fix(ui): jump on text selection

[renefloor]

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Github Issue: fixes #2862

CLA

• I have signed the Stream CLA (required).
• The code changes follow best practices
• Code changes are tested (add some information if not applicable)

Description of the pull request

This PR fixes the specific case of text selection, but we might want a better fix.

Summary by CodeRabbit

• Bug Fixes

  • Fixed desktop and web text selection causing StreamMessageListView to jump multiple screens.
  • Improved item reveal behavior for standard, reversed, and shrink-wrapped lists.
  • Prevented repeated reveal operations from causing unintended scrolling.

• Tests

  • Added coverage for anchor-aware scrolling, exact item reveals, repeated reveals, and text selection behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 1750517b-5aea-42f8-a700-ecc20042c5c5

📥 Commits

Reviewing files that changed from the base of the PR and between afc6643 and e07290b.

📒 Files selected for processing (2)

• packages/stream_chat_flutter/lib/scrollable_positioned_list/src/wrapping.dart
• packages/stream_chat_flutter/test/scrollable_positioned_list/reveal_anchor_test.dart

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/stream_chat_flutter/lib/scrollable_positioned_list/src/wrapping.dart

---

📝 Walkthrough

Walkthrough

The PR adds anchor-aware viewport reveal corrections, removes duplicate anchor adjustments from ScrollablePositionedList, and adds tests for normal, reversed, shrink-wrapped, repeated, and text-selection reveal behavior.

Changes

Anchor-aware reveal behavior

Layer / File(s)	Summary
Viewport reveal corrections packages/stream_chat_flutter/lib/scrollable_positioned_list/src/viewport.dart, packages/stream_chat_flutter/lib/scrollable_positioned_list/src/wrapping.dart	Custom viewports correct reveal offsets and rectangles for anchor displacement, axis direction, zero anchors, and non-finite results.
ScrollablePositionedList reveal integration packages/stream_chat_flutter/lib/scrollable_positioned_list/src/positioned_list.dart	The list removes duplicate anchor calculations and uses reveal offsets relative to the current viewport pixels.
Reveal validation and changelog packages/stream_chat_flutter/test/scrollable_positioned_list/reveal_anchor_test.dart, packages/stream_chat_flutter/CHANGELOG.md	Widget tests cover anchored, reversed, shrink-wrapped, repeated, and text-selection reveals. The changelog records the fix.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant SelectableText
  participant ScrollablePositionedList
  participant AnchoredViewport
  SelectableText->>ScrollablePositionedList: request showOnScreen
  ScrollablePositionedList->>AnchoredViewport: request getOffsetToReveal
  AnchoredViewport-->>ScrollablePositionedList: return corrected offset and rectangle
  ScrollablePositionedList-->>SelectableText: preserve the target reveal position

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Possibly related PRs

• GetStream/stream-chat-flutter#2693: Both PRs modify UnboundedRenderViewport for anchor-related scrolling behavior.
• GetStream/stream-chat-flutter#2703: Both PRs modify viewport scrolling and reveal behavior.

Suggested reviewers: xsahil03x

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the primary fix for unexpected UI jumping during text selection.
Linked Issues check	✅ Passed	The changes address anchor-aware reveal behavior that caused unexpected channel scrolling during selectable message text interactions in issue #2862.
Out of Scope Changes check	✅ Passed	The viewport fixes, regression tests, and changelog entry are directly related to preventing unintended scrolling during text selection.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/jump-on-text-selection

---

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In
`@packages/stream_chat_flutter/lib/scrollable_positioned_list/src/wrapping.dart`:
- Around line 159-170: Update the reveal correction in getOffsetToReveal to use
the layout main-axis extent supplied to _attemptLayout rather than size,
especially for shrinkWrap layouts. Store that _attemptLayout extent on the
relevant state/object and use it for the anchor-based offset and rect
adjustment, preserving the existing finite-offset and zero-correction guards.

In
`@packages/stream_chat_flutter/test/scrollable_positioned_list/reveal_anchor_test.dart`:
- Around line 145-163: Register teardown to restore
debugDefaultTargetPlatformOverride before setting it to TargetPlatform.macOS in
this test, ensuring cleanup runs if pump, gesture operations, or the expectation
throws; remove reliance on the manual reset at the test body’s end.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 3cc7e448-f9c6-4ad0-b67e-75920312ab00

📥 Commits

Reviewing files that changed from the base of the PR and between 1616091 and afc6643.

📒 Files selected for processing (5)

• packages/stream_chat_flutter/CHANGELOG.md
• packages/stream_chat_flutter/lib/scrollable_positioned_list/src/positioned_list.dart
• packages/stream_chat_flutter/lib/scrollable_positioned_list/src/viewport.dart
• packages/stream_chat_flutter/lib/scrollable_positioned_list/src/wrapping.dart
• packages/stream_chat_flutter/test/scrollable_positioned_list/reveal_anchor_test.dart

[codecov]

Codecov Report

❌ Patch coverage is 82.60870% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.87%. Comparing base (1616091) to head (e07290b).

Files with missing lines	Patch %	Lines
...r/lib/scrollable_positioned_list/src/viewport.dart	80.00%	2 Missing ⚠️
...r/lib/scrollable_positioned_list/src/wrapping.dart	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2864      +/-   ##
==========================================
+ Coverage   72.86%   72.87%   +0.01%     
==========================================
  Files         429      429              
  Lines       27698    27716      +18     
==========================================
+ Hits        20183    20199      +16     
- Misses       7515     7517       +2     

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