void draw_bg(Uint8 alpha = 255, bool update = false);
void draw_part(float sx, float sy, float x, float y, float w, float h, Uint8 alpha = 255, bool update = false);
void draw_stretched(float x, float y, int w, int h, Uint8 alpha, bool update = false);
void resize(int w_, int h_);
/// conveniance function
void draw_bg(Uint8 alpha = 255, bool update = false);
void draw_part(float sx, float sy, float x, float y, float w, float h, Uint8 alpha = 255, bool update = false);
void draw_stretched(float x, float y, int w, int h, Uint8 alpha, bool update = false);
void resize(int w_, int h_);
/// conveniance function