gvrender_core_json.c

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/*************************************************************************
 * Copyright (c) 2015 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
 *************************************************************************/
 
#include "config.h"
 
#include <stdarg.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
 
#include <common/macros.h>
#include <common/const.h>
#include <xdot/xdot.h>
 
#include <gvc/gvplugin_render.h>
#include <gvc/gvplugin_device.h>
#include <cgraph/alloc.h>
#include <cgraph/startswith.h>
#include <cgraph/streq.h>
#include <cgraph/unreachable.h>
#include <common/utils.h>
#include <gvc/gvc.h>
#include <gvc/gvio.h>
#include <gvc/gvcint.h>
 
typedef enum {
        FORMAT_JSON,
        FORMAT_JSON0,
        FORMAT_DOT_JSON,
        FORMAT_XDOT_JSON,
} format_type;
 
typedef struct {
    int Level;
    bool isLatin;
    bool doXDot;
} state_t;
 
typedef struct {
    Agrec_t h;
    int id;
} gvid_t;
 
#define ID "id"
#define ND_gid(n) (((gvid_t*)aggetrec(n, ID, 0))->id) 
#define ED_gid(n) (((gvid_t*)aggetrec(n, ID, 0))->id) 
#define GD_gid(n) (((gvid_t*)aggetrec(n, ID, 0))->id) 
 
static bool IS_CLUSTER(Agraph_t *s) {
  return startswith(agnameof(s), "cluster");
}
 
static void json_begin_graph(GVJ_t *job)
{
    if (job->render.id == FORMAT_JSON) {
        GVC_t* gvc = gvCloneGVC (job->gvc); 
        graph_t *g = job->obj->u.g;
        gvRender (gvc, g, "xdot", NULL); 
        gvFreeCloneGVC (gvc);
    }
    else if (job->render.id == FORMAT_JSON0) {
        attach_attrs(job->gvc->g);
    }
}
 
#define LOCALNAMEPREFIX         '%'
 
static void stoj(char *ins, state_t *sp, GVJ_t *job) {
    char* s;
    char* input;
    char c;
 
    if (sp->isLatin)
        input = latin1ToUTF8 (ins);
    else
        input = ins;
 
    gvputc(job, '"');
    for (s = input; (c = *s); s++) {
        switch (c) {
        case '"' :
            gvputs(job, "\\\"");
            break;
        case '\\' :
            gvputs(job, "\\\\");
            break;
        case '/' :
            gvputs(job, "\\/");
            break;
        case '\b' :
            gvputs(job, "\\b");
            break;
        case '\f' :
            gvputs(job, "\\f");
            break;
        case '\n' :
            gvputs(job, "\\n");
            break;
        case '\r' :
            gvputs(job, "\\r");
            break;
        case '\t' :
            gvputs(job, "\\t");
            break;
        default :
            gvputc(job, c);
            break;
        }
    }
    gvputc(job, '"');
 
    if (sp->isLatin)
        free (input);
}
 
static void indent(GVJ_t * job, int level)
{
    int i;
    for (i = level; i > 0; i--)
        gvputs(job, "  ");
}
 
static void set_attrwf(Agraph_t * g, bool toplevel, bool value)
{
    Agraph_t *subg;
    Agnode_t *n;
    Agedge_t *e;
 
    AGATTRWF(g) = value;
    for (subg = agfstsubg(g); subg; subg = agnxtsubg(subg)) {
        set_attrwf(subg, false, value);
    }
    if (toplevel) {
        for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
            AGATTRWF(n) = value;
            for (e = agfstout(g, n); e; e = agnxtout(g, e))
                AGATTRWF(e) = value;
        }
    }
}
 
static void write_polyline (GVJ_t * job, xdot_polyline* polyline)
{
    const size_t cnt = polyline->cnt;
    xdot_point* pts = polyline->pts;
 
    gvprintf(job, "\"points\": [");
    for (size_t i = 0; i < cnt; i++) {
        if (i > 0) gvprintf(job, ",");
        gvprintf(job, "[%.03f,%.03f]", pts[i].x, pts[i].y);
    }
    gvprintf(job, "]\n");
}
 
static void write_stops (GVJ_t * job, int n_stops, xdot_color_stop* stp, state_t* sp)
{
    int i;
 
    gvprintf(job, "\"stops\": [");
    for (i = 0; i < n_stops; i++) {
        if (i > 0) gvprintf(job, ",");
        gvprintf(job, "{\"frac\": %.03f, \"color\": ", stp[i].frac);
        stoj(stp[i].color, sp, job);
        gvputc(job, '}');
    }
    gvprintf(job, "]\n");
} 
 
