, height );
        can_use_mipmaps = true;

        glGenTextures( 1, &mTexture );
        bind();
        glTexImage2D( mTarget, 0, GL_RGBA8, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, 0);
        unbind();
        }
    }

GLTexture::~GLTexture()
    {
    delete m_vbo;
    discard();
    assert( mUnnormalizeActive == 0 );
    assert( mNormalizeActive == 0 );
    }

void GLTexture::init()
    {
    mTexture = None;
    mTarget = 0;
    mFilter = 0;
    y_inverted = false;
    can_use_mipmaps = false;
    has_valid_mipmaps = false;
    mUnnormalizeActive = 0;
    mNormalizeActive = 0;
    m_vbo = 0;
    }

void GLTexture::initStatic()
    {
    mNPOTTextureSupported = hasGLExtension( "GL_ARB_texture_non_power_of_two" );
    mFramebufferObjectSupported = hasGLExtension( "GL_EXT_framebuffer_object" );
    mSaturationSupported = ((hasGLExtension("GL_ARB_texture_env_crossbar")
        && hasGLExtension("GL_ARB_texture_env_dot3")) || hasGLVersion(1, 4))
        && (glTextureUnitsCount >= 4) && glActiveTexture != NULL;
    }

bool GLTexture::isNull() const
    {
    return mTexture == None;
    }

QSize GLTexture::size() const
    {
    return mSize;
    }

bool GLTexture::load( const QImage& image, GLenum target )
    {
    if( image.isNull())
        return false;
    QImage img = image;
    mTarget = target;
    if( mTarget != GL_TEXTURE_RECTANGLE_ARB )
        {
        if( !NPOTTextureSupported()
            && ( !isPowerOfTwo( image.width()) || !isPowerOfTwo( image.height())))
            { // non-rectangular target requires POT texture
            img = img.scaled( nearestPowerOfTwo( image.width()),
                    nearestPowerOfTwo( image.height()));
            }
        mScale.setWidth( 1.0 / img.width());
        mScale.setHeight( 1.0 / img.height());
        can_use_mipmaps = true;
        }
    else
        {
        mScale.setWidth( 1.0 );
        mScale.setHeight( 1.0 );
        can_use_mipmaps = false;
        }
    setFilter( GL_LINEAR );
    mSize = img.size();
    y_inverted = false;

    img = convertToGLFormat( img );

    setDirty();
    if( isNull())
        glGenTextures( 1, &mTexture );
    bind();
    glTexImage2D( mTarget, 0, GL_RGBA8, img.width(), img.height(), 0,
        GL_BGRA, GL_UNSIGNED_BYTE, img.bits());
    unbind();
    return true;
    }

bool GLTexture::load( const QPixmap& pixmap, GLenum target )
    {
    if( pixmap.isNull())
        return false;
    return load( pixmap.toImage(), target );
    }

bool GLTexture::load( const QString& fileName )
    {
    if( fileName.isEmpty())
        return false;
    return load( QImage( fileName ));
    }

void GLTexture::discard()
    {
    setDirty();
    if( mTexture != None )
        glDeleteTextures( 1, &mTexture );
    mTexture = None;
    }

void GLTexture::bind()
    {
    glEnable( mTarget );
    glBindTexture( mTarget, mTexture );
    enableFilter();
    }

void GLTexture::unbind()
    {
    glBindTexture( mTarget, 0 );
    glDisable( mTarget );
    }

