Update

Actually, GL_FRONT and GL_BACK have been deprecated in OpenGL3.2 core. OpenGL ES never had it. GL_POLYGON_MODE as a parameter to glGetIntegerv isn't documented anymore but hasn't been deprecated in the specification. In conclusion, the original was mostly correct and has been restored. However, a version/profile check was added, that restores the separate drawing modes when they are supported.

GL_CONTEXT_PROFILE_MASK and GL_CONTEXT_COMPATIBILITY_PROFILE_BIT are poorly documented. These constants first appeared in the Specification of OpenGL 3.2 and have remained unchanged since.
(checking for macro-versions of constants is ok since IMGUI_IMPL_HAS_POLYGON_MODE is defined in terms of GL_POLYGON_MODE as well)

What a mess :(
Thanks for investigating this.

On Desktop targets all the defines would be automatically existing with our loader (which needs regeneration, see https://github.com/dearimgui/gl3w_stripped)

I am thinking of turning this code into:

ImGui_ImplOpenGL3_Data::

GLint           GlProfileMask;

(Note this is zero-initialized)

ImGui_ImplOpenGL3_Init():

#if !defined(IMGUI_IMPL_OPENGL_ES2)
...
#if defined(GL_CONTEXT_PROFILE_MASK)
    glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &bd->GlProfileMask);
#endif
...
#endif

ImGui_ImplOpenGL3_RenderDrawData():

#ifdef IMGUI_IMPL_HAS_POLYGON_MODE
    // Desktop OpenGL 3.0 and OpenGL 3.1 had separate polygon draw modes for front-facing and back-facing faces of polygons
    if ((bd->GlVersion <= 310) || (bd->GlProfileMask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT))
    {
        glPolygonMode(GL_FRONT, (GLenum)last_polygon_mode[0]);
        glPolygonMode(GL_BACK, (GLenum)last_polygon_mode[1]);
    }
    else
    {
        glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
    }
#endif // IMGUI_IMPL_HAS_POLYGON_MODE

Does it seem equally accurate to you?

EDIT sorry mistyped && instead of || in the version & profile mask check. It should be || afaik.

Sorry mistyped && instead of || in the version && profile mask check.

 if ((bd->GlVersion <= 310) && (bd->GlProfileMask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT))

should be

 if ((bd->GlVersion <= 310) || (bd->GlProfileMask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT))

By uncommenting the #define IMGUI_IMPL_OPENGL_DEBUG at the top I have confirmed that separate restore fails with 3.2 unless GLFW_OPENGL_COMPAT_PROFILE is set.

Hello, if there are no compile-errors the code should indeed produce equivalent results. However, your version is (currently) error-prone to missing constant definitions. I.e. if a (custom) loader doesn't provide GL_FRONT, GL_BACK or GL_CONTEXT_COMPATIBILITY_PROFILE_BIT it won't compile. I think it would be sensible to add the checks for the macros back or define them to arbitrary values yourself #ifndef GL_CONTEXT_PROFILE_MASK.

I have merged d0836aa (yours) + a338b78 (slight amends).

I moved the use of GL_CONTEXT_COMPATIBILITY_PROFILE_BIT in the same location as GL_CONTEXT_PROFILE_MASK in order to make the code less of a ifdef party.

#if defined(GL_CONTEXT_PROFILE_MASK)
    glGetIntegerv(GL_CONTEXT_PROFILE_MASK, &bd->GlProfileMask);
    bd->GlProfileIsCompat = (bd->GlProfileMask & GL_CONTEXT_COMPATIBILITY_PROFILE_BIT) != 0;
#endif

#ifdef IMGUI_IMPL_HAS_POLYGON_MODE
    // Desktop OpenGL 3.0 and OpenGL 3.1 had separate polygon draw modes for front-facing and back-facing faces of polygons
    if (bd->GlVersion <= 310 || bd->GlProfileIsCompat)
    {
        glPolygonMode(GL_FRONT, (GLenum)last_polygon_mode[0]);
        glPolygonMode(GL_BACK, (GLenum)last_polygon_mode[1]);
    }
    else
    {
        glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
    }
#endif // IMGUI_IMPL_HAS_POLYGON_MODE

I believe GL_FRONT and GL_BACK were defined in 1.0 era header and are unlikely to be missing from a custom loader, if it ever does I'm happy to find out and correct.

Thanks!