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//========================================================================
// GLFW 3.3 WGL - www.glfw.org
//------------------------------------------------------------------------
// Copyright (c) 2002-2006 Marcus Geelnard
// Copyright (c) 2006-2016 Camilla Löwy <elmindreda@glfw.org>
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software. If you use this software
// in a product, an acknowledgment in the product documentation would
// be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
// be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
// distribution.
//
//========================================================================
#include "internal.h"
#include <stdlib.h>
#include <malloc.h>
#include <assert.h>
// Returns the specified attribute of the specified pixel format
//
static int getPixelFormatAttrib(_GLFWwindow* window, int pixelFormat, int attrib)
{
int value = 0;
assert(_glfw.wgl.ARB_pixel_format);
if (!_glfw.wgl.GetPixelFormatAttribivARB(window->context.wgl.dc,
pixelFormat,
0, 1, &attrib, &value))
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to retrieve pixel format attribute");
return 0;
}
return value;
}
// Return a list of available and usable framebuffer configs
//
static int choosePixelFormat(_GLFWwindow* window,
const _GLFWctxconfig* ctxconfig,
const _GLFWfbconfig* fbconfig)
{
_GLFWfbconfig* usableConfigs;
const _GLFWfbconfig* closest;
int i, pixelFormat, nativeCount, usableCount;
if (_glfw.wgl.ARB_pixel_format)
{
nativeCount = getPixelFormatAttrib(window,
1,
WGL_NUMBER_PIXEL_FORMATS_ARB);
}
else
{
nativeCount = DescribePixelFormat(window->context.wgl.dc,
1,
sizeof(PIXELFORMATDESCRIPTOR),
NULL);
}
usableConfigs = calloc(nativeCount, sizeof(_GLFWfbconfig));
usableCount = 0;
for (i = 0; i < nativeCount; i++)
{
const int n = i + 1;
_GLFWfbconfig* u = usableConfigs + usableCount;
if (_glfw.wgl.ARB_pixel_format)
{
// Get pixel format attributes through "modern" extension
if (!getPixelFormatAttrib(window, n, WGL_SUPPORT_OPENGL_ARB) ||
!getPixelFormatAttrib(window, n, WGL_DRAW_TO_WINDOW_ARB))
{
continue;
}
if (getPixelFormatAttrib(window, n, WGL_PIXEL_TYPE_ARB) !=
WGL_TYPE_RGBA_ARB)
{
continue;
}
if (getPixelFormatAttrib(window, n, WGL_ACCELERATION_ARB) ==
WGL_NO_ACCELERATION_ARB)
{
continue;
}
u->redBits = getPixelFormatAttrib(window, n, WGL_RED_BITS_ARB);
u->greenBits = getPixelFormatAttrib(window, n, WGL_GREEN_BITS_ARB);
u->blueBits = getPixelFormatAttrib(window, n, WGL_BLUE_BITS_ARB);
u->alphaBits = getPixelFormatAttrib(window, n, WGL_ALPHA_BITS_ARB);
u->depthBits = getPixelFormatAttrib(window, n, WGL_DEPTH_BITS_ARB);
u->stencilBits = getPixelFormatAttrib(window, n, WGL_STENCIL_BITS_ARB);
u->accumRedBits = getPixelFormatAttrib(window, n, WGL_ACCUM_RED_BITS_ARB);
u->accumGreenBits = getPixelFormatAttrib(window, n, WGL_ACCUM_GREEN_BITS_ARB);
u->accumBlueBits = getPixelFormatAttrib(window, n, WGL_ACCUM_BLUE_BITS_ARB);
