/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * This file is part of the LibreOffice project.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

#include "opengl/win/gdiimpl.hxx"

#include <comphelper/windowserrorstring.hxx>
#include <desktop/exithelper.h>
#include <opengl/zone.hxx>
#include <o3tl/lru_map.hxx>
#include <win/wincomp.hxx>
#include <win/saldata.hxx>
#include <win/salframe.h>
#include <win/salinst.h>
#include <GL/wglew.h>

static std::vector<HGLRC> g_vShareList;

class GLWinWindow : public GLWindow
{
public:
    HWND                    hWnd;
    HDC                     hDC;
    HGLRC                   hRC;
    GLWinWindow();
};

GLWinWindow::GLWinWindow()
    : hWnd(nullptr)
    , hDC(nullptr)
    , hRC(nullptr)
{
}

class WinOpenGLContext : public OpenGLContext
{
public:
    bool init( HDC hDC, HWND hWnd );
    virtual bool initWindow() override;
private:
    GLWinWindow m_aGLWin;
    virtual const GLWindow& getOpenGLWindow() const override { return m_aGLWin; }
    virtual GLWindow& getModifiableOpenGLWindow() override { return m_aGLWin; }
    virtual bool ImplInit() override;
    virtual void makeCurrent() override;
    virtual void destroyCurrentContext() override;
    virtual bool isCurrent() override;
    virtual bool isAnyCurrent() override;
    virtual void resetCurrent() override;
    virtual void swapBuffers() override;
};

void WinOpenGLContext::swapBuffers()
{
    OpenGLZone aZone;

    SwapBuffers(m_aGLWin.hDC);

    BuffersSwapped();
}

void WinOpenGLContext::resetCurrent()
{
    clearCurrent();

    OpenGLZone aZone;

    wglMakeCurrent(nullptr, nullptr);
}

bool WinOpenGLContext::isCurrent()
{
    OpenGLZone aZone;
    return wglGetCurrentContext() == m_aGLWin.hRC &&
           wglGetCurrentDC() == m_aGLWin.hDC;
}

bool WinOpenGLContext::isAnyCurrent()
{
    return wglGetCurrentContext() != nullptr;
}

void WinOpenGLContext::makeCurrent()
{
    if (isCurrent())
        return;

    OpenGLZone aZone;

    clearCurrent();

    if (!wglMakeCurrent(m_aGLWin.hDC, m_aGLWin.hRC))
    {
        SAL_WARN("vcl.opengl", "wglMakeCurrent failed: " << WindowsErrorString(GetLastError()));
        return;
    }

    registerAsCurrent();
}

bool WinOpenGLContext::init(HDC hDC, HWND hWnd)
{
    if (isInitialized())
        return true;

    m_aGLWin.hDC = hDC;
    m_aGLWin.hWnd = hWnd;
    return ImplInit();
}

bool WinOpenGLContext::initWindow()
{
    if( !m_pChildWindow )
    {
        SystemWindowData winData = generateWinData(mpWindow, false);
        m_pChildWindow = VclPtr<SystemChildWindow>::Create(mpWindow, 0, &winData, false);
    }

    if (m_pChildWindow)
    {
        InitChildWindow(m_pChildWindow.get());
        const SystemEnvData* sysData(m_pChildWindow->GetSystemData());
        m_aGLWin.hWnd = sysData->hWnd;
    }

    m_aGLWin.hDC = GetDC(m_aGLWin.hWnd);
    return true;
}

void WinOpenGLContext::destroyCurrentContext()
{
    if (m_aGLWin.hRC)
    {
        std::vector<HGLRC>::iterator itr = std::remove(g_vShareList.begin(), g_vShareList.end(), m_aGLWin.hRC);
        if (itr != g_vShareList.end())
            g_vShareList.erase(itr);

        if (wglGetCurrentContext() != nullptr)
            wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext( m_aGLWin.hRC );
        ReleaseDC( m_aGLWin.hWnd, m_aGLWin.hDC );
        m_aGLWin.hRC = nullptr;
    }
}

static LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
        return 0;
    case WM_CLOSE:
        PostQuitMessage(0);
        return 0;
    case WM_DESTROY:
        return 0;
    default:
        return DefWindowProc(hwnd, message, wParam, lParam);
    }
}

bool InitTempWindow(HWND& hwnd, int width, int height, const PIXELFORMATDESCRIPTOR& inPfd, GLWinWindow& glWin)
{
    OpenGLZone aZone;