void GLTexture::render( QRegion region, const QRect& rect )
    {
    if( rect != m_cachedGeometry )
        {
        m_cachedGeometry = rect;
        if( !m_vbo )
            {
            m_vbo = new GLVertexBuffer( KWin::GLVertexBuffer::Static );
            }
        const float verts[ 4 * 2 ] =
            {
            rect.x(), rect.y(),
            rect.x(), rect.y() + rect.height(),
            rect.x() + rect.width(), rect.y(),
            rect.x() + rect.width(), rect.y() + rect.height()
            };
        const float texcoords[ 4 * 2 ] =
            {
            0.0f, y_inverted ? 0.0f : 1.0f, // y needs to be swapped (normalized coords)
            0.0f, y_inverted ? 1.0f : 0.0f,
            1.0f, y_inverted ? 0.0f : 1.0f,
            1.0f, y_inverted ? 1.0f : 0.0f
            };
        m_vbo->setData( 4, 2, verts, texcoords );
        }
    m_vbo->render( region, GL_TRIANGLE_STRIP );
    }

void GLTexture::enableUnnormalizedTexCoords()
    {
    assert( mNormalizeActive == 0 );
    if( mUnnormalizeActive++ != 0 )
        return;
    // update texture matrix to handle GL_TEXTURE_2D and GL_TEXTURE_RECTANGLE
    glMatrixMode( GL_TEXTURE );
    glPushMatrix();
    glLoadIdentity();
    glScalef( mScale.width(), mScale.height(), 1 );
    if( !y_inverted )
        {
        // Modify texture matrix so that we could always use non-opengl
        //  coordinates for textures
        glScalef( 1, -1, 1 );
        glTranslatef( 0, -mSize.height(), 0 );
        }
    glMatrixMode( GL_MODELVIEW );
    }

void GLTexture::disableUnnormalizedTexCoords()
    {
    if( --mUnnormalizeActive != 0 )
        return;
    // Restore texture matrix
    glMatrixMode( GL_TEXTURE );
    glPopMatrix();
    glMatrixMode( GL_MODELVIEW );
    }

void GLTexture::enableNormalizedTexCoords()
    {
    assert( mUnnormalizeActive == 0 );
    if( mNormalizeActive++ != 0 )
        return;
    // update texture matrix to handle GL_TEXTURE_2D and GL_TEXTURE_RECTANGLE
    glMatrixMode( GL_TEXTURE );
    glPushMatrix();
    glLoadIdentity();
    glScalef( mSize.width() * mScale.width(), mSize.height() * mScale.height(), 1 );
    if( y_inverted )
        {
        // Modify texture matrix so that we could always use non-opengl
        //  coordinates for textures
        glScalef( 1, -1, 1 );
        glTranslatef( 0, -1, 0 );
        }
    glMatrixMode( GL_MODELVIEW );
    }

void GLTexture::disableNormalizedTexCoords()
    {
    if( --mNormalizeActive != 0 )
        return;
    // Restore texture matrix
    glMatrixMode( GL_TEXTURE );
    glPopMatrix();
    glMatrixMode( GL_MODELVIEW );
    }

GLuint GLTexture::texture() const
    {
    return mTexture;
    }

GLenum GLTexture::target() const
    {
    return mTarget;
    }

GLenum GLTexture::filter() const
    {
    return mFilter;
    }

bool GLTexture::isDirty() const
    {
    return has_valid_mipmaps;
    }

void GLTexture::setTexture( GLuint texture )
    {
    discard();
    mTexture = texture;
    }

void GLTexture::setTarget( GLenum target )
    {
    mTarget = target;
    }

void GLTexture::setFilter( GLenum filter )
    {
    mFilter = filter;
    }

void GLTexture::setWrapMode( GLenum mode )
    {
    bind();
    glTexParameteri( mTarget, GL_TEXTURE_WRAP_S, mode );
    glTexParameteri( mTarget, GL_TEXTURE_WRAP_T, mode );
    unbind();
    }

