qwindowsglcontext.cpp

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// 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 "qwindowsglcontext.h"
#include "qwindowscontext.h"
#include "qwindowswindow.h"
#include "qwindowsintegration.h"
 
#include <QtCore/qdebug.h>
#include <QtCore/qsysinfo.h>
#include <QtGui/qcolorspace.h>
#include <QtGui/qguiapplication.h>
#include <qpa/qplatformnativeinterface.h>
#include <private/qsystemlibrary_p.h>
#include <algorithm>
 
#include <wingdi.h>
#include <GL/gl.h>
 
// #define DEBUG_GL
 
// ARB extension API
#ifndef WGL_ARB_multisample
#define WGL_SAMPLE_BUFFERS_ARB               0x2041
#define WGL_SAMPLES_ARB                      0x2042
#endif
 
#ifndef WGL_ARB_pixel_format
#define WGL_NUMBER_PIXEL_FORMATS_ARB   0x2000
#define WGL_DRAW_TO_WINDOW_ARB         0x2001
#define WGL_DRAW_TO_BITMAP_ARB         0x2002
#define WGL_ACCELERATION_ARB           0x2003
#define WGL_NEED_PALETTE_ARB           0x2004
#define WGL_NEED_SYSTEM_PALETTE_ARB    0x2005
#define WGL_SWAP_LAYER_BUFFERS_ARB     0x2006
#define WGL_SWAP_METHOD_ARB            0x2007
#define WGL_NUMBER_OVERLAYS_ARB        0x2008
#define WGL_NUMBER_UNDERLAYS_ARB       0x2009
#define WGL_TRANSPARENT_ARB            0x200A
#define WGL_TRANSPARENT_RED_VALUE_ARB  0x2037
#define WGL_TRANSPARENT_GREEN_VALUE_ARB 0x2038
#define WGL_TRANSPARENT_BLUE_VALUE_ARB 0x2039
#define WGL_TRANSPARENT_ALPHA_VALUE_ARB 0x203A
#define WGL_TRANSPARENT_INDEX_VALUE_ARB 0x203B
#define WGL_SHARE_DEPTH_ARB            0x200C
#define WGL_SHARE_STENCIL_ARB          0x200D
#define WGL_SHARE_ACCUM_ARB            0x200E
#define WGL_SUPPORT_GDI_ARB            0x200F
#define WGL_SUPPORT_OPENGL_ARB         0x2010
#define WGL_DOUBLE_BUFFER_ARB          0x2011
#define WGL_STEREO_ARB                 0x2012
#define WGL_PIXEL_TYPE_ARB             0x2013
#define WGL_COLOR_BITS_ARB             0x2014
#define WGL_RED_BITS_ARB               0x2015
#define WGL_RED_SHIFT_ARB              0x2016
#define WGL_GREEN_BITS_ARB             0x2017
#define WGL_GREEN_SHIFT_ARB            0x2018
#define WGL_BLUE_BITS_ARB              0x2019
#define WGL_BLUE_SHIFT_ARB             0x201A
#define WGL_ALPHA_BITS_ARB             0x201B
#define WGL_ALPHA_SHIFT_ARB            0x201C
#define WGL_ACCUM_BITS_ARB             0x201D
#define WGL_ACCUM_RED_BITS_ARB         0x201E
#define WGL_ACCUM_GREEN_BITS_ARB       0x201F
#define WGL_ACCUM_BLUE_BITS_ARB        0x2020
#define WGL_ACCUM_ALPHA_BITS_ARB       0x2021
#define WGL_DEPTH_BITS_ARB             0x2022
#define WGL_STENCIL_BITS_ARB           0x2023
#define WGL_AUX_BUFFERS_ARB            0x2024
#define WGL_NO_ACCELERATION_ARB        0x2025
#define WGL_GENERIC_ACCELERATION_ARB   0x2026
#define WGL_FULL_ACCELERATION_ARB      0x2027
#define WGL_SWAP_EXCHANGE_ARB          0x2028
#define WGL_SWAP_COPY_ARB              0x2029
#define WGL_SWAP_UNDEFINED_ARB         0x202A
#define WGL_TYPE_RGBA_ARB              0x202B
#define WGL_TYPE_COLORINDEX_ARB        0x202C
#endif
 
#ifndef WGL_ARB_create_context
#define WGL_CONTEXT_MAJOR_VERSION_ARB               0x2091
#define WGL_CONTEXT_MINOR_VERSION_ARB               0x2092
#define WGL_CONTEXT_LAYER_PLANE_ARB                 0x2093
#define WGL_CONTEXT_FLAGS_ARB                       0x2094
#define WGL_CONTEXT_PROFILE_MASK_ARB                0x9126
#define WGL_CONTEXT_DEBUG_BIT_ARB                   0x0001
#define WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB      0x0002
#define WGL_CONTEXT_CORE_PROFILE_BIT_ARB            0x0001
#define WGL_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB   0x0002
// Error codes returned by GetLastError().
#define ERROR_INVALID_VERSION_ARB                   0x2095
#define ERROR_INVALID_PROFILE_ARB                   0x2096
#endif
 
#ifndef GL_VERSION_3_2
#define GL_CONTEXT_PROFILE_MASK                     0x9126
#define GL_MAJOR_VERSION                            0x821B
#define GL_MINOR_VERSION                            0x821C
#define GL_NUM_EXTENSIONS                           0x821D
#define GL_CONTEXT_FLAGS                            0x821E
#define GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT      0x0001
#endif
 
#ifndef GL_CONTEXT_FLAG_DEBUG_BIT
#define GL_CONTEXT_FLAG_DEBUG_BIT 0x00000002
#endif
 
// Common GL and WGL constants
#define RESET_NOTIFICATION_STRATEGY_ARB 0x8256
#define LOSE_CONTEXT_ON_RESET_ARB 0x8252
 
#ifndef WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT
#define WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT 0x20A9
#endif
 
QT_BEGIN_NAMESPACE
 
QWindowsOpengl32DLL QOpenGLStaticContext::opengl32;
 
QFunctionPointer QWindowsOpengl32DLL::resolve(const char *name)
{
    return m_lib
        ? reinterpret_cast<QFunctionPointer>(::GetProcAddress(m_lib, name))
        : nullptr;
}
 
bool QWindowsOpengl32DLL::init(bool softwareRendering)
{
    const QByteArray opengl32 = QByteArrayLiteral("opengl32");
    const QByteArray swopengl = QByteArrayLiteral("opengl32sw");
    bool useSystemLib = false;
 
    QByteArray openglDll = qgetenv("QT_OPENGL_DLL");
    if (openglDll.isEmpty()) {
        openglDll = softwareRendering ? swopengl : opengl32;
        useSystemLib = !softwareRendering;
    }
 
    openglDll = openglDll.toLower();
    m_nonOpengl32 = openglDll != opengl32;
 
    qCDebug(lcQpaGl) << "Qt: Using WGL and OpenGL from" << openglDll;
 
    if (useSystemLib)
        m_lib = QSystemLibrary::load((wchar_t*)(QString::fromLatin1(openglDll).utf16()));
    else
        m_lib = LoadLibraryA(openglDll.constData());
    if (!m_lib) {
        qErrnoWarning(::GetLastError(), "Failed to load %s", openglDll.constData());
        return false;
    }
 
    if (moduleIsNotOpengl32()) {
        // Load opengl32.dll always. GDI functions like ChoosePixelFormat do
        // GetModuleHandle for opengl32.dll and behave differently (and call back into
        // opengl32) when the module is present. This is fine for dummy contexts and windows.
        QSystemLibrary::load(L"opengl32");
    }
 