    PIXELFORMATDESCRIPTOR  pfd = inPfd;
    int ret;
    WNDCLASS wc;
    wc.style = 0;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = wc.cbWndExtra = 0;
    wc.hInstance = nullptr;
    wc.hIcon = nullptr;
    wc.hCursor = nullptr;
    wc.hbrBackground = nullptr;
    wc.lpszMenuName = nullptr;
    wc.lpszClassName = "GLRenderer";
    RegisterClass(&wc);
    hwnd = CreateWindow(wc.lpszClassName, nullptr, WS_DISABLED, 0, 0, width, height, nullptr, nullptr, wc.hInstance, nullptr);
    glWin.hDC = GetDC(hwnd);

    int nPixelFormat = ChoosePixelFormat(glWin.hDC, &pfd);
    if (!nPixelFormat)
    {
        ReleaseDC(hwnd, glWin.hDC);
        DestroyWindow(hwnd);
        return false;
    }
    ret = SetPixelFormat(glWin.hDC, nPixelFormat, &pfd);
    if(!ret)
    {
        ReleaseDC(hwnd, glWin.hDC);
        DestroyWindow(hwnd);
        return false;
    }
    glWin.hRC = wglCreateContext(glWin.hDC);
    if(!(glWin.hRC))
    {
        ReleaseDC(hwnd, glWin.hDC);
        DestroyWindow(hwnd);
        return false;
    }
    ret = wglMakeCurrent(glWin.hDC, glWin.hRC);
    if(!ret)
    {
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(glWin.hRC);
        ReleaseDC(hwnd, glWin.hDC);
        DestroyWindow(hwnd);
        return false;
    }

    return true;
}

bool WGLisExtensionSupported(const char *extension)
{
    OpenGLZone aZone;

    const size_t extlen = strlen(extension);
    const char *supported = nullptr;

    // Try to use wglGetExtensionStringARB on current DC, if possible
    PROC wglGetExtString = wglGetProcAddress("wglGetExtensionsStringARB");

    if (wglGetExtString)
        supported = reinterpret_cast<char*(__stdcall*)(HDC)>(wglGetExtString)(wglGetCurrentDC());
    // If that failed, try standard OpenGL extensions string
    if (supported == nullptr)
        supported = reinterpret_cast<char const *>(glGetString(GL_EXTENSIONS));
    // If that failed too, must be no extensions supported
    if (supported == nullptr)
        return false;

    // Begin examination at start of string, increment by 1 on false match
    for (const char* p = supported; ; p++)
    {
        // Advance p up to the next possible match
        p = strstr(p, extension);

        if (p == nullptr)
            return false; // No Match

        // Make sure that match is at the start of the string or that
        // the previous char is a space, or else we could accidentally
        // match "wglFunkywglExtension" with "wglExtension"

        // Also, make sure that the following character is space or null
        // or else "wglExtensionTwo" might match "wglExtension"
        if ((p==supported || p[-1]==' ') && (p[extlen]=='\0' || p[extlen]==' '))
            return true; // Match
    }
}

bool InitMultisample(const PIXELFORMATDESCRIPTOR& pfd, int& rPixelFormat,
        bool bUseDoubleBufferedRendering, bool bRequestVirtualDevice)
{
    OpenGLZone aZone;

    HWND hWnd = nullptr;
    GLWinWindow glWin;
    // Create a temp window to check whether support multi-sample, if support, get the format
    if (!InitTempWindow(hWnd, 32, 32, pfd, glWin))
    {
        SAL_WARN("vcl.opengl", "Can't create temp window to test");
        return false;
    }