u->accumAlphaBits = getPixelFormatAttrib(window, n, WGL_ACCUM_ALPHA_BITS_ARB);
u->auxBuffers = getPixelFormatAttrib(window, n, WGL_AUX_BUFFERS_ARB);
if (getPixelFormatAttrib(window, n, WGL_STEREO_ARB))
u->stereo = GLFW_TRUE;
if (getPixelFormatAttrib(window, n, WGL_DOUBLE_BUFFER_ARB))
u->doublebuffer = GLFW_TRUE;
if (_glfw.wgl.ARB_multisample)
u->samples = getPixelFormatAttrib(window, n, WGL_SAMPLES_ARB);
if (ctxconfig->client == GLFW_OPENGL_API)
{
if (_glfw.wgl.ARB_framebuffer_sRGB ||
_glfw.wgl.EXT_framebuffer_sRGB)
{
if (getPixelFormatAttrib(window, n, WGL_FRAMEBUFFER_SRGB_CAPABLE_ARB))
u->sRGB = GLFW_TRUE;
}
}
else
{
if (_glfw.wgl.EXT_colorspace)
{
if (getPixelFormatAttrib(window, n, WGL_COLORSPACE_EXT) ==
WGL_COLORSPACE_SRGB_EXT)
{
u->sRGB = GLFW_TRUE;
}
}
}
}
else
{
// Get pixel format attributes through legacy PFDs
PIXELFORMATDESCRIPTOR pfd;
if (!DescribePixelFormat(window->context.wgl.dc,
n,
sizeof(PIXELFORMATDESCRIPTOR),
&pfd))
{
continue;
}
if (!(pfd.dwFlags & PFD_DRAW_TO_WINDOW) ||
!(pfd.dwFlags & PFD_SUPPORT_OPENGL))
{
continue;
}
if (!(pfd.dwFlags & PFD_GENERIC_ACCELERATED) &&
(pfd.dwFlags & PFD_GENERIC_FORMAT))
{
continue;
}
if (pfd.iPixelType != PFD_TYPE_RGBA)
continue;
u->redBits = pfd.cRedBits;
u->greenBits = pfd.cGreenBits;
u->blueBits = pfd.cBlueBits;
u->alphaBits = pfd.cAlphaBits;
u->depthBits = pfd.cDepthBits;
u->stencilBits = pfd.cStencilBits;
u->accumRedBits = pfd.cAccumRedBits;
u->accumGreenBits = pfd.cAccumGreenBits;
u->accumBlueBits = pfd.cAccumBlueBits;
u->accumAlphaBits = pfd.cAccumAlphaBits;
u->auxBuffers = pfd.cAuxBuffers;
if (pfd.dwFlags & PFD_STEREO)
u->stereo = GLFW_TRUE;
if (pfd.dwFlags & PFD_DOUBLEBUFFER)
u->doublebuffer = GLFW_TRUE;
}
u->handle = n;
usableCount++;
}
if (!usableCount)
{
_glfwInputError(GLFW_API_UNAVAILABLE,
"WGL: The driver does not appear to support OpenGL");
free(usableConfigs);
return 0;
}
closest = _glfwChooseFBConfig(fbconfig, usableConfigs, usableCount);
if (!closest)
{
_glfwInputError(GLFW_FORMAT_UNAVAILABLE,
"WGL: Failed to find a suitable pixel format");
free(usableConfigs);
return 0;
}
pixelFormat = (int) closest->handle;
free(usableConfigs);
return pixelFormat;
}
static void makeContextCurrentWGL(_GLFWwindow* window)
{
if (window)
{
if (wglMakeCurrent(window->context.wgl.dc, window->context.wgl.handle))
_glfwPlatformSetTls(&_glfw.contextSlot, window);
else
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to make context current");
_glfwPlatformSetTls(&_glfw.contextSlot, NULL);
}
}
else
{
if (!wglMakeCurrent(NULL, NULL))
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to clear current context");
}
_glfwPlatformSetTls(&_glfw.contextSlot, NULL);
}
}
static void swapBuffersWGL(_GLFWwindow* window)
{
if (!window->monitor)
{
if (IsWindowsVistaOrGreater())
{
BOOL enabled;
// HACK: Use DwmFlush when desktop composition is enabled
if (SUCCEEDED(DwmIsCompositionEnabled(&enabled)) && enabled)
{
int count = abs(window->context.wgl.interval);
while (count--)
DwmFlush();
}
}
}
SwapBuffers(window->context.wgl.dc);
}
