fix: prevent empty PNG export for large graphs - #95
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Mathew Benjamin (mathewtbenjamin) wants to merge 1 commit into
Open
Mathew Benjamin (mathewtbenjamin) wants to merge 1 commit into
Mathew Benjamin (mathewtbenjamin) wants to merge 1 commit into
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Exporting the graph as PNG used a fixed scale of 2 with full:true. For
large ontologies the resulting canvas exceeds the browser's maximum
canvas size, and toDataURL() silently returns the empty data URI
('data:,'), producing a 0-byte .png file. The silent catch block hid
the failure entirely.
- Add computeExportScale: clamp the export scale so the largest side of
the rendered canvas stays within a conservative 8192px cross-browser
limit (small graphs keep the crisp 2x scale).
- Validate the data URI before downloading and log an actionable error
instead of writing an empty file.
- Replace the silent catch with console.error.
- Unit tests for the new helpers (9 tests).
Addresses the PNG export bug (item 3) in microsoft#87
Author
|
Friendly nudge 🙂 — this PR has been open ~3 weeks, the CLA check is green, and it's currently mergeable with no conflicts. Is there anything I can do to help move it toward review (rebase, split, or extra context)? Happy to help. Thanks! |
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Summary
Addresses the PNG export produces an empty file bug (item 3) reported in #87.
handleDownloadinsrc/components/OntologyGraph.tsxexported with a fixedcy.png({ scale: 2, full: true }). For large ontologies the rendered canvas exceeds the browser's maximum canvas size, andtoDataURL()then silently returns the empty data URI (data:,) — which is exactly the 0-byteimported-ontology-graph.pngthe reporter saw. Thecatch { /* ignore */ }block hid the failure completely.Changes
src/lib/graphExport.ts:computeExportScale(width, height)— clamps the export scale so the largest side of the canvas stays within a conservative 8192px cross-browser limit. Small/medium graphs keep the crisp 2× scale; large graphs degrade gracefully instead of failing.isValidPngDataUri(value)— detects the empty-data-URI failure mode.OntologyGraph.tsx: compute the scale from the graph's bounding box, validate the data URI before triggering the download (no more 0-byte files), and log actionable errors instead of swallowing them.src/lib/graphExport.test.ts— 9 unit tests covering clamping, exact-limit, degenerate bounding boxes, and data-URI validation.Validation
npx tsc --noEmit— cleannpx vitest run— 25 files, 403/403 tests pass (394 existing + 9 new)Notes