rework of textures, finalization of basic opengl rendering

src/util.h

@@ -48,7 +48,9 @@ void *ccalloc(size_t num, size_t size);
 #define MAX SDL_max
 #define MIN SDL_min
 
+#ifndef M_PI
 #define M_PI 3.14159265358979323846264338327950288   /**< pi */
+#endif
 
 /* sets buf_out to a pointer to a byte buffer which must be freed. */
 /* returns the size of this buffer. */
@@ -94,6 +96,7 @@ typedef struct frect {
 
 bool intersect_frect(const t_frect *a, const t_frect *b, t_frect *result);
 
+/* TODO: generics and specials (see m_to_fvec2() for an example)*/
 t_frect to_frect(t_rect rect);
 
 
@@ -122,6 +125,17 @@ typedef struct shvec2 {
 } t_shvec2;
 
 
+/* aren't macros to prevent double evaluation with side effects */
+/* maybe could be inlined? i hope LTO will resolve this */
+t_fvec2 fvec2_from_vec2(t_vec2 vec);
+t_fvec2 fvec2_from_shvec2(t_shvec2 vec);
+
+#define m_to_fvec2(p_any_vec2) (_Generic((p_any_vec2),          \
+                                    t_vec2:   fvec2_from_vec2,  \
+                                    t_shvec2: fvec2_from_shvec2 \
+                                )(p_any_vec2))
+
+
 /* decrements an lvalue (which should be an int), stopping at 0 */
 /* meant for tick-based timers in game logic */
 /*
@@ -130,7 +144,6 @@ typedef struct shvec2 {
  */
 void tick_timer(int *value);
 
-
 /* decrements a floating point second-based timer, stopping at 0.0 */
 /* meant for poll based real time logic in game logic */
 /* note that it should be decremented only on the next tick after its creation */