static void write_radial_grad (GVJ_t * job, xdot_radial_grad* rg, state_t* sp)
{
    indent(job, sp->Level);
    gvprintf(job, "\"p0\": [%.03f,%.03f,%.03f],\n", rg->x0, rg->y0, rg->r0); 
    indent(job, sp->Level);
    gvprintf(job, "\"p1\": [%.03f,%.03f,%.03f],\n", rg->x1, rg->y1, rg->r1); 
    indent(job, sp->Level);
    write_stops (job, rg->n_stops, rg->stops, sp);
}
 
static void write_linear_grad (GVJ_t * job, xdot_linear_grad* lg, state_t* sp)
{
    indent(job, sp->Level);
    gvprintf(job, "\"p0\": [%.03f,%.03f],\n", lg->x0, lg->y0); 
    indent(job, sp->Level);
    gvprintf(job, "\"p1\": [%.03f,%.03f],\n", lg->x1, lg->y1); 
    indent(job, sp->Level);
    write_stops (job, lg->n_stops, lg->stops, sp);
}
 
static void write_xdot (xdot_op * op, GVJ_t * job, state_t* sp)
{
    indent(job, sp->Level++);
    gvputs(job, "{\n");
    indent(job, sp->Level);
 
    switch (op->kind) {
    case xd_filled_ellipse :
    case xd_unfilled_ellipse :
        gvprintf(job, "\"op\": \"%c\",\n", op->kind == xd_filled_ellipse ? 'E' : 'e');
        indent(job, sp->Level);
        gvprintf(job, "\"rect\": [%.03f,%.03f,%.03f,%.03f]\n", 
            op->u.ellipse.x, op->u.ellipse.y, op->u.ellipse.w, op->u.ellipse.h);
        break;
    case xd_filled_polygon :
    case xd_unfilled_polygon :
        gvprintf(job, "\"op\": \"%c\",\n", op->kind == xd_filled_polygon ? 'P' : 'p');
        indent(job, sp->Level);
        write_polyline (job, &op->u.polygon);
        break;
    case xd_filled_bezier :
    case xd_unfilled_bezier :
        gvprintf(job, "\"op\": \"%c\",\n", op->kind == xd_filled_bezier ? 'B' : 'b');
        indent(job, sp->Level);
        write_polyline (job, &op->u.bezier);
        break;
    case xd_polyline :
        gvprintf(job, "\"op\": \"L\",\n"); 
        indent(job, sp->Level);
        write_polyline (job, &op->u.polyline);
        break;
    case xd_text :
        gvprintf(job, "\"op\": \"T\",\n"); 
        indent(job, sp->Level);
        gvprintf(job, "\"pt\": [%.03f,%.03f],\n", op->u.text.x, op->u.text.y); 
        indent(job, sp->Level);
        gvprintf(job, "\"align\": \"%c\",\n",
            op->u.text.align == xd_left? 'l' :
            (op->u.text.align == xd_center ? 'c' : 'r'));
        indent(job, sp->Level);
        gvprintf(job, "\"width\": %.03f,\n", op->u.text.width); 
        indent(job, sp->Level);
        gvputs(job, "\"text\": ");
        stoj(op->u.text.text, sp, job);
        gvputc(job, '\n');
        break;
    case xd_fill_color :
    case xd_pen_color :
        gvprintf(job, "\"op\": \"%c\",\n", op->kind == xd_fill_color ? 'C' : 'c');
        indent(job, sp->Level);
        gvprintf(job, "\"grad\": \"none\",\n"); 
        indent(job, sp->Level);
        gvputs(job, "\"color\": ");
        stoj(op->u.color, sp, job);
        gvputc(job, '\n');
        break;
    case xd_grad_pen_color :
    case xd_grad_fill_color :
        gvprintf(job, "\"op\": \"%c\",\n", op->kind == xd_grad_fill_color ? 'C' : 'c');
        indent(job, sp->Level);
        if (op->u.grad_color.type == xd_none) {
            gvprintf(job, "\"grad\": \"none\",\n"); 
            indent(job, sp->Level);
            gvputs(job, "\"color\": ");
            stoj(op->u.grad_color.u.clr, sp, job);
            gvputc(job, '\n');
        }
        else {
            if (op->u.grad_color.type == xd_linear) {
                gvprintf(job, "\"grad\": \"linear\",\n"); 
                indent(job, sp->Level);
                write_linear_grad (job, &op->u.grad_color.u.ling, sp);
            }
            else {
                gvprintf(job, "\"grad\": \"radial\",\n"); 
                indent(job, sp->Level);
                write_radial_grad (job, &op->u.grad_color.u.ring, sp);
            }
        }
        break;
    case xd_font :
        gvprintf(job, "\"op\": \"F\",\n");
        indent(job, sp->Level);
        gvprintf(job, "\"size\": %.03f,\n", op->u.font.size); 
        indent(job, sp->Level);
        gvputs(job, "\"face\": ");
        stoj(op->u.font.name, sp, job);
        gvputc(job, '\n');
        break;
    case xd_style :
        gvprintf(job, "\"op\": \"S\",\n");
        indent(job, sp->Level);
        gvputs(job, "\"style\": ");
        stoj(op->u.style, sp, job);
        gvputc(job, '\n');
        break;
    case xd_image :
        break;
    case xd_fontchar :
        gvprintf(job, "\"op\": \"t\",\n");
        indent(job, sp->Level);
        gvprintf(job, "\"fontchar\": %d\n", op->u.fontchar);
        break;
    default:
        UNREACHABLE();
    }
    sp->Level--;
    indent(job, sp->Level);
    gvputs(job, "}");
}
 