void GLTexture::setDirty()
    {
    has_valid_mipmaps = false;
    }


void GLTexture::enableFilter()
    {
    if( mFilter == GL_LINEAR_MIPMAP_LINEAR )
        { // trilinear filtering requested, but is it possible?
        if( NPOTTextureSupported()
            && framebufferObjectSupported()
            && can_use_mipmaps )
            {
            glTexParameteri( mTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR );
            glTexParameteri( mTarget, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
            if( !has_valid_mipmaps )
                {
                glGenerateMipmap( mTarget );
                has_valid_mipmaps = true;
                }
            }
        else
            { // can't use trilinear, so use bilinear
            setFilter( GL_LINEAR );
            glTexParameteri( mTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
            glTexParameteri( mTarget, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
            }
        }
    else if( mFilter == GL_LINEAR )
        {
        glTexParameteri( mTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
        glTexParameteri( mTarget, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
        }
    else
        { // if neither trilinear nor bilinear, default to fast filtering
        setFilter( GL_NEAREST );
        glTexParameteri( mTarget, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
        glTexParameteri( mTarget, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
        }
    }

static void convertToGLFormatHelper(QImage &dst, const QImage &img, GLenum texture_format)
    { // Copied from Qt
    Q_ASSERT(dst.size() == img.size());
    Q_ASSERT(dst.depth() == 32);
    Q_ASSERT(img.depth() == 32);

    const int width = img.width();
    const int height = img.height();
    const uint *p = (const uint*) img.scanLine(img.height() - 1);
    uint *q = (uint*) dst.scanLine(0);

    if (texture_format == GL_BGRA) {
        if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
            // mirror + swizzle
            for (int i=0; i < height; ++i) {
                const uint *end = p + width;
                while (p < end) {
                    *q = ((*p << 24) & 0xff000000)
                         | ((*p >> 24) & 0x000000ff)
                         | ((*p << 8) & 0x00ff0000)
                         | ((*p >> 8) & 0x0000ff00);
                    p++;
                    q++;
                }
                p -= 2 * width;
            }
        } else {
            const uint bytesPerLine = img.bytesPerLine();
            for (int i=0; i < height; ++i) {
                memcpy(q, p, bytesPerLine);
                q += width;
                p -= width;
            }
        }
    } else {
        if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
            for (int i=0; i < height; ++i) {
                const uint *end = p + width;
                while (p < end) {
                    *q = (*p << 8) | ((*p >> 24) & 0xFF);
                    p++;
                    q++;
                }
                p -= 2 * width;
            }
        } else {
            for (int i=0; i < height; ++i) {
                const uint *end = p + width;
                while (p < end) {
                    *q = ((*p << 16) & 0xff0000) | ((*p >> 16) & 0xff) | (*p & 0xff00ff00);
                    p++;
                    q++;
                }
                p -= 2 * width;
            }
        }
    }
}

QImage GLTexture::convertToGLFormat( const QImage& img ) const
    { // Copied from Qt's QGLWidget::convertToGLFormat()
    QImage res(img.size(), QImage::Format_ARGB32);
    convertToGLFormatHelper(res, img.convertToFormat(QImage::Format_ARGB32), GL_BGRA);
    return res;
    }

//****************************************
// GLShader
//****************************************

bool GLShader::mFragmentShaderSupported = false;
bool GLShader::mVertexShaderSupported = false;

void GLShader::initStatic()
{
    mFragmentShaderSupported = mVertexShaderSupported =
            hasGLExtension("GL_ARB_shader_objects") && hasGLExtension("GL_ARB_shading_language_100");
    mVertexShaderSupported &= hasGLExtension("GL_ARB_vertex_shader");
    mFragmentShaderSupported &= hasGLExtension("GL_ARB_fragment_shader");
}


GLShader::GLShader(const QString& vertexfile, const QString& fragmentfile)
    {
    mValid = false;
    mProgram = 0;
    mTextureWidth = -1.0f;
    mTextureHeight = -1.0f;

    loadFromFiles(vertexfile, fragmentfile);
    }

GLShader::~GLShader()
{
    if(mProgram)
    {
        glDeleteProgram(mProgram);
    }
}

bool GLShader::loadFromFiles(const QString& vertexfile, const QString& fragmentfile)
    {
    QFile vf(vertexfile);
    if(!vf.open(QIODevice::ReadOnly))
        {
        kError(1212) << "Couldn't open '" << vertexfile << "' for reading!" << endl;
        return false;
        }
    QString vertexsource(vf.readAll());

