/****************************************************************************
**
** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
**
** This file is part of the QtOpenGL module of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://www.trolltech.com/products/qt/licensing.html or contact the
** sales department at sales@trolltech.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

#include "qglframebufferobject.h"

#include <qdebug.h>
#include <private/qgl_p.h>
#include <private/qpaintengine_opengl_p.h>
#include <qglframebufferobject.h>
#include <qlibrary.h>
#include <qimage.h>

// #define DEPTH_BUFFER
#define QGL_FUNC_CONTEXT QGLContext *ctx = d_ptr->ctx;

#define QT_CHECK_GLERROR()                                \
{                                                         \
    GLenum err = glGetError();                            \
    if (err != GL_NO_ERROR) {                             \
        qDebug("[%s line %d] GL Error: %d",               \
               __FILE__, __LINE__, (int)err);             \
    }                                                     \
}

class QGLFramebufferObjectPrivate
{
public:
    QGLFramebufferObjectPrivate() : depth_stencil_buffer(0), valid(false), ctx(0) {}
    ~QGLFramebufferObjectPrivate() {}

    void init(const QSize& sz, QGLFramebufferObject::Attachments attachments,
              GLenum internal_format, GLenum texture_target);
    bool checkFramebufferStatus() const;
    GLuint texture;
    GLuint fbo;
    GLuint depth_stencil_buffer;
    GLenum target;
    QSize size;
    uint valid : 1;
    QGLFramebufferObject::Attachments fbo_attachments;
    QGLContext *ctx; // for Windows extension ptrs
};

bool QGLFramebufferObjectPrivate::checkFramebufferStatus() const
{
    GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
    switch(status) {
    case GL_NO_ERROR:
    case GL_FRAMEBUFFER_COMPLETE_EXT:
        return true;
        break;
    case GL_FRAMEBUFFER_UNSUPPORTED_EXT:
        qDebug("QGLFramebufferObject: Unsupported framebuffer format.");
        break;
    case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:
        qDebug("QGLFramebufferObject: Framebuffer incomplete attachment.");
        break;
    case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:
        qDebug("QGLFramebufferObject: Framebuffer incomplete, missing attachment.");
        break;
#ifdef GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT
    case GL_FRAMEBUFFER_INCOMPLETE_DUPLICATE_ATTACHMENT_EXT:
        qDebug("QGLFramebufferObject: Framebuffer incomplete, duplicate attachment.");
        break;
#endif
    case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:
        qDebug("QGLFramebufferObject: Framebuffer incomplete, attached images must have same dimensions.");
        break;
    case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:
        qDebug("QGLFramebufferObject: Framebuffer incomplete, attached images must have same format.");
        break;
    case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:
        qDebug("QGLFramebufferObject: Framebuffer incomplete, missing draw buffer.");
        break;
    case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:
        qDebug("QGLFramebufferObject: Framebuffer incomplete, missing read buffer.");
        break;
    default:
        qDebug() <<"QGLFramebufferObject: An undefined error has occurred: "<< status;
        break;
    }
    return false;
}

void QGLFramebufferObjectPrivate::init(const QSize &sz, QGLFramebufferObject::Attachments attachments,
                                       GLenum texture_target, GLenum internal_format)
{
    ctx = const_cast<QGLContext *>(QGLContext::currentContext());
    bool ext_detected = (QGLExtensions::glExtensions & QGLExtensions::FramebufferObject);
    if (!ext_detected || (ext_detected && !qt_resolve_framebufferobject_extensions(ctx)))
        return;

    size = sz;
    target = texture_target;
    // texture dimensions

    while (glGetError() != GL_NO_ERROR) {} // reset error state
    glGenFramebuffersEXT(1, &fbo);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);

    QT_CHECK_GLERROR();
    // init texture
    glGenTextures(1, &texture);
    glBindTexture(target, texture);
    glTexImage2D(target, 0, internal_format, size.width(), size.height(), 0,
                 GL_RGBA, GL_UNSIGNED_BYTE, NULL);

    glTexParameteri(target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(target, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
                              target, texture, 0);

    QT_CHECK_GLERROR();
    valid = checkFramebufferStatus();

