gl_loader 0.1.2

Simple OpenGL function pointer loader based on Glad.
Documentation 
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/*
 * This file his an extract from glad: https://glad.dav1d.de/
 */

#include <stdlib.h>
#include "glad.h"

void *get_proc(const char *namez);

#if defined(_WIN32) || defined(__CYGWIN__)
#include <windows.h>
static HMODULE libGL;

typedef void *(APIENTRYP PFNWGLGETPROCADDRESSPROC_PRIVATE)(const char *);
static PFNWGLGETPROCADDRESSPROC_PRIVATE gladGetProcAddressPtr;

#ifdef _MSC_VER
#ifdef __has_include
#if __has_include(<winapifamily.h>)
#define HAVE_WINAPIFAMILY 1
#endif
#elif _MSC_VER >= 1700 && !_USING_V110_SDK71_
#define HAVE_WINAPIFAMILY 1
#endif
#endif

#ifdef HAVE_WINAPIFAMILY
#include <winapifamily.h>
#if !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP) && WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP)
#define IS_UWP 1
#endif
#endif

int open_gl(void)
{
#ifndef IS_UWP
	libGL = LoadLibraryW(L"opengl32.dll");
	if (libGL != NULL)
	{
		void (*tmp)(void);
		tmp = (void (*)(void))GetProcAddress(libGL, "wglGetProcAddress");
		gladGetProcAddressPtr = (PFNWGLGETPROCADDRESSPROC_PRIVATE)tmp;
		return gladGetProcAddressPtr != NULL;
	}
#endif

	return 0;
}

void close_gl(void)
{
	if (libGL != NULL)
	{
		FreeLibrary((HMODULE)libGL);
		libGL = NULL;
	}
}
#else
#include <dlfcn.h>
static void *libGL;

#if !defined(__APPLE__) && !defined(__HAIKU__)
typedef void *(APIENTRYP PFNGLXGETPROCADDRESSPROC_PRIVATE)(const char *);
static PFNGLXGETPROCADDRESSPROC_PRIVATE gladGetProcAddressPtr;
#endif

int open_gl(void)
{
#ifdef __APPLE__
	static const char *NAMES[] = {
		"../Frameworks/OpenGL.framework/OpenGL",
		"/Library/Frameworks/OpenGL.framework/OpenGL",
		"/System/Library/Frameworks/OpenGL.framework/OpenGL",
		"/System/Library/Frameworks/OpenGL.framework/Versions/Current/OpenGL"};
#else
	static const char *NAMES[] = {"libGL.so.1", "libGL.so"};
#endif

	unsigned int index = 0;
	for (index = 0; index < (sizeof(NAMES) / sizeof(NAMES[0])); index++)
	{
		libGL = dlopen(NAMES[index], RTLD_NOW | RTLD_GLOBAL);

		if (libGL != NULL)
		{
#if defined(__APPLE__) || defined(__HAIKU__)
			return 1;
#else
			gladGetProcAddressPtr = (PFNGLXGETPROCADDRESSPROC_PRIVATE)dlsym(libGL,
																			"glXGetProcAddressARB");
			return gladGetProcAddressPtr != NULL;
#endif
		}
	}

	return 0;
}

void close_gl(void)
{
	if (libGL != NULL)
	{
		dlclose(libGL);
		libGL = NULL;
	}
}
#endif

void *get_proc(const char *namez)
{
	void *result = NULL;
	if (libGL == NULL)
		return NULL;

#if !defined(__APPLE__) && !defined(__HAIKU__)
	if (gladGetProcAddressPtr != NULL)
	{
		result = gladGetProcAddressPtr(namez);
	}
#endif
	if (result == NULL)
	{
#if defined(_WIN32) || defined(__CYGWIN__)
		result = (void *)GetProcAddress((HMODULE)libGL, namez);
#else
		result = dlsym(libGL, namez);
#endif
	}

	return result;
}