Backends: GL3: Implement glbinding opengl loader support. (#2870)

docs/CHANGELOG.txt

@@ -79,6 +79,7 @@ Other Changes:
   automatically use it). [#2919, #2798]
 - Examples: Metal: Wrapped main loop in @autoreleasepool block to ensure allocations get freed
   even if underlying system event loop gets paused due to app nap (#2910, #2917). [@bear24rw]
+- Examples: Added support for glbindings OpenGL loader.
 
 
 -----------------------------------------------------------------------

examples/README.txt

@@ -198,7 +198,7 @@ example_glfw_opengl2/
     GLFW + OpenGL2 example (legacy, fixed pipeline).
     = main.cpp + imgui_impl_glfw.cpp + imgui_impl_opengl2.cpp
     **DO NOT USE OPENGL2 CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
-    **Prefer using OPENGL3 code (with gl3w/glew/glad, you can replace the OpenGL function loader)**
+    **Prefer using OPENGL3 code (with gl3w/glew/glad/glbindings, you can replace the OpenGL function loader)**
     This code is mostly provided as a reference to learn about Dear ImGui integration, because it is shorter.
     If your code is using GL3+ context or any semi modern OpenGL calls, using this renderer is likely to
     make things more complicated, will require your code to reset many OpenGL attributes to their initial
@@ -243,7 +243,7 @@ example_sdl_opengl2/
     SDL2 (Win32, Mac, Linux etc.) + OpenGL example (legacy, fixed pipeline).
     = main.cpp + imgui_impl_sdl.cpp + imgui_impl_opengl2.cpp
     **DO NOT USE OPENGL2 CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
-    **Prefer using OPENGL3 code (with gl3w/glew/glad, you can replace the OpenGL function loader)**
+    **Prefer using OPENGL3 code (with gl3w/glew/glad/glbindings, you can replace the OpenGL function loader)**
     This code is mostly provided as a reference to learn about Dear ImGui integration, because it is shorter.
     If your code is using GL3+ context or any semi modern OpenGL calls, using this renderer is likely to
     make things more complicated, will require your code to reset many OpenGL attributes to their initial

examples/example_glfw_opengl3/main.cpp

@@ -17,6 +17,11 @@
 #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)
+#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
@@ -74,6 +79,9 @@ 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_GLBINDING)
+    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

examples/example_sdl_opengl3/main.cpp

@@ -19,6 +19,10 @@
 #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)
+#include <glbinding/glbinding.h>  // Initialize with glbinding::initialize()
+#include <glbinding/gl/gl.h>
+using namespace gl;
 #else
 #include IMGUI_IMPL_OPENGL_LOADER_CUSTOM
 #endif
@@ -69,6 +73,9 @@ 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_GLBINDING)
+    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

examples/imgui_impl_opengl3.cpp

@@ -13,6 +13,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2020-01-07: OpenGL: Added support for glbindings OpenGL loader.
 //  2019-10-25: OpenGL: Using a combination of GL define and runtime GL version to decide whether to use glDrawElementsBaseVertex(). Fix building with pre-3.2 GL loaders.
 //  2019-09-22: OpenGL: Detect default GL loader using __has_include compiler facility.
 //  2019-09-16: OpenGL: Tweak initialization code to allow application calling ImGui_ImplOpenGL3_CreateFontsTexture() before the first NewFrame() call.
@@ -85,12 +86,14 @@
 #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_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_CUSTOM
 #endif
 #endif
@@ -115,6 +118,10 @@
 #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)
+#include <glbinding/gl/gl.h>  // Initialize with glbinding::initialize()
+#include <glbinding/glbinding.h>
+using namespace gl;
 #else
 #include IMGUI_IMPL_OPENGL_LOADER_CUSTOM
 #endif
@@ -186,6 +193,8 @@ 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_GLBINDING)
+    gl_loader = "glbinding";
 #else // IMGUI_IMPL_OPENGL_LOADER_CUSTOM
     gl_loader = "Custom";
 #endif

examples/imgui_impl_opengl3.h

@@ -46,6 +46,7 @@ IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyDeviceObjects();
 #if !defined(IMGUI_IMPL_OPENGL_LOADER_GL3W) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLEW) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLAD) \
+ && !defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
     #if defined(__has_include)
         #if __has_include(<GL/glew.h>)
@@ -54,6 +55,8 @@ 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>)
+            #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING
         #else
             #error "Cannot detect OpenGL loader!"
         #endif