Backends: OpenGL3: Embed our own minimal GL loader based on gl3w and use it in SDL/GLFW examples. (#4445)

Loader repository at https://github.com/dearimgui/gl3w_stripped
Removed support for using custom loaders in examples/opengl3 backend

backends/imgui_impl_opengl3.cpp

@@ -111,33 +111,14 @@
 #else
 // About Desktop OpenGL function loaders:
 //  Modern desktop OpenGL doesn't have a standard portable header file to load OpenGL function pointers.
-//  Helper libraries are often used for this purpose! Here we are supporting a few common ones (gl3w, glew, glad).
+//  Helper libraries are often used for this purpose! Here we are using our own minimal custom loader based on gl3w.
 //  You may use another loader/header of your choice (glext, glLoadGen, etc.), or chose to manually implement your own.
-#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
+//  If you happen to be developing a new feature for this backend, you may want to get a unstripped version of
-#include <GL/gl3w.h>            // Needs to be initialized with gl3wInit() in user's code
+//  imgui_impl_opengl3_loader.h from https://github.com/dearimgui/gl3w_stripped/releases/ and use that temporarily.
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
+//  When done, changes using new APIs should be accompanied by regenerated stripped loader version (instructions in
-#include <GL/glew.h>            // Needs to be initialized with glewInit() in user's code.
+//  gl3w_stripped README.rst).
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
+#define IMGL3W_IMPL 1
-#include <glad/glad.h>          // Needs to be initialized with gladLoadGL() in user's code.
+#include "imgui_impl_opengl3_loader.h"
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-#include <glad/gl.h>            // Needs to be initialized with gladLoadGL(...) or gladLoaderLoadGL() in user's code.
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
-#ifndef GLFW_INCLUDE_NONE
-#define GLFW_INCLUDE_NONE       // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
-#endif
-#include <glbinding/Binding.h>  // Needs to be initialized with glbinding::Binding::initialize() in user's code.
-#include <glbinding/gl/gl.h>
-using namespace gl;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
-#ifndef GLFW_INCLUDE_NONE
-#define GLFW_INCLUDE_NONE       // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
-#endif
-#include <glbinding/glbinding.h>// Needs to be initialized with glbinding::initialize() in user's code.
-#include <glbinding/gl/gl.h>
-using namespace gl;
-#else
-#include IMGUI_IMPL_OPENGL_LOADER_CUSTOM
-#endif
 #endif
 
 // Vertex arrays are not supported on ES2/WebGL1 unless Emscripten which uses an extension
@@ -207,6 +188,14 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
     ImGuiIO& io = ImGui::GetIO();
     IM_ASSERT(io.BackendRendererUserData == NULL && "Already initialized a renderer backend!");
 
+#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3)
+    if (imgl3wInit() != 0)
+    {
+        fprintf(stderr, "Failed to initialize OpenGL loader!\n");
+        return false;
+    }
+#endif
+
     // Setup backend capabilities flags
     ImGui_ImplOpenGL3_Data* bd = IM_NEW(ImGui_ImplOpenGL3_Data)();;
     io.BackendRendererUserData = (void*)bd;
@@ -252,37 +241,6 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
     strcpy(bd->GlslVersionString, glsl_version);
     strcat(bd->GlslVersionString, "\n");
 
-    // Debugging construct to make it easily visible in the IDE and debugger which GL loader has been selected.
-    // The code actually never uses the 'gl_loader' variable! It is only here so you can read it!
-    // If auto-detection fails or doesn't select the same GL loader file as used by your application,
-    // you are likely to get a crash below.
-    // You can explicitly select a loader by using '#define IMGUI_IMPL_OPENGL_LOADER_XXX' in imconfig.h or compiler command-line.
-    const char* gl_loader = "Unknown";
-    IM_UNUSED(gl_loader);
-#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
-    gl_loader = "GL3W";
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
-    gl_loader = "GLEW";
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
-    gl_loader = "GLAD";
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-    gl_loader = "GLAD2";
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
-    gl_loader = "glbinding2";
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
-    gl_loader = "glbinding3";
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
-    gl_loader = "custom";
-#else
-    gl_loader = "none";
-#endif
-
-    // Make an arbitrary GL call (we don't actually need the result)
-    // IF YOU GET A CRASH HERE: it probably means that you haven't initialized the OpenGL function loader used by this code.
-    // Desktop OpenGL 3/4 need a function loader. See the IMGUI_IMPL_OPENGL_LOADER_xxx explanation above.
-    GLint current_texture;
-    glGetIntegerv(GL_TEXTURE_BINDING_2D, &current_texture);
-
     // Detect extensions we support
     bd->HasClipOrigin = (bd->GlVersion >= 450);
 #ifdef IMGUI_IMPL_OPENGL_MAY_HAVE_EXTENSIONS

backends/imgui_impl_opengl3.h

@@ -41,19 +41,9 @@ IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyDeviceObjects();
 //#define IMGUI_IMPL_OPENGL_ES2     // Auto-detected on Emscripten
 //#define IMGUI_IMPL_OPENGL_ES3     // Auto-detected on iOS/Android
 
-// Attempt to auto-detect the default Desktop GL loader based on available header files.
+// You can explicitly select GLES2 or GLES3 API by using one of the '#define IMGUI_IMPL_OPENGL_LOADER_XXX' in imconfig.h or compiler command-line.
-// If auto-detection fails or doesn't select the same GL loader file as used by your application,
-// you are likely to get a crash in ImGui_ImplOpenGL3_Init().
-// You can explicitly select a loader by using one of the '#define IMGUI_IMPL_OPENGL_LOADER_XXX' in imconfig.h or compiler command-line.
 #if !defined(IMGUI_IMPL_OPENGL_ES2) \
- && !defined(IMGUI_IMPL_OPENGL_ES3) \
+ && !defined(IMGUI_IMPL_OPENGL_ES3)
- && !defined(IMGUI_IMPL_OPENGL_LOADER_GL3W) \
- && !defined(IMGUI_IMPL_OPENGL_LOADER_GLEW) \
- && !defined(IMGUI_IMPL_OPENGL_LOADER_GLAD) \
- && !defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2) \
- && !defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2) \
- && !defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3) \
- && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
 
 // Try to detect GLES on matching platforms
 #if defined(__APPLE__)
@@ -63,26 +53,8 @@ IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyDeviceObjects();
 #define IMGUI_IMPL_OPENGL_ES3               // iOS, Android  -> GL ES 3, "#version 300 es"
 #elif defined(__EMSCRIPTEN__)
 #define IMGUI_IMPL_OPENGL_ES2               // Emscripten    -> GL ES 2, "#version 100"
-
-// Otherwise try to detect supported Desktop OpenGL loaders..
-#elif defined(__has_include)
-#if __has_include(<GL/glew.h>)
-    #define IMGUI_IMPL_OPENGL_LOADER_GLEW
-#elif __has_include(<glad/glad.h>)
-    #define IMGUI_IMPL_OPENGL_LOADER_GLAD
-#elif __has_include(<glad/gl.h>)
-    #define IMGUI_IMPL_OPENGL_LOADER_GLAD2
-#elif __has_include(<GL/gl3w.h>)
-    #define IMGUI_IMPL_OPENGL_LOADER_GL3W
-#elif __has_include(<glbinding/glbinding.h>)
-    #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING3
-#elif __has_include(<glbinding/Binding.h>)
-    #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
 #else
-    #error "Cannot detect OpenGL loader!"
+// Otherwise imgui_impl_opengl3_loader.h will be used.
-#endif
-#else
-    #define IMGUI_IMPL_OPENGL_LOADER_GL3W   // Default to GL3W embedded in our repository
 #endif
 
