RFC: Canvas and SVG Renderer Implementation Plan

[kswenson]

Summary

This PR adds an implementation plan for two new renderers to address WebGL context limitations and SVG export needs:

• CanvasPointRenderer: Canvas 2D fallback when WebGL contexts are exhausted (browsers limit to ~16)
• SVG Export Utility: Clean SVG generation for image export (replacing foreignObject approach)

Purpose

This is a Request for Comments - the PR contains only the plan document (v3/doc/point-rendering-plan.md) for team review before implementation begins.

Key Design Decisions

1. Keep PIXI.js - Continue using PIXI for WebGL rendering rather than writing custom WebGL code
2. Canvas for runtime fallback - Use Canvas 2D when WebGL unavailable (better performance than SVG for large datasets)
3. SVG as utility function - Export-only, no event handling needed, simpler than full renderer class
4. d3-quadtree for hit testing - O(log n) lookups for Canvas event handling

Open Questions

1. Is d3-quadtree already available as a dependency?
2. What performance threshold should trigger degraded experience messaging?
3. Should SVG export read from CanvasPointRenderer state or directly from PointsState?

Review Request

Please review the plan and leave comments on:

• Overall approach
• Implementation phases
• Any concerns or alternative suggestions

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 77.49382% with 273 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.39%. Comparing base (98bcf2b) to head (46addba).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
...nents/data-display/renderer/pixi-point-renderer.ts	61.45%	156 Missing and 19 partials ⚠️
...mponents/graph/plots/scatter-plot/scatter-plot.tsx	13.33%	12 Missing and 1 partial ⚠️
...isplay/components/no-webgl-context-placeholder.tsx	28.57%	10 Missing ⚠️
...onents/data-display/renderer/use-point-renderer.ts	89.15%	9 Missing ⚠️
.../src/components/map/components/map-point-layer.tsx	76.47%	8 Missing ⚠️
...ponents/data-display/hooks/use-connecting-lines.ts	22.22%	4 Missing and 3 partials ⚠️
...nents/data-display/renderer/point-renderer-base.ts	94.91%	6 Missing ⚠️
...s/data-display/renderer/point-renderer-context.tsx	44.44%	4 Missing and 1 partial ⚠️
.../components/data-display/components/background.tsx	55.55%	4 Missing ⚠️
...isplay/hooks/use-renderer-pointer-down-deselect.ts	55.55%	4 Missing ⚠️
... and 15 more

❗ There is a different number of reports uploaded between BASE (98bcf2b) and HEAD (46addba). Click for more details.

HEAD has 9 uploads less than BASE

Flag	BASE (98bcf2b)	HEAD (46addba)
cypress	10	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2299       +/-   ##
===========================================
- Coverage   86.69%   69.39%   -17.30%     
===========================================
  Files         724      733        +9     
  Lines       38770    39292      +522     
  Branches     9588     9688      +100     
===========================================
- Hits        33610    27266     -6344     
- Misses       5151    11288     +6137     
- Partials        9      738      +729     

Flag	Coverage Δ
cypress	40.54% <63.77%> (-31.24%)	⬇️
jest	55.94% <37.01%> (+0.20%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[cypress]

codap-v3    Run #9660

Run Properties:   Passed #9660  •  46addba789: docs: add implementation plan for Canvas and SVG renderers

Project	codap-v3
Branch Review	CODAP-295-canvas-svg-renderer-plan
Run status	Passed #9660
Run duration	03m 13s
Commit	46addba789: docs: add implementation plan for Canvas and SVG renderers
Committer	Kirk Swenson
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	4
View all changes introduced in this branch ↗︎