-                run_callback(callback_id, "ddd->L", tex_font, g->gd[i].gid, streamprovider, &result);
+                run_callback(callback_id, "ddd->L", tex_font, g->gd[i].gid, 2, &result);

It's not clear why now we use 2.

Perhaps it's better to introduce another variable, i.e.

int actual_streamprovider ;

if actual_streamprovider>2 {

  actual_streamprovider=2;

}

run_callback(callback_id, "ddd->L", tex_font, g->gd[i].gid, actual_streamprovider, &result);

Or add a comment  before , something like

/* The streamprovider here is always 2 because... */