tclpathplan.c

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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 v2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
/*
 * Tcl binding to drive Stephen North's and
 * Emden Gansner's shortest path code.
 *
 * ellson@graphviz.org   October 2nd, 1996
 */
 
#include "config.h"
 
#include "../tcl-compat.h"
#include                <sys/types.h>
#include                <stdbool.h>
#include                <stdint.h>
#include                <stdlib.h>
#include                <string.h>
 
#include <assert.h>
#include <limits.h>
#include "makecw.h"
#include <math.h>
#include <pathplan/pathutil.h>
#include <pathplan/vispath.h>
#include <pathplan/tri.h>
#include "Plegal_arrangement.h"
#include <tcl.h>
#include <util/agxbuf.h>
#include <util/alloc.h>
#include <util/itos.h>
#include <util/list.h>
#include <util/prisize_t.h>
 
#if (TCL_MAJOR_VERSION == 8 && TCL_MINOR_VERSION >= 6) || TCL_MAJOR_VERSION > 8
#else
#ifndef Tcl_GetStringResult
#define Tcl_GetStringResult(interp) interp->result
#endif
#endif
 
typedef Ppoint_t point;
 
typedef struct poly_s {
    int id;
    Ppoly_t boundary;
} poly;
 
#define HANDLE_FORMAT ("vgpane%" PRISIZE_T)
 
typedef struct {
    LIST(poly) poly; // set of polygons
    vconfig_t *vc;              /* visibility graph handle */
    Tcl_Interp *interp;         /* interpreter that owns the binding */
    char *triangle_cmd;         /* why is this here any more */
    size_t index; 
    bool valid; 
} vgpane_t;
 
typedef LIST(vgpane_t) vgpanes_t;
 
static vgpanes_t vgpaneTable;
 
static int polyid = 0;          /* unique and unchanging id for each poly */
 
static poly *allocpoly(vgpane_t *vgp, int id, Tcl_Size npts) {
    LIST_APPEND(&vgp->poly, (poly){.id = id});
    poly *rv = LIST_BACK(&vgp->poly);
    rv->boundary.pn = 0;
    rv->boundary.ps = gv_calloc(npts, sizeof(point));
    return rv;
}
 
static void vc_stale(vgpane_t * vgp)
{
    if (vgp->vc) {
        Pobsclose(vgp->vc);
        vgp->vc = NULL;
    }
}
 
static int vc_refresh(vgpane_t * vgp)
{
    if (vgp->vc == NULL) {
        Ppoly_t **obs = gv_calloc(LIST_SIZE(&vgp->poly), sizeof(Ppoly_t*));
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++)
            obs[i] = &LIST_AT(&vgp->poly, i)->boundary;
        if (!Plegal_arrangement(obs, LIST_SIZE(&vgp->poly)))
            fprintf(stderr, "bad arrangement\n");
        else
            vgp->vc = Pobsopen(obs, (int)LIST_SIZE(&vgp->poly));
        free(obs);
    }
    return vgp->vc != NULL;
}
 
static void dgsprintxy(agxbuf *result, int npts, const point p[]) {
    int i;
 
    assert(npts > 1);
    if (agxblen(result) > 0) {
        agxbputc(result, ' ');
    }
    agxbputc(result, '{');
    const char *separator = "";
    for (i = 0; i < npts; i++) {
        agxbprint(result, "%s%g %g", separator, p[i].x, p[i].y);
        separator = " ";
    }
    agxbputc(result, '}');
}
 
static void expandPercentsEval(Tcl_Interp *interp, char *before,
                               size_t vgcanvasHandle, int npts,
                               const point *ppos) {
    agxbuf scripts = {0};
 
    while (1) {
        /*
         * Find everything up to the next % character and append it to the
         * result string.
         */
 
        char *string = strchr(before, '%');
        if (string != NULL) {
            agxbput_n(&scripts, before, (size_t)(string - before));
            before = string;
        }
        if (*before == 0) {
            break;
        }
        /*
         * There's a percent sequence here.  Process it.
         */
 