    // See if the string exists in WGL
    if (!WGLisExtensionSupported("WGL_ARB_multisample"))
    {
        SAL_WARN("vcl.opengl", "Device doesn't support multisample");
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(glWin.hRC);
        ReleaseDC(hWnd, glWin.hDC);
        DestroyWindow(hWnd);
        return false;
    }
    // Get our pixel format
    PFNWGLCHOOSEPIXELFORMATARBPROC fn_wglChoosePixelFormatARB = reinterpret_cast<PFNWGLCHOOSEPIXELFORMATARBPROC>(wglGetProcAddress("wglChoosePixelFormatARB"));
    if (!fn_wglChoosePixelFormatARB)
    {
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(glWin.hRC);
        ReleaseDC(hWnd, glWin.hDC);
        DestroyWindow(hWnd);
        return false;
    }
    // Get our current device context
    HDC hDC = GetDC(hWnd);

    int pixelFormat;
    int valid;
    UINT    numFormats;
    float   fAttributes[] = {0,0};
    // These attributes are the bits we want to test for in our sample.
    // Everything is pretty standard, the only one we want to
    // really focus on is the WGL_SAMPLE_BUFFERS_ARB and WGL_SAMPLES_ARB.
    // These two are going to do the main testing for whether or not
    // we support multisampling on this hardware.
    int iAttributes[] =
    {
        WGL_DOUBLE_BUFFER_ARB,GL_TRUE,
        WGL_DRAW_TO_WINDOW_ARB,GL_TRUE,
        WGL_SUPPORT_OPENGL_ARB,GL_TRUE,
        WGL_ACCELERATION_ARB,WGL_FULL_ACCELERATION_ARB,
        WGL_COLOR_BITS_ARB,24,
        WGL_ALPHA_BITS_ARB,8,
        WGL_DEPTH_BITS_ARB,24,
        WGL_STENCIL_BITS_ARB,0,
        WGL_SAMPLE_BUFFERS_ARB,GL_TRUE,
        WGL_SAMPLES_ARB,8,
        0,0
    };

    if (!bUseDoubleBufferedRendering)
    {
        // Use asserts to make sure the iAttributes array is not changed without changing these ugly
        // hardcode indexes into it.
        assert(iAttributes[0] == WGL_DOUBLE_BUFFER_ARB);
        iAttributes[1] = GL_FALSE;
    }

    if (bRequestVirtualDevice)
    {
        assert(iAttributes[2] == WGL_DRAW_TO_WINDOW_ARB);
        iAttributes[2] = WGL_DRAW_TO_BITMAP_ARB;
    }

    bool bArbMultisampleSupported = false;

    // First we check to see if we can get a pixel format for 8 samples
    valid = fn_wglChoosePixelFormatARB(hDC, iAttributes, fAttributes, 1, &pixelFormat, &numFormats);
    // If we returned true, and our format count is greater than 1
    if (valid && numFormats >= 1)
    {
        bArbMultisampleSupported = true;
        rPixelFormat = pixelFormat;
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(glWin.hRC);
        ReleaseDC(hWnd, glWin.hDC);
        DestroyWindow(hWnd);
        return bArbMultisampleSupported;
    }
    // Our pixel format with 8 samples failed, test for 2 samples
    assert(iAttributes[18] == WGL_SAMPLES_ARB);
    iAttributes[19] = 2;
    valid = fn_wglChoosePixelFormatARB(hDC, iAttributes, fAttributes, 1, &pixelFormat, &numFormats);
    if (valid && numFormats >= 1)
    {
        bArbMultisampleSupported = true;
        rPixelFormat = pixelFormat;
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(glWin.hRC);
        ReleaseDC(hWnd, glWin.hDC);
        DestroyWindow(hWnd);
        return bArbMultisampleSupported;
    }
    // Return the valid format
    wglMakeCurrent(nullptr, nullptr);
    wglDeleteContext(glWin.hRC);
    ReleaseDC(hWnd, glWin.hDC);
    DestroyWindow(hWnd);

    return bArbMultisampleSupported;
}

namespace
{

void disableOpenGLAndTerminateForRestart()
{
    OpenGLZone::hardDisable();
    TerminateProcess(GetCurrentProcess(), EXITHELPER_NORMAL_RESTART);
}

bool tryShaders(const OUString& rVertexShader, const OUString& rFragmentShader, const OUString& rGeometryShader = "", const OString& rPreamble = "")
{
    GLint nId;

