rework of textures, finalization of basic opengl rendering

src/textures.h

@@ -2,10 +2,20 @@
 #define TEXTURES_H
 
 #include "private/textures.h"
+#include "util.h"
 
 #include <SDL2/SDL.h>
 #include <glad/glad.h>
 
+/* type safe structure for persistent texture handles */
+typedef struct { int id; } t_texture_key;
+
+/* tests whether given key structure corresponds to any texture */
+#define m_texture_key_is_valid(p_key) ((p_key).id != 0)
+
+/* tests whether given key corresponds to atlas texture or a loner */
+#define m_texture_is_atlas(p_key) ((p_key).id > 0)
+
 void textures_cache_init(struct texture_cache *cache, SDL_Window *window);
 void textures_cache_deinit(struct texture_cache *cache);
 
@@ -15,25 +25,27 @@ void textures_dump_atlases(struct texture_cache *cache);
 /* loads an image if it isn't in the cache, otherwise a no-op. */
 /* can be called from anywhere at any time after init, useful if you want to */
 /* preload textures you know will definitely be used */
-void textures_load(struct texture_cache *cache, const char *path);
+// void textures_load(struct texture_cache *cache, const char *path);
 
-/* repacks the current texture atlas based on the texture cache */
-void textures_update_current_atlas(struct texture_cache *cache);
+/* repacks the current texture atlas based on the texture cache if needed */
+/* any previously returned srcrect results are invalidated after that */
+/* call it every time before rendering */
+void textures_update_atlas(struct texture_cache *cache);
 
-/* returns a rect in a texture cache atlas based on a path, for drawing */
-/* if the texture is not found, returns a zero-filled rect (so check w or h) */
-SDL_Rect textures_get_srcrect(struct texture_cache *cache, const char *path);
+/* returns a persistent handle to some texture in cache, loading it if needed */
+/* check the result with m_texture_key_is_valid() */
+t_texture_key textures_get_key(struct texture_cache *cache, const char *path);
 
-/* returns which atlas the texture in the path is in, starting from 0 */
-/* if the texture is not found, returns INT_MIN */
-int textures_get_atlas_index(struct texture_cache *cache, const char *path);
+/* returns a rect in a texture cache of the given key */
+t_rect textures_get_srcrect(const struct texture_cache *cache, t_texture_key key);
+
+/* returns a rect of dimensions of the whole texture (whole atlas) */
+t_rect textures_get_dims(const struct texture_cache *cache, t_texture_key key);
 
 /* binds atlas texture in opengl state */
-void textures_bind_atlas(struct texture_cache *cache, int index, GLenum target);
-
-void textures_bind_loner(struct texture_cache *cache, const char *path, GLenum target);
+void textures_bind(const struct texture_cache *cache, t_texture_key key, GLenum target);
 
 /* returns the number of atlases in the cache */
-size_t textures_get_num_atlases(struct texture_cache *cache);
+size_t textures_get_num_atlases(const struct texture_cache *cache);
 
 #endif