        switch (before[1]) {
        case 'r':
            agxbprint(&scripts, HANDLE_FORMAT, vgcanvasHandle);
            break;
        case 't':
            dgsprintxy(&scripts, npts, ppos);
            break;
        default:
            agxbputc(&scripts, before[1]);
            break;
        }
        if (before[1] == '\0') {
            break;
        }
        before += 2;
    }
    const char *script_value = agxbuse(&scripts);
    if (Tcl_GlobalEval(interp, script_value) != TCL_OK)
        fprintf(stderr, "%s while in binding: %s\n\n",
                Tcl_GetStringResult(interp), script_value);
    agxbfree(&scripts);
}
 
static void triangle_callback(void *vgparg, const point pqr[]) {
    vgpane_t *vgp = vgparg;
    if (vgp->triangle_cmd) {
        const size_t vgcanvasHandle = vgp->index;
        expandPercentsEval(vgp->interp, vgp->triangle_cmd, vgcanvasHandle, 3, pqr);
    }
}
 
static char *buildBindings(char *s1, const char *s2)
/*
 * previous binding in s1 binding to be added in s2 result in s3
 *
 * if s2 begins with + then append (separated by \n) else s2 replaces if
 * resultant string is null then bindings are deleted
 */
{
    char *s3;
    size_t l;
 
    if (s2[0] == '+') {
        if (s1) {
            l = strlen(s2) - 1;
            if (l) {
                agxbuf new = {0};
                agxbprint(&new, "%s\n%s", s1, s2 + 1);
                free(s1);
                return agxbdisown(&new);
            } else {
                s3 = s1;
            }
        } else {
            l = strlen(s2) - 1;
            if (l) {
                s3 = gv_strdup(s2 + 1);
            } else {
                s3 = NULL;
            }
        }
    } else {
        free(s1);
        l = strlen(s2);
        if (l) {
            s3 = gv_strdup(s2);
        } else {
            s3 = NULL;
        }
    }
    return s3;
}
 
 
 
/* convert x and y string args to point */
static int scanpoint(Tcl_Interp * interp, const char *argv[], point * p)
{
    if (sscanf(argv[0], "%lg", &p->x) != 1) {
        Tcl_AppendResult(interp, "invalid x coordinate: \"", argv[0], "\"", NULL);
        return TCL_ERROR;
    }
    if (sscanf(argv[1], "%lg", &p->y) != 1) {
        Tcl_AppendResult(interp, "invalid y coordinate: \"", argv[1], "\"", NULL);
        return TCL_ERROR;
    }
    return TCL_OK;
}
 
static point center(point vertex[], size_t n) {
    point c;
 
    c.x = c.y = 0;
    for (size_t i = 0; i < n; i++) {
        c.x += vertex[i].x;
        c.y += vertex[i].y;
    }
    c.x /= (int)n;
    c.y /= (int)n;
    return c;
}
 
static double distance(point p, point q)
{
    double dx, dy;
 
    dx = p.x - q.x;
    dy = p.y - q.y;
    return hypot(dx, dy);
}
 
static point rotate(point c, point p, double alpha)
{
    point q;
    double beta, r;
 
    r = distance(c, p);
    beta = atan2(p.x - c.x, p.y - c.y);
    const double sina = sin(beta + alpha);
    const double cosa = cos(beta + alpha);
    q.x = c.x + r * sina;
    q.y = c.y - r * cosa;       /* adjust for tk y-down */
    return q;
}
 
static point scale(point c, point p, double gain)
{
    point q;
 
    q.x = c.x + gain * (p.x - c.x);
    q.y = c.y + gain * (p.y - c.y);
    return q;
}
 
static bool remove_poly(vgpane_t *vgp, int id) {
    for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
        if (LIST_GET(&vgp->poly, i).id == id) {
            free(LIST_GET(&vgp->poly, i).boundary.ps);
            for (size_t j = i++; i < LIST_SIZE(&vgp->poly); i++, j++) {
                LIST_SET(&vgp->poly, j, LIST_GET(&vgp->poly, i));
            }
            LIST_DROP_BACK(&vgp->poly);
            vc_stale(vgp);
            return true;
        }
    }
    return false;
}
 
static int insert_poly(Tcl_Interp *interp, vgpane_t *vgp, int id,
                       const char *vargv[], Tcl_Size vargc) {
    poly *np;
    int result;
 