static void write_xdots (char * val, GVJ_t * job, state_t* sp)
{
    xdot* cmds;
 
    if (!val || *val == '\0') return;
 
    cmds = parseXDot(val);
    if (!cmds) {
        agwarningf("Could not parse xdot \"%s\"\n", val);
        return;
    }
 
    gvputs(job, "\n");
    indent(job, sp->Level++);
    gvputs(job, "[\n");
    for (size_t i = 0; i < cmds->cnt; i++) {
        if (i > 0)
            gvputs(job, ",\n");
        write_xdot (cmds->ops+i, job, sp);
    }
    sp->Level--;
    gvputs(job, "\n");
    indent(job, sp->Level);
    gvputs(job, "]");
    freeXDot(cmds);
}
 
static bool isXDot(const char* name) {
  return streq(name, "_draw_") || streq(name, "_ldraw_") ||
         streq(name, "_hdraw_") || streq(name, "_tdraw_") ||
         streq(name, "_hldraw_") || streq(name, "_tldraw_");
}
 
static void write_attrs(Agobj_t * obj, GVJ_t * job, state_t* sp)
{
    Agraph_t* g = agroot(obj);
    int type = AGTYPE(obj);
    char* attrval;
    Agsym_t* sym = agnxtattr(g, type, NULL);
    if (!sym) return;
 
    for (; sym; sym = agnxtattr(g, type, sym)) {
        if (!(attrval = agxget(obj, sym))) continue;
        if (*attrval == '\0' && !streq(sym->name, "label")) continue;
        gvputs(job, ",\n");
        indent(job, sp->Level);
        stoj(sym->name, sp, job);
        gvputs(job, ": ");
        if (sp->doXDot && isXDot(sym->name))
            write_xdots(agxget(obj, sym), job, sp);
        else
            stoj(agxget(obj, sym), sp, job);
    }
}
 
static void write_hdr(Agraph_t *g, GVJ_t *job, bool top, state_t *sp) {
    char *name;
 
    name = agnameof(g);
    indent(job, sp->Level);
    gvputs(job, "\"name\": ");
    stoj(name, sp, job);
 
    if (top) {
        gvputs(job, ",\n");
        indent(job, sp->Level);
        gvprintf(job, "\"directed\": %s,\n", agisdirected(g)?"true":"false");
        indent(job, sp->Level);
        gvprintf(job, "\"strict\": %s", agisstrict(g)?"true":"false");
    }
}
 
static void write_graph(Agraph_t *g, GVJ_t *job, bool top, state_t *sp);
 
static void write_subg(Agraph_t * g, GVJ_t * job, state_t* sp)
{
    Agraph_t* sg;
 
    write_graph (g, job, false, sp);
    for (sg = agfstsubg(g); sg; sg = agnxtsubg(sg)) {
        gvputs(job, ",\n");
        write_subg(sg, job, sp);
    }
}
 
static bool write_subgs(Agraph_t *g, GVJ_t *job, bool top, state_t *sp) {
    Agraph_t* sg;
 
    sg = agfstsubg(g);
    if (!sg) return false;
   
