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[Bug / Perf]: Line-breaking bottleneck on massive unspaced text blocks (CJK / Gutenberg EPUBs) #28

Closed
#27
#29
Closed
[Bug / Perf]: Line-breaking bottleneck on massive unspaced text blocks (CJK / Gutenberg EPUBs)#28
#27
#29

Description

@DrkXo
DrkXo
opened on Oct 8, 2026

Summary

When rendering documents with long paragraphs lacking whitespace (common in East Asian / CJK literature, text conversions, and long strings), RenderHyperBox layout suffers severe slowdowns, causing UI freezes lasting 10–15+ seconds per chapter.

Real-World Sample

  • Document: Project Gutenberg Dream of the Red Chamber (紅樓夢) — pg24264-images-3.epub
  • Observed: Section 1 contains long unspaced Chinese paragraphs (up to ~14,000 characters in a single <p>), taking ~13.4 seconds in RenderHyperBox.layout.

Activity

  1. vietnguyentuan2019
    added a commit that references this issue on Oct 10, 2026

    Merge pull request #29: eliminate the O(N^2) line-breaking bottleneck…

    1feb2fc
  2. vietnguyentuan2019
    closed this as completedin #27on Oct 10, 2026

  3. vietnguyentuan2019 commented on Oct 10, 2026

    @vietnguyentuan2019
    vietnguyentuan2019
    on Oct 10, 2026
    Contributor

    Fixed by #29 (thanks @DrkXo 🙏) and merged to main in #27 (merge commit ef062d9). It will ship in 1.13.0 — not published to pub.dev yet.

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