    np = allocpoly(vgp, id, vargc);
    for (Tcl_Size i = 0; i < vargc; i += 2) {
        result = scanpoint(interp, &vargv[i], &np->boundary.ps[np->boundary.pn]);
        if (result != TCL_OK)
            return result;
        np->boundary.pn++;
    }
    make_CW(&np->boundary);
    vc_stale(vgp);
    return TCL_OK;
}
 
static void make_barriers(vgpane_t *vgp, int pp, int qp, Pedge_t **barriers,
                          size_t *n_barriers) {
 
    size_t n = 0;
    for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
        if (LIST_GET(&vgp->poly, i).id == pp)
            continue;
        if (LIST_GET(&vgp->poly, i).id == qp)
            continue;
        n += LIST_GET(&vgp->poly, i).boundary.pn;
    }
    Pedge_t *bar = gv_calloc(n, sizeof(Pedge_t));
    size_t b = 0;
    for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
        if (LIST_GET(&vgp->poly, i).id == pp)
            continue;
        if (LIST_GET(&vgp->poly, i).id == qp)
            continue;
        for (size_t j = 0; j < LIST_GET(&vgp->poly, i).boundary.pn; j++) {
            size_t k = j + 1;
            if (k >= LIST_GET(&vgp->poly, i).boundary.pn)
                k = 0;
            bar[b].a = LIST_GET(&vgp->poly, i).boundary.ps[j];
            bar[b].b = LIST_GET(&vgp->poly, i).boundary.ps[k];
            b++;
        }
    }
    assert(b == n);
    *barriers = bar;
    *n_barriers = n;
}
 
/* append the x and y coordinates of a point to the Tcl result */
static void appendpoint(Tcl_Interp * interp, point p)
{
    char buf[30];
 
    snprintf(buf, sizeof(buf), "%g", p.x);
    Tcl_AppendElement(interp, buf);
    snprintf(buf, sizeof(buf), "%g", p.y);
    Tcl_AppendElement(interp, buf);
}
 
static vgpane_t *find_vgpane(vgpanes_t *panes, const char *handle) {
  assert(panes != NULL);
  assert(handle != NULL);
 
  size_t index;
  if (sscanf(handle, HANDLE_FORMAT, &index) != 1) {
    return NULL;
  }
  if (index >= LIST_SIZE(panes)) {
    return NULL;
  }
  vgpane_t *const pane = LIST_AT(panes, index);
  if (!pane->valid) {
    return NULL;
  }
 
  return pane;
}
 
static void garbage_collect_vgpanes(vgpanes_t *panes) {
  assert(panes != NULL);
 
  // shrink list, discarding previously deallocated entries
  while (!LIST_IS_EMPTY(panes)) {
    if (!LIST_BACK(panes)->valid) {
      LIST_DROP_BACK(panes);
    }
  }
 
  // if this left us with none, fully deallocate to make leak checkers happy
  if (LIST_IS_EMPTY(panes)) {
    LIST_FREE(panes);
  }
}
 
/* process vgpane methods */
static int
vgpanecmd(ClientData clientData, Tcl_Interp * interp, int argc,
          const char *argv[])
{
    (void)clientData;
 
    int result;
    vgpane_t *vgp;
    point p, q, *ps;
    double alpha, gain;
    Ppolyline_t line, spline;
    Pedge_t *barriers;
 
    if (argc < 2) {
        Tcl_AppendResult(interp, "wrong # args: should be \"",
                         " ", argv[0], " method ?arg arg ...?\"", NULL);
        return TCL_ERROR;
    }
    if (!(vgp = find_vgpane(&vgpaneTable, argv[0]))) {
        Tcl_AppendResult(interp, "Invalid handle: \"", argv[0], "\"", NULL);
        return TCL_ERROR;
    }
 