    gvputs(job, ",\n");
    indent(job, sp->Level++);
    if (top)
        gvputs(job, "\"objects\": [\n");
    else {
        gvputs(job, "\"subgraphs\": [\n");
        indent(job, sp->Level);
    }
    const char *separator = "";
    for (; sg; sg = agnxtsubg(sg)) {
        gvputs(job, separator);
        if (top)
            write_subg (sg, job, sp);
        else
            gvprintf(job, "%d", GD_gid(sg));
        separator = ",\n";
    }
    if (!top) {
        sp->Level--;
        gvputs(job, "\n");
        indent(job, sp->Level);
        gvputs(job, "]");
    }
 
    return true;
}
 
static int agseqasc(const void *x, const void *y) {
// Suppress Clang/GCC -Wcast-qual warning. Casting away const here is acceptable
// as the later usage is const. We need the cast because the macros use
// non-const pointers for genericity.
#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-qual"
#endif
  Agedge_t **lhs = (Agedge_t **)x;
  Agedge_t **rhs = (Agedge_t **)y;
#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif
    Agedge_t *e1 = *lhs;
    Agedge_t *e2 = *rhs;
 
    if (AGSEQ(e1) < AGSEQ(e2)) {
        return -1;
    }
    else if (AGSEQ(e1) > AGSEQ(e2)) {
        return 1;
    }
    else {
        return 0;
    }
}
 
static void write_edge(Agedge_t *e, GVJ_t *job, bool top, state_t *sp) {
    if (top) {
        indent(job, sp->Level++);
        gvputs(job, "{\n");
        indent(job, sp->Level);
        gvprintf(job, "\"_gvid\": %d,\n", ED_gid(e));
        indent(job, sp->Level);
        gvprintf(job, "\"tail\": %d,\n", ND_gid(agtail(e)));
        indent(job, sp->Level);
        gvprintf(job, "\"head\": %d", ND_gid(aghead(e)));
        write_attrs((Agobj_t*)e, job, sp);
        gvputs(job, "\n");
        sp->Level--;
        indent(job, sp->Level);
        gvputs(job, "}");
    }
    else {
        gvprintf(job, "%d", ED_gid(e));
    }
}
 
static int write_edges(Agraph_t *g, GVJ_t *job, bool top, state_t *sp) {
    size_t count = 0;
 
    for (Agnode_t *np = agfstnode(g); np; np = agnxtnode(g, np)) {
        for (Agedge_t *ep = agfstout(g, np); ep; ep = agnxtout(g, ep)) {
            ++count;
        }
    }
 
    if (count == 0) {
        return 0;
    }
 
    Agedge_t **edges = gv_calloc(count, sizeof(Agedge_t *));
 
    size_t i = 0;
    for (Agnode_t *np = agfstnode(g); np; np = agnxtnode(g, np)) {
        for (Agedge_t *ep = agfstout(g, np); ep; ep = agnxtout(g, ep)) {
            edges[i] = ep;
            ++i;
        }
    }
 
    qsort(edges, count, sizeof(Agedge_t *), agseqasc);
 
    gvputs(job, ",\n");
    indent(job, sp->Level++);
    gvputs(job, "\"edges\": [\n");
    if (!top)
        indent(job, sp->Level);
    for (size_t j = 0; j < count; ++j) {
        if (j > 0) {
            if (top)
                gvputs(job, ",\n");
            else
                gvputs(job, ",");
        }
        write_edge(edges[j], job, top, sp);
    }
 
    free(edges);
 
    sp->Level--;
    gvputs(job, "\n");
    indent(job, sp->Level);
    gvputs(job, "]");
    return 1;
}
 
static void write_node(Agnode_t *n, GVJ_t *job, bool top, state_t *sp) {
    if (top) {
        indent(job, sp->Level++);
        gvputs(job, "{\n");
        indent(job, sp->Level);
        gvprintf(job, "\"_gvid\": %d,\n", ND_gid(n));
        indent(job, sp->Level);
        gvputs(job, "\"name\": ");
        stoj(agnameof(n), sp, job);
        write_attrs((Agobj_t*)n, job, sp);
        gvputs(job, "\n");
        sp->Level--;
        indent(job, sp->Level);
        gvputs(job, "}");
    }
    else {
        gvprintf(job, "%d", ND_gid(n));
    }
}
 
static int write_nodes(Agraph_t *g, GVJ_t *job, bool top, bool has_subgs, state_t *sp) {
 
