src/opengl/qglpixelbuffer.cpp

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/*!
    \class QGLPixelBuffer
    \inmodule QtOpenGL
    \brief The QGLPixelBuffer class encapsulates an OpenGL pbuffer.
    \since 4.1
    \obsolete

    \ingroup painting-3D

    Rendering into a pbuffer is normally done using full hardware
    acceleration. This can be significantly faster than rendering
    into a QPixmap.

    There are three approaches to using this class:

    \list 1
    \li \b{We can draw into the pbuffer and convert it to a QImage
       using toImage().} This is normally much faster than calling
       QGLWidget::renderPixmap().

    \li \b{We can draw into the pbuffer and copy the contents into
       an OpenGL texture using updateDynamicTexture().} This allows
       us to create dynamic textures and works on all systems
       with pbuffer support.

    \li \b{On systems that support it, we can bind the pbuffer to
       an OpenGL texture.} The texture is then updated automatically
       when the pbuffer contents change, eliminating the need for
       additional copy operations. This is supported only on Windows
       and \macos systems that provide the \c render_texture
       extension. Note that under Windows, a multi-sampled pbuffer
       can't be used in conjunction with the \c render_texture
       extension. If a multi-sampled pbuffer is requested under
       Windows, the \c render_texture extension is turned off for that
       pbuffer.


    \endlist

    \note This class has been deprecated, use QOpenGLFramebufferObject
    for offscreen rendering.

    \section1 Threading

    As of Qt 4.8, it's possible to render into a QGLPixelBuffer using
    a QPainter in a separate thread. Note that OpenGL 2.0 or OpenGL ES
    2.0 is required for this to work.

    Pbuffers are provided by the OpenGL \c pbuffer extension; call
    hasOpenGLPbuffer() to find out if the system provides pbuffers.
*/

#include <private/qopenglextensions_p.h>

#include <QtCore/qglobal.h>
#include <QtGui/qopenglframebufferobject.h>

#include "gl2paintengineex/qpaintengineex_opengl2_p.h"

#include <qglframebufferobject.h>
#include <qglpixelbuffer.h>
#include <private/qglpixelbuffer_p.h>
#include <private/qfont_p.h>
#include <qimage.h>

QT_BEGIN_NAMESPACE

extern QImage qt_gl_read_frame_buffer(const QSize&, bool, bool);


QGLContext* QGLPBufferGLPaintDevice::context() const
{
    return pbuf->d_func()->qctx;
}

void QGLPBufferGLPaintDevice::beginPaint()
{
    pbuf->makeCurrent();
    QGLPaintDevice::beginPaint();
}

void QGLPBufferGLPaintDevice::endPaint()
{
    QOpenGLContext::currentContext()->functions()->glFlush();
    QGLPaintDevice::endPaint();
}

void QGLPBufferGLPaintDevice::setFbo(GLuint fbo)
{
    m_thisFBO = fbo;
}

void QGLPBufferGLPaintDevice::setPBuffer(QGLPixelBuffer* pb)
{
    pbuf = pb;
}

void QGLPixelBufferPrivate::common_init(const QSize &size, const QGLFormat &format, QGLWidget *shareWidget)
{
    Q_Q(QGLPixelBuffer);
    if(init(size, format, shareWidget)) {
        req_size = size;
        req_format = format;
        req_shareWidget = shareWidget;
        invalid = false;
        glDevice.setPBuffer(q);
    }
}

/*!
    Constructs an OpenGL pbuffer of the given \a size. If no \a
    format is specified, the \l{QGLFormat::defaultFormat()}{default
    format} is used. If the \a shareWidget parameter points to a
    valid QGLWidget, the pbuffer will share its context with \a
    shareWidget.

    If you intend to bind this pbuffer as a dynamic texture, the width
    and height components of \c size must be powers of two (e.g., 512
    x 128).

    \sa size(), format()
*/
QGLPixelBuffer::QGLPixelBuffer(const QSize &size, const QGLFormat &format, QGLWidget *shareWidget)
    : d_ptr(new QGLPixelBufferPrivate(this))
{
    Q_D(QGLPixelBuffer);
    d->common_init(size, format, shareWidget);
}


/*! \overload

    Constructs an OpenGL pbuffer with the \a width and \a height. If
    no \a format is specified, the
    \l{QGLFormat::defaultFormat()}{default format} is used. If the \a
    shareWidget parameter points to a valid QGLWidget, the pbuffer
    will share its context with \a shareWidget.

    If you intend to bind this pbuffer as a dynamic texture, the width
    and height components of \c size must be powers of two (e.g., 512
    x 128).

