harvey/sys/src/cmd/gs/src/gdevplnx.h

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/*$Id: gdevplnx.h,v 1.2 2000/09/19 19:00:20 lpd Exp $*/
/* Definitions and API for plane extraction device */
/* Requires gxdevcli.h */

#ifndef gdevplnx_INCLUDED
#  define gdevplnx_INCLUDED

#include "gxrplane.h"

/*
 * A plane-extraction device appears to its client to be a color-capable
 * device, like its target; but it actually extracts a single color plane
 * for rendering to yet another device, called the plane device (normally,
 * but not necessarily, a memory device).  Clients must know the pixel
 * representation in detail, since the plane is specified as a particular
 * group of bits within the pixel.
 *
 * The original purpose of plane-extraction devices is for band list
 * rendering for plane-oriented color printers.  Each per-plane rasterizing
 * pass over the band list sends the output to a plane-extraction device for
 * the plane being printed.  There is one special optimization to support
 * this: on the theory that even bands containing output for multiple bands
 * are likely to have many objects that only write white into that band, we
 * remember whether any (non-white) marks have been made on the page so far,
 * and if not, we simply skip any rendering operations that write white.
 *
 * The depth of the plane_extract device and its target are limited to 32
 * bits; the depth of each plane is limited to 8 bits.  We could raise these
 * without too much trouble if necessary, as long as each plane didn't
 * exceed 32 bits.
 */

typedef struct gx_device_plane_extract_s {
    gx_device_forward_common;
	/* The following are set by the client before opening the device. */
    gx_device *plane_dev;		/* the drawing device for the plane */
    gx_render_plane_t plane;
	/* The following are set by open_device. */
    gx_color_index plane_white;
    uint plane_mask;
    bool plane_dev_is_memory;
	/* The following change dynamically. */
    bool any_marks;
} gx_device_plane_extract;
extern_st(st_device_plane_extract);
#define public_st_device_plane_extract()	/* in gdevplnx.c */\
  gs_public_st_complex_only(st_device_plane_extract, gx_device_plane_extract,\
    "gx_device_plane_extract", 0, device_plane_extract_enum_ptrs,\
    device_plane_extract_reloc_ptrs, gx_device_finalize)

/* Initialize a plane extraction device. */
int plane_device_init(P5(gx_device_plane_extract *edev, gx_device *target,
			 gx_device *plane_dev,
			 const gx_render_plane_t *render_plane,
			 bool clear));

#endif /* gdevplnx_INCLUDED */