 #endif

backends/imgui_impl_opengl3_loader.h

@@ -0,0 +1,729 @@
+/*
+ * This file was generated with gl3w_gen.py, part of imgl3w
+ * (hosted at https://github.com/dearimgui/gl3w_stripped)
+ *
+ * This is free and unencumbered software released into the public domain.
+ *
+ * Anyone is free to copy, modify, publish, use, compile, sell, or
+ * distribute this software, either in source code form or as a compiled
+ * binary, for any purpose, commercial or non-commercial, and by any
+ * means.
+ *
+ * In jurisdictions that recognize copyright laws, the author or authors
+ * of this software dedicate any and all copyright interest in the
+ * software to the public domain. We make this dedication for the benefit
+ * of the public at large and to the detriment of our heirs and
+ * successors. We intend this dedication to be an overt act of
+ * relinquishment in perpetuity of all present and future rights to this
+ * software under copyright law.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+// We embed our own OpenGL loader to not require user to provide their own or to have to use ours, which proved to be endless problems for users.
+// Our loader is custom-generated, based on gl3w but automatically filtered to only include enums/functions that we use in this source file.
+// Regenerate with: python gl3w_gen.py --imgui-dir /path/to/imgui/
+// see https://github.com/dearimgui/gl3w_stripped for more info.
+#ifndef __gl3w_h_
+#define __gl3w_h_
+
+// Adapted from KHR/khrplatform.h to avoid including entire file.
+typedef          float         khronos_float_t;
+typedef signed   char          khronos_int8_t;
+typedef unsigned char          khronos_uint8_t;
+typedef signed   short int     khronos_int16_t;
+typedef unsigned short int     khronos_uint16_t;
+#ifdef _WIN64
+typedef signed   long long int khronos_intptr_t;
+typedef signed   long long int khronos_ssize_t;
+#else
+typedef signed   long  int     khronos_intptr_t;
+typedef signed   long  int     khronos_ssize_t;
+#endif
+
+#if defined(_MSC_VER) && !defined(__clang__)
+typedef signed   __int64       khronos_int64_t;
+typedef unsigned __int64       khronos_uint64_t;
+#elif (defined(__clang__) || defined(__GNUC__)) && (__cplusplus < 201100)
+#include <stdint.h>
+typedef          int64_t       khronos_int64_t;
+typedef          uint64_t      khronos_uint64_t;
+#else
+typedef signed   long long     khronos_int64_t;
+typedef unsigned long long     khronos_uint64_t;
+#endif
+
+#ifndef __gl_glcorearb_h_
+#define __gl_glcorearb_h_ 1
+#ifdef __cplusplus
+extern "C" {
+#endif
+/*
+** Copyright 2013-2020 The Khronos Group Inc.
+** SPDX-License-Identifier: MIT
+**
+** This header is generated from the Khronos OpenGL / OpenGL ES XML
+** API Registry. The current version of the Registry, generator scripts
+** used to make the header, and the header can be found at
+**   https://github.com/KhronosGroup/OpenGL-Registry
+*/
+#if defined(_WIN32) && !defined(APIENTRY) && !defined(__CYGWIN__) && !defined(__SCITECH_SNAP__)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN 1
+#endif
+#include <windows.h>
+#endif
+#ifndef APIENTRY
+#define APIENTRY
+#endif
+#ifndef APIENTRYP
+#define APIENTRYP APIENTRY *
+#endif
+#ifndef GLAPI
+#define GLAPI extern
+#endif
+/* glcorearb.h is for use with OpenGL core profile implementations.
+** It should should be placed in the same directory as gl.h and
+** included as <GL/glcorearb.h>.
+**
+** glcorearb.h includes only APIs in the latest OpenGL core profile
+** implementation together with APIs in newer ARB extensions which 
+** can be supported by the core profile. It does not, and never will
+** include functionality removed from the core profile, such as
+** fixed-function vertex and fragment processing.
+**
+** Do not #include both <GL/glcorearb.h> and either of <GL/gl.h> or
+** <GL/glext.h> in the same source file.
+*/
+/* Generated C header for:
+ * API: gl
+ * Profile: core
+ * Versions considered: .*
+ * Versions emitted: .*
+ * Default extensions included: glcore
+ * Additional extensions included: _nomatch_^
+ * Extensions removed: _nomatch_^
+ */
+#ifndef GL_VERSION_1_0
+typedef void GLvoid;
+typedef unsigned int GLenum;
+
+typedef khronos_float_t GLfloat;
+typedef int GLint;
+typedef int GLsizei;
+typedef unsigned int GLbitfield;
+typedef double GLdouble;
+typedef unsigned int GLuint;
+typedef unsigned char GLboolean;
+typedef khronos_uint8_t GLubyte;
+#define GL_COLOR_BUFFER_BIT               0x00004000
+#define GL_FALSE                          0
+#define GL_TRUE                           1
+#define GL_TRIANGLES                      0x0004
+#define GL_ONE                            1
+#define GL_SRC_ALPHA                      0x0302
+#define GL_ONE_MINUS_SRC_ALPHA            0x0303
+#define GL_FRONT_AND_BACK                 0x0408
+#define GL_POLYGON_MODE                   0x0B40
+#define GL_CULL_FACE                      0x0B44
+#define GL_DEPTH_TEST                     0x0B71
+#define GL_STENCIL_TEST                   0x0B90
+#define GL_VIEWPORT                       0x0BA2
+#define GL_BLEND                          0x0BE2
+#define GL_SCISSOR_BOX                    0x0C10
+#define GL_SCISSOR_TEST                   0x0C11
+#define GL_UNPACK_ROW_LENGTH              0x0CF2
+#define GL_TEXTURE_2D                     0x0DE1
+#define GL_UNSIGNED_BYTE                  0x1401
+#define GL_UNSIGNED_SHORT                 0x1403
+#define GL_UNSIGNED_INT                   0x1405
+#define GL_FLOAT                          0x1406
+#define GL_RGBA                           0x1908
+#define GL_FILL                           0x1B02
+#define GL_VERSION                        0x1F02
+#define GL_EXTENSIONS                     0x1F03
+#define GL_LINEAR                         0x2601
+#define GL_TEXTURE_MAG_FILTER             0x2800
+#define GL_TEXTURE_MIN_FILTER             0x2801
+typedef void (APIENTRYP PFNGLPOLYGONMODEPROC) (GLenum face, GLenum mode);
+typedef void (APIENTRYP PFNGLSCISSORPROC) (GLint x, GLint y, GLsizei width, GLsizei height);
+typedef void (APIENTRYP PFNGLTEXPARAMETERIPROC) (GLenum target, GLenum pname, GLint param);
+typedef void (APIENTRYP PFNGLTEXIMAGE2DPROC) (GLenum target, GLint level, GLint internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const void *pixels);
+typedef void (APIENTRYP PFNGLCLEARPROC) (GLbitfield mask);