    QFile ff(fragmentfile);
    if(!ff.open(QIODevice::ReadOnly))
        {
        kError(1212) << "Couldn't open '" << fragmentfile << "' for reading!" << endl;
        return false;
        }
    QString fragsource(ff.readAll());

    return load(vertexsource, fragsource);
    }

bool GLShader::load(const QString& vertexsource, const QString& fragmentsource)
    {
    // Make sure shaders are actually supported
    if(( !vertexsource.isEmpty() && !vertexShaderSupported() ) ||
          ( !fragmentsource.isEmpty() && !fragmentShaderSupported() ))
        {
        kDebug(1212) << "Shaders not supported";
        return false;
        }

    GLuint vertexshader;
    GLuint fragmentshader;

    GLsizei logsize, logarraysize;
    char* log = 0;

    // Create program object
    mProgram = glCreateProgram();
    if(!vertexsource.isEmpty())
        {
        // Create shader object
        vertexshader = glCreateShader(GL_VERTEX_SHADER);
        // Load it
        const QByteArray& srcba = vertexsource.toLatin1();
        const char* src = srcba.data();
        glShaderSource(vertexshader, 1, &src, NULL);
        // Compile the shader
        glCompileShader(vertexshader);
        // Make sure it compiled correctly
        int compiled;
        glGetShaderiv(vertexshader, GL_COMPILE_STATUS, &compiled);
        // Get info log
        glGetShaderiv(vertexshader, GL_INFO_LOG_LENGTH, &logarraysize);
        log = new char[logarraysize];
        glGetShaderInfoLog(vertexshader, logarraysize, &logsize, log);
        if(!compiled)
            {
            kError(1212) << "Couldn't compile vertex shader! Log:" << endl << log << endl;
            delete[] log;
            return false;
            }
        else if(logsize > 0)
            kDebug(1212) << "Vertex shader compilation log:"<< log;
        // Attach the shader to the program
        glAttachShader(mProgram, vertexshader);
        // Delete shader
        glDeleteShader(vertexshader);
        delete[] log;
        }


    if(!fragmentsource.isEmpty())
        {
        fragmentshader = glCreateShader(GL_FRAGMENT_SHADER);
        // Load it
        const QByteArray& srcba = fragmentsource.toLatin1();
        const char* src = srcba.data();
        glShaderSource(fragmentshader, 1, &src, NULL);
        //glShaderSource(fragmentshader, 1, &fragmentsrc.latin1(), NULL);
        // Compile the shader
        glCompileShader(fragmentshader);
        // Make sure it compiled correctly
        int compiled;
        glGetShaderiv(fragmentshader, GL_COMPILE_STATUS, &compiled);
        // Get info log
        glGetShaderiv(fragmentshader, GL_INFO_LOG_LENGTH, &logarraysize);
        log = new char[logarraysize];
        glGetShaderInfoLog(fragmentshader, logarraysize, &logsize, log);
        if(!compiled)
            {
            kError(1212) << "Couldn't compile fragment shader! Log:" << endl << log << endl;
            delete[] log;
            return false;
            }
        else if(logsize > 0)
            kDebug(1212) << "Fragment shader compilation log:"<< log;
        // Attach the shader to the program
        glAttachShader(mProgram, fragmentshader);
        // Delete shader
        glDeleteShader(fragmentshader);
        delete[] log;
        }