static void swapIntervalWGL(int interval)
{
_GLFWwindow* window = _glfwPlatformGetTls(&_glfw.contextSlot);
window->context.wgl.interval = interval;
if (!window->monitor)
{
if (IsWindowsVistaOrGreater())
{
BOOL enabled;
// HACK: Disable WGL swap interval when desktop composition is enabled to
// avoid interfering with DWM vsync
if (SUCCEEDED(DwmIsCompositionEnabled(&enabled)) && enabled)
interval = 0;
}
}
if (_glfw.wgl.EXT_swap_control)
_glfw.wgl.SwapIntervalEXT(interval);
}
static int extensionSupportedWGL(const char* extension)
{
const char* extensions;
if (_glfw.wgl.GetExtensionsStringEXT)
{
extensions = _glfw.wgl.GetExtensionsStringEXT();
if (extensions)
{
if (_glfwStringInExtensionString(extension, extensions))
return GLFW_TRUE;
}
}
if (_glfw.wgl.GetExtensionsStringARB)
{
extensions = _glfw.wgl.GetExtensionsStringARB(wglGetCurrentDC());
if (extensions)
{
if (_glfwStringInExtensionString(extension, extensions))
return GLFW_TRUE;
}
}
return GLFW_FALSE;
}
static GLFWglproc getProcAddressWGL(const char* procname)
{
const GLFWglproc proc = (GLFWglproc) wglGetProcAddress(procname);
if (proc)
return proc;
return (GLFWglproc) GetProcAddress(_glfw.wgl.instance, procname);
}
// Destroy the OpenGL context
//
static void destroyContextWGL(_GLFWwindow* window)
{
if (window->context.wgl.handle)
{
wglDeleteContext(window->context.wgl.handle);
window->context.wgl.handle = NULL;
}
}
//////////////////////////////////////////////////////////////////////////
////// GLFW internal API //////
//////////////////////////////////////////////////////////////////////////
// Initialize WGL
//
GLFWbool _glfwInitWGL(void)
{
PIXELFORMATDESCRIPTOR pfd;
HGLRC prc, rc;
HDC pdc, dc;
if (_glfw.wgl.instance)
return GLFW_TRUE;
_glfw.wgl.instance = LoadLibraryA("opengl32.dll");
if (!_glfw.wgl.instance)
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to load opengl32.dll");
return GLFW_FALSE;
}
_glfw.wgl.CreateContext = (PFN_wglCreateContext)
GetProcAddress(_glfw.wgl.instance, "wglCreateContext");
_glfw.wgl.DeleteContext = (PFN_wglDeleteContext)
GetProcAddress(_glfw.wgl.instance, "wglDeleteContext");
_glfw.wgl.GetProcAddress = (PFN_wglGetProcAddress)
GetProcAddress(_glfw.wgl.instance, "wglGetProcAddress");
_glfw.wgl.GetCurrentDC = (PFN_wglGetCurrentDC)
GetProcAddress(_glfw.wgl.instance, "wglGetCurrentDC");
_glfw.wgl.GetCurrentContext = (PFN_wglGetCurrentContext)
GetProcAddress(_glfw.wgl.instance, "wglGetCurrentContext");
_glfw.wgl.MakeCurrent = (PFN_wglMakeCurrent)
GetProcAddress(_glfw.wgl.instance, "wglMakeCurrent");
_glfw.wgl.ShareLists = (PFN_wglShareLists)
GetProcAddress(_glfw.wgl.instance, "wglShareLists");
// NOTE: A dummy context has to be created for opengl32.dll to load the
// OpenGL ICD, from which we can then query WGL extensions
// NOTE: This code will accept the Microsoft GDI ICD; accelerated context
// creation failure occurs during manual pixel format enumeration
dc = GetDC(_glfw.win32.helperWindowHandle);;
ZeroMemory(&pfd, sizeof(pfd));
pfd.nSize = sizeof(pfd);