    wglCreateContext = reinterpret_cast<HGLRC (WINAPI *)(HDC)>(resolve("wglCreateContext"));
    wglDeleteContext = reinterpret_cast<BOOL (WINAPI *)(HGLRC)>(resolve("wglDeleteContext"));
    wglGetCurrentContext = reinterpret_cast<HGLRC (WINAPI *)()>(resolve("wglGetCurrentContext"));
    wglGetCurrentDC = reinterpret_cast<HDC (WINAPI *)()>(resolve("wglGetCurrentDC"));
    wglGetProcAddress = reinterpret_cast<PROC (WINAPI *)(LPCSTR)>(resolve("wglGetProcAddress"));
    wglMakeCurrent = reinterpret_cast<BOOL (WINAPI *)(HDC, HGLRC)>(resolve("wglMakeCurrent"));
    wglShareLists = reinterpret_cast<BOOL (WINAPI *)(HGLRC, HGLRC)>(resolve("wglShareLists"));
    wglSwapBuffers = reinterpret_cast<BOOL (WINAPI *)(HDC)>(resolve("wglSwapBuffers"));
    wglSetPixelFormat = reinterpret_cast<BOOL (WINAPI *)(HDC, int, const PIXELFORMATDESCRIPTOR *)>(resolve("wglSetPixelFormat"));
    wglDescribePixelFormat = reinterpret_cast<int (WINAPI *)(HDC, int, UINT, PIXELFORMATDESCRIPTOR *)>(resolve("wglDescribePixelFormat"));
 
    glGetError = reinterpret_cast<GLenum (APIENTRY *)()>(resolve("glGetError"));
    glGetIntegerv = reinterpret_cast<void (APIENTRY *)(GLenum , GLint *)>(resolve("glGetIntegerv"));
    glGetString = reinterpret_cast<const GLubyte * (APIENTRY *)(GLenum )>(resolve("glGetString"));
 
    return wglCreateContext && glGetError && glGetString;
}
 
BOOL QWindowsOpengl32DLL::swapBuffers(HDC dc)
{
    return moduleIsNotOpengl32() ? wglSwapBuffers(dc) : SwapBuffers(dc);
}
 
BOOL QWindowsOpengl32DLL::setPixelFormat(HDC dc, int pf, const PIXELFORMATDESCRIPTOR *pfd)
{
    return moduleIsNotOpengl32() ? wglSetPixelFormat(dc, pf, pfd) : SetPixelFormat(dc, pf, pfd);
}
 
int QWindowsOpengl32DLL::describePixelFormat(HDC dc, int pf, UINT size, PIXELFORMATDESCRIPTOR *pfd)
{
    return moduleIsNotOpengl32() ? wglDescribePixelFormat(dc, pf, size, pfd) : DescribePixelFormat(dc, pf, size, pfd);
}
 
QWindowsOpenGLContext *QOpenGLStaticContext::createContext(QOpenGLContext *context)
{
    return new QWindowsGLContext(this, context);
}
 
QWindowsOpenGLContext *QOpenGLStaticContext::createContext(HGLRC context, HWND window)
{
    return new QWindowsGLContext(this, context, window);
}
 
template <class MaskType, class FlagType> inline bool testFlag(MaskType mask, FlagType flag)
{
    return (mask & MaskType(flag)) != 0;
}
 
static inline bool hasGLOverlay(const PIXELFORMATDESCRIPTOR &pd)
{ return (pd.bReserved & 0x0f) != 0; }
 
static inline bool isDirectRendering(const PIXELFORMATDESCRIPTOR &pfd)
{ return (pfd.dwFlags & PFD_GENERIC_ACCELERATED) || !(pfd.dwFlags & PFD_GENERIC_FORMAT); }
 
static inline void initPixelFormatDescriptor(PIXELFORMATDESCRIPTOR *d)
{
    memset(d, 0, sizeof(PIXELFORMATDESCRIPTOR));
    d->nSize = sizeof(PIXELFORMATDESCRIPTOR);
    d->nVersion = 1;
}
 
#ifndef QT_NO_DEBUG_STREAM
QDebug operator<<(QDebug d, const PIXELFORMATDESCRIPTOR &pd)
{
    QDebugStateSaver saver(d);
    d.nospace();
    d << "PIXELFORMATDESCRIPTOR "
        << "dwFlags=" << Qt::hex << Qt::showbase << pd.dwFlags << Qt::dec << Qt::noshowbase;
    if (pd.dwFlags & PFD_DRAW_TO_WINDOW) d << " PFD_DRAW_TO_WINDOW";
    if (pd.dwFlags & PFD_DRAW_TO_BITMAP) d << " PFD_DRAW_TO_BITMAP";
    if (pd.dwFlags & PFD_SUPPORT_GDI) d << " PFD_SUPPORT_GDI";
    if (pd.dwFlags & PFD_SUPPORT_OPENGL) d << " PFD_SUPPORT_OPENGL";
    if (pd.dwFlags & PFD_GENERIC_ACCELERATED) d << " PFD_GENERIC_ACCELERATED";
    if (pd.dwFlags & PFD_SUPPORT_DIRECTDRAW) d << " PFD_SUPPORT_DIRECTDRAW";
    if (pd.dwFlags & PFD_DIRECT3D_ACCELERATED) d << " PFD_DIRECT3D_ACCELERATED";
    if (pd.dwFlags & PFD_SUPPORT_COMPOSITION) d << " PFD_SUPPORT_COMPOSITION";
    if (pd.dwFlags & PFD_GENERIC_FORMAT) d << " PFD_GENERIC_FORMAT";
    if (pd.dwFlags & PFD_NEED_PALETTE) d << " PFD_NEED_PALETTE";
    if (pd.dwFlags & PFD_NEED_SYSTEM_PALETTE) d << " PFD_NEED_SYSTEM_PALETTE";
    if (pd.dwFlags & PFD_DOUBLEBUFFER) d << " PFD_DOUBLEBUFFER";
    if (pd.dwFlags & PFD_STEREO) d << " PFD_STEREO";
    if (pd.dwFlags & PFD_SWAP_LAYER_BUFFERS) d << " PFD_SWAP_LAYER_BUFFERS";
    if (hasGLOverlay(pd)) d << " overlay";
    d << " iPixelType=" << pd.iPixelType << " cColorBits=" << pd.cColorBits
        << " cRedBits=" << pd.cRedBits << " cRedShift=" << pd.cRedShift
        << " cGreenBits=" << pd.cGreenBits << " cGreenShift=" << pd.cGreenShift
        << " cBlueBits=" << pd.cBlueBits << " cBlueShift=" << pd.cBlueShift;
    d  << " cDepthBits=" << pd.cDepthBits;
    if (pd.cStencilBits)
        d << " cStencilBits=" << pd.cStencilBits;
    if (pd.cAuxBuffers)
        d << " cAuxBuffers=" << pd.cAuxBuffers;
    d << " iLayerType=" << pd.iLayerType;
    if (pd.dwVisibleMask)
        d << " dwVisibleMask=" << pd.dwVisibleMask;
    if (pd.cAlphaBits)
        d << " cAlphaBits=" << pd.cAlphaBits << " cAlphaShift=" << pd.cAlphaShift;
    if (pd.cAccumBits)
        d << " cAccumBits=" << pd.cAccumBits << " cAccumRedBits=" << pd.cAccumRedBits
        << " cAccumGreenBits=" << pd.cAccumGreenBits << " cAccumBlueBits=" << pd.cAccumBlueBits
        << " cAccumAlphaBits=" << pd.cAccumAlphaBits;
    return d;
}
 
QDebug operator<<(QDebug d, const QOpenGLStaticContext &s)
{
    QDebugStateSaver saver(d);
    d.nospace();
    d << "OpenGL: " << s.vendor << ',' << s.renderer << " default "
        <<  s.defaultFormat;
    if (s.extensions &  QOpenGLStaticContext::SampleBuffers)
        d << ",SampleBuffers";
    if (s.hasExtensions())
        d << ", Extension-API present";
    d << "\nExtensions: " << (s.extensionNames.count(' ') + 1);
    if (QWindowsContext::verbose > 1)
        d << s.extensionNames;
    return d;
}
 
