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fix: prevent browser freeze when tessellating >50k vertices (#8219 )#8555

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Nixxx19:nityam/tessellation-freeze-fix
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fix: prevent browser freeze when tessellating >50k vertices (#8219 )#8555
Nixxx19 wants to merge 4 commits intoprocessing:mainfrom
Nixxx19:nityam/tessellation-freeze-fix

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@Nixxx19 Nixxx19 commented Feb 22, 2026 •
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Resolves #8219

Summary

  • Adds a one‑time confirmation prompt before tessellating very large TESS shapes (>50,000 vertices) to avoid browser freezes in libtess during _triangulate().
  • Cancel: skips tessellation and draws nothing for that shape (no TRIANGLE_FAN fallback), keeping behavior explicit and predictable.
  • OK: remembers the choice for the lifetime of the renderer via _largeTessellationAcknowledged and tessellates normally without prompting again.
  • Respects p5.disableFriendlyErrors / minified builds: when friendly errors are disabled, tessellation always runs with no prompt.

Tests

  • Adds / updates WebGL unit tests in test/unit/webgl/p5.RendererGL.js to cover:
    • Prompting once for large shapes and including the vertex count in the message.
    • Skipping tessellation entirely on cancel (no TRIANGLE_FAN fallback).
    • Only prompting once per renderer when the user approves.
    • Skipping the prompt when p5.disableFriendlyErrors is true.
    • Normal tessellation behavior for shapes below the 50k‑vertex threshold.

Screenshot

Screenshot 2026-03-17 at 4 20 38 PM

PR Checklist

  • npm run lint passes
  • Inline reference is included / updated (not applicable – bug fix only)
  • Unit tests are included / updated

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welcome bot commented Feb 22, 2026

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@davepagurek
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davepagurek commented Apr 9, 2026

Thanks for working on this! As this is into the main branch, we'll want another PR after this making similar changes into the dev-2.0 branch, where p5 2.x is developed. The code looks like it could largely be the same (but you'll likely want to manually change it on the new base because so much has changed between the branches, merging/rebasing won't be easy), and also how mocking works in tests is a little different as 2.x switched to using vitest.

davepagurek
davepagurek reviewed Apr 9, 2026
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Comment thread test/unit/webgl/p5.RendererGL.js

test('TESS mode skips prompt when p5.disableFriendlyErrors is true', function(done) {
var renderer = myp5.createCanvas(10, 10, myp5.WEBGL);
var confirmStub = sinon.stub(window, 'confirm').returns(false);
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@davepagurek davepagurek Apr 9, 2026

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It looks like tests are currently failing here:

   2) Graphics
       p5.Graphics.resizeCanvas
         Rendering
           p5.prototype.resizeCanvas
             p5.Framebuffer
               sizing
                 p5.RendererGL
                   beginShape() in WEBGL mode
                     TESS mode skips prompt when p5.disableFriendlyErrors is true:
     Error: Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

Does this test also take a while locally?

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@Nixxx19 Nixxx19 Apr 15, 2026 •
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sorry about that! the test was timing out because when p5.disableFriendlyErrors is true, the prompt is skipped and tessellation actually runs on 60k vertices, which is the freeze we're trying to guard against. fixed by stubbing _tesselateShape in the tests that would otherwise trigger real tessellation. also added an assertion that _tesselateShape is called in the disableFriendlyErrors case to confirm the code path is exercised. applied the same stub to the "only prompts once" test as well since confirm returns true there.

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Browser freeze when creating >65k vertices in draw() loop (no validation or warning)

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