allow custom opengl loader

include/render/GL.h

@@ -1,8 +1,62 @@
 #pragma once
 
-#ifdef __ANDROID__
-#include <GLES3/gl3.h>
+#if !defined(TD_IMPL_OPENGL_ES2) \
+ && !defined(TD_IMPL_OPENGL_ES3) \
+ && !defined(TD_IMPL_OPENGL_LOADER_GL3W) \
+ && !defined(TD_IMPL_OPENGL_LOADER_GLEW) \
+ && !defined(TD_IMPL_OPENGL_LOADER_GLAD) \
+ && !defined(TD_IMPL_OPENGL_LOADER_GLBINDING2) \
+ && !defined(TD_IMPL_OPENGL_LOADER_GLBINDING3) \
+ && !defined(TD_IMPL_OPENGL_LOADER_CUSTOM) \
+ && !defined(__ANDROID__)
+
+#if defined(__has_include)
+
+#if __has_include(<GL/glew.h>)
+    #define TD_IMPL_OPENGL_LOADER_GLEW
+#elif __has_include(<glad/glad.h>)
+    #define TD_IMPL_OPENGL_LOADER_GLAD
+#elif __has_include(<GL/gl3w.h>)
+    #define TD_IMPL_OPENGL_LOADER_GL3W
+#elif __has_include(<glbinding/glbinding.h>)
+    #define TD_IMPL_OPENGL_LOADER_GLBINDING3
+#elif __has_include(<glbinding/Binding.h>)
+    #define TD_IMPL_OPENGL_LOADER_GLBINDING2
 #else
-#include "glbinding/gl/gl.h"
-using namespace gl;
+    #error "Cannot detect OpenGL loader!"
+#endif
+
+#else
+	#error "Cannot detect loader with include detection !"
+#endif
+#endif
+
+
+
+// Include correct files
+
+#if defined(__ANDROID__)
+	#include <GLES3/gl3.h>
+#elif defined(TD_IMPL_OPENGL_LOADER_GL3W)
+	#include <GL/gl3w.h>            // Needs to be initialized with gl3wInit() in user's code
+#elif defined(TD_IMPL_OPENGL_LOADER_GLEW)
+	#include <GL/glew.h>            // Needs to be initialized with glewInit() in user's code.
+#elif defined(TD_IMPL_OPENGL_LOADER_GLAD)
+	#include <glad/glad.h>          // Needs to be initialized with gladLoadGL() in user's code.
+#elif defined(TD_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(TD_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 TD_IMPL_OPENGL_LOADER_CUSTOM
 #endif

include/render/gui/imgui/imconfig.h

@@ -107,8 +107,20 @@ namespace ImGui
 }
 */
 
-#ifdef __ANDROID__
-#define IMGUI_IMPL_OPENGL_ES3
+#include "render/GL.h"
+
+#if defined(__ANDROID__)
+#define IMGUI_IMPL_OPENGL_LOADER_ES3
+#elif defined(TD_IMPL_OPENGL_LOADER_GL3W)
+    #define IMGUI_IMPL_OPENGL_LOADER_GL3W
+#elif defined(TD_IMPL_OPENGL_LOADER_GLEW)
+    #define IMGUI_IMPL_OPENGL_LOADER_GLEW
+#elif defined(TD_IMPL_OPENGL_LOADER_GLAD)
+    #define IMGUI_IMPL_OPENGL_LOADER_GLAD
+#elif defined(TD_IMPL_OPENGL_LOADER_GLBINDING2)
+    #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
+#elif defined(TD_IMPL_OPENGL_LOADER_GLBINDING3)
+    #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING3
 #else
-#define IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
+    #define IMGUI_IMPL_OPENGL_LOADER_CUSTOM
 #endif