    // Somewhat mysteriously, the OpenGLHelper::LoadShaders() API saves a compiled binary of the
    // shader only if you give it the digest of the shaders. We have API to calculate the digest
    // only of the combination of vertex and fragment (but not geometry) shader. So if we have a
    // geometry shader, we should not save the binary.
    if (rGeometryShader.isEmpty())
    {
        nId = OpenGLHelper::LoadShaders(rVertexShader, rFragmentShader, rPreamble, OpenGLHelper::GetDigest( rVertexShader, rFragmentShader, rPreamble));
    }
    else
    {
        assert(rPreamble.isEmpty());
        nId = OpenGLHelper::LoadShaders(rVertexShader, rFragmentShader, rGeometryShader);
    }
    if (!nId)
        return false;
    glDeleteProgram(nId);
    return glGetError() == GL_NO_ERROR;
}

bool compiledShaderBinariesWork()
{
    static bool bBeenHere = false;
    static bool bResult;

    if (bBeenHere)
        return bResult;

    bBeenHere = true;

    bResult =
        (
#if 0 // Only look at shaders used by vcl for now
         // canvas
         tryShaders("dummyVertexShader", "linearMultiColorGradientFragmentShader") &&
         tryShaders("dummyVertexShader", "linearTwoColorGradientFragmentShader") &&
         tryShaders("dummyVertexShader", "radialMultiColorGradientFragmentShader") &&
         tryShaders("dummyVertexShader", "radialTwoColorGradientFragmentShader") &&
         tryShaders("dummyVertexShader", "rectangularMultiColorGradientFragmentShader") &&
         tryShaders("dummyVertexShader", "rectangularTwoColorGradientFragmentShader") &&
         // chart2
         (GLEW_VERSION_3_3 ?
          (tryShaders("shape3DVertexShader", "shape3DFragmentShader") &&
           tryShaders("shape3DVertexShaderBatchScroll", "shape3DFragmentShaderBatchScroll") &&
           tryShaders("shape3DVertexShaderBatch", "shape3DFragmentShaderBatch") &&
           tryShaders("textVertexShaderBatch", "textFragmentShaderBatch")) :
          (tryShaders("shape3DVertexShaderV300", "shape3DFragmentShaderV300"))) &&
         tryShaders("textVertexShader", "textFragmentShader") &&
         tryShaders("screenTextVertexShader", "screenTextFragmentShader") &&
         tryShaders("commonVertexShader", "commonFragmentShader") &&
         tryShaders("pickingVertexShader", "pickingFragmentShader") &&
         tryShaders("backgroundVertexShader", "backgroundFragmentShader") &&
         tryShaders("symbolVertexShader", "symbolFragmentShader") &&
         tryShaders("symbolVertexShader", "symbolFragmentShader") &&
         // slideshow
         tryShaders("reflectionVertexShader", "reflectionFragmentShader") &&
         tryShaders("basicVertexShader", "basicFragmentShader") &&
         tryShaders("vortexVertexShader", "vortexFragmentShader", "vortexGeometryShader") &&
         tryShaders("basicVertexShader", "rippleFragmentShader") &&
         tryShaders("glitterVertexShader", "glitterFragmentShader") &&
         tryShaders("honeycombVertexShader", "honeycombFragmentShader", "honeycombGeometryShader") &&
#endif
         // vcl
         tryShaders("combinedVertexShader", "combinedFragmentShader") &&
         tryShaders("dumbVertexShader", "invert50FragmentShader") &&
         tryShaders("combinedTextureVertexShader", "combinedTextureFragmentShader") &&
         tryShaders("textureVertexShader", "areaScaleFragmentShader") &&
         tryShaders("transformedTextureVertexShader", "maskedTextureFragmentShader") &&
         tryShaders("transformedTextureVertexShader", "areaScaleFastFragmentShader") &&
         tryShaders("transformedTextureVertexShader", "areaScaleFastFragmentShader", "", "#define MASKED") &&
         tryShaders("transformedTextureVertexShader", "areaScaleFragmentShader") &&
         tryShaders("transformedTextureVertexShader", "areaScaleFragmentShader", "", "#define MASKED") &&
         tryShaders("transformedTextureVertexShader", "textureFragmentShader") &&
         tryShaders("combinedTextureVertexShader", "combinedTextureFragmentShader") &&
         tryShaders("combinedTextureVertexShader", "combinedTextureFragmentShader", "", "// flush shader\n") &&
         tryShaders("textureVertexShader", "linearGradientFragmentShader") &&
         tryShaders("textureVertexShader", "radialGradientFragmentShader") &&
         tryShaders("textureVertexShader", "areaHashCRC64TFragmentShader") &&
         tryShaders("textureVertexShader", "replaceColorFragmentShader") &&
         tryShaders("textureVertexShader", "greyscaleFragmentShader") &&
         tryShaders("textureVertexShader", "textureFragmentShader") &&
         tryShaders("textureVertexShader", "convolutionFragmentShader") &&
         tryShaders("textureVertexShader", "areaScaleFastFragmentShader"));