QDebug operator<<(QDebug d, const QWindowsOpenGLContextFormat &f)
{
    QDebugStateSaver saver(d);
    d.nospace();
    d << "ContextFormat: v" << (f.version >> 8) << '.' << (f.version & 0xFF)
        << " profile: " << f.profile << " options: " << f.options;
    return d;
}
#endif // !QT_NO_DEBUG_STREAM
 
// Check whether an obtained PIXELFORMATDESCRIPTOR matches the request.
static inline bool
    isAcceptableFormat(const QWindowsOpenGLAdditionalFormat &additional,
                       const PIXELFORMATDESCRIPTOR &pfd,
                       bool ignoreGLSupport = false) // ARB format may not contain it.
{
    const bool pixmapRequested = testFlag(additional.formatFlags, QWindowsGLRenderToPixmap);
    const bool pixmapOk = !pixmapRequested || testFlag(pfd.dwFlags, PFD_DRAW_TO_BITMAP);
    const bool colorOk =  !pixmapRequested || pfd.cColorBits == additional.pixmapDepth;
    const bool glOk = ignoreGLSupport || testFlag(pfd.dwFlags, PFD_SUPPORT_OPENGL);
    const bool overlayOk = hasGLOverlay(pfd) == testFlag(additional.formatFlags, QWindowsGLOverlay);
    return pixmapOk && glOk && overlayOk && colorOk;
}
 
static void describeFormats(HDC hdc)
{
    const int pfiMax = QOpenGLStaticContext::opengl32.describePixelFormat(hdc, 0, 0, nullptr);
    for (int i = 1; i <= pfiMax; i++) {
        PIXELFORMATDESCRIPTOR pfd;
        initPixelFormatDescriptor(&pfd);
        QOpenGLStaticContext::opengl32.describePixelFormat(hdc, i, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
        qCDebug(lcQpaGl) << '#' << i << '/' << pfiMax << ':' << pfd;
    }
}
 
// Classic GDI API
namespace GDI {
static QSurfaceFormat
    qSurfaceFormatFromPixelFormat(const PIXELFORMATDESCRIPTOR &pfd,
                                         QWindowsOpenGLAdditionalFormat *additionalIn = nullptr)
{
    QSurfaceFormat format;
    format.setRenderableType(QSurfaceFormat::OpenGL);
    if (pfd.dwFlags & PFD_DOUBLEBUFFER)
        format.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
    format.setDepthBufferSize(pfd.cDepthBits);
 
    if (pfd.iPixelType == PFD_TYPE_RGBA)
        format.setAlphaBufferSize(pfd.cAlphaBits);
    format.setRedBufferSize(pfd.cRedBits);
    format.setGreenBufferSize(pfd.cGreenBits);
    format.setBlueBufferSize(pfd.cBlueBits);
    format.setStencilBufferSize(pfd.cStencilBits);
    format.setStereo(pfd.dwFlags & PFD_STEREO);
    if (additionalIn) {
        QWindowsOpenGLAdditionalFormat additional;
        if (isDirectRendering(pfd))
            additional.formatFlags |= QWindowsGLDirectRendering;
        if (hasGLOverlay(pfd))
            additional.formatFlags |= QWindowsGLOverlay;
        if (pfd.cAccumRedBits)
            additional.formatFlags |= QWindowsGLAccumBuffer;
        if (testFlag(pfd.dwFlags, PFD_DRAW_TO_BITMAP)) {
            additional.formatFlags |= QWindowsGLRenderToPixmap;
            additional.pixmapDepth = pfd.cColorBits;
        }
        *additionalIn = additional;
    }
    return format;
}
 
static PIXELFORMATDESCRIPTOR
    qPixelFormatFromSurfaceFormat(const QSurfaceFormat &format,
                                  const QWindowsOpenGLAdditionalFormat &additional)
{
    PIXELFORMATDESCRIPTOR pfd;
    initPixelFormatDescriptor(&pfd);
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.iLayerType  = PFD_MAIN_PLANE;
    pfd.dwFlags = PFD_SUPPORT_OPENGL | PFD_SUPPORT_COMPOSITION;
    const bool isPixmap = (additional.formatFlags & QWindowsGLRenderToPixmap) != 0;
    pfd.dwFlags |= isPixmap ? PFD_DRAW_TO_BITMAP : PFD_DRAW_TO_WINDOW;
    if (!(additional.formatFlags & QWindowsGLDirectRendering))
        pfd.dwFlags |= PFD_GENERIC_FORMAT;
 
    if (format.stereo())
        pfd.dwFlags |= PFD_STEREO;
    if (format.swapBehavior() != QSurfaceFormat::SingleBuffer && !isPixmap)
        pfd.dwFlags |= PFD_DOUBLEBUFFER;
    pfd.cDepthBits =
        format.depthBufferSize() >= 0 ? format.depthBufferSize() : 32;
    const int redBufferSize = format.redBufferSize();
    if (redBufferSize != -1)
        pfd.cRedBits = BYTE(redBufferSize);
    const int greenBufferSize = format.greenBufferSize();
    if (greenBufferSize != -1)
        pfd.cGreenBits = BYTE(greenBufferSize);
    const int blueBufferSize = format.blueBufferSize();
    if (blueBufferSize != -1)
        pfd.cBlueBits = BYTE(blueBufferSize);
    pfd.cAlphaBits = format.alphaBufferSize() > 0 ? format.alphaBufferSize() : 8;
    pfd.cStencilBits = format.stencilBufferSize() > 0 ? format.stencilBufferSize() : 8;
    if (additional.formatFlags & QWindowsGLAccumBuffer)
        pfd.cAccumRedBits = pfd.cAccumGreenBits = pfd.cAccumBlueBits = pfd.cAccumAlphaBits = 16;
    return pfd;
}
 
// Choose a suitable pixelformat using GDI WinAPI in case ARB
// functions cannot be found. First tries to find a suitable
// format using GDI function ChoosePixelFormat(). Since that
// does not handle overlay and direct-rendering requests, manually loop
// over the available formats to find the best one.
// Note: As of Windows 7, it seems direct-rendering is handled, so,
// the code might be obsolete?
//
// NB! When using an implementation with a name different than opengl32.dll
// this code path should not be used since it will result in a mess due to GDI
// relying on and possibly calling back into functions in opengl32.dll (and not
// the one we are using). This is not a problem usually since for Mesa, which
// we are most likely to ship with a name other than opengl32.dll, the ARB code
// path should work. Hence the early bail out below.
//
static int choosePixelFormat(HDC hdc, const QSurfaceFormat &format,
                            const QWindowsOpenGLAdditionalFormat &additional,
                            PIXELFORMATDESCRIPTOR *obtainedPfd)
{
    if (QOpenGLStaticContext::opengl32.moduleIsNotOpengl32()) {
        qWarning("Attempted to use GDI functions with a non-opengl32.dll library");
        return 0;
    }
 