    // is every subcomponent of this graph a cluster?
    bool only_clusters = true;
    for (Agnode_t *n = agfstnode(g); n; n = agnxtnode(g, n)) {
        if (!IS_CLUST_NODE(n)) {
            only_clusters = false;
            break;
        }
    }
 
    if (only_clusters) {
        if (has_subgs && top) {
            sp->Level--;
            gvputs(job, "\n");
            indent(job, sp->Level);
            gvputs(job, "]");
        }
        return 0;
    }
    gvputs(job, ",\n");
    if (top) {
        if (!has_subgs) {
            indent(job, sp->Level++);
            gvputs(job, "\"objects\": [\n");
        }
    }
    else {
        indent(job, sp->Level++);
        gvputs(job, "\"nodes\": [\n");
        indent(job, sp->Level);
    }
    const char *separator = "";
    for (Agnode_t *n = agfstnode(g); n; n = agnxtnode(g, n)) {
        if (IS_CLUST_NODE(n)) continue;
        gvputs(job, separator);
        write_node (n, job, top, sp);
        separator = top ? ",\n" : ",";
    }
    sp->Level--;
    gvputs(job, "\n");
    indent(job, sp->Level);
    gvputs(job, "]");
    return 1;
}
 
typedef struct {
    Dtlink_t link;
    char* id;
    int v;
} intm;
 
static void freef(void *ident) {
    intm *obj = ident;
    free(obj->id);
    free(obj);
}
 
static Dtdisc_t intDisc = {
    offsetof(intm, id),
    -1,
    offsetof(intm, link),
    (Dtmake_f) NULL,
    freef,
    (Dtcompar_f) NULL,
};
 
static int lookup (Dt_t* map, char* name)
{
    intm* ip = dtmatch(map, name);
    if (ip) return ip->v;
    else return -1;
}
 
static void insert (Dt_t* map, char* name, int v)
{
    intm* ip = dtmatch(map, name);
 
    if (ip) {
        if (ip->v != v)
            agwarningf("Duplicate cluster name \"%s\"\n", name);
        return;
    }
    ip = gv_alloc(sizeof(intm));
    ip->id = gv_strdup(name);
    ip->v = v;
    dtinsert (map, ip);
}
 
static int label_subgs(Agraph_t* g, int lbl, Dt_t* map)
{
    Agraph_t* sg;
 
    if (g != agroot(g)) {
        GD_gid(g) = lbl++;
        if (IS_CLUSTER(g))
            insert (map, agnameof(g), GD_gid(g)); 
    }
    for (sg = agfstsubg(g); sg; sg = agnxtsubg(sg)) {
        lbl = label_subgs(sg, lbl, map);
    }
    return lbl;
}
 
 
static void write_graph(Agraph_t *g, GVJ_t *job, bool top, state_t *sp) {
    Agnode_t* np; 
    Agedge_t* ep; 
    int ncnt = 0;
    int ecnt = 0;
    int sgcnt = 0;
    Dt_t* map;
 
    if (top) {
        map = dtopen (&intDisc, Dtoset);
        aginit(g, AGNODE, ID, sizeof(gvid_t), false);
        aginit(g, AGEDGE, ID, sizeof(gvid_t), false);
        aginit(g, AGRAPH, ID, -((int)sizeof(gvid_t)), false);
        sgcnt = label_subgs(g, sgcnt, map);
        for (np = agfstnode(g); np; np = agnxtnode(g,np)) {
            if (IS_CLUST_NODE(np)) {
                ND_gid(np) = lookup(map, agnameof(np));
            }
            else {
                ND_gid(np) = sgcnt + ncnt++;
            }
            for (ep = agfstout(g, np); ep; ep = agnxtout(g,ep)) {
                ED_gid(ep) = ecnt++;
            }
        }
        dtclose(map);
    }
 
    indent(job, sp->Level++);
    gvputs(job, "{\n");
    write_hdr(g, job, top, sp);
    write_attrs((Agobj_t*)g, job, sp);
    if (top) {
        gvputs(job, ",\n");
        indent(job, sp->Level);
        gvprintf(job, "\"_subgraph_cnt\": %d", sgcnt);
    } else {
        gvputs(job, ",\n");
        indent(job, sp->Level);
        gvprintf(job, "\"_gvid\": %d", GD_gid(g));
    }
    bool has_subgs = write_subgs(g, job, top, sp);
    write_nodes (g, job, top, has_subgs, sp);
    write_edges (g, job, top, sp);
    gvputs(job, "\n");
    sp->Level--;
    indent(job, sp->Level);
    if (top)
        gvputs(job, "}\n");
    else
        gvputs(job, "}");
}
 