    return bResult;
}

} // unnamed namespace

bool WinOpenGLContext::ImplInit()
{
    // Failures here typically means that OpenGL can't be used. Returning false is fairly pointless
    // as the calling code doesn't even check, but oh well. If we notice that OpenGL is broken the
    // first time being called, it is not too late to call
    // disableOpenGLAndTerminateForRestart(). The first time this will be called is from displaying
    // the splash screen, so if OpenGL is broken, it is "early enough" for us to be able to disable
    // OpenGL and terminate bluntly with EXITHELPER_NORMAL_RESTART, thus causing the wrapper process
    // to restart us, then without using OpenGL.

    static bool bFirstCall = true;

    OpenGLZone aZone;

    VCL_GL_INFO("OpenGLContext::ImplInit----start");
    // PixelFormat tells Windows how we want things to be
    PIXELFORMATDESCRIPTOR PixelFormatFront =
    {
        sizeof(PIXELFORMATDESCRIPTOR),
        1,                              // Version Number
        PFD_SUPPORT_OPENGL,
        PFD_TYPE_RGBA,                  // Request An RGBA Format
        (BYTE)32,                       // Select Our Color Depth
        0, 0, 0, 0, 0, 0,               // Color Bits Ignored
        0,                              // No Alpha Buffer
        0,                              // Shift Bit Ignored
        0,                              // No Accumulation Buffer
        0, 0, 0, 0,                     // Accumulation Bits Ignored
        24,                             // 24 bit z-buffer
        8,                              // stencil buffer
        0,                              // No Auxiliary Buffer
        0,                              // now ignored
        0,                              // Reserved
        0, 0, 0                         // Layer Masks Ignored
    };

    if (mbUseDoubleBufferedRendering)
        PixelFormatFront.dwFlags |= PFD_DOUBLEBUFFER;

    PixelFormatFront.dwFlags |= PFD_DRAW_TO_WINDOW;

    //  we must check whether can set the MSAA
    int WindowPix = 0;
    bool bMultiSampleSupport = false;

    if (!mbVCLOnly)
        bMultiSampleSupport = InitMultisample(PixelFormatFront, WindowPix, mbUseDoubleBufferedRendering, false);
    else
        VCL_GL_INFO("Skipping multisample detection for VCL.");

    if (bMultiSampleSupport && WindowPix != 0)
    {
        m_aGLWin.bMultiSampleSupported = true;
    }
    else
    {
        WindowPix = ChoosePixelFormat(m_aGLWin.hDC, &PixelFormatFront);
#if OSL_DEBUG_LEVEL > 0
        PIXELFORMATDESCRIPTOR pfd;
        DescribePixelFormat(m_aGLWin.hDC, WindowPix, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
        SAL_WARN("vcl.opengl", "Render Target: Window: " << (int) ((pfd.dwFlags & PFD_DRAW_TO_WINDOW) != 0) << ", Bitmap: " << (int) ((pfd.dwFlags & PFD_DRAW_TO_BITMAP) != 0));
        SAL_WARN("vcl.opengl", "Supports OpenGL: " << (int) ((pfd.dwFlags & PFD_SUPPORT_OPENGL) != 0));
#endif
    }

    if (WindowPix == 0)
    {
        SAL_WARN("vcl.opengl", "Invalid pixelformat");
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    if (!SetPixelFormat(m_aGLWin.hDC, WindowPix, &PixelFormatFront))
    {
        SAL_WARN("vcl.opengl", "SetPixelFormat failed: " << WindowsErrorString(GetLastError()));
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    HGLRC hTempRC = wglCreateContext(m_aGLWin.hDC);
    if (hTempRC == nullptr)
    {
        SAL_WARN("vcl.opengl", "wglCreateContext failed: "<< WindowsErrorString(GetLastError()));
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    if (!wglMakeCurrent(m_aGLWin.hDC, hTempRC))
    {
        SAL_WARN("vcl.opengl", "wglMakeCurrent failed: "<< WindowsErrorString(GetLastError()));
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    if (!InitGLEW())
    {
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    HGLRC hSharedCtx = nullptr;
    if (!g_vShareList.empty())
        hSharedCtx = g_vShareList.front();