    // 1) Try ChoosePixelFormat().
    PIXELFORMATDESCRIPTOR requestedPfd = qPixelFormatFromSurfaceFormat(format, QWindowsGLDirectRendering);
    initPixelFormatDescriptor(obtainedPfd);
    int pixelFormat = ChoosePixelFormat(hdc, &requestedPfd);
    if (pixelFormat >= 0) {
        DescribePixelFormat(hdc, pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), obtainedPfd);
        if (isAcceptableFormat(additional, *obtainedPfd))
            return pixelFormat;
    }
    // 2) No matching format found, manual search loop.
    const int pfiMax = DescribePixelFormat(hdc, 0, 0, nullptr);
    int bestScore = -1;
    int bestPfi = -1;
    const bool stereoRequested = format.stereo();
    const bool accumBufferRequested = testFlag(additional.formatFlags, QWindowsGLAccumBuffer);
    const bool doubleBufferRequested = format.swapBehavior() == QSurfaceFormat::DoubleBuffer;
    const bool directRenderingRequested = testFlag(additional.formatFlags, QWindowsGLDirectRendering);
    for (int pfi = 1; pfi <= pfiMax; pfi++) {
        PIXELFORMATDESCRIPTOR checkPfd;
        initPixelFormatDescriptor(&checkPfd);
        DescribePixelFormat(hdc, pfi, sizeof(PIXELFORMATDESCRIPTOR), &checkPfd);
        if (isAcceptableFormat(additional, checkPfd)) {
            int score = checkPfd.cColorBits + checkPfd.cAlphaBits + checkPfd.cStencilBits;
            if (accumBufferRequested)
                score += checkPfd.cAccumBits;
            if (doubleBufferRequested == testFlag(checkPfd.dwFlags, PFD_DOUBLEBUFFER))
                score += 1000;
            if (stereoRequested == testFlag(checkPfd.dwFlags, PFD_STEREO))
                score += 2000;
            if (directRenderingRequested == isDirectRendering(checkPfd))
                score += 4000;
            if (checkPfd.iPixelType == PFD_TYPE_RGBA)
                score += 8000;
            if (score > bestScore) {
                bestScore = score;
                bestPfi = pfi;
                *obtainedPfd = checkPfd;
            }
            qCDebug(lcQpaGl) << __FUNCTION__ << "    checking  " << pfi << '/' << pfiMax
                << " score=" << score << " (best " << bestPfi << '/' << bestScore << ") " << checkPfd;
        }
    } // for
    if (bestPfi > 0)
        pixelFormat = bestPfi;
    return pixelFormat;
}
 
static inline HGLRC createContext(HDC hdc, HGLRC shared)
{
    HGLRC result = QOpenGLStaticContext::opengl32.wglCreateContext(hdc);
    if (!result) {
        qErrnoWarning("%s: wglCreateContext failed.", __FUNCTION__);
        return nullptr;
    }
    if (shared && !QOpenGLStaticContext::opengl32.wglShareLists(shared, result))
        qErrnoWarning("%s: wglShareLists() failed.", __FUNCTION__);
    return result;
}
} // namespace GDI
 
// ARB OpenGL extension API
namespace ARB {
// Choose a suitable pixelformat using ARB extension functions.
static int choosePixelFormat(HDC hdc,
                             const QOpenGLStaticContext &staticContext,
                             const QSurfaceFormat &format,
                             const QWindowsOpenGLAdditionalFormat &additional,
                             PIXELFORMATDESCRIPTOR *obtainedPfd)
{
    enum { attribSize = 42 };
    if ((additional.formatFlags & QWindowsGLRenderToPixmap) || !staticContext.hasExtensions())
        return 0;
 
    int iAttributes[attribSize];
    std::fill(iAttributes, iAttributes + attribSize, int(0));
    int i = 0;
    iAttributes[i++] = WGL_ACCELERATION_ARB;
    iAttributes[i++] = testFlag(additional.formatFlags, QWindowsGLDirectRendering) ?
                       WGL_FULL_ACCELERATION_ARB : WGL_NO_ACCELERATION_ARB;
    iAttributes[i++] = WGL_SUPPORT_OPENGL_ARB;
    iAttributes[i++] = TRUE;
    iAttributes[i++] = WGL_DRAW_TO_WINDOW_ARB;
    iAttributes[i++] = TRUE;
    iAttributes[i++] = WGL_COLOR_BITS_ARB;
 
    iAttributes[i++] = (format.redBufferSize() > 0)
                       && (format.greenBufferSize() > 0)
                       && (format.blueBufferSize() > 0) ?
                       format.redBufferSize() + format.greenBufferSize() + format.blueBufferSize() :
                       24;
    switch (format.swapBehavior()) {
    case QSurfaceFormat::SingleBuffer:
        iAttributes[i++] = WGL_DOUBLE_BUFFER_ARB;
        iAttributes[i++] = FALSE;
        break;
    case QSurfaceFormat::DefaultSwapBehavior:
    case QSurfaceFormat::DoubleBuffer:
    case QSurfaceFormat::TripleBuffer:
        iAttributes[i++] = WGL_DOUBLE_BUFFER_ARB;
        iAttributes[i++] = TRUE;
        break;
    }
    if (format.stereo()) {
        iAttributes[i++] = WGL_STEREO_ARB;
        iAttributes[i++] = TRUE;
    }
    if (format.depthBufferSize() >= 0) {
        iAttributes[i++] = WGL_DEPTH_BITS_ARB;
        iAttributes[i++] = format.depthBufferSize();
    }
    iAttributes[i++] = WGL_PIXEL_TYPE_ARB;
    iAttributes[i++] = WGL_TYPE_RGBA_ARB;
    if (format.redBufferSize() >= 0) {
        iAttributes[i++] = WGL_RED_BITS_ARB;
        iAttributes[i++] = format.redBufferSize();
    }
    if (format.greenBufferSize() >= 0) {
        iAttributes[i++] = WGL_GREEN_BITS_ARB;
        iAttributes[i++] = format.greenBufferSize();
    }
    if (format.blueBufferSize() >= 0) {
        iAttributes[i++] = WGL_BLUE_BITS_ARB;
        iAttributes[i++] = format.blueBufferSize();
    }
    iAttributes[i++] = WGL_ALPHA_BITS_ARB;
    iAttributes[i++] = format.alphaBufferSize() >= 0 ? format.alphaBufferSize() : 8;
    if (additional.formatFlags & QWindowsGLAccumBuffer) {
        iAttributes[i++] = WGL_ACCUM_BITS_ARB;
        iAttributes[i++] = 16;
    }
    iAttributes[i++] = WGL_STENCIL_BITS_ARB;
    iAttributes[i++] = 8;
    if (additional.formatFlags & QWindowsGLOverlay) {
        iAttributes[i++] = WGL_NUMBER_OVERLAYS_ARB;
        iAttributes[i++] = 1;
    }
    // must be the one before the last one
    const int samples = format.samples();
    const bool sampleBuffersRequested = samples > 1
            && testFlag(staticContext.extensions, QOpenGLStaticContext::SampleBuffers);
    int sampleBuffersKeyPosition = 0;
    int samplesValuePosition = 0;
    if (sampleBuffersRequested) {
        sampleBuffersKeyPosition = i;
        iAttributes[i++] = WGL_SAMPLE_BUFFERS_ARB;
        iAttributes[i++] = TRUE;
        iAttributes[i++] = WGL_SAMPLES_ARB;
        samplesValuePosition = i;
        iAttributes[i++] = format.samples();
    } else {
        iAttributes[i++] = WGL_SAMPLE_BUFFERS_ARB;
        iAttributes[i++] = FALSE;
    }
    // must be the last
    bool srgbRequested = format.colorSpace() == QColorSpace::SRgb;
    int srgbCapableKeyPosition = 0;
    if (srgbRequested) {
        srgbCapableKeyPosition = i;
        iAttributes[i++] = WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT;
        iAttributes[i++] = TRUE;
    }
    // If sample or sRGB request cannot be satisfied, reduce request.
    int pixelFormat = 0;
    uint numFormats = 0;
    while (true) {
        const bool valid =
            staticContext.wglChoosePixelFormatARB(hdc, iAttributes, nullptr, 1,
                                               &pixelFormat, &numFormats)
                && numFormats >= 1;
        if (valid || (!sampleBuffersRequested && !srgbRequested))
            break;
        // NB reductions must be done in reverse order (disable the last first, then move on to the one before that, etc.)
        if (srgbRequested) {
            iAttributes[srgbCapableKeyPosition] = 0;
            srgbRequested = false;
        } else if (sampleBuffersRequested) {
            if (iAttributes[samplesValuePosition] > 1) {
                iAttributes[samplesValuePosition] /= 2;
            } else if (iAttributes[samplesValuePosition] == 1) {
                // Fallback in case it is unable to initialize with any
                // samples to avoid falling back to the GDI path
                iAttributes[sampleBuffersKeyPosition] = 0;
                iAttributes[samplesValuePosition] = 0;
            } else {
                break;
            }
        }
    }
    // Verify if format is acceptable. Note that the returned
    // formats have been observed to not contain PFD_SUPPORT_OPENGL, ignore.
    initPixelFormatDescriptor(obtainedPfd);
    QOpenGLStaticContext::opengl32.describePixelFormat(hdc, pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), obtainedPfd);
    if (!isAcceptableFormat(additional, *obtainedPfd, true)) {
        qCDebug(lcQpaGl) << __FUNCTION__ << " obtained px #" << pixelFormat
            << " not acceptable=" << *obtainedPfd;
        pixelFormat = 0;
    }
 
