How can I reduce the amount of GLSL code written?

Question

I am writing a game engine for Linux. It has a sufficiently large number of effects that can be turned on / off. Effects are defined before compiling with #ifdef. But the problem is that I literally have to “wrap” each variable in #ifdef. Another problem is that when adding new effects, I have to rewrite the conditions, since one variable can refer to several effects at once. For example:

#if defined ALGINE_LIGHTING_MODE_ENABLED || defined ALGINE_SHADOW_MAPPING_MODE_ENABLED
uniform vec3 viewPos;                       // Camera position
#endif

#ifdef ALGINE_DOF_MODE_ENABLED
uniform float focalDepth;
uniform float focalRange;
#endif

How could I reduce the amount of re-write needed when adding new effects?

Answer 1

If you are using macros for defining the variables, then there is really no way around it. You could, however, do something like this:

// constants.h
#if defined ALGINE_LIGHTING_MODE_ENABLED || defined 
ALGINE_SHADOW_MAPPING_MODE_ENABLED
uniform vec3 viewPos;                       // Camera position
#endif

#ifdef ALGINE_DOF_MODE_ENABLED
uniform float focalDepth;
uniform float focalRange;
#endif

And then include this file in your shader code:

// vertex-shader.glsl
#include "constants.h"
// [...]