    if (!wglCreateContextAttribsARB)
    {
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(hTempRC);
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    // now setup the shared context; this needs a temporary context already
    // set up in order to work
    int attribs [] =
    {
#ifdef DBG_UTIL
        WGL_CONTEXT_FLAGS_ARB, WGL_CONTEXT_DEBUG_BIT_ARB,
#endif
        0
    };
    m_aGLWin.hRC = wglCreateContextAttribsARB(m_aGLWin.hDC, hSharedCtx, attribs);
    if (m_aGLWin.hRC == nullptr)
    {
        SAL_WARN("vcl.opengl", "wglCreateContextAttribsARB failed: "<< WindowsErrorString(GetLastError()));
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(hTempRC);
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    if (!compiledShaderBinariesWork())
    {
        wglMakeCurrent(nullptr, nullptr);
        wglDeleteContext(hTempRC);
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    wglMakeCurrent(nullptr, nullptr);
    wglDeleteContext(hTempRC);

    if (!wglMakeCurrent(m_aGLWin.hDC, m_aGLWin.hRC))
    {
        SAL_WARN("vcl.opengl", "wglMakeCurrent failed: " << WindowsErrorString(GetLastError()));
        if (bFirstCall)
            disableOpenGLAndTerminateForRestart();
        bFirstCall = false;
        return false;
    }

    if (bFirstCall)
    {
        // Checking texture size
        GLint nMaxTextureSize;
        glGetIntegerv(GL_MAX_TEXTURE_SIZE, &nMaxTextureSize);
        if (nMaxTextureSize <= 4096)
            SAL_WARN("vcl.opengl", "Max texture size is " << nMaxTextureSize
                                    << ". This may not be enough for normal operation.");
        else
            VCL_GL_INFO("Max texture size: " << nMaxTextureSize);

        // Trying to make a texture and check its size
        for (GLint nWidthHeight = 1023; nWidthHeight < nMaxTextureSize; nWidthHeight += (nWidthHeight + 1))
        {
            glTexImage2D(GL_PROXY_TEXTURE_2D, 0, 4, nWidthHeight, nWidthHeight, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8, nullptr);
            CHECK_GL_ERROR();
            if (glGetError() == GL_NO_ERROR)
            {
                GLint nWidth = 0;
                GLint nHeight = 0;
                glGetTexLevelParameteriv(GL_PROXY_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &nWidth);
                glGetTexLevelParameteriv(GL_PROXY_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &nHeight);
                VCL_GL_INFO("Created texture " << nWidthHeight << "," << nWidthHeight << " reports size: " << nWidth << ", " << nHeight);
            }
            else
            {
                SAL_WARN("vcl.opengl", "Error when creating a " << nWidthHeight << ", " << nWidthHeight << " test texture.");
            }
        }
    }

    InitGLEWDebugging();

    g_vShareList.push_back(m_aGLWin.hRC);

    RECT clientRect;
    GetClientRect(WindowFromDC(m_aGLWin.hDC), &clientRect);
    m_aGLWin.Width = clientRect.right - clientRect.left;
    m_aGLWin.Height = clientRect.bottom - clientRect.top;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

    registerAsCurrent();

    bFirstCall = false;

    static OString aVendor(reinterpret_cast<const char*>(glGetString(GL_VENDOR)));

    if (aVendor.equalsIgnoreAsciiCase("intel"))
        maOpenGLCapabilitySwitch.mbLimitedShaderRegisters = true;

    return true;
}

OpenGLContext* WinSalInstance::CreateOpenGLContext()
{
    return new WinOpenGLContext;
}