#ifndef QT_NO_DEBUG_OUTPUT
    if (lcQpaGl().isDebugEnabled()) {
        QString message;
        QDebug nsp(&message);
        nsp << __FUNCTION__;
        if (sampleBuffersRequested)
            nsp << " samples=" << iAttributes[samplesValuePosition];
        nsp << " Attributes: " << Qt::hex << Qt::showbase;
        for (int ii = 0; ii < i; ++ii)
            nsp << iAttributes[ii] << ',';
        nsp << Qt::noshowbase << Qt::dec << "\n    obtained px #" << pixelFormat
            << " of " << numFormats << "\n    " << *obtainedPfd;
        qCDebug(lcQpaGl) << message;
    } // Debug
#endif
 
    return pixelFormat;
}
 
static QSurfaceFormat
    qSurfaceFormatFromHDC(const QOpenGLStaticContext &staticContext,
                          HDC hdc, int pixelFormat,
                          QWindowsOpenGLAdditionalFormat *additionalIn = nullptr)
{
    enum { attribSize = 42 };
 
    QSurfaceFormat result;
    result.setRenderableType(QSurfaceFormat::OpenGL);
    if (!staticContext.hasExtensions())
        return result;
    int iAttributes[attribSize];
    int iValues[attribSize];
    std::fill(iAttributes, iAttributes + attribSize, int(0));
    std::fill(iValues, iValues + attribSize, int(0));
 
    int i = 0;
    const bool hasSampleBuffers = testFlag(staticContext.extensions, QOpenGLStaticContext::SampleBuffers);
    const bool hasSrgbSupport = testFlag(staticContext.extensions, QOpenGLStaticContext::sRGBCapableFramebuffer);
 
    iAttributes[i++] = WGL_DOUBLE_BUFFER_ARB; // 0
    iAttributes[i++] = WGL_DEPTH_BITS_ARB; // 1
    iAttributes[i++] = WGL_PIXEL_TYPE_ARB; // 2
    iAttributes[i++] = WGL_RED_BITS_ARB; // 3
    iAttributes[i++] = WGL_GREEN_BITS_ARB; // 4
    iAttributes[i++] = WGL_BLUE_BITS_ARB; // 5
    iAttributes[i++] = WGL_ALPHA_BITS_ARB; // 6
    iAttributes[i++] = WGL_ACCUM_BITS_ARB; // 7
    iAttributes[i++] = WGL_STENCIL_BITS_ARB; // 8
    iAttributes[i++] = WGL_STEREO_ARB; // 9
    iAttributes[i++] = WGL_ACCELERATION_ARB; // 10
    iAttributes[i++] = WGL_NUMBER_OVERLAYS_ARB; // 11
    if (hasSampleBuffers) {
        iAttributes[i++] = WGL_SAMPLE_BUFFERS_ARB; // 12
        iAttributes[i++] = WGL_SAMPLES_ARB; // 13
    }
    if (hasSrgbSupport)
        iAttributes[i++] = WGL_FRAMEBUFFER_SRGB_CAPABLE_EXT; // 12 or 14
 
    if (!staticContext.wglGetPixelFormatAttribIVARB(hdc, pixelFormat, 0, i,
                                        iAttributes, iValues)) {
        qErrnoWarning("%s: wglGetPixelFormatAttribIVARB() failed for basic parameters.", __FUNCTION__);
        return result;
    }
    result.setSwapBehavior(iValues[0] ? QSurfaceFormat::DoubleBuffer : QSurfaceFormat::SingleBuffer);
    result.setDepthBufferSize(iValues[1]);
    result.setRedBufferSize(iValues[3]);
    result.setGreenBufferSize(iValues[4]);
    result.setBlueBufferSize(iValues[5]);
    result.setAlphaBufferSize(iValues[6]);
    result.setStencilBufferSize(iValues[8]);
    if (iValues[9])
        result.setOption(QSurfaceFormat::StereoBuffers);
 
    if (hasSampleBuffers) {
        result.setSamples(iValues[13]);
        if (hasSrgbSupport && iValues[14])
            result.setColorSpace(QColorSpace::SRgb);
    } else {
        if (hasSrgbSupport && iValues[12])
            result.setColorSpace(QColorSpace::SRgb);
    }
    if (additionalIn) {
        if (iValues[7])
            additionalIn->formatFlags |= QWindowsGLAccumBuffer;
        if (iValues[10] == WGL_FULL_ACCELERATION_ARB)
            additionalIn->formatFlags |= QWindowsGLDirectRendering;
        if (iValues[11])
            additionalIn->formatFlags |= QWindowsGLOverlay;
    }
    return result;
}
 
static HGLRC createContext(const QOpenGLStaticContext &staticContext,
                           HDC hdc,
                           const QSurfaceFormat &format,
                           const QWindowsOpenGLAdditionalFormat &,
                           HGLRC shared = nullptr)
{
    enum { attribSize = 11 };
 
    if (!staticContext.hasExtensions())
        return nullptr;
    int attributes[attribSize];
    int attribIndex = 0;
    std::fill(attributes, attributes + attribSize, int(0));
 
    // We limit the requested version by the version of the static context as
    // wglCreateContextAttribsARB fails and returns NULL if the requested context
    // version is not supported. This means that we will get the closest supported
    // context format that that which was requested and is supported by the driver
    const int requestedVersion = qMin((format.majorVersion() << 8) + format.minorVersion(),
                                      staticContext.defaultFormat.version);
    const int majorVersion = requestedVersion >> 8;
    const int minorVersion = requestedVersion & 0xFF;
 
    if (requestedVersion > 0x0101) {
        attributes[attribIndex++] = WGL_CONTEXT_MAJOR_VERSION_ARB;
        attributes[attribIndex++] = majorVersion;
        attributes[attribIndex++] = WGL_CONTEXT_MINOR_VERSION_ARB;
        attributes[attribIndex++] = minorVersion;
    }
 
    int flags = 0;
    if (format.testOption(QSurfaceFormat::DebugContext))
        flags |= WGL_CONTEXT_DEBUG_BIT_ARB;
    if (requestedVersion >= 0x0300) {
        if (!format.testOption(QSurfaceFormat::DeprecatedFunctions))
            flags |= WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB;
    }
    attributes[attribIndex++] = WGL_CONTEXT_FLAGS_ARB;
    attributes[attribIndex++] = flags;
 
    if (requestedVersion >= 0x0302) {
        switch (format.profile()) {
        case QSurfaceFormat::NoProfile:
            break;
        case QSurfaceFormat::CoreProfile:
            attributes[attribIndex++] = WGL_CONTEXT_PROFILE_MASK_ARB;
            attributes[attribIndex++] = WGL_CONTEXT_CORE_PROFILE_BIT_ARB;
            break;
        case QSurfaceFormat::CompatibilityProfile:
            attributes[attribIndex++] = WGL_CONTEXT_PROFILE_MASK_ARB;
            attributes[attribIndex++] = WGL_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB;
            break;
        }
    }
 
    if (format.testOption(QSurfaceFormat::ResetNotification)) {
        attributes[attribIndex++] = RESET_NOTIFICATION_STRATEGY_ARB;
        attributes[attribIndex++] = LOSE_CONTEXT_ON_RESET_ARB;
    }
 
    qCDebug(lcQpaGl) << __FUNCTION__ << "Creating context version"
        << majorVersion << '.' << minorVersion <<  attribIndex / 2 << "attributes";
 
    const HGLRC result =
        staticContext.wglCreateContextAttribsARB(hdc, shared, attributes);
    if (!result) {
        QString message;
        QDebug(&message).nospace() << __FUNCTION__ << ": wglCreateContextAttribsARB() failed (GL error code: 0x"
            << Qt::hex << staticContext.opengl32.glGetError() << Qt::dec << ") for format: " << format << ", shared context: " << shared;
        qErrnoWarning("%s", qPrintable(message));
    }
    return result;
}
 