    // Link the program
    glLinkProgram(mProgram);
    // Make sure it linked correctly
    int linked;
    glGetProgramiv(mProgram, GL_LINK_STATUS, &linked);
    // Get info log
    glGetProgramiv(mProgram, GL_INFO_LOG_LENGTH, &logarraysize);
    log = new char[logarraysize];
    glGetProgramInfoLog(mProgram, logarraysize, &logsize, log);
    if(!linked)
        {
        kError(1212) << "Couldn't link the program! Log" << endl << log << endl;
        delete[] log;
        return false;
        }
    else if(logsize > 0)
        kDebug(1212) << "Shader linking log:"<< log;
    delete[] log;

    mValid = true;
    return true;
    }

void GLShader::bind()
    {
    glUseProgram(mProgram);
    }

void GLShader::unbind()
    {
    glUseProgram(0);
    }

int GLShader::uniformLocation(const char* name)
    {
    int location = glGetUniformLocation(mProgram, name);
    return location;
    }

bool GLShader::setUniform(const char* name, float value)
    {
    int location = uniformLocation(name);
    if(location >= 0)
        {
        glUniform1f(location, value);
        }
    return (location >= 0);
    }

bool GLShader::setUniform(const char* name, int value)
    {
    int location = uniformLocation(name);
    if(location >= 0)
        {
        glUniform1i(location, value);
        }
    return (location >= 0);
    }

int GLShader::attributeLocation(const char* name)
    {
    int location = glGetAttribLocation(mProgram, name);
    return location;
    }

bool GLShader::setAttribute(const char* name, float value)
    {
    int location = attributeLocation(name);
    if(location >= 0)
        {
        glVertexAttrib1f(location, value);
        }
    return (location >= 0);
    }

void GLShader::setTextureHeight(float height)
    {
    mTextureHeight = height;
    }

void GLShader::setTextureWidth(float width)
    {
    mTextureWidth = width;
    }

float GLShader::textureHeight()
    {
    return mTextureHeight;
    }

float GLShader::textureWidth()
    {
    return mTextureWidth;
    }


/***  GLRenderTarget  ***/
bool GLRenderTarget::mSupported = false;

void GLRenderTarget::initStatic()
    {
    mSupported = hasGLExtension("GL_EXT_framebuffer_object") && glFramebufferTexture2D;
    }

GLRenderTarget::GLRenderTarget(GLTexture* color)
    {
    // Reset variables
    mValid = false;

    mTexture = color;

    // Make sure FBO is supported
    if(mSupported && mTexture && !mTexture->isNull())
        {
        initFBO();
        }
    else
        kError(1212) << "Render targets aren't supported!" << endl;
    }

GLRenderTarget::~GLRenderTarget()
    {
    if(mValid)
        {
        glDeleteFramebuffers(1, &mFramebuffer);
        }
    }

bool GLRenderTarget::enable()
    {
    if(!valid())
        {
        kError(1212) << "Can't enable invalid render target!" << endl;
        return false;
        }

    glBindFramebuffer(GL_FRAMEBUFFER_EXT, mFramebuffer);
    mTexture->setDirty();

    return true;
    }

bool GLRenderTarget::disable()
    {
    if(!valid())
        {
        kError(1212) << "Can't disable invalid render target!" << endl;
        return false;
        }

    glBindFramebuffer(GL_FRAMEBUFFER_EXT, 0);
    mTexture->setDirty();

    return true;
    }

static QString formatFramebufferStatus( GLenum status )
    {
    switch( status )
        {
        case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:
            // An attachment is the wrong type / is invalid / has 0 width or height
            return "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT";
        case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:
            // There are no images attached to the framebuffer
            return "GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT";
        case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:
            // Not all attached images have the same width and height
            return "GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT";
        case GL_FRAMEBUFFER_UNSUPPORTED_EXT:
            // A format or the combination of formats of the attachments is unsupported
            return "GL_FRAMEBUFFER_UNSUPPORTED";
        case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:
            // The color attachments don't have the same format
            return "GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT";
        case GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE_EXT:
            // The attachments don't have the same number of samples
            return "GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE";
        case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:
            // The draw buffer is missing
            return "GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER";
        case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:
            // The read buffer is missing
            return "GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER";
        default:
            return "Unknown (0x" + QString::number(status, 16) + ')';
        }
    }

void GLRenderTarget::initFBO()
    {
#if DEBUG_GLRENDERTARGET
    GLenum err = glGetError();
    if( err != GL_NO_ERROR )
        kError(1212) << "Error status when entering GLRenderTarget::initFBO: " << formatGLError( err );
#endif

    glGenFramebuffers(1, &mFramebuffer);