    \sa size(), format()
*/
QGLPixelBuffer::QGLPixelBuffer(int width, int height, const QGLFormat &format, QGLWidget *shareWidget)
    : d_ptr(new QGLPixelBufferPrivate(this))
{
    Q_D(QGLPixelBuffer);
    d->common_init(QSize(width, height), format, shareWidget);
}


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

    Destroys the pbuffer and frees any allocated resources.
*/
QGLPixelBuffer::~QGLPixelBuffer()
{
    Q_D(QGLPixelBuffer);

    // defined in qpaintengine_opengl.cpp
    QGLContext *current = const_cast<QGLContext *>(QGLContext::currentContext());
    if (current != d->qctx)
        makeCurrent();
    d->cleanup();
    if (current && current != d->qctx)
        current->makeCurrent();
}

/*! \fn bool QGLPixelBuffer::makeCurrent()

    Makes this pbuffer the current OpenGL rendering context. Returns
    true on success; otherwise returns \c false.

    \sa QGLContext::makeCurrent(), doneCurrent()
*/

bool QGLPixelBuffer::makeCurrent()
{
    Q_D(QGLPixelBuffer);
    if (d->invalid)
        return false;
    d->qctx->makeCurrent();
    if (!d->fbo) {
        QOpenGLFramebufferObjectFormat format;
        if (d->req_format.stencil())
            format.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
        else if (d->req_format.depth())
            format.setAttachment(QOpenGLFramebufferObject::Depth);
        if (d->req_format.sampleBuffers())
            format.setSamples(d->req_format.samples());
        d->fbo = new QOpenGLFramebufferObject(d->req_size, format);
        d->fbo->bind();
        d->glDevice.setFbo(d->fbo->handle());
        QOpenGLContext::currentContext()->functions()->glViewport(0, 0, d->req_size.width(), d->req_size.height());
    }
    return true;
}

/*! \fn bool QGLPixelBuffer::doneCurrent()

    Makes no context the current OpenGL context. Returns \c true on
    success; otherwise returns \c false.
*/

bool QGLPixelBuffer::doneCurrent()
{
    Q_D(QGLPixelBuffer);
    if (d->invalid)
        return false;
    d->qctx->doneCurrent();
    return true;
}

/*!
    Returns the context of this pixelbuffer.
*/
QGLContext *QGLPixelBuffer::context() const
{
    Q_D(const QGLPixelBuffer);
    return d->qctx;
}

/*!
    \fn GLuint QGLPixelBuffer::generateDynamicTexture() const

    Generates and binds a 2D GL texture that is the same size as the
    pbuffer, and returns the texture's ID. This can be used in
    conjunction with bindToDynamicTexture() and
    updateDynamicTexture().

    \sa size()
*/

/*! \fn bool QGLPixelBuffer::bindToDynamicTexture(GLuint texture_id)

    Binds the texture specified by \a texture_id to this pbuffer.
    Returns \c true on success; otherwise returns \c false.

    The texture must be of the same size and format as the pbuffer.

    To unbind the texture, call releaseFromDynamicTexture(). While
    the texture is bound, it is updated automatically when the
    pbuffer contents change, eliminating the need for additional copy
    operations.

    Example:

    \snippet code/src_opengl_qglpixelbuffer.cpp 0

    \warning This function uses the \c {render_texture} extension,
    which is currently not supported under X11. An alternative that
    works on all systems (including X11) is to manually copy the
    pbuffer contents to a texture using updateDynamicTexture().

    \warning For the bindToDynamicTexture() call to succeed on the
    \macos, the pbuffer needs a shared context, i.e. the
    QGLPixelBuffer must be created with a share widget.

    \sa generateDynamicTexture(), releaseFromDynamicTexture()
*/

/*! \fn void QGLPixelBuffer::releaseFromDynamicTexture()

    Releases the pbuffer from any previously bound texture.

    \sa bindToDynamicTexture()
*/

/*! \fn bool QGLPixelBuffer::hasOpenGLPbuffers()

    Returns \c true if the OpenGL \c pbuffer extension is present on
    this system; otherwise returns \c false.
*/

/*!
    Copies the pbuffer contents into the texture specified with \a
    texture_id.

    The texture must be of the same size and format as the pbuffer.

    Example:

    \snippet code/src_opengl_qglpixelbuffer.cpp 1

    An alternative on Windows and \macos systems that support the
    \c render_texture extension is to use bindToDynamicTexture() to
    get dynamic updates of the texture.