    if (strcmp(argv[1], "coords") == 0) {
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " id ?x1 y1 x2 y2...?\"", NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[2], "%d", &polyid) != 1) {
            Tcl_AppendResult(interp, "not an integer: ", argv[2], NULL);
            return TCL_ERROR;
        }
        if (argc == 3) {
            /* find poly and return its coordinates */
            for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
                if (LIST_GET(&vgp->poly, i).id == polyid) {
                    const size_t n = LIST_GET(&vgp->poly, i).boundary.pn;
                    for (size_t j = 0; j < n; j++) {
                        appendpoint(interp, LIST_GET(&vgp->poly, i).boundary.ps[j]);
                    }
                    return TCL_OK;
                }
            }
            Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
            return TCL_ERROR;
        }
        /* accept either inline or delimited list */
        Tcl_Size vargc;
        const char **vargv;
        bool vargv_needs_free = false;
        if (argc == 4) {
            result = Tcl_SplitList(interp, argv[3], &vargc, &vargv);
            if (result != TCL_OK) {
                return result;
            }
            vargv_needs_free = true;
        } else {
            vargc = (Tcl_Size)argc - 3;
            vargv = &argv[3];
        }
        if (!vargc || vargc % 2) {
            Tcl_AppendResult(interp,
                             "There must be a multiple of two terms in the list.", NULL);
            if (vargv_needs_free) {
                Tcl_Free((char *)vargv);
            }
            return TCL_ERROR;
        }
 
        /* remove old poly, add modified polygon to the end with 
           the same id as the original */
 
        if (!remove_poly(vgp, polyid)) {
            Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
            if (vargv_needs_free) {
                Tcl_Free((char *)vargv);
            }
            return TCL_ERROR;
        }
 
        result = insert_poly(interp, vgp, polyid, vargv, vargc);
        if (vargv_needs_free) {
            Tcl_Free((char *)vargv);
        }
        return result;
 
    } else if (strcmp(argv[1], "debug") == 0) {
        /* debug only */
        printf("debug output goes here\n");
        return TCL_OK;
 
    } else if (strcmp(argv[1], "delete") == 0) {
        /* delete a vgpane and all memory associated with it */
        free(vgp->triangle_cmd);
        if (vgp->vc)
            Pobsclose(vgp->vc);
        LIST_FREE(&vgp->poly);
        Tcl_DeleteCommand(interp, argv[0]);
        vgp->valid = false;
        garbage_collect_vgpanes(&vgpaneTable);
        return TCL_OK;
 
    } else if (strcmp(argv[1], "find") == 0) {
        /* find the polygon that the point is inside and return it
           id, or null */
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " x y\"", NULL);
            return TCL_ERROR;
        }
        const char **vargv;
        bool vargv_needs_free = false;
        if (argc == 3) {
            result = Tcl_SplitList(interp, argv[2], &(Tcl_Size){0}, &vargv);
            if (result != TCL_OK) {
                return result;
            }
            vargv_needs_free = true;
        } else {
            vargv = &argv[2];
        }
        result = scanpoint(interp, &vargv[0], &p);
        if (vargv_needs_free) {
            Tcl_Free((char *)vargv);
        }
        if (result != TCL_OK)
            return result;
 
        /* determine the polygons (if any) that contain the point */
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            if (in_poly(LIST_GET(&vgp->poly, i).boundary, p)) {
                Tcl_AppendElement(interp, ITOS(LIST_GET(&vgp->poly, i).id));
            }
        }
        return TCL_OK;
 
    } else if (strcmp(argv[1], "insert") == 0) {
        /* add poly to end poly list, and it coordinates to the end of 
           the point list */
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " x1 y1 x2 y2 ...\"", NULL);
            return TCL_ERROR;
        }
        /* accept either inline or delimited list */
        Tcl_Size vargc;
        const char **vargv;
        bool vargv_needs_free = false;
        if (argc == 3) {
            result = Tcl_SplitList(interp, argv[2], &vargc, &vargv);
            if (result != TCL_OK) {
                return result;
            }
            vargv_needs_free = true;
        } else {
            vargc = (Tcl_Size)argc - 2;
            vargv = &argv[2];
        }
 
        if (!vargc || vargc % 2) {
            Tcl_AppendResult(interp,
                             "There must be a multiple of two terms in the list.", NULL);
            if (vargv_needs_free) {
                Tcl_Free((char *)vargv);
            }
            return TCL_ERROR;
        }
 
        polyid++;
 
        result = insert_poly(interp, vgp, polyid, vargv, vargc);
        if (vargv_needs_free) {
            Tcl_Free((char *)vargv);
        }
        if (result != TCL_OK)
            return result;
 
        Tcl_AppendResult(interp, ITOS(polyid), NULL);
        return TCL_OK;
 
