[mmustafasenoglu]

Closes #426

When using --one-file mode, base64-encoded video data URIs are split into multiple <source> elements by RevealJS. The existing fixBase64VideoBackground only ran on the ready event, so dynamically created video elements (when navigating to slides outside the initial viewDistance) were never fixed, causing a visible blank frame flicker on slide transitions.

This adds a slidechanged handler that re-runs the fix on every slide transition. A WeakSet tracks already-processed backgrounds to avoid duplicate MutationObserver setup.

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[codacy-production]

Up to standards ✅

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[jeertmans]

Hi @mmustafasenoglu, thanks for your contribution! I'll properly review this later, but can you make sure to address my small request change, and also sync the changes to docs/source/_static/template.html and docs/source/_static/firebase_sync_demo.html. Thanks!

[mmustafasenoglu]

Done! Changes applied:

• manim_slides/templates/firebase_sync.html: same WeakSet + slidechanged fix
• manim_slides/templates/revealjs.html: var → const per your suggestion
• docs/source/_static/template.html: synced with main template
• docs/source/_static/firebase_sync_demo.html: synced with firebase template

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.09%. Comparing base (722c2ae) to head (d2820ee).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #663      +/-   ##
==========================================
- Coverage   79.23%   79.09%   -0.14%     
==========================================
  Files          23       23              
  Lines        2177     2177              
==========================================
- Hits         1725     1722       -3     
- Misses        452      455       +3     

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[jeertmans]

Hi @mmustafasenoglu, my apologies for the delay. I have reviewed your changes and tested locally, and I cannot observe any repeatable, visual change. I rendered the ConvertExample slides from example.py in 4K and converted to HTML with --one-file, and I cannot see any difference. I.e., the slides transitions are usually smooth, but flickering can occur in some cases, both using the reference Manim Slides version and yours.

Do you have a set of example slides on which I could validate your contribution?

[aniruddhaadak80]

Hi @mmustafasenoglu, nice fix! I have PR #678 open that also addresses #426 from a different angle — it pre-converts data URIs to Blob URLs at load time so the browser doesn't re-decode massive base64 strings on every transition.

Your approach (listening to slidechanged + WeakSet tracking) handles the root cause for dynamically created slides, while the Blob URL pre-conversion is a complementary performance optimization. Both can coexist without conflicts since they modify non-overlapping sections of the templates.

FYI @jeertmans — these two PRs are complementary and can be merged together.