--- a/demo.c	Mon Aug 21 15:42:21 2017 +0300
+++ b/demo.c	Mon Apr 29 13:48:22 2019 +0300
@@ -149,19 +149,19 @@
 }
 
 
-static inline float dmCY(DMEngineData *engine, const float y)
+static inline float dmCY(const DMEngineData *engine, const float y)
 {
     return (y * engine->screen->h);
 }
 
 
-static inline float dmQX(DMEngineData *engine, SDL_Surface *img, const float x)
+static inline float dmQX(const DMEngineData *engine, const SDL_Surface *img, const float x)
 {
     return engine->optVidNative ? (img->w * x) : (img->w * engine->screen->w * x) / 640.0f;
 }
 
 
-static inline float dmQY(DMEngineData *engine, SDL_Surface *img, const float y)
+static inline float dmQY(const DMEngineData *engine, const SDL_Surface *img, const float y)
 {
     return engine->optVidNative ? (img->h * y) : (img->h * engine->screen->h * y) / 480.0f;
 }