    } else if (strcmp(argv[1], "list") == 0) {
        /* return list of polygon ids */
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            Tcl_AppendElement(interp, ITOS(LIST_GET(&vgp->poly, i).id));
        }
        return TCL_OK;
 
    } else if (strcmp(argv[1], "path") == 0) {
        /* return a list of points corresponding to the shortest path
           that does not cross the remaining "visible" polygons. */
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " x1 y1 x2 y2\"", NULL);
            return TCL_ERROR;
        }
        Tcl_Size vargc;
        const char **vargv;
        bool vargv_needs_free = false;
        if (argc == 3) {
            result = Tcl_SplitList(interp, argv[2], &vargc, &vargv);
            if (result != TCL_OK) {
                return result;
            }
            vargv_needs_free = true;
        } else {
            vargc = (Tcl_Size)argc - 2;
            vargv = &argv[2];
        }
        if (vargc < 4) {
            Tcl_AppendResult(interp,
                             "invalid points: should be: \"x1 y1 x2 y2\"", NULL);
            if (vargv_needs_free) {
                Tcl_Free((char *)vargv);
            }
            return TCL_ERROR;
        }
        result = scanpoint(interp, &vargv[0], &p);
        if (result != TCL_OK) {
            if (vargv_needs_free) {
                Tcl_Free((char *)vargv);
            }
            return result;
        }
        result = scanpoint(interp, &vargv[2], &q);
        if (vargv_needs_free) {
            Tcl_Free((char *)vargv);
        }
        if (result != TCL_OK)
            return result;
 
        /* only recompute the visibility graph if we have to */
        if (vc_refresh(vgp)) {
            Pobspath(vgp->vc, p, POLYID_UNKNOWN, q, POLYID_UNKNOWN, &line);
 
            for (size_t i = 0; i < line.pn; i++) {
                appendpoint(interp, line.ps[i]);
            }
        }
 
        return TCL_OK;
 
    } else if (strcmp(argv[1], "bind") == 0) {
        if (argc < 2 || argc > 4) {
            Tcl_AppendResult(interp, "wrong # args: should be \"",
                             argv[0], " bind triangle ?command?\"", NULL);
            return TCL_ERROR;
        }
        if (argc == 2) {
            Tcl_AppendElement(interp, "triangle");
            return TCL_OK;
        }
        char *s = NULL;
        if (strcmp(argv[2], "triangle") == 0) {
            s = vgp->triangle_cmd;
            if (argc == 4)
                vgp->triangle_cmd = buildBindings(s, argv[3]);
        } else {
            Tcl_AppendResult(interp, "unknown event \"", argv[2],
                             "\": must be one of:\n\ttriangle.", NULL);
            return TCL_ERROR;
        }
        if (argc == 3)
            Tcl_AppendResult(interp, s, NULL);
        return TCL_OK;
 
    } else if (strcmp(argv[1], "bpath") == 0) {
        /* return a list of points corresponding to the shortest path
           that does not cross the remaining "visible" polygons. */
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " x1 y1 x2 y2\"", NULL);
            return TCL_ERROR;
        }
        Tcl_Size vargc;
        const char **vargv;
        bool vargv_needs_free = false;
        if (argc == 3) {
            result = Tcl_SplitList(interp, argv[2], &vargc, &vargv);
            if (result != TCL_OK) {
                return result;
            }
            vargv_needs_free = true;
        } else {
            vargc = (Tcl_Size)argc - 2;
            vargv = &argv[2];
        }
        if (vargc < 4) {
            Tcl_AppendResult(interp,
                             "invalid points: should be: \"x1 y1 x2 y2\"", NULL);
            return TCL_ERROR;
        }
 
        result = scanpoint(interp, &vargv[0], &p);
        if (result != TCL_OK) {
            if (vargv_needs_free) {
                Tcl_Free((char *)vargv);
            }
            return result;
        }
        result = scanpoint(interp, &vargv[2], &q);
        if (vargv_needs_free) {
            Tcl_Free((char *)vargv);
        }
        if (result != TCL_OK)
            return result;
 
