/*	@(#)trap_step.h 9.2 88/01/19 SMI	*/

/*
 * Copyright (c) 1985 by Sun Microsystems, Inc.
 */

/*-
	Macros for stepping down chain defined traps.

	trap_step.h, Wed Jun 26 21:38:50 1985

		James Gosling,
		Sun Microsystems
 */

#ifndef step_down_trap

struct fine_trap_state {
    short y, x1, x2;
    struct shape_trapseg next;
    short used;
    struct shape_trapseg *limit;
    struct shape_trapseg *start;
    struct shape_trapseg *seg;
};


/* advances the given trap state by k pixels in y */
#define step_down_trap(t,k) {				\
    (t)->y += k;					\
    while ((t)->y >= (t)->next.y && (t)->seg<=(t)->limit) {	\
	(t)->x1 = (t)->next.x1;				\
	(t)->x2 = (t)->next.x2;				\
	(t)->next = *(t)->seg++;			\
    }							\
}

/* Initialize to scan down an trap */
#define init_fine_trap(t, T) {		\
    (t)->y = -1;			\
    (t)->seg = (T)->segs;		\
    (t)->used = (T)->used;		\
    (t)->start = (T)->segs;		\
    (t)->limit = &(T)->segs[(T)->used];	\
    (t)->next = *(t)->seg++;		\
}

#define stepping_up_trap(t, T) {		\
    (t)->seg -= 3;				\
    (t)->next = *(t)->seg;			\
}

#define fast_step_up_trap_to(t,dy) {		\
    (t)->y = dy;				\
    while ((t)->next.y > (t)->y && (t)->seg > (t)->start) \
	(t)->next = *--(t)->seg;		\
    (t)->x1 = (t)->next.x1;			\
    (t)->x2 = (t)->next.x2;			\
    if ((t)->next.y == (t)->y && (t)->seg > (t)->start) (t)->next = *--(t)->seg;	\
}

#define grab_trap_segment(skip)					\
    short       x1 = dx,					\
                x2 = xlimit;					\
    register    height;						\
    if (trap.x1 > x1) {						\
	sx1 = sx + trap.x1 - x1;				\
	x1 = trap.x1;						\
    }								\
								\
    else							\
	sx1 = sx;						\
    if (trap.x2 < x2)						\
	x2 = trap.x2;						\
    if (skip) {							\
	if (dst.pos.x == x1)					\
	    if (xlimit == x2)					\
		while (trap.next.x1 <= x1 && trap.next.x2 >= x2 && trap.next.y < ylimit) \
		    trap.next = *trap.seg++;			\
	    else						\
		while (trap.next.x1 <= x1 && trap.next.x2 == x2 && trap.next.y < ylimit) \
		    trap.next = *trap.seg++;			\
	else if (xlimit == x2)					\
	    while (trap.next.x1 == x1 && trap.next.x2 >= x2 && trap.next.y < ylimit) \
		trap.next = *trap.seg++;			\
	else							\
	    while (trap.next.x1 == x1 && trap.next.x2 == x2 && trap.next.y < ylimit) \
		trap.next = *trap.seg++;			\
    }								\
    height = (trap.seg < trap.limit ? trap.next.y		\
	      : shape->trapset->bottom) - trap.y;		\
    if (height <= 0)						\
	break;							\
    if (height > dst.size.y)					\
	height = dst.size.y;					\
    step_down_trap(&trap, height);

#define step_up_trap(t,k) fast_step_up_trap_to(t,(t)->y-k)
#endif