    \sa generateDynamicTexture(), bindToDynamicTexture()
*/
void QGLPixelBuffer::updateDynamicTexture(GLuint texture_id) const
{
    Q_D(const QGLPixelBuffer);
    if (d->invalid || !d->fbo)
        return;

    const QGLContext *ctx = QGLContext::currentContext();
    if (!ctx)
        return;

#undef glBindFramebuffer

#ifndef GL_READ_FRAMEBUFFER
#define GL_READ_FRAMEBUFFER 0x8CA8
#endif

#ifndef GL_DRAW_FRAMEBUFFER
#define GL_DRAW_FRAMEBUFFER 0x8CA9
#endif

    QOpenGLExtensions extensions(ctx->contextHandle());

    ctx->d_ptr->refreshCurrentFbo();

    if (d->blit_fbo) {
        QOpenGLFramebufferObject::blitFramebuffer(d->blit_fbo, d->fbo);
        extensions.glBindFramebuffer(GL_READ_FRAMEBUFFER, d->blit_fbo->handle());
    }

    extensions.glBindTexture(GL_TEXTURE_2D, texture_id);
#ifndef QT_OPENGL_ES
    GLenum format = ctx->contextHandle()->isOpenGLES() ? GL_RGBA : GL_RGBA8;
    extensions.glCopyTexImage2D(GL_TEXTURE_2D, 0, format, 0, 0, d->req_size.width(), d->req_size.height(), 0);
#else
    extensions.glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, d->req_size.width(), d->req_size.height(), 0);
#endif

    if (d->blit_fbo)
        extensions.glBindFramebuffer(GL_READ_FRAMEBUFFER, ctx->d_func()->current_fbo);
}

/*!
    Returns the size of the pbuffer.
*/
QSize QGLPixelBuffer::size() const
{
    Q_D(const QGLPixelBuffer);
    return d->req_size;
}

/*!
    Returns the contents of the pbuffer as a QImage.
*/
QImage QGLPixelBuffer::toImage() const
{
    Q_D(const QGLPixelBuffer);
    if (d->invalid)
        return QImage();

    const_cast<QGLPixelBuffer *>(this)->makeCurrent();
    if (d->fbo)
        d->fbo->bind();
    return qt_gl_read_frame_buffer(d->req_size, d->format.alpha(), true);
}

/*!
    Returns the native pbuffer handle.
*/
Qt::HANDLE QGLPixelBuffer::handle() const
{
    Q_D(const QGLPixelBuffer);
    if (d->invalid)
        return 0;
    return (Qt::HANDLE) d->pbuf;
}

/*!
    Returns \c true if this pbuffer is valid; otherwise returns \c false.
*/
bool QGLPixelBuffer::isValid() const
{
    Q_D(const QGLPixelBuffer);
    return !d->invalid;
}

Q_GLOBAL_STATIC(QGLEngineThreadStorage<QGL2PaintEngineEx>, qt_buffer_2_engine)

/*! \reimp */
QPaintEngine *QGLPixelBuffer::paintEngine() const
{
    return qt_buffer_2_engine()->engine();
}

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

    float dpmx = qt_defaultDpiX()*100./2.54;
    float dpmy = qt_defaultDpiY()*100./2.54;
    int w = d->req_size.width();
    int h = d->req_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 qRound(dpmx * 0.0254);

    case PdmDpiY:
        return qRound(dpmy * 0.0254);

    case PdmPhysicalDpiX:
        return qRound(dpmx * 0.0254);

    case PdmPhysicalDpiY:
        return qRound(dpmy * 0.0254);

    case QPaintDevice::PdmDevicePixelRatio:
        return 1;

    case QPaintDevice::PdmDevicePixelRatioScaled:
        return QPaintDevice::devicePixelRatioFScale();

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

/*!
    Generates and binds a 2D GL texture to the current context, based
    on \a image. The generated texture id is returned and can be used
    in later glBindTexture() calls.

    The \a target parameter specifies the texture target.

    Equivalent to calling QGLContext::bindTexture().

    \sa deleteTexture()
*/
GLuint QGLPixelBuffer::bindTexture(const QImage &image, GLenum target)
{
    Q_D(QGLPixelBuffer);
#ifndef QT_OPENGL_ES
    GLenum format = QOpenGLContext::currentContext()->isOpenGLES() ? GL_RGBA : GL_RGBA8;
    return d->qctx->bindTexture(image, target, GLint(format));
#else
    return d->qctx->bindTexture(image, target, GL_RGBA);
#endif
}

/*! \overload

    Generates and binds a 2D GL texture based on \a pixmap.

