trap.h

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/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
#pragma once
 
#include <stdbool.h>
#include <stddef.h>
 
/* Segment attributes */
 
typedef struct {
  pointf v0, v1;       /* two endpoints */ 
  bool is_inserted;      /* inserted in trapezoidation yet ? */
  int root0, root1;     /* root nodes in Q */
  int next;         /* Next logical segment */
  int prev;         /* Previous segment */
} segment_t;
 
 
/* Trapezoid attributes */
 
typedef struct {
  int lseg, rseg;       /* two adjoining segments */
  pointf hi, lo;       /* max/min y-values */ 
  int u0, u1;
  int d0, d1;
  int sink;         /* pointer to corresponding in Q */
  int usave, uside;     /* I forgot what this means */
  int state;
} trap_t; 
 
typedef struct {
  size_t length;
  trap_t *data;
} traps_t;
 
#define ST_VALID 1      /* for trapezium state */
#define ST_INVALID 2
 
#define C_EPS 1.0e-7        /* tolerance value: Used for making */
                /* all decisions about collinearity or */
                /* left/right of segment. Decrease */
                /* this value if the input points are */
                /* spaced very close together */
#define FP_EQUAL(s, t) (fabs(s - t) <= C_EPS)
 
static inline int dfp_cmp(double f1, double f2) {
  double d = f1 - f2;
  if (d < -C_EPS)
    return -1;
  if (d > C_EPS)
    return 1;
  return 0;
}
 
#define _equal_to(v0,v1) \
  (FP_EQUAL((v0)->y, (v1)->y) && FP_EQUAL((v0)->x, (v1)->x))
 
#define _greater_than(v0, v1) \
  (((v0)->y > (v1)->y + C_EPS) ? true : (((v0)->y < (v1)->y - C_EPS) ? false : ((v0)->x > (v1)->x)))
 
extern traps_t construct_trapezoids(int, segment_t*, int*);