    if (attachments == QGLFramebufferObject::DepthStencil
        && QGLExtensions::glExtensions & QGLExtensions::PackedDepthStencil) {
        // depth and stencil buffer needs another extension
        glGenRenderbuffersEXT(1, &depth_stencil_buffer);
        Q_ASSERT(!glIsRenderbufferEXT(depth_stencil_buffer));
        glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depth_stencil_buffer);
        Q_ASSERT(glIsRenderbufferEXT(depth_stencil_buffer));
        glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH24_STENCIL8_EXT, size.width(), size.height());
        GLint i = 0;
        glGetRenderbufferParameterivEXT(GL_RENDERBUFFER_EXT, GL_RENDERBUFFER_DEPTH_SIZE_EXT, &i);
        glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
                                     GL_RENDERBUFFER_EXT, depth_stencil_buffer);
        glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_STENCIL_ATTACHMENT_EXT,
                                     GL_RENDERBUFFER_EXT, depth_stencil_buffer);
        fbo_attachments = QGLFramebufferObject::DepthStencil;
    } else if (attachments == QGLFramebufferObject::Depth
               || attachments == QGLFramebufferObject::DepthStencil)
    {
        glGenRenderbuffersEXT(1, &depth_stencil_buffer);
        Q_ASSERT(!glIsRenderbufferEXT(depth_stencil_buffer));
        glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depth_stencil_buffer);
        Q_ASSERT(glIsRenderbufferEXT(depth_stencil_buffer));
        glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, size.width(), size.height());
        GLint i = 0;
        glGetRenderbufferParameterivEXT(GL_RENDERBUFFER_EXT, GL_RENDERBUFFER_DEPTH_SIZE_EXT, &i);
        glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT,
                                     GL_RENDERBUFFER_EXT, depth_stencil_buffer);
        fbo_attachments = QGLFramebufferObject::Depth;
    } else {
        fbo_attachments = QGLFramebufferObject::NoDepthStencil;
    }

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    valid = checkFramebufferStatus();
    QT_CHECK_GLERROR();
}

/*!
    \class QGLFramebufferObject
    \brief The QGLFramebufferObject class encapsulates an OpenGL framebuffer object.
    \since 4.2

    \ingroup multimedia

    The QGLFramebufferObject class encapsulates an OpenGL framebuffer
    object, defined by the \c{GL_EXT_framebuffer_object} extension. In
    addition it provides a rendering surface that can be painted on
    with a QPainter, rendered to using native GL calls, or both. This
    surface can be bound and used as a regular texture in your own GL
    drawing code.  By default, the QGLFramebufferObject class
    generates a 2D GL texture (using the \c{GL_TEXTURE_2D} target),
    which is used as the internal rendering target.

    \bold{It is important to have a current GL context when creating a
    QGLFramebufferObject, otherwise initialization will fail.}

    OpenGL framebuffer objects and pbuffers (see
    \l{QGLPixelBuffer}{QGLPixelBuffer}) can both be used to render to
    offscreen surfaces, but there are a number of advantages with
    using framebuffer objects instead of pbuffers:

    \list 1
    \o A framebuffer object does not require a separate rendering
    context, so no context switching will occur when switching
    rendering targets. There is an overhead involved in switching
    targets, but in general it is cheaper than a context switch to a
    pbuffer.

    \o Rendering to dynamic textures (i.e. render-to-texture
    functionality) works on all platforms. No need to do explicit copy
    calls from a render buffer into a texture, as was necessary on
    systems that did not support the \c{render_texture} extension.

    \o It is possible to attach several rendering buffers (or texture
    objects) to the same framebuffer object, and render to all of them
    without doing a context switch.

    \o The OpenGL framebuffer extension is a pure GL extension with no
    system dependant WGL, AGL or GLX parts. This makes using
    framebuffer objects more portable.
    \endlist

    Note that QPainter antialiasing of drawing primitives will not
    work when using a QGLFramebufferObject as a paintdevice. This is
    because sample buffers, which are needed for antialiasing, are not
    yet supported in application-defined framebuffer objects. However,
    an extension to solve this has already been approved by the OpenGL
    ARB (\c{GL_EXT_framebuffer_multisample}), and will most likely be
    available in the near future.

    \sa {Framebuffer Object Example}
*/


/*!
    \enum QGLFramebufferObject::Attachments

    This enum type is used to configure the depth and stencil buffers
    attached to the framebuffer object when it is created.

    \value NoDepthStencil  No depth or stencil buffers are attached. Note that the OpenGL depth and
                           stencil tests won't work when rendering to a framebuffer object without
                           any depth or stencil buffers.

    \value DepthStencil    If the \c GL_EXT_packed_depth_stencil is present, a depth and stencil
                           buffer is attached, otherwise only a depth buffer is attached.

    \value Depth           A depth buffer is attached to the framebuffer object.

    \sa attachments()
*/


/*! \fn QGLFramebufferObject::QGLFramebufferObject(const QSize &size, GLenum target)

    Constructs an OpenGL framebuffer object and binds a 2D GL texture
    to the buffer of the size \a size. The texture is bound to the
    \c GL_COLOR_ATTACHMENT0 target in the framebuffer object.

    The \a target parameter is used to specify the GL texture
    target. The default target is \c GL_TEXTURE_2D. Keep in mind that
    \c GL_TEXTURE_2D textures must have a power of 2 width and height
    (e.g. 256x512), unless you are using OpenGL 2.0 or higher.

