void clip(drawing *dr, int x, int y, int w, int h);
void unclip(drawing *dr);
void start_draw(drawing *dr);
void draw_update(drawing *dr, int x, int y, int w, int h);
void end_draw(drawing *dr);
void clip(drawing *dr, int x, int y, int w, int h);
void unclip(drawing *dr);
void start_draw(drawing *dr);
void draw_update(drawing *dr, int x, int y, int w, int h);
void end_draw(drawing *dr);