pfd.nVersion = 1;
pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.cColorBits = 24;
if (!SetPixelFormat(dc, ChoosePixelFormat(dc, &pfd), &pfd))
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to set pixel format for dummy context");
return GLFW_FALSE;
}
rc = wglCreateContext(dc);
if (!rc)
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to create dummy context");
return GLFW_FALSE;
}
pdc = wglGetCurrentDC();
prc = wglGetCurrentContext();
if (!wglMakeCurrent(dc, rc))
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to make dummy context current");
wglMakeCurrent(pdc, prc);
wglDeleteContext(rc);
return GLFW_FALSE;
}
// NOTE: Functions must be loaded first as they're needed to retrieve the
// extension string that tells us whether the functions are supported
_glfw.wgl.GetExtensionsStringEXT = (PFNWGLGETEXTENSIONSSTRINGEXTPROC)
wglGetProcAddress("wglGetExtensionsStringEXT");
_glfw.wgl.GetExtensionsStringARB = (PFNWGLGETEXTENSIONSSTRINGARBPROC)
wglGetProcAddress("wglGetExtensionsStringARB");
_glfw.wgl.CreateContextAttribsARB = (PFNWGLCREATECONTEXTATTRIBSARBPROC)
wglGetProcAddress("wglCreateContextAttribsARB");
_glfw.wgl.SwapIntervalEXT = (PFNWGLSWAPINTERVALEXTPROC)
wglGetProcAddress("wglSwapIntervalEXT");
_glfw.wgl.GetPixelFormatAttribivARB = (PFNWGLGETPIXELFORMATATTRIBIVARBPROC)
wglGetProcAddress("wglGetPixelFormatAttribivARB");
// NOTE: WGL_ARB_extensions_string and WGL_EXT_extensions_string are not
// checked below as we are already using them
_glfw.wgl.ARB_multisample =
extensionSupportedWGL("WGL_ARB_multisample");
_glfw.wgl.ARB_framebuffer_sRGB =
extensionSupportedWGL("WGL_ARB_framebuffer_sRGB");
_glfw.wgl.EXT_framebuffer_sRGB =
extensionSupportedWGL("WGL_EXT_framebuffer_sRGB");
_glfw.wgl.ARB_create_context =
extensionSupportedWGL("WGL_ARB_create_context");
_glfw.wgl.ARB_create_context_profile =
extensionSupportedWGL("WGL_ARB_create_context_profile");
_glfw.wgl.EXT_create_context_es2_profile =
extensionSupportedWGL("WGL_EXT_create_context_es2_profile");
_glfw.wgl.ARB_create_context_robustness =
extensionSupportedWGL("WGL_ARB_create_context_robustness");
_glfw.wgl.ARB_create_context_no_error =
extensionSupportedWGL("WGL_ARB_create_context_no_error");
_glfw.wgl.EXT_swap_control =
extensionSupportedWGL("WGL_EXT_swap_control");
_glfw.wgl.EXT_colorspace =
extensionSupportedWGL("WGL_EXT_colorspace");
_glfw.wgl.ARB_pixel_format =
extensionSupportedWGL("WGL_ARB_pixel_format");
_glfw.wgl.ARB_context_flush_control =
extensionSupportedWGL("WGL_ARB_context_flush_control");
wglMakeCurrent(pdc, prc);
wglDeleteContext(rc);
return GLFW_TRUE;
}
// Terminate WGL
//
void _glfwTerminateWGL(void)
{
if (_glfw.wgl.instance)
FreeLibrary(_glfw.wgl.instance);
}
#define setAttrib(a, v) \
{ \
assert((size_t) (index + 1) < sizeof(attribs) / sizeof(attribs[0])); \
attribs[index++] = a; \
attribs[index++] = v; \
}
// Create the OpenGL or OpenGL ES context
//
GLFWbool _glfwCreateContextWGL(_GLFWwindow* window,
const _GLFWctxconfig* ctxconfig,