    By default, if the \c GL_EXT_packed_depth_stencil extension is
    present, a depth and stencil buffer is attached. If not, only a
    depth buffer is attached. This behavior can be toggled using one
    of the overloaded constructors.

    The default internal texture format is \c GL_RGBA8.

    It is important that you have a current GL context set when
    creating the QGLFramebufferObject, otherwise the initialization
    will fail.

    \sa size(), texture(), attachments()
*/

#ifndef Q_WS_QWS
#define DEFAULT_FORMAT GL_RGBA8
#else
#define DEFAULT_FORMAT GL_RGBA
#endif

QGLFramebufferObject::QGLFramebufferObject(const QSize &size, GLenum target)
    : d_ptr(new QGLFramebufferObjectPrivate)
{
    Q_D(QGLFramebufferObject);
    d->init(size, DepthStencil, target, DEFAULT_FORMAT);
}


/*! \overload

    Constructs an OpenGL framebuffer object and binds a 2D GL texture
    to the buffer of the given \a width and \a height.

    \sa size(), texture()
*/
QGLFramebufferObject::QGLFramebufferObject(int width, int height, GLenum target)
    : d_ptr(new QGLFramebufferObjectPrivate)
{
    Q_D(QGLFramebufferObject);
    d->init(QSize(width, height), DepthStencil, target, DEFAULT_FORMAT);
}

/*! \overload

    Constructs an OpenGL framebuffer object and binds a texture to the
    buffer of the given \a width and \a height.

    The \a attachments parameter describes the depth/stencil buffer
    configuration, \a target the texture target and \a internal_format
    the internal texture format. The default texture target is \c
    GL_TEXTURE_2D, while the default internal format is \c GL_RGBA8.

    \sa size(), texture(), attachments()
*/
QGLFramebufferObject::QGLFramebufferObject(int width, int height, Attachments attachments,
                                           GLenum target, GLenum internal_format)
    : d_ptr(new QGLFramebufferObjectPrivate)
{
    Q_D(QGLFramebufferObject);
    d->init(QSize(width, height), attachments, target, internal_format);
}

/*! \overload

    Constructs an OpenGL framebuffer object and binds a texture to the
    buffer of the given \a size.

    The \a attachments parameter describes the depth/stencil buffer
    configuration, \a target the texture target and \a internal_format
    the internal texture format. The default texture target is \c
    GL_TEXTURE_2D, while the default internal format is \c GL_RGBA8.

    \sa size(), texture(), attachments()
*/
QGLFramebufferObject::QGLFramebufferObject(const QSize &size, Attachments attachments,
                                           GLenum target, GLenum internal_format)
    : d_ptr(new QGLFramebufferObjectPrivate)
{
    Q_D(QGLFramebufferObject);
    d->init(size, attachments, target, internal_format);
}



/*!
    \fn QGLFramebufferObject::~QGLFramebufferObject()

    Destroys the framebuffer object and frees any allocated resources.
*/
QGLFramebufferObject::~QGLFramebufferObject()
{
    Q_D(QGLFramebufferObject);
    QGL_FUNC_CONTEXT;

    if (isValid()
        && (d->ctx == QGLContext::currentContext()
            || qgl_share_reg()->checkSharing(d->ctx, QGLContext::currentContext())))
    {
        glDeleteTextures(1, &d->texture);
        if (d->depth_stencil_buffer)
            glDeleteRenderbuffersEXT(1, &d->depth_stencil_buffer);
        glDeleteFramebuffersEXT(1, &d->fbo);
    }
    delete d_ptr;
}

/*!
    \fn bool QGLFramebufferObject::isValid() const

    Returns true if the framebuffer object is valid.

    The framebuffer can become invalid if the initialization process
    fails, the user attaches an invalid buffer to the framebuffer
    object, or a non-power of 2 width/height is specified as the
    texture size if the texture target is \c{GL_TEXTURE_2D}.
*/
bool QGLFramebufferObject::isValid() const
{
    Q_D(const QGLFramebufferObject);
    return d->valid;
}

/*!
    \fn bool QGLFramebufferObject::bind()

    Switches rendering from the default, windowing system provided
    framebuffer to this framebuffer object.
    Returns true upon success, false otherwise.
*/
bool QGLFramebufferObject::bind()
{
    if (!isValid())
        return false;
    Q_D(QGLFramebufferObject);
    QGL_FUNC_CONTEXT;
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, d->fbo);
    d->valid = d->checkFramebufferStatus();
    return d->valid;
}

/*!
    \fn bool QGLFramebufferObject::release()

    Switches rendering back to the default, windowing system provided
    framebuffer.
    Returns true upon success, false otherwise.
*/
bool QGLFramebufferObject::release()
{
    if (!isValid())
        return false;
    Q_D(QGLFramebufferObject);
    QGL_FUNC_CONTEXT;
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    d->valid = d->checkFramebufferStatus();
    return d->valid;
}