#if DEBUG_GLRENDERTARGET
    if( (err = glGetError()) != GL_NO_ERROR )
        {
        kError(1212) << "glGenFramebuffers failed: " << formatGLError( err );
        return;
        }
#endif

    glBindFramebuffer(GL_FRAMEBUFFER_EXT, mFramebuffer);

#if DEBUG_GLRENDERTARGET
    if( (err = glGetError()) != GL_NO_ERROR )
        {
        kError(1212) << "glBindFramebuffer failed: " << formatGLError( err );
        glDeleteFramebuffers(1, &mFramebuffer);
        return;
        }
#endif

    glFramebufferTexture2D(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
                           mTexture->target(), mTexture->texture(), 0);

#if DEBUG_GLRENDERTARGET
    if( (err = glGetError()) != GL_NO_ERROR )
        {
        kError(1212) << "glFramebufferTexture2D failed: " << formatGLError( err );
        glBindFramebuffer(GL_FRAMEBUFFER_EXT, 0);
        glDeleteFramebuffers(1, &mFramebuffer);
        return;
        }
#endif

    const GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER_EXT);

    glBindFramebuffer(GL_FRAMEBUFFER_EXT, 0);

    if( status != GL_FRAMEBUFFER_COMPLETE_EXT )
        { // We have an incomplete framebuffer, consider it invalid
        if (status == 0)
            kError(1212) << "glCheckFramebufferStatus failed: " << formatGLError( glGetError() );
        else
            kError(1212) << "Invalid framebuffer status: " << formatFramebufferStatus( status );
        glDeleteFramebuffers(1, &mFramebuffer);
        return;
        }

    mValid = true;
    }


//*********************************
// GLVertexBufferPrivate
//*********************************
class GLVertexBufferPrivate
    {
    public:
        GLVertexBufferPrivate( GLVertexBuffer::UsageHint usageHint )
            : hint( usageHint )
            , numberVertices( 0 )
            , dimension( 2 )
            {
            if( GLVertexBufferPrivate::supported )
                {
                glGenBuffers( 2, buffers );
                }
            }
        ~GLVertexBufferPrivate()
            {
            if( GLVertexBufferPrivate::supported )
                {
                glDeleteBuffers( 2, buffers );
                }
            }
        GLVertexBuffer::UsageHint hint;
        GLuint buffers[2];
        int numberVertices;
        int dimension;
        static bool supported;
        QVector<float> legacyVertices;
        QVector<float> legacyTexCoords;

        void legacyPainting( QRegion region, GLenum primitiveMode );
    };
bool GLVertexBufferPrivate::supported = false;

void GLVertexBufferPrivate::legacyPainting( QRegion region, GLenum primitiveMode )
    {
    // Enable arrays
    glEnableClientState( GL_VERTEX_ARRAY );
    glVertexPointer( dimension, GL_FLOAT, 0, legacyVertices.constData() );
    glEnableClientState( GL_TEXTURE_COORD_ARRAY );
    glTexCoordPointer( 2, GL_FLOAT, 0, legacyTexCoords.constData() );

    // Clip using scissoring
    PaintClipper pc( region );
    for( PaintClipper::Iterator iterator;
        !iterator.isDone();
        iterator.next())
        {
        glDrawArrays( primitiveMode, 0, numberVertices );
        }

    glDisableClientState( GL_VERTEX_ARRAY );
    glDisableClientState( GL_TEXTURE_COORD_ARRAY );
    }

