Backends: OpenGL: Fixed loader auto-detection to not interfere with ES2/ES3 defines. (#3246)

docs/CHANGELOG.txt

@@ -66,6 +66,7 @@ Other Changes:
 - Backends: OpenGL: Fixed handling of GL 4.5+ glClipControl(GL_UPPER_LEFT) by inverting the
   projection matrix top and bottom values. (#3143, #3146) [@u3shit]
 - Backends: OpenGL: On OSX, if unspecified by app, made default GLSL version 150. (#3199) [@albertvaka]
+- Backends: OpenGL: Fixed loader auto-detection to not interfere with ES2/ES3 defines. (#3246) [@funchal]
 - Backends: Vulkan: Fixed error in if initial frame has no vertices. (#3177)
 - Backends: Vulkan: Fixed edge case where render callbacks wouldn't be called if the ImDrawData
   structure didn't have any vertices. (#2697) [@kudaba]

examples/imgui_impl_opengl3.cpp

@@ -79,27 +79,7 @@
 #else
 #include <stdint.h>     // intptr_t
 #endif
-#if defined(__APPLE__)
-#include "TargetConditionals.h"
-#endif
 
-// Auto-enable GLES on matching platforms
-#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3)
-#if (defined(__APPLE__) && (TARGET_OS_IOS || TARGET_OS_TV)) || (defined(__ANDROID__))
-#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"
-#endif
-#endif
-
-#if defined(IMGUI_IMPL_OPENGL_ES2) || defined(IMGUI_IMPL_OPENGL_ES3)
-#undef IMGUI_IMPL_OPENGL_LOADER_GL3W
-#undef IMGUI_IMPL_OPENGL_LOADER_GLEW
-#undef IMGUI_IMPL_OPENGL_LOADER_GLAD
-#undef IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
-#undef IMGUI_IMPL_OPENGL_LOADER_GLBINDING3
-#undef IMGUI_IMPL_OPENGL_LOADER_CUSTOM
-#endif
 
 // GL includes
 #if defined(IMGUI_IMPL_OPENGL_ES2)

examples/imgui_impl_opengl3.h

@@ -12,7 +12,7 @@
 // https://github.com/ocornut/imgui
 
 // About Desktop OpenGL function loaders:
-//  Modern desktop OpenGL doesn't have a standard portable header file to load OpenGL function pointers.
+//  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.
 
@@ -36,36 +36,49 @@ IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyFontsTexture();
 IMGUI_IMPL_API bool     ImGui_ImplOpenGL3_CreateDeviceObjects();
 IMGUI_IMPL_API void     ImGui_ImplOpenGL3_DestroyDeviceObjects();
 
-// Specific OpenGL versions
+// Specific OpenGL ES versions
 //#define IMGUI_IMPL_OPENGL_ES2     // Auto-detected on Emscripten
 //#define IMGUI_IMPL_OPENGL_ES3     // Auto-detected on iOS/Android
 
-// Desktop OpenGL: attempt to detect default GL loader based on available header files.
+// Attempt to auto-detect the default Desktop GL loader based on available header files.
 // 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 '#define IMGUI_IMPL_OPENGL_LOADER_XXX' in imconfig.h or compiler command-line.
-#if !defined(IMGUI_IMPL_OPENGL_LOADER_GL3W) \
+// 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_LOADER_GL3W) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLEW) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLAD) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING2) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_GLBINDING3) \
  && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
-    #if defined(__has_include)
-        #if __has_include(<GL/glew.h>)
+
+// Try to detect GLES on matching platforms
+#if defined(__APPLE__)
+#include "TargetConditionals.h"
+#endif
+#if (defined(__APPLE__) && (TARGET_OS_IOS || TARGET_OS_TV)) || (defined(__ANDROID__))
+#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>)
+#elif __has_include(<glad/glad.h>)
     #define IMGUI_IMPL_OPENGL_LOADER_GLAD
-        #elif __has_include(<GL/gl3w.h>)
+#elif __has_include(<GL/gl3w.h>)
     #define IMGUI_IMPL_OPENGL_LOADER_GL3W
-        #elif __has_include(<glbinding/glbinding.h>)
+#elif __has_include(<glbinding/glbinding.h>)
     #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING3
-        #elif __has_include(<glbinding/Binding.h>)
+#elif __has_include(<glbinding/Binding.h>)
     #define IMGUI_IMPL_OPENGL_LOADER_GLBINDING2
-        #else
+#else
     #error "Cannot detect OpenGL loader!"
-        #endif
-    #else
-        #define IMGUI_IMPL_OPENGL_LOADER_GL3W       // Default to GL3W
-    #endif
+#endif
+#else
+    #define IMGUI_IMPL_OPENGL_LOADER_GL3W   // Default to GL3W embedded in our repository
 #endif
 
+#endif