Added support for desktop full screen with pillarboxing and letterboxing

and started adding some comments to the code

include/ObjectStore.h

@@ -17,13 +17,36 @@ typedef void (*RenderFuncPtr)(void *object);
 
 typedef struct object_store ObjectStore;
 
+/**
+ * Attempts to allocate an ObjectStore object on the heap.
+ *
+ * Returns the pointer to the object when it succeeds, or NULL if it fails.
+ */
 ObjectStore *create_object_store();
+
+/**
+ * Attempts to add an object to the store.
+ *
+ * Returns the ObjectID on success or an INVALID_ID in the case of failure.
+ */
 ObjectID add_object_to_store(ObjectStore *os, void *object, EventHandlerPtr eh,
                              UpdateFuncPtr uf, RenderFuncPtr rf);
+
+/**
+ * Removes an object from the store using its ID.
+ *
+ * Does nothing if the ID is not valid.
+ */
 void remove_object_from_store(ObjectStore *os, ObjectID *id_ptr);
+
 void handle_all_objects_events(ObjectStore *os, const SDL_Event *event);
 void update_all_objects(ObjectStore *os, float delta);
 void render_all_objects(ObjectStore *os);
+
+/**
+ * Frees the memory allocated to the ObjectStore object and performs the
+ * necessary cleanup.
+ */
 void destroy_object_store(ObjectStore **os);
 
 #ifdef DEBUG_ENGINE