+typedef void (APIENTRYP PFNGLCLEARCOLORPROC) (GLfloat red, GLfloat green, GLfloat blue, GLfloat alpha);
+typedef void (APIENTRYP PFNGLDISABLEPROC) (GLenum cap);
+typedef void (APIENTRYP PFNGLENABLEPROC) (GLenum cap);
+typedef void (APIENTRYP PFNGLPIXELSTOREIPROC) (GLenum pname, GLint param);
+typedef void (APIENTRYP PFNGLGETINTEGERVPROC) (GLenum pname, GLint *data);
+typedef const GLubyte *(APIENTRYP PFNGLGETSTRINGPROC) (GLenum name);
+typedef GLboolean (APIENTRYP PFNGLISENABLEDPROC) (GLenum cap);
+typedef void (APIENTRYP PFNGLVIEWPORTPROC) (GLint x, GLint y, GLsizei width, GLsizei height);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glPolygonMode (GLenum face, GLenum mode);
+GLAPI void APIENTRY glScissor (GLint x, GLint y, GLsizei width, GLsizei height);
+GLAPI void APIENTRY glTexParameteri (GLenum target, GLenum pname, GLint param);
+GLAPI void APIENTRY glTexImage2D (GLenum target, GLint level, GLint internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const void *pixels);
+GLAPI void APIENTRY glClear (GLbitfield mask);
+GLAPI void APIENTRY glClearColor (GLfloat red, GLfloat green, GLfloat blue, GLfloat alpha);
+GLAPI void APIENTRY glDisable (GLenum cap);
+GLAPI void APIENTRY glEnable (GLenum cap);
+GLAPI void APIENTRY glPixelStorei (GLenum pname, GLint param);
+GLAPI void APIENTRY glGetIntegerv (GLenum pname, GLint *data);
+GLAPI const GLubyte *APIENTRY glGetString (GLenum name);
+GLAPI GLboolean APIENTRY glIsEnabled (GLenum cap);
+GLAPI void APIENTRY glViewport (GLint x, GLint y, GLsizei width, GLsizei height);
+#endif
+#endif /* GL_VERSION_1_0 */
+#ifndef GL_VERSION_1_1
+typedef khronos_float_t GLclampf;
+typedef double GLclampd;
+#define GL_TEXTURE_BINDING_2D             0x8069
+typedef void (APIENTRYP PFNGLDRAWELEMENTSPROC) (GLenum mode, GLsizei count, GLenum type, const void *indices);
+typedef void (APIENTRYP PFNGLBINDTEXTUREPROC) (GLenum target, GLuint texture);
+typedef void (APIENTRYP PFNGLDELETETEXTURESPROC) (GLsizei n, const GLuint *textures);
+typedef void (APIENTRYP PFNGLGENTEXTURESPROC) (GLsizei n, GLuint *textures);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glDrawElements (GLenum mode, GLsizei count, GLenum type, const void *indices);
+GLAPI void APIENTRY glBindTexture (GLenum target, GLuint texture);
+GLAPI void APIENTRY glDeleteTextures (GLsizei n, const GLuint *textures);
+GLAPI void APIENTRY glGenTextures (GLsizei n, GLuint *textures);
+#endif
+#endif /* GL_VERSION_1_1 */
+#ifndef GL_VERSION_1_3
+#define GL_TEXTURE0                       0x84C0
+#define GL_ACTIVE_TEXTURE                 0x84E0
+typedef void (APIENTRYP PFNGLACTIVETEXTUREPROC) (GLenum texture);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glActiveTexture (GLenum texture);
+#endif
+#endif /* GL_VERSION_1_3 */
+#ifndef GL_VERSION_1_4
+#define GL_BLEND_DST_RGB                  0x80C8
+#define GL_BLEND_SRC_RGB                  0x80C9
+#define GL_BLEND_DST_ALPHA                0x80CA
+#define GL_BLEND_SRC_ALPHA                0x80CB
+#define GL_FUNC_ADD                       0x8006
+typedef void (APIENTRYP PFNGLBLENDFUNCSEPARATEPROC) (GLenum sfactorRGB, GLenum dfactorRGB, GLenum sfactorAlpha, GLenum dfactorAlpha);
+typedef void (APIENTRYP PFNGLBLENDEQUATIONPROC) (GLenum mode);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glBlendFuncSeparate (GLenum sfactorRGB, GLenum dfactorRGB, GLenum sfactorAlpha, GLenum dfactorAlpha);
+GLAPI void APIENTRY glBlendEquation (GLenum mode);
+#endif
+#endif /* GL_VERSION_1_4 */
+#ifndef GL_VERSION_1_5
+typedef khronos_ssize_t GLsizeiptr;
+typedef khronos_intptr_t GLintptr;
+#define GL_ARRAY_BUFFER                   0x8892
+#define GL_ELEMENT_ARRAY_BUFFER           0x8893
+#define GL_ARRAY_BUFFER_BINDING           0x8894
+#define GL_ELEMENT_ARRAY_BUFFER_BINDING   0x8895
+#define GL_STREAM_DRAW                    0x88E0
+typedef void (APIENTRYP PFNGLBINDBUFFERPROC) (GLenum target, GLuint buffer);
+typedef void (APIENTRYP PFNGLDELETEBUFFERSPROC) (GLsizei n, const GLuint *buffers);
+typedef void (APIENTRYP PFNGLGENBUFFERSPROC) (GLsizei n, GLuint *buffers);
+typedef void (APIENTRYP PFNGLBUFFERDATAPROC) (GLenum target, GLsizeiptr size, const void *data, GLenum usage);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glBindBuffer (GLenum target, GLuint buffer);
+GLAPI void APIENTRY glDeleteBuffers (GLsizei n, const GLuint *buffers);
+GLAPI void APIENTRY glGenBuffers (GLsizei n, GLuint *buffers);
+GLAPI void APIENTRY glBufferData (GLenum target, GLsizeiptr size, const void *data, GLenum usage);
+#endif
+#endif /* GL_VERSION_1_5 */
+#ifndef GL_VERSION_2_0
+typedef char GLchar;
+typedef khronos_int16_t GLshort;
+typedef khronos_int8_t GLbyte;
+typedef khronos_uint16_t GLushort;
+#define GL_BLEND_EQUATION_RGB             0x8009
+#define GL_BLEND_EQUATION_ALPHA           0x883D
+#define GL_FRAGMENT_SHADER                0x8B30
+#define GL_VERTEX_SHADER                  0x8B31
+#define GL_COMPILE_STATUS                 0x8B81
+#define GL_LINK_STATUS                    0x8B82
+#define GL_INFO_LOG_LENGTH                0x8B84
+#define GL_CURRENT_PROGRAM                0x8B8D
+#define GL_UPPER_LEFT                     0x8CA2
+typedef void (APIENTRYP PFNGLBLENDEQUATIONSEPARATEPROC) (GLenum modeRGB, GLenum modeAlpha);
+typedef void (APIENTRYP PFNGLATTACHSHADERPROC) (GLuint program, GLuint shader);
+typedef void (APIENTRYP PFNGLCOMPILESHADERPROC) (GLuint shader);
+typedef GLuint (APIENTRYP PFNGLCREATEPROGRAMPROC) (void);
+typedef GLuint (APIENTRYP PFNGLCREATESHADERPROC) (GLenum type);
+typedef void (APIENTRYP PFNGLDELETEPROGRAMPROC) (GLuint program);
+typedef void (APIENTRYP PFNGLDELETESHADERPROC) (GLuint shader);
+typedef void (APIENTRYP PFNGLDETACHSHADERPROC) (GLuint program, GLuint shader);
+typedef void (APIENTRYP PFNGLENABLEVERTEXATTRIBARRAYPROC) (GLuint index);
+typedef GLint (APIENTRYP PFNGLGETATTRIBLOCATIONPROC) (GLuint program, const GLchar *name);
+typedef void (APIENTRYP PFNGLGETPROGRAMIVPROC) (GLuint program, GLenum pname, GLint *params);
+typedef void (APIENTRYP PFNGLGETPROGRAMINFOLOGPROC) (GLuint program, GLsizei bufSize, GLsizei *length, GLchar *infoLog);
+typedef void (APIENTRYP PFNGLGETSHADERIVPROC) (GLuint shader, GLenum pname, GLint *params);
+typedef void (APIENTRYP PFNGLGETSHADERINFOLOGPROC) (GLuint shader, GLsizei bufSize, GLsizei *length, GLchar *infoLog);
