extern Font*		checkfont(Draw_Font*);extern Image*		checkimage(Draw_Image*);extern Screen*		checkscreen(Draw_Screen*);extern Display*		checkdisplay(Draw_Display*);extern void		freedrawdisplay(Heap*, int);extern void		freedrawfont(Heap*, int);extern void		freedrawimage(Heap*, int);extern void		freedrawscreen(Heap*, int);extern Font*		lookupfont(Draw_Font*);extern Image*		lookupimage(Draw_Image*);extern Screen*		lookupscreen(Draw_Screen*);extern Draw_Image*	mkdrawimage(Image*, Draw_Screen*, Draw_Display*, void*);