virtual int draw_bg(Uint8 alpha, bool update) = 0;
virtual int draw_part(float sx, float sy, float x, float y, float w, float h, Uint8 alpha, bool update) = 0;
virtual int draw_stretched(float x, float y, int w, int h, Uint8 alpha, bool update) = 0;
virtual int draw_bg(Uint8 alpha, bool update) = 0;
virtual int draw_part(float sx, float sy, float x, float y, float w, float h, Uint8 alpha, bool update) = 0;
virtual int draw_stretched(float x, float y, int w, int h, Uint8 alpha, bool update) = 0;