+typedef GLint (APIENTRYP PFNGLGETUNIFORMLOCATIONPROC) (GLuint program, const GLchar *name);
+typedef void (APIENTRYP PFNGLLINKPROGRAMPROC) (GLuint program);
+typedef void (APIENTRYP PFNGLSHADERSOURCEPROC) (GLuint shader, GLsizei count, const GLchar *const*string, const GLint *length);
+typedef void (APIENTRYP PFNGLUSEPROGRAMPROC) (GLuint program);
+typedef void (APIENTRYP PFNGLUNIFORM1IPROC) (GLint location, GLint v0);
+typedef void (APIENTRYP PFNGLUNIFORMMATRIX4FVPROC) (GLint location, GLsizei count, GLboolean transpose, const GLfloat *value);
+typedef void (APIENTRYP PFNGLVERTEXATTRIBPOINTERPROC) (GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const void *pointer);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glBlendEquationSeparate (GLenum modeRGB, GLenum modeAlpha);
+GLAPI void APIENTRY glAttachShader (GLuint program, GLuint shader);
+GLAPI void APIENTRY glCompileShader (GLuint shader);
+GLAPI GLuint APIENTRY glCreateProgram (void);
+GLAPI GLuint APIENTRY glCreateShader (GLenum type);
+GLAPI void APIENTRY glDeleteProgram (GLuint program);
+GLAPI void APIENTRY glDeleteShader (GLuint shader);
+GLAPI void APIENTRY glDetachShader (GLuint program, GLuint shader);
+GLAPI void APIENTRY glEnableVertexAttribArray (GLuint index);
+GLAPI GLint APIENTRY glGetAttribLocation (GLuint program, const GLchar *name);
+GLAPI void APIENTRY glGetProgramiv (GLuint program, GLenum pname, GLint *params);
+GLAPI void APIENTRY glGetProgramInfoLog (GLuint program, GLsizei bufSize, GLsizei *length, GLchar *infoLog);
+GLAPI void APIENTRY glGetShaderiv (GLuint shader, GLenum pname, GLint *params);
+GLAPI void APIENTRY glGetShaderInfoLog (GLuint shader, GLsizei bufSize, GLsizei *length, GLchar *infoLog);
+GLAPI GLint APIENTRY glGetUniformLocation (GLuint program, const GLchar *name);
+GLAPI void APIENTRY glLinkProgram (GLuint program);
+GLAPI void APIENTRY glShaderSource (GLuint shader, GLsizei count, const GLchar *const*string, const GLint *length);
+GLAPI void APIENTRY glUseProgram (GLuint program);
+GLAPI void APIENTRY glUniform1i (GLint location, GLint v0);
+GLAPI void APIENTRY glUniformMatrix4fv (GLint location, GLsizei count, GLboolean transpose, const GLfloat *value);
+GLAPI void APIENTRY glVertexAttribPointer (GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const void *pointer);
+#endif
+#endif /* GL_VERSION_2_0 */
+#ifndef GL_VERSION_3_0
+typedef khronos_uint16_t GLhalf;
+#define GL_MAJOR_VERSION                  0x821B
+#define GL_MINOR_VERSION                  0x821C
+#define GL_NUM_EXTENSIONS                 0x821D
+#define GL_VERTEX_ARRAY_BINDING           0x85B5
+typedef void (APIENTRYP PFNGLGETBOOLEANI_VPROC) (GLenum target, GLuint index, GLboolean *data);
+typedef void (APIENTRYP PFNGLGETINTEGERI_VPROC) (GLenum target, GLuint index, GLint *data);
+typedef const GLubyte *(APIENTRYP PFNGLGETSTRINGIPROC) (GLenum name, GLuint index);
+typedef void (APIENTRYP PFNGLBINDVERTEXARRAYPROC) (GLuint array);
+typedef void (APIENTRYP PFNGLDELETEVERTEXARRAYSPROC) (GLsizei n, const GLuint *arrays);
+typedef void (APIENTRYP PFNGLGENVERTEXARRAYSPROC) (GLsizei n, GLuint *arrays);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI const GLubyte *APIENTRY glGetStringi (GLenum name, GLuint index);
+GLAPI void APIENTRY glBindVertexArray (GLuint array);
+GLAPI void APIENTRY glDeleteVertexArrays (GLsizei n, const GLuint *arrays);
+GLAPI void APIENTRY glGenVertexArrays (GLsizei n, GLuint *arrays);
+#endif
+#endif /* GL_VERSION_3_0 */
+#ifndef GL_VERSION_3_1
+#define GL_VERSION_3_1 1
+#define GL_PRIMITIVE_RESTART              0x8F9D
+#endif /* GL_VERSION_3_1 */
+#ifndef GL_VERSION_3_2
+#define GL_VERSION_3_2 1
+typedef struct __GLsync *GLsync;
+typedef khronos_uint64_t GLuint64;
+typedef khronos_int64_t GLint64;
+typedef void (APIENTRYP PFNGLDRAWELEMENTSBASEVERTEXPROC) (GLenum mode, GLsizei count, GLenum type, const void *indices, GLint basevertex);
+typedef void (APIENTRYP PFNGLGETINTEGER64I_VPROC) (GLenum target, GLuint index, GLint64 *data);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glDrawElementsBaseVertex (GLenum mode, GLsizei count, GLenum type, const void *indices, GLint basevertex);
+#endif
+#endif /* GL_VERSION_3_2 */
+#ifndef GL_VERSION_3_3
+#define GL_VERSION_3_3 1
+#define GL_SAMPLER_BINDING                0x8919
+typedef void (APIENTRYP PFNGLBINDSAMPLERPROC) (GLuint unit, GLuint sampler);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glBindSampler (GLuint unit, GLuint sampler);
+#endif
+#endif /* GL_VERSION_3_3 */
+#ifndef GL_VERSION_4_1
+typedef void (APIENTRYP PFNGLGETFLOATI_VPROC) (GLenum target, GLuint index, GLfloat *data);
+typedef void (APIENTRYP PFNGLGETDOUBLEI_VPROC) (GLenum target, GLuint index, GLdouble *data);
+#endif /* GL_VERSION_4_1 */
+#ifndef GL_VERSION_4_3
+typedef void (APIENTRY  *GLDEBUGPROC)(GLenum source,GLenum type,GLuint id,GLenum severity,GLsizei length,const GLchar *message,const void *userParam);
+#endif /* GL_VERSION_4_3 */
+#ifndef GL_VERSION_4_5
+#define GL_CLIP_ORIGIN                    0x935C
+typedef void (APIENTRYP PFNGLCLIPCONTROLPROC) (GLenum origin, GLenum depth);
+typedef void (APIENTRYP PFNGLGETTRANSFORMFEEDBACKI_VPROC) (GLuint xfb, GLenum pname, GLuint index, GLint *param);
+typedef void (APIENTRYP PFNGLGETTRANSFORMFEEDBACKI64_VPROC) (GLuint xfb, GLenum pname, GLuint index, GLint64 *param);
+#ifdef GL_GLEXT_PROTOTYPES
+GLAPI void APIENTRY glClipControl (GLenum origin, GLenum depth);
+#endif
+#endif /* GL_VERSION_4_5 */
+#ifndef GL_ARB_bindless_texture
+typedef khronos_uint64_t GLuint64EXT;
+#endif /* GL_ARB_bindless_texture */
+#ifndef GL_ARB_cl_event
+struct _cl_context;
+struct _cl_event;
+#endif /* GL_ARB_cl_event */
+#ifndef GL_ARB_clip_control
+#define GL_ARB_clip_control 1
+#endif /* GL_ARB_clip_control */
+#ifndef GL_ARB_debug_output
+typedef void (APIENTRY  *GLDEBUGPROCARB)(GLenum source,GLenum type,GLuint id,GLenum severity,GLsizei length,const GLchar *message,const void *userParam);
+#endif /* GL_ARB_debug_output */
+#ifndef GL_EXT_EGL_image_storage
+typedef void *GLeglImageOES;
+#endif /* GL_EXT_EGL_image_storage */
+#ifndef GL_EXT_direct_state_access
+typedef void (APIENTRYP PFNGLGETFLOATI_VEXTPROC) (GLenum pname, GLuint index, GLfloat *params);
+typedef void (APIENTRYP PFNGLGETDOUBLEI_VEXTPROC) (GLenum pname, GLuint index, GLdouble *params);
