radial: configurable offsets

[coderobe]

Fixes #69 (extended discussion)

[jarcode-foss]

This unfortunately is a breaking change (wrt. local configuration files), radial/1.glsl needs something like:

#ifndef CENTER_OFFSET_X
#define CENTER_OFFSET_X 0
#endif
/* ... repeat for `Y` */

I unfortunately have introduced similar breaking changes in the past; it's probably best to adopt this practice for patch-level version increments.

On the other hand, this adds a lot of boilerplate. I'm thinking about adding a special #config directive to the GLSL extensions (glsl_ext.c) that includes the local configuration while parsing the system copy for defaults (if applicable).

[mmhobi7]

you could also change the 1.frag to include the glsl from etc first (by like including 0.glsl which is a symlink to the /etc) and then the variables in that frag can override the defaults

[jarcode-foss]

@aaahh that will causes either errors or warnings (depending on the vendor) in the GLSL compiler due to re-defining macros.

[mmhobi7]

Check if the variable already exist first, already made a test case and it works fine