Annotations and theme color blend disappear at maximum zoom levels

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Xianpi Duan

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Aug 25, 2025, 12:22:02 AM (14 days ago) Aug 25
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Hi team,

I've discovered an issue with the latest Zotero reader on GitHub (also on beta Zotero 8.0-beta.7+bdf49b9b0_win-x64) where annotations and theme color blending disappear when zooming to maximum levels.

Issue Details:

  • Annotations become invisible at maximum zoom levels
  • Theme color blending also disappears
  • Reproducible in beta versions, but not in the stable version (7.0.24)
Snipaste_2025-08-23_05-07-36.pngSnipaste_2025-08-23_05-07-16.png

After investigating, I think this is related to recent PDF.js changes. Specifically, when users zoom beyond a certain threshold, PDF.js now renders high-resolution partial page views using a new sectioned canvas instead of the complete original canvas (see this commit).

This canvas switching behavior appears to cause Zotero's annotation layer and visual elements to be lost.

I tried to work on a potential fix, but I am still very new to the Zotero reader codebase and need to better understand how Zotero's reader integrates with PDF.js rendering. Would it be possible to get some guidance on:

  • How the annotation layer is currently synchronized with PDF.js canvases
  • Where in the codebase I should focus for this canvas issue (inside pdf.js or under src/pdf)

I'm happy to contribute a fix once I have a better understanding of the architecture.

Thanks for your time.

Best Regards,

Xianpi Duan

Martynas Bagdonas

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Aug 25, 2025, 9:48:12 AM (13 days ago) Aug 25
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We are working on a fix. Thanks for reporting.
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