+typedef void (APIENTRYP PFNGLGETPOINTERI_VEXTPROC) (GLenum pname, GLuint index, void **params);
+typedef void (APIENTRYP PFNGLGETVERTEXARRAYINTEGERI_VEXTPROC) (GLuint vaobj, GLuint index, GLenum pname, GLint *param);
+typedef void (APIENTRYP PFNGLGETVERTEXARRAYPOINTERI_VEXTPROC) (GLuint vaobj, GLuint index, GLenum pname, void **param);
+#endif /* GL_EXT_direct_state_access */
+#ifndef GL_NV_draw_vulkan_image
+typedef void (APIENTRY  *GLVULKANPROCNV)(void);
+#endif /* GL_NV_draw_vulkan_image */
+#ifndef GL_NV_gpu_shader5
+typedef khronos_int64_t GLint64EXT;
+#endif /* GL_NV_gpu_shader5 */
+#ifndef GL_NV_vertex_buffer_unified_memory
+typedef void (APIENTRYP PFNGLGETINTEGERUI64I_VNVPROC) (GLenum value, GLuint index, GLuint64EXT *result);
+#endif /* GL_NV_vertex_buffer_unified_memory */
+#ifdef __cplusplus
+}
+#endif
+#endif
+
+#ifndef GL3W_API
+#define GL3W_API
+#endif
+
+#ifndef __gl_h_
+#define __gl_h_
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define GL3W_OK 0
+#define GL3W_ERROR_INIT -1
+#define GL3W_ERROR_LIBRARY_OPEN -2
+#define GL3W_ERROR_OPENGL_VERSION -3
+
+typedef void (*GL3WglProc)(void);
+typedef GL3WglProc (*GL3WGetProcAddressProc)(const char *proc);
+
+/* gl3w api */
+GL3W_API int imgl3wInit(void);
+GL3W_API int imgl3wInit2(GL3WGetProcAddressProc proc);
+GL3W_API int imgl3wIsSupported(int major, int minor);
+GL3W_API GL3WglProc imgl3wGetProcAddress(const char *proc);
+
+/* gl3w internal state */
+union GL3WProcs {
+    GL3WglProc ptr[52];
+    struct {
+        PFNGLACTIVETEXTUREPROC           ActiveTexture;
+        PFNGLATTACHSHADERPROC            AttachShader;
+        PFNGLBINDBUFFERPROC              BindBuffer;
+        PFNGLBINDSAMPLERPROC             BindSampler;
+        PFNGLBINDTEXTUREPROC             BindTexture;
+        PFNGLBINDVERTEXARRAYPROC         BindVertexArray;
+        PFNGLBLENDEQUATIONPROC           BlendEquation;
+        PFNGLBLENDEQUATIONSEPARATEPROC   BlendEquationSeparate;
+        PFNGLBLENDFUNCSEPARATEPROC       BlendFuncSeparate;
+        PFNGLBUFFERDATAPROC              BufferData;
+        PFNGLCLEARPROC                   Clear;
+        PFNGLCLEARCOLORPROC              ClearColor;
+        PFNGLCLIPCONTROLPROC             ClipControl;
+        PFNGLCOMPILESHADERPROC           CompileShader;
+        PFNGLCREATEPROGRAMPROC           CreateProgram;
+        PFNGLCREATESHADERPROC            CreateShader;
+        PFNGLDELETEBUFFERSPROC           DeleteBuffers;
+        PFNGLDELETEPROGRAMPROC           DeleteProgram;
+        PFNGLDELETESHADERPROC            DeleteShader;
+        PFNGLDELETETEXTURESPROC          DeleteTextures;
+        PFNGLDELETEVERTEXARRAYSPROC      DeleteVertexArrays;
+        PFNGLDETACHSHADERPROC            DetachShader;
+        PFNGLDISABLEPROC                 Disable;
+        PFNGLDRAWELEMENTSPROC            DrawElements;
+        PFNGLDRAWELEMENTSBASEVERTEXPROC  DrawElementsBaseVertex;
+        PFNGLENABLEPROC                  Enable;
+        PFNGLENABLEVERTEXATTRIBARRAYPROC EnableVertexAttribArray;
+        PFNGLGENBUFFERSPROC              GenBuffers;
+        PFNGLGENTEXTURESPROC             GenTextures;
+        PFNGLGENVERTEXARRAYSPROC         GenVertexArrays;
+        PFNGLGETATTRIBLOCATIONPROC       GetAttribLocation;
+        PFNGLGETINTEGERVPROC             GetIntegerv;
+        PFNGLGETPROGRAMINFOLOGPROC       GetProgramInfoLog;
+        PFNGLGETPROGRAMIVPROC            GetProgramiv;
+        PFNGLGETSHADERINFOLOGPROC        GetShaderInfoLog;
+        PFNGLGETSHADERIVPROC             GetShaderiv;
+        PFNGLGETSTRINGPROC               GetString;
+        PFNGLGETSTRINGIPROC              GetStringi;
+        PFNGLGETUNIFORMLOCATIONPROC      GetUniformLocation;
+        PFNGLISENABLEDPROC               IsEnabled;
+        PFNGLLINKPROGRAMPROC             LinkProgram;
+        PFNGLPIXELSTOREIPROC             PixelStorei;
+        PFNGLPOLYGONMODEPROC             PolygonMode;
+        PFNGLSCISSORPROC                 Scissor;
+        PFNGLSHADERSOURCEPROC            ShaderSource;
+        PFNGLTEXIMAGE2DPROC              TexImage2D;
+        PFNGLTEXPARAMETERIPROC           TexParameteri;
+        PFNGLUNIFORM1IPROC               Uniform1i;
+        PFNGLUNIFORMMATRIX4FVPROC        UniformMatrix4fv;
+        PFNGLUSEPROGRAMPROC              UseProgram;
+        PFNGLVERTEXATTRIBPOINTERPROC     VertexAttribPointer;
+        PFNGLVIEWPORTPROC                Viewport;
+    } gl;
+};
+
+GL3W_API extern union GL3WProcs gl3wProcs;
+
+/* OpenGL functions */
+#define glActiveTexture                  gl3wProcs.gl.ActiveTexture
+#define glAttachShader                   gl3wProcs.gl.AttachShader
+#define glBindBuffer                     gl3wProcs.gl.BindBuffer
+#define glBindSampler                    gl3wProcs.gl.BindSampler
+#define glBindTexture                    gl3wProcs.gl.BindTexture
+#define glBindVertexArray                gl3wProcs.gl.BindVertexArray
+#define glBlendEquation                  gl3wProcs.gl.BlendEquation
+#define glBlendEquationSeparate          gl3wProcs.gl.BlendEquationSeparate
+#define glBlendFuncSeparate              gl3wProcs.gl.BlendFuncSeparate
+#define glBufferData                     gl3wProcs.gl.BufferData
+#define glClear                          gl3wProcs.gl.Clear
+#define glClearColor                     gl3wProcs.gl.ClearColor
+#define glClipControl                    gl3wProcs.gl.ClipControl
+#define glCompileShader                  gl3wProcs.gl.CompileShader
+#define glCreateProgram                  gl3wProcs.gl.CreateProgram
+#define glCreateShader                   gl3wProcs.gl.CreateShader
+#define glDeleteBuffers                  gl3wProcs.gl.DeleteBuffers
+#define glDeleteProgram                  gl3wProcs.gl.DeleteProgram
+#define glDeleteShader                   gl3wProcs.gl.DeleteShader
+#define glDeleteTextures                 gl3wProcs.gl.DeleteTextures
+#define glDeleteVertexArrays             gl3wProcs.gl.DeleteVertexArrays
+#define glDetachShader                   gl3wProcs.gl.DetachShader
+#define glDisable                        gl3wProcs.gl.Disable
+#define glDrawElements                   gl3wProcs.gl.DrawElements
+#define glDrawElementsBaseVertex         gl3wProcs.gl.DrawElementsBaseVertex
+#define glEnable                         gl3wProcs.gl.Enable
