Decode SVG icon data urls in place instead of fetching them

[kmcginnes]

Summary

Every stored icon is a lucide: reference or a base64 data: url, so the icon registry no longer needs a fetch, a retry cap or per-icon failure counts to resolve an SVG icon. It now decodes the url in place, and SVG icons resolve synchronously like rasters.

 request(sources)
   raster
     resolve now
   svg
-    fetch(url) → text → sanitizeSvg, async
-    on failure: count, retry up to 3 times
+    atob + TextDecoder (UTF-8) → sanitizeSvg, resolve now
+    on failure: remember it, never retry
   lucide
     import() → markup, async (unchanged)

• The only failures left are deterministic: a payload that does not decode or sanitize, or an unknown Lucide name. The canvas requests on every render, so a failure is remembered rather than retried, which keeps it from being decoded and logged again on each render.
• The one transient case left is a Lucide chunk that fails to load. It now stays blank on the canvas until the page reloads, where it previously got three tries. DOM surfaces render Lucide through DynamicIcon and are unaffected.
• The "Unusable svg icon" warning now names the icon by the first 100 characters of its url, matching the unsupported-icon warning on load.
• Test fixtures are base64 data: urls built by a new createSvgIconDataUrl helper instead of https://example.test urls behind a stubbed fetch.
• useResolvedIcons is unchanged: its effect still triggers the Lucide import().

Evidence

Before: SVG icons resolved after an async fetch of their own data: url, and the registry tests depended on a stubbed fetch.

After: custom SVG icons render on the canvas with no fetch: one with non-ASCII text (airport), a width/height-only SVG with no viewBox (continent), and a Lucide icon (country).

Verified live: in Chrome against a Neptune air-routes database, I uploaded SVG icons with non-ASCII text, no viewBox, and invalid markup, then checked the graph canvas, legend, search results, style dialog preview, and schema view, including after a reload that restored the session. A window.fetch wrapper recorded no data: url fetches. The invalid icon showed no icon and logged one warning across repeated re-renders.

Merge Danger

Door: two-way

Stored data and the icon value format are unchanged, so reverting restores the old resolution path.

Impact: icons

A Lucide icon whose chunk fails to load stays blank on the canvas until reload instead of retrying.

Related

• Closes Read data: SVG icons directly instead of fetching them in the icon registry #2354
• Related to Render VertexIcon through the icon registry and drop react-inlinesvg #2408

[kmcginnes]

Approved