qplatformopenglcontext.cpp

// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#include "qplatformopenglcontext.h"

#include <QOpenGLFunctions>

QT_BEGIN_NAMESPACE

/*!
    \class QPlatformOpenGLContext
    \since 4.8
    \internal
    \preliminary
    \ingroup qpa

    \brief The QPlatformOpenGLContext class provides an abstraction for native GL contexts.

    In QPA the way to support OpenGL or OpenVG or other technologies that requires a native GL
    context is through the QPlatformOpenGLContext wrapper.

    There is no factory function for QPlatformOpenGLContexts, but rather only one accessor function.
    The only place to retrieve a QPlatformOpenGLContext from is through a QPlatformWindow.

    The context which is current for a specific thread can be collected by the currentContext()
    function. This is how QPlatformOpenGLContext also makes it possible to use the Qt GUI module
    withhout using QOpenGLWidget. When using QOpenGLContext::currentContext(), it will ask
    QPlatformOpenGLContext for the currentContext. Then a corresponding QOpenGLContext will be returned,
    which maps to the QPlatformOpenGLContext.
*/

/*! \fn void QPlatformOpenGLContext::swapBuffers(QPlatformSurface *surface)
    Reimplement in subclass to native swap buffers calls

    The implementation must support being called in a thread different than the gui-thread.
*/

/*! \fn QFunctionPointer QPlatformOpenGLContext::getProcAddress(const char *procName)

    Reimplement in subclass to allow dynamic querying of OpenGL symbols. As opposed to e.g. the wglGetProcAddress
    function on Windows, Qt expects this methods to be able to return valid function pointers even for standard
    OpenGL symbols.
*/

class QPlatformOpenGLContextPrivate
{
public:
    QPlatformOpenGLContextPrivate() : context(nullptr) {}

    QOpenGLContext *context;
};

QPlatformOpenGLContext::QPlatformOpenGLContext()
    : d_ptr(new QPlatformOpenGLContextPrivate)
{
}

QPlatformOpenGLContext::~QPlatformOpenGLContext()
{
}

/*!
  Called after a new instance is constructed. The default implementation does nothing.

  Subclasses can use this function to perform additional initialization that relies on
  virtual functions.
 */
void QPlatformOpenGLContext::initialize()
{
}

/*!
    Reimplement in subclass if your platform uses framebuffer objects for surfaces.

    The default implementation returns 0.
*/
GLuint QPlatformOpenGLContext::defaultFramebufferObject(QPlatformSurface *) const
{
    return 0;
}

QOpenGLContext *QPlatformOpenGLContext::context() const
{
    Q_D(const QPlatformOpenGLContext);
    return d->context;
}

void QPlatformOpenGLContext::setContext(QOpenGLContext *context)
{
    Q_D(QPlatformOpenGLContext);
    d->context = context;
}

bool QPlatformOpenGLContext::parseOpenGLVersion(const QByteArray &versionString, int &major, int &minor)
{
    bool majorOk = false;
    bool minorOk = false;
    QList<QByteArray> parts = versionString.split(' ');
    if (versionString.startsWith(QByteArrayLiteral("OpenGL ES"))) {
        if (parts.size() >= 3) {
            QList<QByteArray> versionParts = parts.at(2).split('.');
            if (versionParts.size() >= 2) {
                major = versionParts.at(0).toInt(&majorOk);
                minor = versionParts.at(1).toInt(&minorOk);
                // Nexus 6 has "OpenGL ES 3.0V@95.0 (GIT@I86da836d38)"
                if (!minorOk)
                    if (int idx = versionParts.at(1).indexOf('V'))
                        minor = versionParts.at(1).left(idx).toInt(&minorOk);
            } else {
                qWarning("Unrecognized OpenGL ES version");
            }
        } else {
            // If < 3 parts to the name, it is an unrecognised OpenGL ES
            qWarning("Unrecognised OpenGL ES version");
        }
    } else {
        // Not OpenGL ES, but regular OpenGL, the version numbers are first in the string
        QList<QByteArray> versionParts = parts.at(0).split('.');
        if (versionParts.size() >= 2) {
            major = versionParts.at(0).toInt(&majorOk);
            minor = versionParts.at(1).toInt(&minorOk);
        } else {
            qWarning("Unrecognized OpenGL version");
        }
    }

    if (!majorOk || !minorOk)
        qWarning("Unrecognized OpenGL version");
    return (majorOk && minorOk);
}

/*!
   Called when the RHI begins rendering a new frame in the context. Will always be paired with a
   call to \l endFrame().
*/
void QPlatformOpenGLContext::beginFrame()
{
}

/*!
   Called when the RHI ends rendering a in the context. Is always preceded by a call to
   \l beginFrame().
*/
void QPlatformOpenGLContext::endFrame()
{
}

QT_END_NAMESPACE