        /* determine the polygons (if any) that contain the endpoints */
        int pp = POLYID_NONE;
        int qp = POLYID_NONE;
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            const poly tpp = LIST_GET(&vgp->poly, i);
            if (pp == POLYID_NONE && in_poly(tpp.boundary, p))
                pp = (int)i;
            if (qp == POLYID_NONE && in_poly(tpp.boundary, q))
                qp = (int)i;
        }
 
        if (vc_refresh(vgp)) {
            Pobspath(vgp->vc, p, POLYID_UNKNOWN, q, POLYID_UNKNOWN, &line);
            size_t n_barriers;
            make_barriers(vgp, pp, qp, &barriers, &n_barriers);
            Proutespline(barriers, n_barriers, line, (Pvector_t[2]){0}, &spline);
 
            for (size_t i = 0; i < spline.pn; i++) {
                appendpoint(interp, spline.ps[i]);
            }
        }
        return TCL_OK;
 
    } else if (strcmp(argv[1], "bbox") == 0) {
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " id\"", NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[2], "%d", &polyid) != 1) {
            Tcl_AppendResult(interp, "not an integer: ", argv[2], NULL);
            return TCL_ERROR;
        }
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            if (LIST_GET(&vgp->poly, i).id == polyid) {
                Ppoly_t pp = LIST_GET(&vgp->poly, i).boundary;
                point LL, UR;
                LL = UR = pp.ps[0];
                for (size_t j = 1; j < pp.pn; j++) {
                    p = pp.ps[j];
                    UR.x = fmax(UR.x, p.x);
                    UR.y = fmax(UR.y, p.y);
                    LL.x = fmin(LL.x, p.x);
                    LL.y = fmin(LL.y, p.y);
                }
                appendpoint(interp, LL);
                appendpoint(interp, UR);
                return TCL_OK;
            }
        }
        Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
        return TCL_ERROR;
 
    } else if (strcmp(argv[1], "center") == 0) {
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " id\"", NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[2], "%d", &polyid) != 1) {
            Tcl_AppendResult(interp, "not an integer: ", argv[2], NULL);
            return TCL_ERROR;
        }
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            if (LIST_GET(&vgp->poly, i).id == polyid) {
                appendpoint(interp, center(LIST_GET(&vgp->poly, i).boundary.ps,
                                           LIST_GET(&vgp->poly, i).boundary.pn));
                return TCL_OK;
            }
        }
        Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
        return TCL_ERROR;
 
    } else if (strcmp(argv[1], "triangulate") == 0) {
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " id\"", NULL);
            return TCL_ERROR;
        }
 
        if (sscanf(argv[2], "%d", &polyid) != 1) {
            Tcl_AppendResult(interp, "not an integer: ", argv[2], NULL);
            return TCL_ERROR;
        }
 
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            if (LIST_GET(&vgp->poly, i).id == polyid) {
                Ppoly_t *polygon = &LIST_AT(&vgp->poly, i)->boundary;
                if (polygon->pn < 3) {
                    Tcl_AppendResult(interp, "polygon ", argv[2], " has fewer than 3 points "
                                     "and thus cannot be triangulated", NULL);
                    return TCL_ERROR;
                }
                Ptriangulate(polygon, triangle_callback, vgp);
                return TCL_OK;
            }
        }
        Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
        return TCL_ERROR;
    } else if (strcmp(argv[1], "rotate") == 0) {
        if (argc < 4) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " id alpha\"", NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[2], "%d", &polyid) != 1) {
            Tcl_AppendResult(interp, "not an integer: ", argv[2], NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[3], "%lg", &alpha) != 1) {
            Tcl_AppendResult(interp, "not an angle in radians: ", argv[3], NULL);
            return TCL_ERROR;
        }
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            if (LIST_GET(&vgp->poly, i).id == polyid) {
                const size_t n = LIST_GET(&vgp->poly, i).boundary.pn;
                ps = LIST_GET(&vgp->poly, i).boundary.ps;
                p = center(ps, n);
                for (size_t j = 0; j < n; j++) {
                    appendpoint(interp, rotate(p, ps[j], alpha));
                }
                return TCL_OK;
            }
        }
        Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
        return TCL_ERROR;
 
