Detecting OpenGL ES in LibGDX to adjust shader code accordingly

Question

I have a LibGDX app that runs on mobile and desktop systems just fine except for one tiny issue:

On mobile devices I need to include precision qualifiers in my shaders (precision highp float), but on Mac OS this leads to an error when I compile the shader since precision qualifiers technically only exist on OpenGL ES (although Windows just ignores them).

Is there a way in LibGDX to determine whether I am running under OpenGL ES or under regular OpenGL so I can adjust my shader code accordingly? Other than the obvious super-inelegant solution, of course: Try to compile the shader with the qualifiers, if it fails try again without.

Answer 1

Yes, you can use preprocessing directives at the top of your fragment shader.

#ifdef GL_ES 
precision highp float;
#endif

You can also use placeholders so you can adjust precision of specific variables.

#ifdef GL_ES 
#define LOWP lowp
#define MEDP mediump
#define HIGHP highp
precision highp float;
#else
#define LOWP
#define MEDP
#define HIGHP
#endif

Then you can use the text LOWP in place of lowp and it will evaluate blank on desktop:

varying LOWP vec4 v_color;