Add basic app interface

- Add pool struct for data pools

include/window/window.h

@@ -4,10 +4,6 @@
 #include "pch.h"
 #include "utils.h"
 
-using ImageID = uint32_t;
-using FontID = uint32_t;
-using TextID = uint32_t;
-
 struct Font {
   TTF_Font *font;
   bool pixel_art;
@@ -52,6 +48,12 @@ struct Event {
   };
 };
 
+struct Animation {
+  std::vector<int> frames;
+  float frame_rate;
+  bool loop;
+};
+
 struct Window {
 public:
   // title can be free'd by the caller after the window is created, as it's copied internally.
@@ -61,19 +63,21 @@ public:
 
   // Rendering functions
 
-  ImageID load_image(const char *path, bool pixel_art = false);
-  void unload_image(ImageID image_id);
+  int load_image(const char *path, bool pixel_art = false);
+  void unload_image(int image_id);
+  Vec2<float> get_image_size(int image_id);
 
-  FontID load_font(const char *path, int font_size, bool bold = false, bool italic = false, bool underline = false, bool pixel_art = false);
-  void unload_font(FontID font_id);
+  int load_font(const char *path, int font_size, bool bold = false, bool italic = false, bool underline = false, bool pixel_art = false);
+  void unload_font(int font_id);
 
   // text is copied internally, so it can be free'd by the caller after the text is created.
-  TextID create_text(FontID font_id, const char *text, uint32_t length, Color color);
-  void unload_text(TextID text_id);
+  int create_text(int font_id, const char *text, uint32_t length, Color color);
+  void unload_text(int text_id);
+  Vec2<float> get_text_size(int text_id);
 
-  bool write(TextID text_id, Vec2<float> position, float z, float angle = 0.0f, Vec2<float> scale = {1.0f, 1.0f});
+  bool write(int text_id, Vec2<float> position, float z, float angle = 0.0f, Vec2<float> scale = {1.0f, 1.0f});
 
-  bool draw(ImageID image_id, Vec2<float> position, float z, float angle = 0.0f, Vec2<float> scale = {1.0f, 1.0f}, float alpha = 1.0f);
+  bool draw(int image_id, Vec2<float> position, float z, float angle = 0.0f, Vec2<float> scale = {1.0f, 1.0f}, float alpha = 1.0f);
 
   bool draw_rect(Rect rect, Color color, float z, float angle = 0.0f);
 
@@ -119,16 +123,13 @@ private:
   SDL_Texture *white_tex;
 
   // Image pool
-  std::vector<SDL_Texture *> images;
-  std::vector<int> free_image_indices;
+  Pool<SDL_Texture *> image_pool;
 
   // Font pool
-  std::vector<struct Font> fonts;
-  std::vector<int> free_font_indices;
+  Pool<struct Font> font_pool;
 
   // Text pool
-  std::vector<SDL_Texture *> texts;
-  std::vector<int> free_text_indices;
+  Pool<SDL_Texture *> text_pool;
 
   struct RenderInstruction {
     enum Type {
@@ -143,13 +144,13 @@ private:
 
     union {
       struct {
-        ImageID image_id;
+        int image_id;
         Vec2<float> position;
         float alpha;
       } draw_image;
 
       struct {
-        TextID text_id;
+        int text_id;
         Vec2<float> position;
       } draw_text;