    } else if (strcmp(argv[1], "scale") == 0) {
        if (argc < 4) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " id gain\"", NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[2], "%d", &polyid) != 1) {
            Tcl_AppendResult(interp, "not an integer: ", argv[2], NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[3], "%lg", &gain) != 1) {
            Tcl_AppendResult(interp, "not a number: ", argv[3], NULL);
            return TCL_ERROR;
        }
        for (size_t i = 0; i < LIST_SIZE(&vgp->poly); i++) {
            if (LIST_GET(&vgp->poly, i).id == polyid) {
                const size_t n = LIST_GET(&vgp->poly, i).boundary.pn;
                ps = LIST_GET(&vgp->poly, i).boundary.ps;
                p = center(ps, n);
                for (size_t j = 0; j < n; j++) {
                    appendpoint(interp, scale(p, ps[j], gain));
                }
                return TCL_OK;
            }
        }
        Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
        return TCL_ERROR;
 
    } else if (strcmp(argv[1], "remove") == 0) {
        if (argc < 3) {
            Tcl_AppendResult(interp, "wrong # args: should be \"", argv[0],
                             " ", argv[1], " id\"", NULL);
            return TCL_ERROR;
        }
        if (sscanf(argv[2], "%d", &polyid) != 1) {
            Tcl_AppendResult(interp, "not an integer: ", argv[2], NULL);
            return TCL_ERROR;
        }
 
        if (remove_poly(vgp, polyid))
            return TCL_OK;
 
        Tcl_AppendResult(interp, " no such polygon: ", argv[2], NULL);
        return TCL_ERROR;
    }
 
    Tcl_AppendResult(interp, "bad method \"", argv[1],
                     "\" must be one of:",
                     "\n\tbbox, bind, bpath, center, coords, delete, find,",
                     "\n\tinsert, list, path, remove, rotate, scale, triangulate.", NULL);
    return TCL_ERROR;
}
 
static int
vgpane(ClientData clientData, Tcl_Interp * interp, int argc, const char *argv[])
{
    (void)clientData;
    (void)argc;
    (void)argv;
 
    const vgpane_t vg = {.interp = interp};
    LIST_APPEND(&vgpaneTable, vg);
    vgpane_t *const vgp = LIST_BACK(&vgpaneTable);
    vgp->index = LIST_SIZE(&vgpaneTable) - 1;
    vgp->valid = true;
 
    agxbuf buffer = {0};
    agxbprint(&buffer, HANDLE_FORMAT, vgp->index);
    const char *const vbuf = agxbuse(&buffer);
 
    Tcl_CreateCommand(interp, vbuf, vgpanecmd, NULL, NULL);
    Tcl_AppendResult(interp, vbuf, NULL);
    agxbfree(&buffer);
    return TCL_OK;
}
 
#ifdef GVDLL
__declspec(dllexport)
#endif
int Tclpathplan_Init(Tcl_Interp *interp);
int Tclpathplan_Init(Tcl_Interp * interp)
{
#ifdef USE_TCL_STUBS
    if (Tcl_InitStubs(interp, TCL_VERSION, 0) == NULL) {
        return TCL_ERROR;
    }
#else
    if (Tcl_PkgRequire(interp, "Tcl", TCL_VERSION, 0) == NULL) {
        return TCL_ERROR;
    }
#endif
    // inter-release Graphviz versions have a number including '~dev.' that does
    // not comply with TCL version number rules, so replace this with 'b'
    char adjusted_version[sizeof(PACKAGE_VERSION)] = PACKAGE_VERSION;
    char *tilde_dev = strstr(adjusted_version, "~dev.");
    if (tilde_dev != NULL) {
        *tilde_dev = 'b';
        memmove(tilde_dev + 1, tilde_dev + strlen("~dev."),
                strlen(tilde_dev + strlen("~dev.")) + 1);
    }
    if (Tcl_PkgProvide(interp, "Tclpathplan", adjusted_version) != TCL_OK) {
        return TCL_ERROR;
    }
 
    Tcl_CreateCommand(interp, "vgpane", vgpane, NULL, NULL);
 
    return TCL_OK;
}
 
#ifdef GVDLL
__declspec(dllexport)
#endif
int Tclpathplan_SafeInit(Tcl_Interp *interp);
int Tclpathplan_SafeInit(Tcl_Interp * interp)
{
    return Tclpathplan_Init(interp);
}