WinOpenGLSalGraphicsImpl::WinOpenGLSalGraphicsImpl(WinSalGraphics& rGraphics,
                                                   SalGeometryProvider *mpProvider):
    OpenGLSalGraphicsImpl(rGraphics,mpProvider),
    mrParent(rGraphics)
{
}

void WinOpenGLSalGraphicsImpl::copyBits( const SalTwoRect& rPosAry, SalGraphics* pSrcGraphics )
{
    OpenGLSalGraphicsImpl *pImpl = pSrcGraphics ? static_cast< OpenGLSalGraphicsImpl* >(pSrcGraphics->GetImpl()) : static_cast< OpenGLSalGraphicsImpl *>(mrParent.GetImpl());
    OpenGLSalGraphicsImpl::DoCopyBits( rPosAry, *pImpl );
}

rtl::Reference<OpenGLContext> WinOpenGLSalGraphicsImpl::CreateWinContext()
{
    rtl::Reference<WinOpenGLContext> xContext(new WinOpenGLContext);
    xContext->setVCLOnly();
    if (!xContext->init(mrParent.mhLocalDC, mrParent.mhWnd))
    {
        SAL_WARN("vcl.opengl", "Context could not be created.");
        return rtl::Reference<OpenGLContext>();
    }
    return rtl::Reference<OpenGLContext>(xContext.get());
}

void WinOpenGLSalGraphicsImpl::Init()
{
    if (!IsOffscreen() && mpContext.is() && mpContext->isInitialized())
    {
        const GLWinWindow& rGLWindow = static_cast<const GLWinWindow&>(mpContext->getOpenGLWindow());
        if (rGLWindow.hWnd != mrParent.mhWnd || rGLWindow.hDC == mrParent.mhLocalDC)
        {
            // This can legitimately happen, SalFrame keeps 2x
            // SalGraphics which share the same hWnd and hDC.
            // The shape 'Area' dialog does reparenting to trigger this.
            SAL_WARN("vcl.opengl", "Unusual: Windows handle / DC changed without DeInit");
            DeInit();
        }
    }

    OpenGLSalGraphicsImpl::Init();
}

namespace
{

typedef std::pair<ControlCacheKey, std::unique_ptr<TextureCombo>> ControlCachePair;
typedef o3tl::lru_map<ControlCacheKey, std::unique_ptr<TextureCombo>, ControlCacheHashFunction> ControlCacheType;

ControlCacheType gTextureCache(200);

}

bool WinOpenGLSalGraphicsImpl::TryRenderCachedNativeControl(ControlCacheKey& rControlCacheKey, int nX, int nY)
{
    static bool gbCacheEnabled = !getenv("SAL_WITHOUT_WIDGET_CACHE");

    if (!gbCacheEnabled)
        return false;

    ControlCacheType::const_iterator iterator = gTextureCache.find(rControlCacheKey);

    if (iterator == gTextureCache.end())
        return false;

    const std::unique_ptr<TextureCombo>& pCombo = iterator->second;

    bool bRet = false;

    PreDraw();

    bRet = RenderTextureCombo(*pCombo, nX, nY);

    PostDraw();

    return bRet;
}

bool WinOpenGLSalGraphicsImpl::RenderTextureCombo(TextureCombo& rCombo, int nX, int nY)
{
    OpenGLTexture& rTexture = *rCombo.mpTexture;

    SalTwoRect aPosAry(0,   0, rTexture.GetWidth(), rTexture.GetHeight(),
                       nX, nY, rTexture.GetWidth(), rTexture.GetHeight());

    DrawTextureDiff(rTexture, *rCombo.mpMask, aPosAry, false);

    return true;
}

bool WinOpenGLSalGraphicsImpl::RenderCompatibleDC(OpenGLCompatibleDC& rWhite, OpenGLCompatibleDC& rBlack,
                                                  int nX, int nY, TextureCombo& rCombo)
{
    bool bRet = false;

    PreDraw();

    rCombo.mpTexture.reset(rWhite.getTexture());
    rCombo.mpMask.reset(rBlack.getTexture());

    bRet = RenderTextureCombo(rCombo, nX, nY);

    PostDraw();
    return bRet;
}

bool WinOpenGLSalGraphicsImpl::RenderAndCacheNativeControl(OpenGLCompatibleDC& rWhite, OpenGLCompatibleDC& rBlack,
                                                           int nX, int nY , ControlCacheKey& aControlCacheKey)
{
    std::unique_ptr<TextureCombo> pCombo(new TextureCombo);

    bool bResult = RenderCompatibleDC(rWhite, rBlack, nX, nY, *pCombo);
    if (!bResult)
        return false;

    if (!aControlCacheKey.canCacheControl())
        return true;

    ControlCachePair pair(aControlCacheKey, std::move(pCombo));
    gTextureCache.insert(std::move(pair));

    return bResult;
}

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