    Equivalent to calling QGLContext::bindTexture().

    \sa deleteTexture()
*/
GLuint QGLPixelBuffer::bindTexture(const QPixmap &pixmap, GLenum target)
{
    Q_D(QGLPixelBuffer);
#ifndef QT_OPENGL_ES
    GLenum format = QOpenGLContext::currentContext()->isOpenGLES() ? GL_RGBA : GL_RGBA8;
    return d->qctx->bindTexture(pixmap, target, GLint(format));
#else
    return d->qctx->bindTexture(pixmap, target, GL_RGBA);
#endif
}

/*! \overload

    Reads the DirectDrawSurface (DDS) compressed file \a fileName and
    generates a 2D GL texture from it.

    Equivalent to calling QGLContext::bindTexture().

    \sa deleteTexture()
*/
GLuint QGLPixelBuffer::bindTexture(const QString &fileName)
{
    Q_D(QGLPixelBuffer);
    return d->qctx->bindTexture(fileName);
}

/*!
    Removes the texture identified by \a texture_id from the texture cache.

    Equivalent to calling QGLContext::deleteTexture().
 */
void QGLPixelBuffer::deleteTexture(GLuint texture_id)
{
    Q_D(QGLPixelBuffer);
    d->qctx->deleteTexture(texture_id);
}

/*!
    \since 4.4

    Draws the given texture, \a textureId, to the given target rectangle,
    \a target, in OpenGL model space. The \a textureTarget should be a 2D
    texture target.

    Equivalent to the corresponding QGLContext::drawTexture().
*/
void QGLPixelBuffer::drawTexture(const QRectF &target, GLuint textureId, GLenum textureTarget)
{
    Q_D(QGLPixelBuffer);
    d->qctx->drawTexture(target, textureId, textureTarget);
}

/*!
    \since 4.4

    Draws the given texture, \a textureId, at the given \a point in OpenGL model
    space. The textureTarget parameter should be a 2D texture target.

    Equivalent to the corresponding QGLContext::drawTexture().
*/
void QGLPixelBuffer::drawTexture(const QPointF &point, GLuint textureId, GLenum textureTarget)
{
    Q_D(QGLPixelBuffer);
    d->qctx->drawTexture(point, textureId, textureTarget);
}

/*!
    Returns the format of the pbuffer. The format may be different
    from the one that was requested.
*/
QGLFormat QGLPixelBuffer::format() const
{
    Q_D(const QGLPixelBuffer);
    return d->format;
}

/*! \fn int QGLPixelBuffer::devType() const
    \internal
*/

bool QGLPixelBufferPrivate::init(const QSize &, const QGLFormat &f, QGLWidget *shareWidget)
{
    widget = new QGLWidget(f, 0, shareWidget);
    widget->resize(1, 1);
    qctx = const_cast<QGLContext *>(widget->context());
    return widget->isValid();
}

bool QGLPixelBufferPrivate::cleanup()
{
    delete fbo;
    fbo = 0;
    delete blit_fbo;
    blit_fbo = 0;
    delete widget;
    widget = 0;
    return true;
}

bool QGLPixelBuffer::bindToDynamicTexture(GLuint texture_id)
{
    Q_UNUSED(texture_id);
    return false;
}

void QGLPixelBuffer::releaseFromDynamicTexture()
{
}

GLuint QGLPixelBuffer::generateDynamicTexture() const
{
    Q_D(const QGLPixelBuffer);
    if (!d->fbo)
        return 0;

    if (d->fbo->format().samples() > 0
        && QOpenGLExtensions(QOpenGLContext::currentContext())
           .hasOpenGLExtension(QOpenGLExtensions::FramebufferBlit))
    {
        if (!d->blit_fbo)
            const_cast<QOpenGLFramebufferObject *&>(d->blit_fbo) = new QOpenGLFramebufferObject(d->req_size);
    } else {
        return d->fbo->texture();
    }

    GLuint texture;
    QOpenGLFunctions *funcs = QOpenGLContext::currentContext()->functions();

    funcs->glGenTextures(1, &texture);
    funcs->glBindTexture(GL_TEXTURE_2D, texture);

    funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    funcs->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    funcs->glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, d->req_size.width(), d->req_size.height(), 0,
                        GL_RGBA, GL_UNSIGNED_BYTE, 0);

    return texture;
}

bool QGLPixelBuffer::hasOpenGLPbuffers()
{
    return QGLFramebufferObject::hasOpenGLFramebufferObjects();
}

QT_END_NAMESPACE