+#define glEnableVertexAttribArray        gl3wProcs.gl.EnableVertexAttribArray
+#define glGenBuffers                     gl3wProcs.gl.GenBuffers
+#define glGenTextures                    gl3wProcs.gl.GenTextures
+#define glGenVertexArrays                gl3wProcs.gl.GenVertexArrays
+#define glGetAttribLocation              gl3wProcs.gl.GetAttribLocation
+#define glGetIntegerv                    gl3wProcs.gl.GetIntegerv
+#define glGetProgramInfoLog              gl3wProcs.gl.GetProgramInfoLog
+#define glGetProgramiv                   gl3wProcs.gl.GetProgramiv
+#define glGetShaderInfoLog               gl3wProcs.gl.GetShaderInfoLog
+#define glGetShaderiv                    gl3wProcs.gl.GetShaderiv
+#define glGetString                      gl3wProcs.gl.GetString
+#define glGetStringi                     gl3wProcs.gl.GetStringi
+#define glGetUniformLocation             gl3wProcs.gl.GetUniformLocation
+#define glIsEnabled                      gl3wProcs.gl.IsEnabled
+#define glLinkProgram                    gl3wProcs.gl.LinkProgram
+#define glPixelStorei                    gl3wProcs.gl.PixelStorei
+#define glPolygonMode                    gl3wProcs.gl.PolygonMode
+#define glScissor                        gl3wProcs.gl.Scissor
+#define glShaderSource                   gl3wProcs.gl.ShaderSource
+#define glTexImage2D                     gl3wProcs.gl.TexImage2D
+#define glTexParameteri                  gl3wProcs.gl.TexParameteri
+#define glUniform1i                      gl3wProcs.gl.Uniform1i
+#define glUniformMatrix4fv               gl3wProcs.gl.UniformMatrix4fv
+#define glUseProgram                     gl3wProcs.gl.UseProgram
+#define glVertexAttribPointer            gl3wProcs.gl.VertexAttribPointer
+#define glViewport                       gl3wProcs.gl.Viewport
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+#ifdef IMGL3W_IMPL
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdlib.h>
+
+#define ARRAY_SIZE(x)  (sizeof(x) / sizeof((x)[0]))
+
+#if defined(_WIN32)
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN 1
+#endif
+#include <windows.h>
+
+static HMODULE libgl;
+typedef PROC(__stdcall* GL3WglGetProcAddr)(LPCSTR);
+static GL3WglGetProcAddr wgl_get_proc_address;
+
+static int open_libgl(void)
+{
+    libgl = LoadLibraryA("opengl32.dll");
+    if (!libgl)
+        return GL3W_ERROR_LIBRARY_OPEN;
+    wgl_get_proc_address = (GL3WglGetProcAddr)GetProcAddress(libgl, "wglGetProcAddress");
+    return GL3W_OK;
+}
+
+static void close_libgl(void) { FreeLibrary(libgl); }
+static GL3WglProc get_proc(const char *proc)
+{
+    GL3WglProc res;
+    res = (GL3WglProc)wgl_get_proc_address(proc);
+    if (!res)
+        res = (GL3WglProc)GetProcAddress(libgl, proc);
+    return res;
+}
+#elif defined(__APPLE__)
+#include <dlfcn.h>
+
+static void *libgl;
+static int open_libgl(void)
+{
+    libgl = dlopen("/System/Library/Frameworks/OpenGL.framework/OpenGL", RTLD_LAZY | RTLD_LOCAL);
+    if (!libgl)
+        return GL3W_ERROR_LIBRARY_OPEN;
+    return GL3W_OK;
+}
+
+static void close_libgl(void) { dlclose(libgl); }
+
+static GL3WglProc get_proc(const char *proc)
+{
+    GL3WglProc res;
+    *(void **)(&res) = dlsym(libgl, proc);
+    return res;
+}
+#else
+#include <dlfcn.h>
+
+static void *libgl;
+static GL3WglProc (*glx_get_proc_address)(const GLubyte *);
+
+static int open_libgl(void)
+{
+    libgl = dlopen("libGL.so.1", RTLD_LAZY | RTLD_LOCAL);
+    if (!libgl)
+        return GL3W_ERROR_LIBRARY_OPEN;
+    *(void **)(&glx_get_proc_address) = dlsym(libgl, "glXGetProcAddressARB");
+    return GL3W_OK;
+}
+
+static void close_libgl(void) { dlclose(libgl); }
+
+static GL3WglProc get_proc(const char *proc)
+{
+    GL3WglProc res;
+    res = glx_get_proc_address((const GLubyte *)proc);
+    if (!res)
+        *(void **)(&res) = dlsym(libgl, proc);
+    return res;
+}
+#endif
+
+static struct { int major, minor; } version;
+
+static int parse_version(void)
+{
+    if (!glGetIntegerv)
+        return GL3W_ERROR_INIT;
+    glGetIntegerv(GL_MAJOR_VERSION, &version.major);
+    glGetIntegerv(GL_MINOR_VERSION, &version.minor);
+    if (version.major < 3)
+        return GL3W_ERROR_OPENGL_VERSION;
+    return GL3W_OK;
+}
+
+static void load_procs(GL3WGetProcAddressProc proc);
+
+int imgl3wInit(void)
+{
+    int res = open_libgl();
+    if (res)
+        return res;
+    atexit(close_libgl);
+    return imgl3wInit2(get_proc);
+}
+
+int imgl3wInit2(GL3WGetProcAddressProc proc)
+{
+    load_procs(proc);
+    return parse_version();
+}
+
+int imgl3wIsSupported(int major, int minor)
+{
+    if (major < 3)
+        return 0;
+    if (version.major == major)
+        return version.minor >= minor;
+    return version.major >= major;
+}
+
+GL3WglProc imgl3wGetProcAddress(const char *proc) { return get_proc(proc); }
+
+static const char *proc_names[] = {
+    "glActiveTexture",
+    "glAttachShader",
+    "glBindBuffer",
+    "glBindSampler",
+    "glBindTexture",
+    "glBindVertexArray",
+    "glBlendEquation",
+    "glBlendEquationSeparate",
+    "glBlendFuncSeparate",
+    "glBufferData",
+    "glClear",
+    "glClearColor",
+    "glClipControl",
+    "glCompileShader",
+    "glCreateProgram",
+    "glCreateShader",
+    "glDeleteBuffers",
+    "glDeleteProgram",
+    "glDeleteShader",
+    "glDeleteTextures",
+    "glDeleteVertexArrays",
+    "glDetachShader",
+    "glDisable",
+    "glDrawElements",
+    "glDrawElementsBaseVertex",
+    "glEnable",
+    "glEnableVertexAttribArray",
+    "glGenBuffers",
+    "glGenTextures",
+    "glGenVertexArrays",
+    "glGetAttribLocation",
+    "glGetIntegerv",
+    "glGetProgramInfoLog",
+    "glGetProgramiv",
+    "glGetShaderInfoLog",
+    "glGetShaderiv",
+    "glGetString",
+    "glGetStringi",
+    "glGetUniformLocation",
+    "glIsEnabled",
+    "glLinkProgram",
+    "glPixelStorei",
+    "glPolygonMode",
+    "glScissor",
+    "glShaderSource",
+    "glTexImage2D",
+    "glTexParameteri",
+    "glUniform1i",
+    "glUniformMatrix4fv",
+    "glUseProgram",
+    "glVertexAttribPointer",
+    "glViewport",
+};
+
+GL3W_API union GL3WProcs gl3wProcs;
+
+static void load_procs(GL3WGetProcAddressProc proc)
+{
+    size_t i;
+    for (i = 0; i < ARRAY_SIZE(proc_names); i++)
+        gl3wProcs.ptr[i] = proc(proc_names[i]);
+}
+
+#ifdef __cplusplus
+}
+#endif
+#endif

