Examples: Comments about GLSL version not being the same as GL context version. (#1828)

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -360,7 +360,7 @@ bool    ImGui_ImplGlfwGL3_Init(GLFWwindow* window, bool install_callbacks, const
     g_Window = window;
     g_Time = 0.0;
 
-    // Store GL version string so we can refer to it later in case we recreate shaders.
+    // Store GLSL version string so we can refer to it later in case we recreate shaders. Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
     if (glsl_version == NULL)
         glsl_version = "#version 150";
     IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(g_GlslVersion));

examples/opengl3_example/imgui_impl_glfw_gl3.h

@@ -11,6 +11,10 @@
 // If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.
 // https://github.com/ocornut/imgui
 
+// About GLSL version:
+// The 'glsl_version' initialization parameter defaults to "#version 150" if NULL.
+// Only override if your GL version doesn't handle this GLSL version. Keep NULL if unsure!
+
 struct GLFWwindow;
 
 IMGUI_API bool        ImGui_ImplGlfwGL3_Init(GLFWwindow* window, bool install_callbacks, const char* glsl_version = NULL);

examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp

@@ -358,7 +358,7 @@ void    ImGui_ImplSdlGL3_InvalidateDeviceObjects()
 
 bool    ImGui_ImplSdlGL3_Init(SDL_Window* window, const char* glsl_version)
 {
-    // Store GL version string so we can refer to it later in case we recreate shaders.
+    // Store GLSL version string so we can refer to it later in case we recreate shaders. Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
     if (glsl_version == NULL)
         glsl_version = "#version 150";
     IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(g_GlslVersion));

examples/sdl_opengl3_example/imgui_impl_sdl_gl3.h

@@ -12,6 +12,10 @@
 // If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.
 // https://github.com/ocornut/imgui
 
+// About GLSL version:
+// The 'glsl_version' initialization parameter defaults to "#version 150" if NULL.
+// Only override if your GL version doesn't handle this GLSL version. Keep NULL if unsure!
+
 struct SDL_Window;
 typedef union SDL_Event SDL_Event;