} // namespace ARB
 
// Helpers for temporary contexts
static inline HWND createDummyGLWindow()
{
    return QWindowsContext::instance()->
        createDummyWindow(QStringLiteral("OpenGLDummyWindow"),
                          L"OpenGLDummyWindow", nullptr, WS_OVERLAPPED | WS_CLIPCHILDREN | WS_CLIPSIBLINGS);
}
 
// Create a dummy GL context (see QOpenGLTemporaryContext).
static inline HGLRC createDummyGLContext(HDC dc)
{
    if (!dc)
        return nullptr;
    PIXELFORMATDESCRIPTOR pixelFormDescriptor;
    initPixelFormatDescriptor(&pixelFormDescriptor);
    pixelFormDescriptor.dwFlags = PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW | PFD_GENERIC_FORMAT;
    pixelFormDescriptor.iPixelType = PFD_TYPE_RGBA;
    // Use the GDI variant, for the dummy this is fine, even when using something other than opengl32.dll.
    const int pixelFormat = ChoosePixelFormat(dc, &pixelFormDescriptor);
    if (!pixelFormat) {
        qErrnoWarning("%s: ChoosePixelFormat failed.", __FUNCTION__);
        return nullptr;
    }
    if (!QOpenGLStaticContext::opengl32.setPixelFormat(dc, pixelFormat, &pixelFormDescriptor)) {
        qErrnoWarning("%s: SetPixelFormat failed.", __FUNCTION__);
        return nullptr;
    }
    HGLRC rc = QOpenGLStaticContext::opengl32.wglCreateContext(dc);
    if (!rc) {
        qErrnoWarning("%s: wglCreateContext failed.", __FUNCTION__);
        return nullptr;
    }
    return rc;
}
 
static inline QOpenGLContextData currentOpenGLContextData()
{
    QOpenGLContextData result;
    result.hdc = QOpenGLStaticContext::opengl32.wglGetCurrentDC();
    result.renderingContext = QOpenGLStaticContext::opengl32.wglGetCurrentContext();
    return result;
}
 
static inline QOpenGLContextData createDummyWindowOpenGLContextData()
{
    QOpenGLContextData result;
    result.hwnd = createDummyGLWindow();
    result.hdc = GetDC(result.hwnd);
    result.renderingContext = createDummyGLContext(result.hdc);
    return result;
}
 
QWindowsOpenGLContextFormat QWindowsOpenGLContextFormat::current()
{
    QWindowsOpenGLContextFormat result;
    const QByteArray version = QOpenGLStaticContext::getGlString(GL_VERSION);
    int major, minor;
    if (QPlatformOpenGLContext::parseOpenGLVersion(version, major, minor))
        result.version = (major << 8) + minor;
    else
        result.version = 0x0200;
    result.profile = QSurfaceFormat::NoProfile;
    if (result.version < 0x0300) {
        result.options |= QSurfaceFormat::DeprecatedFunctions;
        return result;
    }
    // v3 onwards
    GLint value = 0;
    QOpenGLStaticContext::opengl32.glGetIntegerv(GL_CONTEXT_FLAGS, &value);
    if (!(value & GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT))
        result.options |= QSurfaceFormat::DeprecatedFunctions;
    if (value & GL_CONTEXT_FLAG_DEBUG_BIT)
        result.options |= QSurfaceFormat::DebugContext;
    if (result.version < 0x0302)
        return result;
    // v3.2 onwards: Profiles
    value = 0;
    QOpenGLStaticContext::opengl32.glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &value);
    if (value & GL_CONTEXT_CORE_PROFILE_BIT)
        result.profile = QSurfaceFormat::CoreProfile;
    else if (value & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT)
        result.profile = QSurfaceFormat::CompatibilityProfile;
    return result;
}
 
void QWindowsOpenGLContextFormat::apply(QSurfaceFormat *format) const
{
    format->setMajorVersion(version >> 8);
    format->setMinorVersion(version & 0xFF);
    format->setProfile(profile);
    if (options & QSurfaceFormat::DebugContext)
        format->setOption(QSurfaceFormat::DebugContext);
    if (options & QSurfaceFormat::DeprecatedFunctions)
        format->setOption(QSurfaceFormat::DeprecatedFunctions);
}
 
class QOpenGLTemporaryContext
{
    Q_DISABLE_COPY_MOVE(QOpenGLTemporaryContext)
public:
    QOpenGLTemporaryContext();
    ~QOpenGLTemporaryContext();
 
private:
    const QOpenGLContextData m_previous;
    const QOpenGLContextData m_current;
};
 
QOpenGLTemporaryContext::QOpenGLTemporaryContext() :
    m_previous(currentOpenGLContextData()),
    m_current(createDummyWindowOpenGLContextData())
{
    QOpenGLStaticContext::opengl32.wglMakeCurrent(m_current.hdc, m_current.renderingContext);
}
 
QOpenGLTemporaryContext::~QOpenGLTemporaryContext()
{
    QOpenGLStaticContext::opengl32.wglMakeCurrent(m_previous.hdc, m_previous.renderingContext);
    ReleaseDC(m_current.hwnd, m_current.hdc);
    DestroyWindow(m_current.hwnd);
    QOpenGLStaticContext::opengl32.wglDeleteContext(m_current.renderingContext);
}
 
#define SAMPLE_BUFFER_EXTENSION "GL_ARB_multisample"
#define ROBUSTNESS_EXTENSION "GL_ARB_robustness"
 
QOpenGLStaticContext::QOpenGLStaticContext() :
    vendor(QOpenGLStaticContext::getGlString(GL_VENDOR)),
    renderer(QOpenGLStaticContext::getGlString(GL_RENDERER)),
    extensionNames(QOpenGLStaticContext::getGlString(GL_EXTENSIONS)),
    extensions(0),
    defaultFormat(QWindowsOpenGLContextFormat::current()),
    wglGetPixelFormatAttribIVARB(reinterpret_cast<WglGetPixelFormatAttribIVARB>(
        reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("wglGetPixelFormatAttribivARB")))),
    wglChoosePixelFormatARB(reinterpret_cast<WglChoosePixelFormatARB>(
        reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("wglChoosePixelFormatARB")))),
    wglCreateContextAttribsARB(reinterpret_cast<WglCreateContextAttribsARB>(
        reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("wglCreateContextAttribsARB")))),
    wglSwapInternalExt(reinterpret_cast<WglSwapInternalExt>(
        reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("wglSwapIntervalEXT")))),
    wglGetSwapInternalExt(reinterpret_cast<WglGetSwapInternalExt>(
        reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("wglGetSwapIntervalEXT")))),
    wglGetExtensionsStringARB(reinterpret_cast<WglGetExtensionsStringARB>(
        reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("wglGetExtensionsStringARB"))))
{
    if (defaultFormat.version < 0x0300) {
        if (extensionNames.startsWith(SAMPLE_BUFFER_EXTENSION " ")
                || extensionNames.indexOf(" " SAMPLE_BUFFER_EXTENSION " ") != -1)
            extensions |= SampleBuffers;
        if (extensionNames.startsWith(ROBUSTNESS_EXTENSION " ")
                || extensionNames.indexOf(" " ROBUSTNESS_EXTENSION " ") != -1)
            extensions |= Robustness;
    } else {
        typedef const GLubyte * (APIENTRY *glGetStringi_t)(GLenum, GLuint);
        auto glGetStringi = reinterpret_cast<glGetStringi_t>(
            reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("glGetStringi")));
        if (glGetStringi) {
            GLint n = 0;
            QOpenGLStaticContext::opengl32.glGetIntegerv(GL_NUM_EXTENSIONS, &n);
            for (GLint i = 0; i < n; ++i) {
                const char *p = reinterpret_cast<const char *>(glGetStringi(GL_EXTENSIONS, i));
                if (p) {
                    if (!strcmp(p, SAMPLE_BUFFER_EXTENSION))
                        extensions |= SampleBuffers;
                    else if (!strcmp(p, ROBUSTNESS_EXTENSION))
                        extensions |= Robustness;
                }
            }
        }
    }
}
 