docs/CHANGELOG.txt

@@ -130,6 +130,9 @@ Other Changes:
   Other OSX examples were not affected. (#4253, #1873) [@rokups]
 - Examples: Updated all .vcxproj to VS2015 (toolset v140) to facilitate usage with vcpkg.
 - Examples: SDL2: Accomodate for vcpkg install having headers in SDL2/SDL.h vs SDL.h.
+- Examples: OpenGL3+GLFW/SDL: Added minimal OpenGL loader imgui_impl_opengl3_loader.h and use it in OpenGL3 backend.
+  Support for using custom OpenGL loader in the backend is removed, IMGUI_IMPL_OPENGL_LOADER_XX (except ES2/ES3) are
+  no longer used. [@rokups]
 
 
 -----------------------------------------------------------------------

examples/example_glfw_opengl3/Makefile

@@ -31,35 +31,6 @@ LIBS =
 ## OPENGL LOADER / OPENGL ES
 ##---------------------------------------------------------------------
 
-## See below for OpenGL ES option (no loader required) - comment out
-## the following if you want to use OpenGL ES instead of Desktop GL.
-
-## Using OpenGL loader: gl3w [default]
-SOURCES += ../libs/gl3w/GL/gl3w.c
-CXXFLAGS += -I../libs/gl3w -DIMGUI_IMPL_OPENGL_LOADER_GL3W
-
-## Using OpenGL loader: glew
-## (This assumes a system-wide installation)
-# CXXFLAGS += -DIMGUI_IMPL_OPENGL_LOADER_GLEW
-# LIBS += -lGLEW
-
-## Using OpenGL loader: glad
-# SOURCES += ../libs/glad/src/glad.c
-# CXXFLAGS += -I../libs/glad/include -DIMGUI_IMPL_OPENGL_LOADER_GLAD
-
-## Using OpenGL loader: glad2
-# SOURCES += ../libs/glad/src/gl.c
-# CXXFLAGS += -I../libs/glad/include -DIMGUI_IMPL_OPENGL_LOADER_GLAD2
-
-## Using OpenGL loader: glbinding
-## This assumes a system-wide installation
-## of either version 3.0.0 (or newer)
-# CXXFLAGS += -DIMGUI_IMPL_OPENGL_LOADER_GLBINDING3
-# LIBS += -lglbinding
-## or the older version 2.x
-# CXXFLAGS += -DIMGUI_IMPL_OPENGL_LOADER_GLBINDING2
-# LIBS += -lglbinding
-
 ## Using OpenGL ES, no loader required
 ## This assumes a GL ES library available in the system, e.g. libGLESv2.so
 # CXXFLAGS += -DIMGUI_IMPL_OPENGL_ES2

examples/example_glfw_opengl3/example_glfw_opengl3.vcxproj

@@ -90,7 +90,7 @@
     <ClCompile>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
       <GenerateDebugInformation>true</GenerateDebugInformation>
@@ -104,7 +104,7 @@
     <ClCompile>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
       <GenerateDebugInformation>true</GenerateDebugInformation>
@@ -120,7 +120,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <BufferSecurityCheck>false</BufferSecurityCheck>
     </ClCompile>
     <Link>
@@ -140,7 +140,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;..\libs\glfw\include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <BufferSecurityCheck>false</BufferSecurityCheck>
     </ClCompile>
     <Link>
@@ -162,7 +162,6 @@
     <ClCompile Include="..\..\imgui_widgets.cpp" />
     <ClCompile Include="..\..\backends\imgui_impl_glfw.cpp" />
     <ClCompile Include="..\..\backends\imgui_impl_opengl3.cpp" />
-    <ClCompile Include="..\libs\gl3w\GL\gl3w.c" />
     <ClCompile Include="main.cpp" />
   </ItemGroup>
   <ItemGroup>
@@ -171,8 +170,7 @@
     <ClInclude Include="..\..\imgui_internal.h" />
     <ClInclude Include="..\..\backends\imgui_impl_glfw.h" />
     <ClInclude Include="..\..\backends\imgui_impl_opengl3.h" />
-    <ClInclude Include="..\libs\gl3w\GL\gl3w.h" />
+    <ClInclude Include="..\..\backends\imgui_impl_opengl3_loader.h" />
-    <ClInclude Include="..\libs\gl3w\GL\glcorearb.h" />
   </ItemGroup>
   <ItemGroup>
     <None Include="..\..\misc\debuggers\imgui.natvis" />

examples/example_glfw_opengl3/example_glfw_opengl3.vcxproj.filters

@@ -8,9 +8,6 @@
       <UniqueIdentifier>{f18ab499-84e1-499f-8eff-9754361e0e52}</UniqueIdentifier>
       <Extensions>cpp;c;cc;cxx;def;odl;idl;hpj;bat;asm;asmx</Extensions>
     </Filter>
-    <Filter Include="gl3w">
-      <UniqueIdentifier>{42f99867-3108-43b8-99d0-fabefaf1f2e3}</UniqueIdentifier>
-    </Filter>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="main.cpp">
@@ -19,9 +16,6 @@
     <ClCompile Include="..\..\imgui.cpp">
       <Filter>imgui</Filter>
     </ClCompile>
-    <ClCompile Include="..\libs\gl3w\GL\gl3w.c">
-      <Filter>gl3w</Filter>
-    </ClCompile>
     <ClCompile Include="..\..\imgui_demo.cpp">
       <Filter>imgui</Filter>
     </ClCompile>
@@ -48,12 +42,6 @@
     <ClInclude Include="..\..\imgui.h">
       <Filter>imgui</Filter>
     </ClInclude>
-    <ClInclude Include="..\libs\gl3w\GL\gl3w.h">
-      <Filter>gl3w</Filter>
-    </ClInclude>
-    <ClInclude Include="..\libs\gl3w\GL\glcorearb.h">
-      <Filter>gl3w</Filter>
-    </ClInclude>
     <ClInclude Include="..\..\imgui_internal.h">
       <Filter>imgui</Filter>
     </ClInclude>
@@ -63,6 +51,9 @@
     <ClInclude Include="..\..\backends\imgui_impl_opengl3.h">
       <Filter>sources</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\backends\imgui_impl_opengl3_loader.h">
+      <Filter>sources</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <None Include="..\README.txt" />

examples/example_glfw_opengl3/main.cpp

@@ -10,30 +10,12 @@
 
 #if defined(IMGUI_IMPL_OPENGL_ES2)
 #include <GLES2/gl2.h>
+#else
 // About Desktop OpenGL function loaders:
 //  Modern desktop OpenGL doesn't have a standard portable header file to load OpenGL function pointers.
-//  Helper libraries are often used for this purpose! Here we are supporting a few common ones (gl3w, glew, glad).
+//  Here we are using our own minimal loader based on gl3w. You may use another loader/header of your choice (glext, glLoadGen, etc.),
-//  You may use another loader/header of your choice (glext, glLoadGen, etc.), or chose to manually implement your own.
+//  or chose to manually implement your own.
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
+#include "imgui_impl_opengl3_loader.h"
-#include <GL/gl3w.h>            // Initialize with gl3wInit()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
-#include <GL/glew.h>            // Initialize with glewInit()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
-#include <glad/glad.h>          // Initialize with gladLoadGL()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-#include <glad/gl.h>            // Initialize with gladLoadGL(...) or gladLoaderLoadGL()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
-#define GLFW_INCLUDE_NONE       // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
-#include <glbinding/Binding.h>  // Initialize with glbinding::Binding::initialize()
-#include <glbinding/gl/gl.h>
-using namespace gl;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
-#define GLFW_INCLUDE_NONE       // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
-#include <glbinding/glbinding.h>// Initialize with glbinding::initialize()
-#include <glbinding/gl/gl.h>
-using namespace gl;
-#else
-#include IMGUI_IMPL_OPENGL_LOADER_CUSTOM
 #endif
 
 // Include glfw3.h after our OpenGL definitions
@@ -88,30 +70,6 @@ int main(int, char**)
     glfwMakeContextCurrent(window);
     glfwSwapInterval(1); // Enable vsync
 
-    // Initialize OpenGL loader
-#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
-    bool err = gl3wInit() != 0;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
-    bool err = glewInit() != GLEW_OK;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
-    bool err = gladLoadGL() == 0;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-    bool err = gladLoadGL(glfwGetProcAddress) == 0; // glad2 recommend using the windowing library loader instead of the (optionally) bundled one.
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
-    bool err = false;
-    glbinding::Binding::initialize();
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
-    bool err = false;
-    glbinding::initialize([](const char* name) { return (glbinding::ProcAddress)glfwGetProcAddress(name); });
-#else
-    bool err = false; // If you use IMGUI_IMPL_OPENGL_LOADER_CUSTOM, your loader is likely to requires some form of initialization.
-#endif
-    if (err)
-    {
-        fprintf(stderr, "Failed to initialize OpenGL loader!\n");
-        return 1;
-    }
-
     // Setup Dear ImGui context
     IMGUI_CHECKVERSION();
     ImGui::CreateContext();

examples/example_sdl_opengl3/Makefile

@@ -31,35 +31,6 @@ LIBS =
 ## OPENGL LOADER / OPENGL ES
 ##---------------------------------------------------------------------
 
