create-html-embed

name	create-html-embed
description	Create self-contained D3 HTML embed charts for the research article template. Use when the user asks to create a chart, visualization, embed, D3 chart, line chart, bar chart, scatter plot, sankey diagram, or any data visualization as an HTML embed file.

Create HTML Embed

Create self-contained D3.js chart embeds for the research article template.

Before you start

Read the full directives file for all conventions, patterns, and checklists:

• directives.md — single source of truth for embed authoring rules

This covers: colors & palettes, layout, SVG scope, mounting, theming, controls, tooltips, data loading, responsiveness, legends, accessibility, performance, error handling, printing, and the full agent checklist.

Workflow

Step 1: Understand the request

Clarify with the user:

• What type of chart? (line, bar, scatter, sankey, waffle, heatmap, custom)
• What data source? (CSV path, JSON, inline data)
• Interactive controls needed? (metric selector, filters)
• Any specific design requirements?

Step 2: Create the HTML file

• Location: app/src/content/embeds/
• Naming: d3-<descriptive-name>.html (e.g., d3-training-loss.html)
• Root class: .d3-<descriptive-name> (must match filename)

Step 3: Follow the mandatory structure

Every embed must have this structure:

<div class="d3-yourname"></div>
<style>
  .d3-yourname { /* scoped styles */ }
</style>
<script>
  (() => {
    const ensureD3 = (cb) => { /* D3 CDN loader */ };
    const bootstrap = () => {
      /* mount guard + container selection */
      /* tooltip setup */
      /* SVG scaffolding */
      /* data loading */
      /* render function with ResizeObserver */
    };
    if (document.readyState === 'loading') {
      document.addEventListener('DOMContentLoaded', () => ensureD3(bootstrap), { once: true });
    } else { ensureD3(bootstrap); }
  })();
</script>

Step 4: Integrate in MDX

Import and use the HtmlEmbed component:

import HtmlEmbed from '../../components/HtmlEmbed.astro';

<HtmlEmbed src="d3-yourname.html" title="Chart Title" desc="Description text" />

HtmlEmbed props

Prop	Type	Description
src	string	Path to HTML file in embeds/ (required)
title	string	Title above the card
desc	string	Description below (supports HTML)
frameless	boolean	Removes card background/border
wide	boolean	Wide layout (~1100px)
data	string or string[]	Path(s) to data files
config	object	JSON config passed via data-config attribute

Usage examples

<!-- Simple embed -->
<HtmlEmbed src="d3-training-loss.html" title="Training Loss" />

<!-- With external data -->
<HtmlEmbed src="d3-line-simple.html" title="Attention" data="attention_loss.csv" />

<!-- With config -->
<HtmlEmbed
  src="d3-line-simple.html"
  title="Learning Rate"
  data="lr_loss.csv"
  config={{ defaultMetric: 'loss', xDomain: [0, 45e9] }}
/>

<!-- Multiple data files -->
<HtmlEmbed
  src="d3-comparison.html"
  title="A vs B"
  data={['formatting_filters.csv', 'relevance_filters.csv']}
/>

<!-- Frameless -->
<HtmlEmbed frameless src="d3-banner.html" />

Key conventions (quick reference)

Full details in the directives file. The critical ones:

1. Colors: Use window.ColorPalettes.getColors('categorical', n) — never hardcode palettes
2. CSS variables: --text-color, --surface-bg, --border-color, --axis-color, --tick-color, --grid-color
3. Dark mode: Check document.documentElement.getAttribute('data-theme') === 'dark'
4. Mount guard: Always set container.dataset.mounted = 'true'
5. Data loading: Try /data/<file> first, then ./assets/data/<file> — use fetchFirstAvailable()
6. Responsiveness: ResizeObserver on container, recompute on resize
7. Legend: HTML-based, title "Legend", swatch 14x14px
8. Controls: HTML only (no SVG UI), selects labeled "Metric" when applicable
9. Tooltip: Single .d3-tooltip absolutely positioned inside container
10. No globals: Everything in IIFE, nothing on window

Data files

• Store data in: app/src/content/assets/data/
• Served from: /data/ (public) at build time
• Formats: CSV (preferred for tabular), JSON (for nested/hierarchical)

Post-creation checklist

After creating the embed, verify against the Agent Checklist (section 14.1) and Definition of Done (section 14.2) in directives.md.