fix(ui): share the markdown style sheet between message texts by renefloor · Pull Request #192 · GetStream/stream-core-flutter

renefloor · 2026-09-30T08:21:53Z

Why

A livestream load test on stream_chat_flutter showed about one janky frame per incoming message, with build time over budget. On every build of every message, DefaultStreamMessageText.build:

copied ThemeData with textTheme.apply(...)
built a full MarkdownStyleSheet.fromTheme(...)
created a new _StreamMentionSyntax, recompiling its RegExp

What

The theme-derived style sheet is cached per ThemeData instance (held weakly in an Expando), keyed by the effective text style and link style. Messages with the same styles share one sheet. The cache holds at most 32 entries per theme and drops the oldest when it's full.
The caller's styleSheet is merged on top after the lookup.
The mention syntax is stateless, so it is now a single static final instance.

Testing

stream_message_text_style_sheet_test.dart covers:
- messages with the same styles get the identical sheet;
- a different text style gets its own sheet;
- each message's styleSheet override stays separate;
- a new theme produces a new sheet.
The full stream_core_flutter suite passes. Against the CI goldens, the same 50 local host-drift failures occur with and without this change, so there is no visual diff.
Pixel 4, profile mode, 100 messages at 10/s, mean build time per message:

Chat message list 0.5.2 This PR

Every row rebuilds 25.2 ms 23.1 ms

With row caching 12.3 ms 12.0 ms

Companion to the stream-chat-flutter PR that stops StreamMessageListView rebuilding unchanged rows.

🤖 Generated with Claude Code

Summary by CodeRabbit

Performance
- Improved message rendering performance in long lists by reusing markdown styles when theme and text styles match.
- Updated theme typography and custom style overrides continue to apply correctly.

coderabbitai · 2026-09-30T08:22:02Z

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📒 Files selected for processing (3)

packages/stream_core_flutter/CHANGELOG.md
packages/stream_core_flutter/lib/src/components/message/stream_message_text.dart
packages/stream_core_flutter/test/components/message/stream_message_text_style_sheet_test.dart

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codecov · 2026-09-30T08:26:13Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.05%. Comparing base (0c66009) to head (758c541).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #192      +/-   ##
==========================================
+ Coverage   68.77%   70.05%   +1.28%     
==========================================
  Files         213      213              
  Lines        8762     8773      +11     
==========================================
+ Hits         6026     6146     +120     
+ Misses       2736     2627     -109

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The row cache was cleared on every didUpdateWidget, so a parent that rebuilds StreamMessageListView often (for example a call-state builder around a livestream overlay) emptied it on each rebuild. It is now only cleared when a value the rows are built from changes: the configuration, the parent message, the message and row builders, and the row callbacks. Also bumps stream_core_flutter to include the shared markdown style sheet (GetStream/stream-core-flutter#192). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

…hmark Points stream_chat_flutter at GetStream/stream-chat-flutter#3024 (message rows are only rebuilt when they change), stream_core_flutter at GetStream/stream-core-flutter#192 (shared markdown style sheet), and stream_video_flutter at GetStream/stream-video-flutter#1392 (repaint boundaries around the livestream player). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

The row cache was cleared on every didUpdateWidget, so a parent that rebuilds StreamMessageListView often (for example a call-state builder around a livestream overlay) emptied it on each rebuild. It is now only cleared when a value the rows are built from changes: the configuration, the parent message, the message and row builders, and the row callbacks. Also bumps stream_core_flutter to include the shared markdown style sheet (GetStream/stream-core-flutter#192). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

DefaultStreamMessageText built a ThemeData copy, a full MarkdownStyleSheet and a new mention syntax (recompiling its pattern) on every build of every message. Style sheets are now memoized per theme and style inputs, and the mention syntax is a single shared instance. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

MarkdownStyleSheet's == and hashCode skip tableScrollbarThumbVisibility, so keying the cache on the caller's sheet let two different sheets share one entry. Key on the text and link style only and merge the caller's sheet after the lookup. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* fix(ui): only rebuild message rows that changed StreamMessageListView rebuilt every visible row in full on each new message, costing about one janky frame per message in busy channels. Rows are now reused while their message, neighbours and the current user are unchanged, so a new message rebuilds only its own row and the one it lands next to. The cache is cleared whenever the list widget or its dependencies change. StreamMessageText also resubscribed to the current user stream on every rebuild because it passed a freshly mapped stream; it now passes the stream unmapped and compares on language. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * fix(ui): cap the message row cache at 64 rows Only rows that are still mounted benefit from the cache, so it is now a least-recently-used cache of at most 64 rows instead of one entry per loaded message. This keeps memory constant in long-running channels where maximumMessageLimit is not set. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * fix(ui): keep cached message rows when the list's parent rebuilds The row cache was cleared on every didUpdateWidget, so a parent that rebuilds StreamMessageListView often (for example a call-state builder around a livestream overlay) emptied it on each rebuild. It is now only cleared when a value the rows are built from changes: the configuration, the parent message, the message and row builders, and the row callbacks. Also bumps stream_core_flutter to include the shared markdown style sheet (GetStream/stream-core-flutter#192). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> * perf(ui): reuse message rows until what they're built from changes Replace the message row cache with an internal MemoizedBuilder keyed on each row's StreamMessageItemProps, layout data and builder. A new message now rebuilds its own row, plus its neighbor's when that row's place in a run of messages changes; an edit or reaction rebuilds only its own row. This covers threads and lists with any number of mounted rows, and removes the 64-row cap and the cache clears. - StreamMessageItemProps now compares by value (Equatable). - The thread parent row is memoized the same way. System, ephemeral and moderated rows are unchanged, so custom builders keep the list's context and can still reach the page's ScaffoldMessenger. - The content kind is resolved only when a row rebuilds. - Point stream_core_flutter at the merged core#192 (1546087), which also restores #193. - Document when messageBuilder and the parent message builder run again. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> * chore: Update Goldens * test(docs): stub isMarkedAsUnread in the docs channel state mock The message list reads it when it attaches to a channel; unstubbed, the mock returned null and the docs screenshots rendered an error screen. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> * chore: Update Goldens --------- Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Sahil Kumar <sahil@getstream.io> Co-authored-by: xsahil03x <25670178+xsahil03x@users.noreply.github.com>

renefloor mentioned this pull request Sep 30, 2026

fix(ui): only rebuild message rows that changed GetStream/stream-chat-flutter#3024

Merged

xsahil03x self-assigned this Oct 2, 2026

renefloor and others added 3 commits October 2, 2026 17:50

test(ui): show the style sheet before and after a theme change

801c431

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

xsahil03x force-pushed the fix/message-text-style-sheet-cache branch from b6f5e1c to 801c431 Compare October 2, 2026 15:54

xsahil03x marked this pull request as ready for review October 2, 2026 15:56

xsahil03x requested a review from a team as a code owner October 2, 2026 15:56

xsahil03x approved these changes Oct 2, 2026

View reviewed changes

docs(ui): tighten the style sheet cache comments

758c541

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

xsahil03x enabled auto-merge (squash) October 2, 2026 16:06

xsahil03x merged commit 1546087 into main Oct 2, 2026
16 of 17 checks passed

xsahil03x deleted the fix/message-text-style-sheet-cache branch October 2, 2026 16:07

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fix(ui): share the markdown style sheet between message texts - #192

fix(ui): share the markdown style sheet between message texts#192
xsahil03x merged 4 commits into
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Chat message list	0.5.2	This PR
Every row rebuilds	25.2 ms	23.1 ms
With row caching	12.3 ms	12.0 ms

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