imgui_impl_opengl3: Comments. (#1987)

examples/imgui_impl_opengl3.cpp

@@ -61,7 +61,11 @@
 #ifdef __EMSCRIPTEN__
 #include <GLES3/gl3.h>  // Use GL ES 3
 #else
-#include <GL/gl3w.h>    // This example is using gl3w to access OpenGL functions. You may use another OpenGL loader/header such as: glew, glext, glad, glLoadGen, etc.
+// About OpenGL function loaders:
+// Modern OpenGL requires individual functions to be loaded manually. Helper libraries are often used for this purpose.
+// Here we are using gl3w.h, which requires a call to gl3wInit(). 
+// You may use another any other loader/header of your choice, such as glew, glext, glad, glLoadGen, etc.
+#include <GL/gl3w.h>
 //#include <glew.h>
 //#include <glext.h>
 //#include <glad/glad.h>

examples/imgui_impl_opengl3.h

@@ -9,6 +9,11 @@
 // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
 // https://github.com/ocornut/imgui
 
+// About OpenGL function loaders:
+// Modern OpenGL requires individual functions to be loaded manually. Helper libraries are often used for this purpose.
+// Here we are using gl3w.h, which requires a call to gl3wInit(). 
+// You may use another any other loader/header of your choice, such as glew, glext, glad, glLoadGen, etc.
+
 // About GLSL version:
 // The 'glsl_version' initialization parameter defaults to "#version 130" if NULL.
 // Only override if your GL version doesn't handle this GLSL version (see table at the top of imgui_impl_opengl3.cpp). Keep NULL if unsure!