typedef int (*putstrfn) (void *chan, const char *str);
typedef int (*flushfn) (void *chan);
 
static void json_end_graph(GVJ_t *job)
{
    graph_t *g = job->obj->u.g;
    state_t sp;
    static Agiodisc_t io;
 
    if (io.afread == NULL) {
        io.afread = AgIoDisc.afread;
        io.putstr = (putstrfn)gvputs;
        io.flush = (flushfn)gvflush;
    }
 
    g->clos->disc.io = &io;
 
    set_attrwf(g, true, false);
    sp.Level = 0;
    sp.isLatin = GD_charset(g) == CHAR_LATIN1;
    sp.doXDot = job->render.id == FORMAT_JSON || job->render.id == FORMAT_XDOT_JSON;
    write_graph(g, job, true, &sp);
}
 
gvrender_engine_t json_engine = {
    0,                          /* json_begin_job */
    0,                          /* json_end_job */
    json_begin_graph,
    json_end_graph,
    0,                          /* json_begin_layer */
    0,                          /* json_end_layer */
    0,                          /* json_begin_page */
    0,                          /* json_end_page */
    0,                          /* json_begin_cluster */
    0,                          /* json_end_cluster */
    0,                          /* json_begin_nodes */
    0,                          /* json_end_nodes */
    0,                          /* json_begin_edges */
    0,                          /* json_end_edges */
    0,                          /* json_begin_node */
    0,                          /* json_end_node */
    0,                          /* json_begin_edge */
    0,                          /* json_end_edge */
    0,                          /* json_begin_anchor */
    0,                          /* json_end_anchor */
    0,                          /* json_begin_label */
    0,                          /* json_end_label */
    0,                          /* json_textspan */
    0,                          /* json_resolve_color */
    0,                          /* json_ellipse */
    0,                          /* json_polygon */
    0,                          /* json_bezier */
    0,                          /* json_polyline */
    0,                          /* json_comment */
    0,                          /* json_library_shape */
};
 
gvrender_features_t render_features_json1 = {
    GVRENDER_DOES_TRANSFORM,    /* not really - uses raw graph coords */  /* flags */
    0.,                         /* default pad - graph units */
    NULL,                       /* knowncolors */
    0,                          /* sizeof knowncolors */
    COLOR_STRING,               /* color_type */
};
 
gvrender_features_t render_features_json = {
    GVRENDER_DOES_TRANSFORM     /* not really - uses raw graph coords */
        | GVRENDER_DOES_MAPS
        | GVRENDER_DOES_TARGETS
        | GVRENDER_DOES_TOOLTIPS, /* flags */
    0.,                         /* default pad - graph units */
    NULL,                       /* knowncolors */
    0,                          /* sizeof knowncolors */
    COLOR_STRING,               /* color_type */
};
 
gvdevice_features_t device_features_json_nop = {
    LAYOUT_NOT_REQUIRED,        /* flags */
    {0.,0.},                    /* default margin - points */
    {0.,0.},                    /* default page width, height - points */
    {72.,72.},                  /* default dpi */
};
 
gvdevice_features_t device_features_json = {
    0,                          /* flags */
    {0.,0.},                    /* default margin - points */
    {0.,0.},                    /* default page width, height - points */
    {72.,72.},                  /* default dpi */
};
 
gvplugin_installed_t gvrender_json_types[] = {
    {FORMAT_JSON, "json", 1, &json_engine, &render_features_json},
    {FORMAT_JSON0, "json0", 1, &json_engine, &render_features_json},
    {FORMAT_DOT_JSON, "dot_json", 1, &json_engine, &render_features_json},
    {FORMAT_XDOT_JSON, "xdot_json", 1, &json_engine, &render_features_json},
    {0, NULL, 0, NULL, NULL}
};
 
gvplugin_installed_t gvdevice_json_types[] = {
    {FORMAT_JSON, "json:json", 1, NULL, &device_features_json},
    {FORMAT_JSON0, "json0:json", 1, NULL, &device_features_json},
    {FORMAT_DOT_JSON, "dot_json:json", 1, NULL, &device_features_json_nop},
    {FORMAT_XDOT_JSON, "xdot_json:json", 1, NULL, &device_features_json_nop},
    {0, NULL, 0, NULL, NULL}
};