//*********************************
// GLVertexBuffer
//*********************************
GLVertexBuffer::GLVertexBuffer( UsageHint hint )
    : d( new GLVertexBufferPrivate( hint ) )
    {
    }

GLVertexBuffer::~GLVertexBuffer()
    {
    delete d;
    }

void GLVertexBuffer::setData( int numberVertices, int dim, const float* vertices, const float* texcoords )
    {
    d->numberVertices = numberVertices;
    d->dimension = dim;
    if( !GLVertexBufferPrivate::supported )
        {
        // legacy data
        d->legacyVertices.clear();
        d->legacyVertices.reserve( numberVertices * dim );
        for( int i=0; i<numberVertices*dim; ++i)
            {
            d->legacyVertices << vertices[i];
            }
        d->legacyTexCoords.clear();
        d->legacyTexCoords.reserve( numberVertices * 2 );
        for( int i=0; i<numberVertices*2; ++i)
            {
            d->legacyTexCoords << texcoords[i];
            }
        return;
        }
    GLenum hint;
    switch( d->hint )
        {
        case Dynamic:
            hint = GL_DYNAMIC_DRAW;
            break;
        case Static:
            hint = GL_STATIC_DRAW;
            break;
        case Stream:
            hint = GL_STREAM_DRAW;
            break;
        default:
            // just to make the compiler happy
            hint = GL_STREAM_DRAW;
            break;
        }
    glEnableClientState( GL_VERTEX_ARRAY );
    glEnableClientState( GL_TEXTURE_COORD_ARRAY );
    glBindBuffer( GL_ARRAY_BUFFER, d->buffers[ 0 ] );
    glBufferData( GL_ARRAY_BUFFER, sizeof(GLfloat)*numberVertices*d->dimension, vertices, hint );

    glBindBuffer( GL_ARRAY_BUFFER, d->buffers[ 1 ] );
    glBufferData( GL_ARRAY_BUFFER, sizeof(GLfloat)*numberVertices*2, texcoords, hint );

    glBindBuffer( GL_ARRAY_BUFFER, 0 );

    glDisableClientState( GL_VERTEX_ARRAY );
    glDisableClientState( GL_TEXTURE_COORD_ARRAY );
    }

void GLVertexBuffer::render( GLenum primitiveMode )
    {
    render( infiniteRegion(), primitiveMode );
    }

void GLVertexBuffer::render( const QRegion& region, GLenum primitiveMode )
    {
    if( !GLVertexBufferPrivate::supported )
        {
        d->legacyPainting( region, primitiveMode );
        return;
        }
    glEnableClientState( GL_VERTEX_ARRAY );
    glEnableClientState( GL_TEXTURE_COORD_ARRAY );
    glBindBuffer( GL_ARRAY_BUFFER, d->buffers[ 0 ] );
    glVertexPointer( d->dimension, GL_FLOAT, 0, 0 );

    glBindBuffer( GL_ARRAY_BUFFER, d->buffers[ 1 ] );
    glTexCoordPointer( 2, GL_FLOAT, 0, 0 );

    // Clip using scissoring
    PaintClipper pc( region );
    for( PaintClipper::Iterator iterator;
        !iterator.isDone();
        iterator.next())
        {
        glDrawArrays( primitiveMode, 0, d->numberVertices );
        }

    glBindBuffer( GL_ARRAY_BUFFER, 0 );

    glDisableClientState( GL_VERTEX_ARRAY );
    glDisableClientState( GL_TEXTURE_COORD_ARRAY );
    }


bool GLVertexBuffer::isSupported()
    {
    return GLVertexBufferPrivate::supported;
    }

void GLVertexBuffer::initStatic()
    {
    GLVertexBufferPrivate::supported = hasGLExtension( "GL_ARB_vertex_buffer_object" );
    }


} // namespace

#endif