/*!
    \fn GLuint QGLFramebufferObject::texture() const

    Returns the texture id for the texture attached as the default
    rendering target in this framebuffer object. This texture id can
    be bound as a normal texture in your own GL code.
*/
GLuint QGLFramebufferObject::texture() const
{
    Q_D(const QGLFramebufferObject);
    return d->texture;
}

/*!
    \fn QSize QGLFramebufferObject::size() const

    Returns the size of the texture attached to this framebuffer
    object.
*/
QSize QGLFramebufferObject::size() const
{
    Q_D(const QGLFramebufferObject);
    return d->size;
}

/*!
    \fn QImage QGLFramebufferObject::toImage() const

    Returns the contents of this framebuffer object as a QImage.
*/
QImage QGLFramebufferObject::toImage() const
{
    Q_D(const QGLFramebufferObject);
    if (!d->valid)
        return QImage();

    const_cast<QGLFramebufferObject *>(this)->bind();
    QImage::Format image_format = QImage::Format_RGB32;
    if (d->ctx->format().alpha())
        image_format = QImage::Format_ARGB32_Premultiplied;
    QImage img(d->size, image_format);
    int w = d->size.width();
    int h = d->size.height();
    // ### fix the read format so that we don't have to do all the byte swapping
    glReadPixels(0, 0, d->size.width(), d->size.height(), GL_RGBA, GL_UNSIGNED_BYTE, img.bits());
    if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
        // OpenGL gives RGBA; Qt wants ARGB
        uint *p = (uint*)img.bits();
        uint *end = p + w*h;
        if (1) {
            while (p < end) {
                uint a = *p << 24;
                *p = (*p >> 8) | a;
                p++;
            }
        } else {
            while (p < end) {
                *p = 0xFF000000 | (*p>>8);
                ++p;
            }
        }
    } else {
        // OpenGL gives ABGR (i.e. RGBA backwards); Qt wants ARGB
        img = img.rgbSwapped();
    }
    const_cast<QGLFramebufferObject *>(this)->release();
    return img.mirrored();
}

Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_buffer_paintengine)

/*! \reimp */
QPaintEngine *QGLFramebufferObject::paintEngine() const
{
    return qt_buffer_paintengine();
}

/*!
    \fn bool QGLFramebufferObject::hasOpenGLFramebufferObjects()

    Returns true if the OpenGL \c{GL_EXT_framebuffer_object} extension
    is present on this system; otherwise returns false.
*/
bool QGLFramebufferObject::hasOpenGLFramebufferObjects()
{
    QGLWidget dmy; // needed to detect and init the QGLExtensions object
    return (QGLExtensions::glExtensions & QGLExtensions::FramebufferObject);
}

extern int qt_defaultDpi();

/*! \reimp */
int QGLFramebufferObject::metric(PaintDeviceMetric metric) const
{
    Q_D(const QGLFramebufferObject);

    float dpmx = qt_defaultDpi()*100./2.54;
    float dpmy = qt_defaultDpi()*100./2.54;
    int w = d->size.width();
    int h = d->size.height();
    switch (metric) {
    case PdmWidth:
        return w;

    case PdmHeight:
        return h;

    case PdmWidthMM:
        return qRound(w * 1000 / dpmx);

    case PdmHeightMM:
        return qRound(h * 1000 / dpmy);

    case PdmNumColors:
        return 0;

    case PdmDepth:
        return 32;//d->depth;

    case PdmDpiX:
        return (int)(dpmx * 0.0254);

    case PdmDpiY:
        return (int)(dpmy * 0.0254);

    case PdmPhysicalDpiX:
        return (int)(dpmx * 0.0254);

    case PdmPhysicalDpiY:
        return (int)(dpmy * 0.0254);

    default:
        qWarning("QGLFramebufferObject::metric(), Unhandled metric type: %d.\n", metric);
        break;
    }
    return 0;
}

/*!
    \fn GLuint QGLFramebufferObject::handle() const

    Returns the GL framebuffer object handle for this framebuffer
    object (returned by the \c{glGenFrameBuffersEXT()} function). This
    handle can be used to attach new images or buffers to the
    framebuffer. The user is responsible for cleaning up and
    destroying these objects.
*/
GLuint QGLFramebufferObject::handle() const
{
    Q_D(const QGLFramebufferObject);
    return d->fbo;
}

/*! \fn int QGLFramebufferObject::devType() const

    \reimp
*/


/*!
    Returns the status of the depth and stencil buffers attached to
    this framebuffer object.
*/

QGLFramebufferObject::Attachments QGLFramebufferObject::attachments() const
{
    Q_D(const QGLFramebufferObject);
    if (d->valid)
        return d->fbo_attachments;
    return NoDepthStencil;
}
