[web] Fall back to full CJK fonts for characters not covered by split slices#188890
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… slices Allows the web engine to download and use the full CJK fallback fonts when encountering rare characters (such as archaic Jamo) that are not included in the smaller, split CJK font slices.
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This pull request introduces support for split-slice fallback fonts (such as CJK fonts) to optimize font downloads by preferring smaller slices over monolithic parent fonts unless required. It updates the font rolling script to decompress .woff2 files, compute exclusive character sets, and serialize parent-slice relationships, while updating the fallback service to manage registration and pending states across slices and parents. Feedback suggests using path.setExtension instead of replaceAll in the font rolling script to safely change file extensions.
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The approach looks good overall, but I left a couple of test coverage comments that I think should be addressed before landing.
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| // 0x1100 is combining Jamo (triggers monolithic Noto Sans KR) | ||
| // 0x4E00 is standard CJK (triggers Noto Sans KR split slice, e.g., Noto Sans KR 0) | ||
| FallbackFontService.instance.addMissingCodePoints(<int>[0x1100, 0x4E00]); |
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Could you add a reverse-order test for the same-batch parent plus slice case? The current [0x1100, 0x4E00] order covers rare-character-first. Adding [0x4E00, 0x1100], ideally with debugUserPreferredLanguage = 'ko', would cover the case where the split slice is inserted before the full parent candidate.
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Good catch! This actually uncovered a problem with the original implementation where the order of the codepoints could change which fonts get downloaded. I fixed it so that we will never download a parent font and one of the split fonts in the same batch
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flutter/flutter@cf9e8af...846664b 2026-07-14 [email protected] Roll Skia from dfcff99566c3 to 88954ef8f36d (1 revision) (flutter/flutter#189440) 2026-07-14 [email protected] refactor: remove material import from scrollable_semantics_test and selectable_region_context_menu_test (flutter/flutter#186611) 2026-07-14 [email protected] Roll Skia from 3d1fc554f1a2 to dfcff99566c3 (17 revisions) (flutter/flutter#189428) 2026-07-14 [email protected] Roll Dart SDK from 2c587df8f05a to 05bf153370c4 (5 revisions) (flutter/flutter#189426) 2026-07-14 [email protected] [flutter_tools] Remove web hot reload flag (flutter/flutter#185994) 2026-07-14 [email protected] [iOS] Fix flaky keyboard animation test (flutter/flutter#189353) 2026-07-14 [email protected] [Impeller] Playground expanded role (flutter/flutter#188889) 2026-07-14 [email protected] Roll pub packages (flutter/flutter#189409) 2026-07-13 [email protected] Update lock-threads dependency to 6.0.2 (flutter/flutter#189053) 2026-07-13 49699333+dependabot[bot]@users.noreply.github.com Bump actions/labeler from 6.1.0 to 6.2.0 in the all-github-actions group (flutter/flutter#189396) 2026-07-13 [email protected] Remove outdated todo about `analysis bug on Windows` and update condition to also perform `analysis on windows` (flutter/flutter#189283) 2026-07-13 [email protected] Add more 0x0 size tests part 4 (flutter/flutter#185187) 2026-07-13 [email protected] Roll Packages from 20928d5 to ad2eab1 (18 revisions) (flutter/flutter#189387) 2026-07-13 [email protected] [flutter_tools] Fix ADB device listing output parsing regression (flutter/flutter#189369) 2026-07-13 [email protected] Stop running most Mac x64 builders that have Mac ARM equivalents on master (flutter/flutter#189301) 2026-07-13 [email protected] Move a few benchmarks from x64 Intel Macs to ARM (flutter/flutter#189377) 2026-07-13 [email protected] Add note that `hcpp` needs impeller (flutter/flutter#189382) 2026-07-13 [email protected] Roll Fuchsia Linux SDK from vhIlDkWIy21IrlB9E... to oOETA0ISPouDt2xBo... (flutter/flutter#189349) 2026-07-13 [email protected] [flutter_tools] Respect mustMatchAppBuild on Windows native assets (flutter/flutter#186788) 2026-07-13 [email protected] Roll Skia from 8bf65996caba to 3d1fc554f1a2 (2 revisions) (flutter/flutter#189350) 2026-07-13 [email protected] Roll Dart SDK from 0fc1668c4af4 to 2c587df8f05a (9 revisions) (flutter/flutter#189351) 2026-07-13 [email protected] [web] Fall back to full CJK fonts for characters not covered by split slices (flutter/flutter#188890) 2026-07-13 [email protected] Take Mac tool_integration_tests_* out of bringup (flutter/flutter#189368) 2026-07-13 [email protected] [hooks] Roll record_use to 1.0 and unpin (flutter/flutter#189366) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected],[email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
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Allows the web engine to download and use the full CJK fallback fonts when encountering rare characters (such as archaic Jamo) that are not included in the smaller, split CJK font slices.
Fixes #188255
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