JSON Export

This example writes a scene to a compact JSON diagnostic file.

Preview

No screenshot

Run And Adapt

Commands below assume a Datoviz source checkout and start at the repository root. Use your configured build environment; Python routes additionally require local bindings.

Route	Availability	Command or action
C	Canonical native source	just example-c features/json_export (build and run), or rerun ./build/examples/c/features/json_export
Python	No verified adaptation on this page	Start from the C source.
Browser	Native only	scene JSON is a native diagnostic/fixture surface, not a live browser route

Use this example as capability or integration evidence, not as a minimal copy-paste template. Start from the nearest supported, copy-safe example and add this feature after verifying the linked API reference.

What To Look For

The live view is intentionally small, with three point items whose position, color, and diameter_px arrays are uploaded before the scene is serialized. The useful output is also the generated json_export.json file: it should contain the figure/panel/visual structure rather than just pixels. This helps beginners see that Datoviz scenes keep inspectable state that can be exported for debugging or tooling.

Source

C

/*
 * Copyright (c) 2021 Cyrille Rossant and contributors. All rights reserved.
 * Licensed under the MIT license. See LICENSE file in the project root for details.
 * SPDX-License-Identifier: MIT
 */

/* This example writes a retained scene to a compact JSON diagnostic file.
 *
 * What to look for: the live view is intentionally small, with three point items whose position,
 * color, and diameter_px arrays are uploaded before the scene is serialized. The useful output is
 * also the generated json_export.json file: it should contain the figure/panel/visual structure
 * rather than just pixels. This helps beginners see that Datoviz scenes keep inspectable state that
 * can be exported for debugging or tooling.
 *
 * Scenario: features_json_export
 * Style: features, graphite_cyan, 1280x720 window target
 *
 * Build:  just example-c features/json_export
 * Run:    ./build/examples/c/features/json_export --live
 * Smoke:  ./build/examples/c/features/json_export --png
 */



/*************************************************************************************************/
/*  Includes                                                                                     */
/*************************************************************************************************/

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#include "_assertions.h"
#include "datoviz/fileio.h"
#include "datoviz/scene.h"
#include "example_style.h"
#include "runner/scenario_runner.h"



/*************************************************************************************************/
/*  Constants                                                                                    */
/*************************************************************************************************/

#define WIDTH  EXAMPLE_WINDOW_WIDTH
#define HEIGHT EXAMPLE_WINDOW_HEIGHT
#define POINT_COUNT 3u
#define JSON_PATH   "json_export.json"



/*************************************************************************************************/
/*  Helpers                                                                                      */
/*************************************************************************************************/

/**
 * Add a tiny retained point visual.
 *
 * @param scene scene owning the visual
 * @param panel target panel
 * @return true when the visual was added
 */
static bool _add_points(DvzScene* scene, DvzPanel* panel)
{
    ANN(scene);
    ANN(panel);

    const vec3 positions[POINT_COUNT] = {
        {-0.45f, -0.18f, 0.0f},
        {+0.00f, +0.28f, 0.0f},
        {+0.45f, -0.18f, 0.0f},
    };
    DvzColor colors[POINT_COUNT] = {
        example_graphite_cyan_color(EXAMPLE_STYLE_COLOR_ACCENT_PRIMARY),
        example_graphite_cyan_color(EXAMPLE_STYLE_COLOR_WARNING),
        example_graphite_cyan_color(EXAMPLE_STYLE_COLOR_ACCENT_SECONDARY),
    };
    const float diameters[POINT_COUNT] = {32.0f, 44.0f, 32.0f};

    DvzVisual* point = dvz_point(scene, 0);
    if (point == NULL)
        return false;
    DvzVisualDataUpdate updates[] = {
        {.attr_name = "position", .data = positions, .item_count = POINT_COUNT},
        {.attr_name = "color", .data = colors, .item_count = POINT_COUNT},
        {.attr_name = "diameter_px", .data = diameters, .item_count = POINT_COUNT},
    };
    if (dvz_visual_set_data_many(point, updates, 3) != 0)
        return false;
    return dvz_panel_add_visual(panel, point, NULL) == 0;
}



/**
 * Serialize the scene once and save a compact diagnostic artifact.
 *
 * @param scene scene to serialize
 * @return true when serialization returned a plausible JSON document
 */
static bool _serialize_scene(DvzScene* scene)
{
    ANN(scene);

    char* json = dvz_scene_json(scene);
    if (json == NULL)
        return false;

    const size_t length = strlen(json);
    const bool ok = length > 2u && json[0] == '{' && strstr(json, "\"figures\"") != NULL;
    if (ok)
    {
        const int rc = dvz_write_bytes(JSON_PATH, "wb", (DvzSize)length, (const uint8_t*)json);
        if (rc == 0)
            fprintf(stdout, "json_export: wrote ./%s (%zu bytes)\n", JSON_PATH, length);
        else
            fprintf(stderr, "json_export: failed to write %s\n", JSON_PATH);
        dvz_scene_json_destroy(json);
        return rc == 0;
    }

    dvz_scene_json_destroy(json);
    return false;
}



/*************************************************************************************************/
/*  Scenario callbacks                                                                           */
/*************************************************************************************************/

/**
 * Initialize the scene-JSON feature example.
 *
 * @param ctx scenario context
 * @param out_user scenario state output
 * @return true on success
 */
static bool _scenario_init(DvzScenarioContext* ctx, void** out_user)
{
    if (ctx == NULL)
        return false;
    if (out_user != NULL)
        *out_user = NULL;

    ctx->figure = dvz_figure(ctx->scene, ctx->width, ctx->height, 0);
    if (ctx->figure == NULL)
        return false;

    DvzPanel* panel = dvz_panel_full(ctx->figure);
    if (panel == NULL)
        return false;
    example_graphite_cyan_set_panel_background(panel);

    if (!_add_points(ctx->scene, panel))
        return false;
    return _serialize_scene(ctx->scene);
}



/**
 * Return the scene-JSON scenario specification.
 *
 * @return scenario specification
 */
static DvzScenarioSpec _json_export_scenario(void)
{
    return (DvzScenarioSpec){
        .id = "features_json_export",
        .title = "JSON Export",
        .width = WIDTH,
        .height = HEIGHT,
        .fps = 60.0,
        .init = _scenario_init,
    };
}



/*************************************************************************************************/
/*  Functions                                                                                    */
/*************************************************************************************************/

/**
 * Run the scene-JSON feature example through the native scenario runner.
 *
 * @param argc command-line argument count
 * @param argv command-line argument vector
 * @return process exit code
 */
int main(int argc, char** argv)
{
    DvzScenarioSpec spec = _json_export_scenario();
    return dvz_scenario_run_native_cli(&spec, argc, argv) == 0 ? 0 : 1;
}

Example details

• ID: features_json_export
• Category: feature
• Lane: features
• Status: experimental
• Source: examples/c/features/json_export.c
• Approved adaptation starter: no
• Browser support: Native only
• Browser note: scene JSON is a native diagnostic/fixture surface, not a live browser route
• Browser capability tags: diagnostics
• Validation: smoke+stdout

Data

Field	Value
kind	synthetic