Support older 2.x series of glbinding as loader for OpenGL3

For the moment I have only the older 2.x series available on my system
which uses slightly different header filenames and initialisation, so
as a slight variation of the 3.x series support recently implemented
here the glue needed to make 2.x series work.

I would hope a potential 4.x will not change filenames and such, so the
existing flag isn't rebranded to 3 which also avoids breaking compat.

References: #2870, 5e2329b

examples/example_glfw_opengl3/Makefile

@@ -44,6 +44,8 @@ CXXFLAGS += -I../libs/gl3w -DIMGUI_IMPL_OPENGL_LOADER_GL3W
 ## Using OpenGL loader: glbinding
 ## (This assumes a system-wide installation)
 # CXXFLAGS += -lglbinding -DIMGUI_IMPL_OPENGL_LOADER_GLBINDING
+## or for the older 2.x series of glbinding
+# CXXFLAGS += -lglbinding -DIMGUI_IMPL_OPENGL_LOADER_GLBINDING2
 
 ##---------------------------------------------------------------------
 ## BUILD FLAGS PER PLATFORM

examples/example_glfw_opengl3/main.cpp

@@ -17,9 +17,13 @@
 #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_GLBINDING)
+#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING) || defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
 #define GLFW_INCLUDE_NONE         // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
+#if defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
+#include <glbinding/Binding.h>    // Initialize with glbinding::Binding::initialize()
+#else
 #include <glbinding/glbinding.h>  // Initialize with glbinding::initialize()
+#endif
 #include <glbinding/gl/gl.h>
 using namespace gl;
 #else
@@ -79,6 +83,9 @@ int main(int, char**)
     bool err = glewInit() != GLEW_OK;
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
     bool err = gladLoadGL() == 0;
+#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
+    bool err = false;
+    glbinding::Binding::initialize();
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING)
     bool err = false;
     glbinding::initialize([](const char* name) { return (glbinding::ProcAddress)glfwGetProcAddress(name); });

examples/imgui_impl_opengl3.cpp

@@ -87,13 +87,15 @@
 #undef IMGUI_IMPL_OPENGL_LOADER_GLEW
 #undef IMGUI_IMPL_OPENGL_LOADER_GLAD
 #undef IMGUI_IMPL_OPENGL_LOADER_GLBINDING
+#undef IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
 #undef IMGUI_IMPL_OPENGL_LOADER_CUSTOM
 #elif defined(__EMSCRIPTEN__)
 #define IMGUI_IMPL_OPENGL_ES2           // Emscripten    -> GL ES 2, "#version 100"
 #undef IMGUI_IMPL_OPENGL_LOADER_GL3W
 #undef IMGUI_IMPL_OPENGL_LOADER_GLEW
 #undef IMGUI_IMPL_OPENGL_LOADER_GLAD
 #undef IMGUI_IMPL_OPENGL_LOADER_GLBINDING
+#undef IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
 #undef IMGUI_IMPL_OPENGL_LOADER_CUSTOM
 #endif
 #endif
@@ -118,9 +120,13 @@
 #include <GL/glew.h>    // Needs to be initialized with glewInit() in user's code
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
 #include <glad/glad.h>  // Needs to be initialized with gladLoadGL() in user's code
-#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING)
+#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING) || defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
 #include <glbinding/gl/gl.h>  // Initialize with glbinding::initialize()
+#if defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
+#include <glbinding/Binding.h>
+#else
 #include <glbinding/glbinding.h>
+#endif
 using namespace gl;
 #else
 #include IMGUI_IMPL_OPENGL_LOADER_CUSTOM
@@ -193,6 +199,8 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
     gl_loader = "GLEW";
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLAD)
     gl_loader = "GLAD";
+#elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2)
+    gl_loader = "glbinding2";
 #elif defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING)
     gl_loader = "glbinding";
 #else // IMGUI_IMPL_OPENGL_LOADER_CUSTOM

examples/imgui_impl_opengl3.h

@@ -47,6 +47,7 @@ IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyDeviceObjects();
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLEW) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLAD) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING) \
+ && !defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
     #if defined(__has_include)
         #if __has_include(<GL/glew.h>)
@@ -55,8 +56,10 @@ IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyDeviceObjects();
             #define IMGUI_IMPL_OPENGL_LOADER_GLAD
         #elif __has_include(<GL/gl3w.h>)
             #define IMGUI_IMPL_OPENGL_LOADER_GL3W
-        #elif __has_include(<glbinding/gl/gl.h>)
+        #elif __has_include(<glbinding/glbinding.h>)
             #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING
+        #elif __has_include(<glbinding/Binding.h>)
+            #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
         #else
             #error "Cannot detect OpenGL loader!"
         #endif