#pragma	src	"/sys/src/liblayer"#pragma	lib	"liblayer.a" typedef struct Layer Layer;typedef struct Cover Cover; typedef enum Lvis{	Visible,	Obscured,	Invisible,}Lvis; struct Layer{	Bitmap;			/* Bitmap.cache!=0 ==> layer */	Layer	*next;		/* next layer from front to back */	Cover	*cover;		/* layer etc. from which this is derived */	int	user;		/* a place for the user to stick stuff */	Lvis	vis;		/* visibility state */}; struct Cover{	Layer	*layer;		/* layer on which these are painted */	Layer	*front;		/* first sublayer */	Bitmap	*ground;	/* background texture */}; extern void	layerop(void (*)(Layer*, Rectangle, Layer*, void*),			Rectangle, Layer*, void*);extern Layer	*lalloc(Cover*, Rectangle);extern void	 lfree(Layer*);extern void	 ltofront(Layer*);extern void	 ltoback(Layer*);extern void	 lupdate(Layer*, Rectangle, Layer *, void *);extern void	 lcstring(Bitmap*, int, int, uchar*, uchar*, int); extern void	_bitblt(Bitmap*, Point, Bitmap*, Rectangle, Fcode);extern void	_linsertback(Layer*);extern void	_linsertfront(Layer*);extern void	_ldelete(Layer*);extern void	_point(Bitmap*, Point, int, Fcode);extern void	_polysegment(Bitmap*, int, Point*, int, Fcode);extern Point	_string(Bitmap*, Point, Font*, char*, Fcode);extern void	_segment(Bitmap*, Point, Point, int, Fcode);extern void	_texture(Bitmap*, Rectangle, Bitmap*, Fcode);extern Point	_subfontstring(Bitmap*, Point, Subfont*, char*, Fcode, int);extern void	_lvis(Layer *);