const _GLFWfbconfig* fbconfig)
{
int attribs[40];
int pixelFormat;
PIXELFORMATDESCRIPTOR pfd;
HGLRC share = NULL;
if (ctxconfig->share)
share = ctxconfig->share->context.wgl.handle;
window->context.wgl.dc = GetDC(window->win32.handle);
if (!window->context.wgl.dc)
{
_glfwInputError(GLFW_PLATFORM_ERROR,
"WGL: Failed to retrieve DC for window");
return GLFW_FALSE;
}
pixelFormat = choosePixelFormat(window, ctxconfig, fbconfig);
if (!pixelFormat)
return GLFW_FALSE;
if (!DescribePixelFormat(window->context.wgl.dc,
pixelFormat, sizeof(pfd), &pfd))
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to retrieve PFD for selected pixel format");
return GLFW_FALSE;
}
if (!SetPixelFormat(window->context.wgl.dc, pixelFormat, &pfd))
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to set selected pixel format");
return GLFW_FALSE;
}
if (ctxconfig->client == GLFW_OPENGL_API)
{
if (ctxconfig->forward)
{
if (!_glfw.wgl.ARB_create_context)
{
_glfwInputError(GLFW_VERSION_UNAVAILABLE,
"WGL: A forward compatible OpenGL context requested but WGL_ARB_create_context is unavailable");
return GLFW_FALSE;
}
}
if (ctxconfig->profile)
{
if (!_glfw.wgl.ARB_create_context_profile)
{
_glfwInputError(GLFW_VERSION_UNAVAILABLE,
"WGL: OpenGL profile requested but WGL_ARB_create_context_profile is unavailable");
return GLFW_FALSE;
}
}
}
else
{
if (!_glfw.wgl.ARB_create_context ||
!_glfw.wgl.ARB_create_context_profile ||
!_glfw.wgl.EXT_create_context_es2_profile)
{
_glfwInputError(GLFW_API_UNAVAILABLE,
"WGL: OpenGL ES requested but WGL_ARB_create_context_es2_profile is unavailable");
return GLFW_FALSE;
}
}
if (_glfw.wgl.ARB_create_context)
{
int index = 0, mask = 0, flags = 0;
if (ctxconfig->client == GLFW_OPENGL_API)
{
if (ctxconfig->forward)
flags |= WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB;
if (ctxconfig->profile == GLFW_OPENGL_CORE_PROFILE)
mask |= WGL_CONTEXT_CORE_PROFILE_BIT_ARB;
else if (ctxconfig->profile == GLFW_OPENGL_COMPAT_PROFILE)
mask |= WGL_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB;
}
else
mask |= WGL_CONTEXT_ES2_PROFILE_BIT_EXT;
if (ctxconfig->debug)
flags |= WGL_CONTEXT_DEBUG_BIT_ARB;
if (ctxconfig->robustness)
{
if (_glfw.wgl.ARB_create_context_robustness)
{
if (ctxconfig->robustness == GLFW_NO_RESET_NOTIFICATION)
{
setAttrib(WGL_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB,
WGL_NO_RESET_NOTIFICATION_ARB);
}
else if (ctxconfig->robustness == GLFW_LOSE_CONTEXT_ON_RESET)
{
setAttrib(WGL_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB,
WGL_LOSE_CONTEXT_ON_RESET_ARB);
}
flags |= WGL_CONTEXT_ROBUST_ACCESS_BIT_ARB;
}
}
if (ctxconfig->release)
{
if (_glfw.wgl.ARB_context_flush_control)
{
if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_NONE)
{
setAttrib(WGL_CONTEXT_RELEASE_BEHAVIOR_ARB,
WGL_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB);
}
else if (ctxconfig->release == GLFW_RELEASE_BEHAVIOR_FLUSH)
{
setAttrib(WGL_CONTEXT_RELEASE_BEHAVIOR_ARB,
WGL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB);
}
}
}