QByteArray QOpenGLStaticContext::getGlString(unsigned int which)
{
    if (const GLubyte *s = opengl32.glGetString(which))
        return QByteArray(reinterpret_cast<const char*>(s));
    return QByteArray();
}
 
QOpenGLStaticContext *QOpenGLStaticContext::create(bool softwareRendering)
{
    if (!opengl32.init(softwareRendering)) {
        qWarning("Failed to load and resolve WGL/OpenGL functions");
        return nullptr;
    }
 
    // We need a current context for wglGetProcAdress()/getGLString() to work.
    QScopedPointer<QOpenGLTemporaryContext> temporaryContext;
    if (!QOpenGLStaticContext::opengl32.wglGetCurrentContext())
        temporaryContext.reset(new QOpenGLTemporaryContext);
    auto *result = new QOpenGLStaticContext;
    qCDebug(lcQpaGl) << __FUNCTION__ << *result;
    return result;
}
 
QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext,
                                     QOpenGLContext *context) :
    m_staticContext(staticContext)
{
    if (!m_staticContext) // Something went very wrong. Stop here, isValid() will return false.
        return;
 
    QSurfaceFormat format = context->format();
    if (format.renderableType() == QSurfaceFormat::DefaultRenderableType)
        format.setRenderableType(QSurfaceFormat::OpenGL);
    if (format.renderableType() != QSurfaceFormat::OpenGL)
        return;
 
    // workaround for matrox driver:
    // make a cheap call to opengl to force loading of DLL
    static bool opengl32dll = false;
    if (!opengl32dll) {
        GLint params;
        staticContext->opengl32.glGetIntegerv(GL_DEPTH_BITS, &params);
        opengl32dll = true;
    }
 
    // SetPixelFormat (as of Windows 7) requires a real window.
    // Create a dummy one as we are not associated with a window yet.
    // Try to find a suitable pixel format using preferably ARB extensions
    // (default to GDI) and store that.
    HWND dummyWindow = nullptr;
    HDC hdc = nullptr;
    bool tryExtensions = false;
    int obtainedSwapInterval = -1;
    do {
        dummyWindow = createDummyGLWindow();
        if (!dummyWindow)
            break;
        hdc = GetDC(dummyWindow);
        if (!hdc)
            break;
 
        if (QWindowsContext::verbose > 1)
            describeFormats(hdc);
        // Preferably use direct rendering and ARB extensions (unless pixmap
        // or explicitly turned off on command line).
        const QWindowsOpenGLAdditionalFormat
            requestedAdditional(QWindowsGLDirectRendering);
        tryExtensions = m_staticContext->hasExtensions()
                && !testFlag(requestedAdditional.formatFlags, QWindowsGLRenderToPixmap)
                && !(QWindowsIntegration::instance()->options() & QWindowsIntegration::DisableArb);
        QWindowsOpenGLAdditionalFormat obtainedAdditional;
        if (tryExtensions) {
            if (m_staticContext->wglGetExtensionsStringARB) {
                const char *exts = m_staticContext->wglGetExtensionsStringARB(hdc);
                if (exts) {
                    qCDebug(lcQpaGl) << __FUNCTION__ << "WGL extensions:" << exts;
                    if (strstr(exts, "WGL_EXT_framebuffer_sRGB"))
                        m_staticContext->extensions |= QOpenGLStaticContext::sRGBCapableFramebuffer;
                }
            }
            m_pixelFormat =
                ARB::choosePixelFormat(hdc, *m_staticContext, format,
                                       requestedAdditional, &m_obtainedPixelFormatDescriptor);
            if (m_pixelFormat > 0) {
                m_obtainedFormat =
                    ARB::qSurfaceFormatFromHDC(*m_staticContext, hdc, m_pixelFormat,
                                                &obtainedAdditional);
                m_extensionsUsed = true;
            }
        } // tryExtensions
        if (!m_pixelFormat) { // Failed, try GDI
            m_pixelFormat = GDI::choosePixelFormat(hdc, format, requestedAdditional,
                                                   &m_obtainedPixelFormatDescriptor);
            if (m_pixelFormat)
                m_obtainedFormat =
                    GDI::qSurfaceFormatFromPixelFormat(m_obtainedPixelFormatDescriptor,
                                                       &obtainedAdditional);
        } // try GDI
        if (!m_pixelFormat) {
            qWarning("%s: Unable find a suitable pixel format.", __FUNCTION__);
            break;
        }
        if (!QOpenGLStaticContext::opengl32.setPixelFormat(hdc, m_pixelFormat, &m_obtainedPixelFormatDescriptor)) {
            qErrnoWarning("SetPixelFormat failed.");
            break;
        }
        // Create context with sharing, again preferably using ARB.
        HGLRC sharingRenderingContext = nullptr;
        if (const QPlatformOpenGLContext *sc = context->shareHandle())
            sharingRenderingContext = static_cast<const QWindowsGLContext *>(sc)->renderingContext();
 
        if (m_extensionsUsed)
            m_renderingContext =
                ARB::createContext(*m_staticContext, hdc,
                                   format,
                                   requestedAdditional,
                                   sharingRenderingContext);
        if (!m_renderingContext)
            m_renderingContext = GDI::createContext(hdc, sharingRenderingContext);
 
        if (!m_renderingContext) {
            qWarning("Unable to create a GL Context.");
            break;
        }
 
        // Query obtained parameters and apply swap interval.
        if (!updateObtainedParams(hdc, &obtainedSwapInterval))
            break;
 
    } while (false);
 
    if (hdc)
        ReleaseDC(dummyWindow, hdc);
    if (dummyWindow)
        DestroyWindow(dummyWindow);
 
    qCDebug(lcQpaGl) << __FUNCTION__ << this << (tryExtensions ? "ARB" : "GDI")
        << " requested: " << context->format()
        << "\n    obtained #" << m_pixelFormat << (m_extensionsUsed ? "ARB" : "GDI") << m_obtainedFormat
        << "\n    " << m_obtainedPixelFormatDescriptor << " swap interval: " << obtainedSwapInterval
        << "\n    default: " << m_staticContext->defaultFormat
        << "\n    HGLRC=" << m_renderingContext;
}
 
QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext, HGLRC wglcontext, HWND wnd)
    : m_staticContext(staticContext)
{
    if (!m_staticContext) // Something went very wrong. Stop here, isValid() will return false.
        return;
 
    HDC dc = GetDC(wnd);
    // A window with an associated pixel format is mandatory.
    // When no SetPixelFormat() call has been made, the following will fail.
    m_pixelFormat = GetPixelFormat(dc);
    bool ok = m_pixelFormat != 0;
    if (!ok)
        qWarning("QWindowsGLContext: Failed to get pixel format");
    ok = DescribePixelFormat(dc, m_pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &m_obtainedPixelFormatDescriptor);
    if (!ok) {
        qWarning("QWindowsGLContext: Failed to describe pixel format");
    } else {
        QWindowsOpenGLAdditionalFormat obtainedAdditional;
        m_obtainedFormat = GDI::qSurfaceFormatFromPixelFormat(m_obtainedPixelFormatDescriptor, &obtainedAdditional);
        m_renderingContext = wglcontext;
        ok = updateObtainedParams(dc);
    }
 
    ReleaseDC(wnd, dc);
 
    if (ok)
        m_ownsContext = false;
    else
        m_renderingContext = nullptr;
}
 