-## See below for OpenGL ES option (no loader required) - comment out
-## the following if you want to use OpenGL ES instead of Desktop GL.
-
-## Using OpenGL loader: gl3w [default]
-SOURCES += ../libs/gl3w/GL/gl3w.c
-CXXFLAGS += -I../libs/gl3w -DIMGUI_IMPL_OPENGL_LOADER_GL3W
-
-## Using OpenGL loader: glew
-## (This assumes a system-wide installation)
-# CXXFLAGS += -DIMGUI_IMPL_OPENGL_LOADER_GLEW
-# LIBS += -lGLEW
-
-## Using OpenGL loader: glad
-# SOURCES += ../libs/glad/src/glad.c
-# CXXFLAGS += -I../libs/glad/include -DIMGUI_IMPL_OPENGL_LOADER_GLAD
-
-## Using OpenGL loader: glad2
-# SOURCES += ../libs/glad/src/gl.c
-# CXXFLAGS += -I../libs/glad/include -DIMGUI_IMPL_OPENGL_LOADER_GLAD2
-
-## Using OpenGL loader: glbinding
-## This assumes a system-wide installation
-## of either version 3.0.0 (or newer)
-# CXXFLAGS += -DIMGUI_IMPL_OPENGL_LOADER_GLBINDING3
-# LIBS += -lglbinding
-## or the older version 2.x
-# CXXFLAGS += -DIMGUI_IMPL_OPENGL_LOADER_GLBINDING2
-# LIBS += -lglbinding
-
 ## Using OpenGL ES, no loader required
 ## This assumes a GL ES library available in the system, e.g. libGLESv2.so
 # CXXFLAGS += -DIMGUI_IMPL_OPENGL_ES2

examples/example_sdl_opengl3/example_sdl_opengl3.vcxproj

@@ -90,7 +90,7 @@
     <ClCompile>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
       <GenerateDebugInformation>true</GenerateDebugInformation>
@@ -104,7 +104,7 @@
     <ClCompile>
       <WarningLevel>Level4</WarningLevel>
       <Optimization>Disabled</Optimization>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
       <GenerateDebugInformation>true</GenerateDebugInformation>
@@ -120,7 +120,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <BufferSecurityCheck>false</BufferSecurityCheck>
     </ClCompile>
     <Link>
@@ -140,7 +140,7 @@
       <Optimization>MaxSpeed</Optimization>
       <FunctionLevelLinking>true</FunctionLevelLinking>
       <IntrinsicFunctions>true</IntrinsicFunctions>
-      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;..\libs\gl3w;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\..;..\..\backends;%SDL2_DIR%\include;$(VcpkgCurrentInstalledDir)include\SDL2;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <BufferSecurityCheck>false</BufferSecurityCheck>
     </ClCompile>
     <Link>
@@ -162,7 +162,6 @@
     <ClCompile Include="..\..\imgui_widgets.cpp" />
     <ClCompile Include="..\..\backends\imgui_impl_opengl3.cpp" />
     <ClCompile Include="..\..\backends\imgui_impl_sdl.cpp" />
-    <ClCompile Include="..\libs\gl3w\GL\gl3w.c" />
     <ClCompile Include="main.cpp" />
   </ItemGroup>
   <ItemGroup>
@@ -170,9 +169,8 @@
     <ClInclude Include="..\..\imgui.h" />
     <ClInclude Include="..\..\imgui_internal.h" />
     <ClInclude Include="..\..\backends\imgui_impl_opengl3.h" />
+    <ClInclude Include="..\..\backends\imgui_impl_opengl3_loader.h" />
     <ClInclude Include="..\..\backends\imgui_impl_sdl.h" />
-    <ClInclude Include="..\libs\gl3w\GL\gl3w.h" />
-    <ClInclude Include="..\libs\gl3w\GL\glcorearb.h" />
   </ItemGroup>
   <ItemGroup>
     <None Include="..\..\misc\debuggers\imgui.natvis" />

examples/example_sdl_opengl3/example_sdl_opengl3.vcxproj.filters

@@ -8,9 +8,6 @@
       <UniqueIdentifier>{f18ab499-84e1-499f-8eff-9754361e0e52}</UniqueIdentifier>
       <Extensions>cpp;c;cc;cxx;def;odl;idl;hpj;bat;asm;asmx</Extensions>
     </Filter>
-    <Filter Include="gl3w">
-      <UniqueIdentifier>{f9997b32-5479-4756-9ffc-77793ad3764f}</UniqueIdentifier>
-    </Filter>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="..\..\imgui.cpp">
@@ -25,9 +22,6 @@
     <ClCompile Include="main.cpp">
       <Filter>sources</Filter>
     </ClCompile>
-    <ClCompile Include="..\libs\gl3w\GL\gl3w.c">
-      <Filter>gl3w</Filter>
-    </ClCompile>
     <ClCompile Include="..\..\backends\imgui_impl_opengl3.cpp">
       <Filter>sources</Filter>
     </ClCompile>
@@ -51,15 +45,12 @@
     <ClInclude Include="..\..\imgui_internal.h">
       <Filter>imgui</Filter>
     </ClInclude>
-    <ClInclude Include="..\libs\gl3w\GL\gl3w.h">
-      <Filter>gl3w</Filter>
-    </ClInclude>
-    <ClInclude Include="..\libs\gl3w\GL\glcorearb.h">
-      <Filter>gl3w</Filter>
-    </ClInclude>
     <ClInclude Include="..\..\backends\imgui_impl_opengl3.h">
       <Filter>sources</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\backends\imgui_impl_opengl3_loader.h">
+      <Filter>sources</Filter>
+    </ClInclude>
     <ClInclude Include="..\..\backends\imgui_impl_sdl.h">
       <Filter>sources</Filter>
     </ClInclude>

examples/example_sdl_opengl3/main.cpp

@@ -9,33 +9,10 @@
 #include "imgui_impl_opengl3.h"
 #include <stdio.h>
 #include <SDL.h>
+#include <SDL_opengl.h>
 
 #if defined(IMGUI_IMPL_OPENGL_ES2)
-#include <GLES2/gl2.h>
+#include <SDL_opengles2.h>
-// About Desktop OpenGL function loaders:
-//  Modern desktop OpenGL doesn't have a standard portable header file to load OpenGL function pointers.
-//  Helper libraries are often used for this purpose! Here we are supporting a few common ones (gl3w, glew, glad).
-//  You may use another loader/header of your choice (glext, glLoadGen, etc.), or chose to manually implement your own.
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
-#include <GL/gl3w.h>            // Initialize with gl3wInit()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
-#include <GL/glew.h>            // Initialize with glewInit()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
-#include <glad/glad.h>          // Initialize with gladLoadGL()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-#include <glad/gl.h>            // Initialize with gladLoadGL(...) or gladLoaderLoadGL()
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
-#define GLFW_INCLUDE_NONE       // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
-#include <glbinding/Binding.h>  // Initialize with glbinding::Binding::initialize()
-#include <glbinding/gl/gl.h>
-using namespace gl;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
-#define GLFW_INCLUDE_NONE       // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
-#include <glbinding/glbinding.h>// Initialize with glbinding::initialize()
-#include <glbinding/gl/gl.h>
-using namespace gl;
-#else
-#include IMGUI_IMPL_OPENGL_LOADER_CUSTOM
 #endif
 
 // Main code
@@ -84,30 +61,6 @@ int main(int, char**)
     SDL_GL_MakeCurrent(window, gl_context);
     SDL_GL_SetSwapInterval(1); // Enable vsync
 
-    // Initialize OpenGL loader
-#if defined(IMGUI_IMPL_OPENGL_LOADER_GL3W)
-    bool err = gl3wInit() != 0;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLEW)
-    bool err = glewInit() != GLEW_OK;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
-    bool err = gladLoadGL() == 0;
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD2)
-    bool err = gladLoadGL((GLADloadfunc)SDL_GL_GetProcAddress) == 0; // glad2 recommend using the windowing library loader instead of the (optionally) bundled one.
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
-    bool err = false;
-    glbinding::Binding::initialize();
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3)
-    bool err = false;
-    glbinding::initialize([](const char* name) { return (glbinding::ProcAddress)SDL_GL_GetProcAddress(name); });
-#else
-    bool err = false; // If you use IMGUI_IMPL_OPENGL_LOADER_CUSTOM, your loader is likely to requires some form of initialization.
-#endif
-    if (err)
-    {
-        fprintf(stderr, "Failed to initialize OpenGL loader!\n");
-        return 1;
-    }
-
     // Setup Dear ImGui context
     IMGUI_CHECKVERSION();
     ImGui::CreateContext();