if (ctxconfig->noerror)
{
if (_glfw.wgl.ARB_create_context_no_error)
setAttrib(WGL_CONTEXT_OPENGL_NO_ERROR_ARB, GLFW_TRUE);
}
// NOTE: Only request an explicitly versioned context when necessary, as
// explicitly requesting version 1.0 does not always return the
// highest version supported by the driver
if (ctxconfig->major != 1 || ctxconfig->minor != 0)
{
setAttrib(WGL_CONTEXT_MAJOR_VERSION_ARB, ctxconfig->major);
setAttrib(WGL_CONTEXT_MINOR_VERSION_ARB, ctxconfig->minor);
}
if (flags)
setAttrib(WGL_CONTEXT_FLAGS_ARB, flags);
if (mask)
setAttrib(WGL_CONTEXT_PROFILE_MASK_ARB, mask);
setAttrib(0, 0);
window->context.wgl.handle =
_glfw.wgl.CreateContextAttribsARB(window->context.wgl.dc,
share, attribs);
if (!window->context.wgl.handle)
{
const DWORD error = GetLastError();
if (error == (0xc0070000 | ERROR_INVALID_VERSION_ARB))
{
if (ctxconfig->client == GLFW_OPENGL_API)
{
_glfwInputError(GLFW_VERSION_UNAVAILABLE,
"WGL: Driver does not support OpenGL version %i.%i",
ctxconfig->major,
ctxconfig->minor);
}
else
{
_glfwInputError(GLFW_VERSION_UNAVAILABLE,
"WGL: Driver does not support OpenGL ES version %i.%i",
ctxconfig->major,
ctxconfig->minor);
}
}
else if (error == (0xc0070000 | ERROR_INVALID_PROFILE_ARB))
{
_glfwInputError(GLFW_VERSION_UNAVAILABLE,
"WGL: Driver does not support the requested OpenGL profile");
}
else if (error == (0xc0070000 | ERROR_INCOMPATIBLE_DEVICE_CONTEXTS_ARB))
{
_glfwInputError(GLFW_INVALID_VALUE,
"WGL: The share context is not compatible with the requested context");
}
else
{
if (ctxconfig->client == GLFW_OPENGL_API)
{
_glfwInputError(GLFW_VERSION_UNAVAILABLE,
"WGL: Failed to create OpenGL context");
}
else
{
_glfwInputError(GLFW_VERSION_UNAVAILABLE,
"WGL: Failed to create OpenGL ES context");
}
}
return GLFW_FALSE;
}
}
else
{
window->context.wgl.handle = wglCreateContext(window->context.wgl.dc);
if (!window->context.wgl.handle)
{
_glfwInputErrorWin32(GLFW_VERSION_UNAVAILABLE,
"WGL: Failed to create OpenGL context");
return GLFW_FALSE;
}
if (share)
{
if (!wglShareLists(share, window->context.wgl.handle))
{
_glfwInputErrorWin32(GLFW_PLATFORM_ERROR,
"WGL: Failed to enable sharing with specified OpenGL context");
return GLFW_FALSE;
}
}
}
window->context.makeCurrent = makeContextCurrentWGL;
window->context.swapBuffers = swapBuffersWGL;
window->context.swapInterval = swapIntervalWGL;
window->context.extensionSupported = extensionSupportedWGL;
window->context.getProcAddress = getProcAddressWGL;
window->context.destroy = destroyContextWGL;
return GLFW_TRUE;
}
#undef setAttrib
//////////////////////////////////////////////////////////////////////////
////// GLFW native API //////
//////////////////////////////////////////////////////////////////////////
GLFWAPI HGLRC glfwGetWGLContext(GLFWwindow* handle)
{
_GLFWwindow* window = (_GLFWwindow*) handle;
_GLFW_REQUIRE_INIT_OR_RETURN(NULL);
if (window->context.client == GLFW_NO_API)
{
_glfwInputError(GLFW_NO_WINDOW_CONTEXT, NULL);
return NULL;
}
return window->context.wgl.handle;
}