QWindowsGLContext::~QWindowsGLContext()
{
    if (m_renderingContext && m_ownsContext)
        QOpenGLStaticContext::opengl32.wglDeleteContext(m_renderingContext);
    releaseDCs();
}
 
bool QWindowsGLContext::updateObtainedParams(HDC hdc, int *obtainedSwapInterval)
{
    HGLRC prevContext = QOpenGLStaticContext::opengl32.wglGetCurrentContext();
    HDC prevSurface = QOpenGLStaticContext::opengl32.wglGetCurrentDC();
 
    if (!QOpenGLStaticContext::opengl32.wglMakeCurrent(hdc, m_renderingContext)) {
        qWarning("Failed to make context current.");
        return false;
    }
 
    QWindowsOpenGLContextFormat::current().apply(&m_obtainedFormat);
 
    if (m_staticContext->wglGetSwapInternalExt && obtainedSwapInterval)
        *obtainedSwapInterval = m_staticContext->wglGetSwapInternalExt();
 
    if (testFlag(m_staticContext->extensions, QOpenGLStaticContext::Robustness)) {
        GLint value = 0;
        QOpenGLStaticContext::opengl32.glGetIntegerv(RESET_NOTIFICATION_STRATEGY_ARB, &value);
        if (value == LOSE_CONTEXT_ON_RESET_ARB)
            m_obtainedFormat.setOption(QSurfaceFormat::ResetNotification);
        m_getGraphicsResetStatus = reinterpret_cast<GlGetGraphicsResetStatusArbType>(
            reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress("glGetGraphicsResetStatusARB")));
    }
 
    QOpenGLStaticContext::opengl32.wglMakeCurrent(prevSurface, prevContext);
    return true;
}
 
void QWindowsGLContext::releaseDCs()
{
    for (const auto &e : m_windowContexts)
        ReleaseDC(e.hwnd, e.hdc);
    m_windowContexts.clear();
}
 
static inline QWindowsWindow *glWindowOf(QPlatformSurface *s)
{
    return static_cast<QWindowsWindow *>(s);
}
 
static inline HWND handleOf(QPlatformSurface *s)
{
    return glWindowOf(s)->handle();
}
 
// Find a window in a context list.
static inline const QOpenGLContextData *
    findByHWND(const std::vector<QOpenGLContextData> &data, HWND hwnd)
{
    for (const auto &e : data) {
        if (e.hwnd == hwnd)
            return &e;
    }
    return nullptr;
}
 
void QWindowsGLContext::swapBuffers(QPlatformSurface *surface)
{
    if (QWindowsContext::verbose > 1)
        qCDebug(lcQpaGl) << __FUNCTION__ << surface;
 
    if (const QOpenGLContextData *contextData = findByHWND(m_windowContexts, handleOf(surface)))
        QOpenGLStaticContext::opengl32.swapBuffers(contextData->hdc);
    else
        qWarning("%s: Cannot find window %p", __FUNCTION__, handleOf(surface));
}
 
bool QWindowsGLContext::makeCurrent(QPlatformSurface *surface)
{
#ifdef DEBUG_GL
    if (QWindowsContext::verbose > 1)
        qCDebug(lcQpaGl) << __FUNCTION__ << this << m_windowContexts.size() << "contexts";
#endif // DEBUG_GL
 
    Q_ASSERT(surface->surface()->supportsOpenGL());
 
    // Do we already have a DC entry for that window?
    auto *window = static_cast<QWindowsWindow *>(surface);
    window->aboutToMakeCurrent();
    const HWND hwnd = window->handle();
    if (const QOpenGLContextData *contextData = findByHWND(m_windowContexts, hwnd)) {
        // Repeated calls to wglMakeCurrent when vsync is enabled in the driver will
        // often result in 100% cpuload. This check is cheap and avoids the problem.
        // This is reproducible on NVidia cards and Intel onboard chips.
        if (QOpenGLStaticContext::opengl32.wglGetCurrentContext() == contextData->renderingContext
                && QOpenGLStaticContext::opengl32.wglGetCurrentDC() == contextData->hdc) {
            return true;
        }
        const bool success = QOpenGLStaticContext::opengl32.wglMakeCurrent(contextData->hdc, contextData->renderingContext);
        if (!success)
            qErrnoWarning("%s: wglMakeCurrent() failed for existing context data", __FUNCTION__);
        return success;
    }
    // Create a new entry.
    const QOpenGLContextData newContext(m_renderingContext, hwnd, GetDC(hwnd));
    if (!newContext.hdc)
        return false;
    // Initialize pixel format first time. This will apply to
    // the HWND as well and  must be done only once.
    if (!window->testFlag(QWindowsWindow::OpenGlPixelFormatInitialized)) {
        if (!QOpenGLStaticContext::opengl32.setPixelFormat(newContext.hdc, m_pixelFormat, &m_obtainedPixelFormatDescriptor)) {
            qErrnoWarning("%s: SetPixelFormat() failed", __FUNCTION__);
            ReleaseDC(newContext.hwnd, newContext.hdc);
            return false;
        }
        window->setFlag(QWindowsWindow::OpenGlPixelFormatInitialized);
        if (m_obtainedFormat.swapBehavior() == QSurfaceFormat::DoubleBuffer)
            window->setFlag(QWindowsWindow::OpenGLDoubleBuffered);
    }
    m_windowContexts.push_back(newContext);
 
    m_lost = false;
    bool success = QOpenGLStaticContext::opengl32.wglMakeCurrent(newContext.hdc, newContext.renderingContext);
    if (!success) {
        if (m_getGraphicsResetStatus && m_getGraphicsResetStatus()) {
            m_lost = true;
            qCDebug(lcQpaGl) << "makeCurrent(): context loss detected" << this;
            // Drop the surface. Will recreate on the next makeCurrent.
            window->invalidateSurface();
        } else {
            qErrnoWarning("%s: wglMakeCurrent() failed", __FUNCTION__);
        }
    }
 
    // Set the swap interval
    if (m_staticContext->wglSwapInternalExt) {
        const int interval = surface->format().swapInterval();
        if (m_swapInterval != interval)
            m_swapInterval = interval;
        if (interval >= 0)
            m_staticContext->wglSwapInternalExt(interval);
    }
 
    return success;
}
 
void QWindowsGLContext::doneCurrent()
{
#ifdef DEBUG_GL
    if (QWindowsContext::verbose > 1)
        qCDebug(lcQpaGl) << __FUNCTION__ << this << m_windowContexts.size() << "contexts";
#endif // DEBUG_GL
    QOpenGLStaticContext::opengl32.wglMakeCurrent(nullptr, nullptr);
    releaseDCs();
}
 
QFunctionPointer QWindowsGLContext::getProcAddress(const char *procName)
{
    // Even though we use QFunctionPointer, it does not mean the function can be called.
    // It will need to be cast to the proper function type with the correct calling
    // convention. QFunctionPointer is nothing more than a glorified void* here.
    auto procAddress = reinterpret_cast<QFunctionPointer>(QOpenGLStaticContext::opengl32.wglGetProcAddress(procName));
 
    // We support AllGLFunctionsQueryable, which means this function must be able to
    // return a function pointer even for functions that are in GL.h and exported
    // normally from opengl32.dll. wglGetProcAddress() is not guaranteed to work for such
    // functions, however in QT_OPENGL_DYNAMIC builds QOpenGLFunctions will just blindly
    // call into here for _any_ OpenGL function.
    if (procAddress == nullptr || reinterpret_cast<quintptr>(procAddress) < 4u
        || procAddress == reinterpret_cast<QFunctionPointer>(-1)) {
        procAddress = QOpenGLStaticContext::opengl32.resolve(procName);
    }
 
    if (QWindowsContext::verbose > 1)
        qCDebug(lcQpaGl) << __FUNCTION__ <<  procName << QOpenGLStaticContext::opengl32.wglGetCurrentContext() << "returns" << procAddress;
 
    return reinterpret_cast<QFunctionPointer>(procAddress);
}
 
QT_END_NAMESPACE