SelectableRegion _flushAdditions crash reproduction

Live Demo

https://davidmigloz.github.io/flutter_selection_crash/

Minimal reproduction for flutter/flutter#151536: StateError: Bad state: RenderBox was not laid out thrown from MultiSelectableSelectionContainerDelegate._compareScreenOrder when _RenderTheater skips laying out an obscured OverlayEntry while its SelectionContainerDelegate keeps processing registered selectables.

TL;DR

• Bug: open, P2, unfixed on Flutter 3.41.6 stable and current master.
• Mechanism: _RenderTheater skips layout of non-topmost OverlayEntry; their registered selectables have no size; _flushAdditions sort crashes.
• Three reproductions of the same root cause in different code paths: A (_getBoundingBox via paintBounds), B (_SelectableTextContainerDelegate via getBoxesForSelection), C (getTransformTo via RenderFractionalTranslation.applyPaintTransform).
• Proof-of-concept branch: fix/non-opaque-selectable-page — wrapping the top Page in opaque: false prevents _RenderTheater from skipping the parent's layout, proving the mechanism. Not production-ready for full-screen routes (causes visual overlap).
• Framework fix: flutter/flutter#184900 (open) — try/catch guard in both _compareScreenOrder overrides (selectable_region.dart and text.dart), catching the crash at its exact throw site with zero behavioral regressions. Route-level SelectionContainer.disabled wrappers were invalidated (nested SelectionArea creates its own registrar that shadows the disabled scope).

Reproduce

git clone https://github.com/davidmigloz/flutter_selection_crash.git
cd flutter_selection_crash
flutter run -d chrome --wasm

Click into any of the three approach cards. Browser console shows the crash immediately — no interaction required. Each approach hits a different frame in the same _compareScreenOrder method. See investigation/2026-04-10_verification.md for the full stack traces.

Proof of concept (opaque: false)

git checkout fix/non-opaque-selectable-page
flutter run -d chrome --wasm

Approach C now uses a local _NonOpaquePage extends Page<void> that creates a PageRouteBuilder(opaque: false, ...). The bottom route stays laid out, the comparator sees valid sizes/transforms, no crash.

Caveat: opaque: false causes the parent route to be painted behind the child (both Scaffolds render), creating visual text/widget overlap on full-screen routes. This branch proves the crash mechanism but is NOT suitable for production use.

App-level workaround

The fix applied in production apps uses a route-aware SelectionArea toggle: when the route is current, child is wrapped in SelectionArea (text selectable); when another route covers it, child is wrapped in SelectionContainer.disabled (selectables deregister). Uses ModalRoute.of(context)?.isCurrent + GlobalKey + KeyedSubtree.

This works at the app level because the app controls where SelectionArea is placed. It cannot be applied at the framework level because SelectionArea/SelectableRegion create their own registrar that shadows any outer disabled scope — see INVESTIGATION.md for the detailed analysis of why route-level SelectionContainer.disabled wrappers don't work.

Framework fix (PR open)

flutter/flutter#184900 — guards both _compareScreenOrder overrides (selectable_region.dart and text.dart) with a try/catch for StateError/AssertionError when accessing geometry on unlaid-out RenderBoxes. Minimal, surgical, zero behavioral regressions. Covered by two widget-level regression guards plus four mock-based red/green tests (one StateError + one AssertionError case per guarded method).

See INVESTIGATION.md for the full proposal, why route-level SelectionContainer.disabled wrappers don't work at the framework level, and known limitations (dead zones in #182573 unchanged).

Documentation

• INVESTIGATION.md — full investigation summary, the framework fix, and why route-level SelectionContainer.disabled wrappers don't work. Also documents the sibling bug in PlatformSelectableRegionContextMenu._activeClient (web right-click during route transitions) that #184900 does not cover.
• investigation/2026-04-10_verification.md — stack traces for all three approaches and the opaque: false isolation test.

Related issues and PRs

• flutter/flutter#151536 — canonical issue, open
• flutter/flutter#184900 — framework fix PR (open): try/catch guard in both _compareScreenOrder overrides
• flutter/flutter#189575 — sibling issue (open): web right-click _activeClient race, three lifecycle defects
• flutter/flutter#189587 — sibling fix PR (open): corrects the three lifecycle defects behind #189575
• flutter/flutter#151536 (comment 4225683042) — upstream analysis comment: repro + mechanism + initial fix direction (later revised)
• flutter/flutter#151536 (comment 4227118235) — upstream follow-up: pivot from _ModalScopeState wrapper to _compareScreenOrder guard, links the framework PR
• flutter/packages#11062 — go_router PR (closed, unmerged, superseded): app-level route-aware SelectionArea toggle; reviewed by @Renzo-Olivares
• flutter/flutter#182573 — sibling dead-zone variant (not fixed by the framework PR)
• flutter/flutter#117527 — related, recently resolved (different code path)
• flutter/flutter#119776 — related, resolved (different code path)
• flutter/flutter#157996 — Gustl22's incomplete draft (prior art)
• flutter/flutter#158918 — Gustl22's diagnostic draft (prior art)

Build matrix

Command	Reproduces?
flutter run -d chrome (DDC debug)	Yes
flutter run -d chrome --wasm (dart2wasm debug)	Yes
flutter run -d chrome --release --wasm (dart2wasm release)	Yes
flutter run -d chrome --release (dart2js release)	Yes
flutter test (VM)	No (synchronous pump)

Production impact

This bug has been observed in production Flutter web apps: 640+ Sentry events across 5+ users. Routes affected: any child route stacked on a parent that wraps its content in SelectionArea. Workaround applied: route-aware SelectionArea toggle using ModalRoute.isCurrent + SelectionContainer.disabled (see "Production workaround" above).

Sibling bug observed post-workaround (web right-click)

On 2026-04-22, with _RouteAwareSelectionArea and Flutter 3.41.6 in place, a distinct crash surfaced in production:

Assertion failed: .../widgets/selection_container.dart:303:7
_selectionContainerContext?.findRenderObject() != null
"getTransformTo cannot be called before SelectionContainer is laid out."
  at package:flutter/src/widgets/_platform_selectable_region_context_menu_web.dart:96:41
  at package:flutter/src/widgets/_platform_selectable_region_context_menu_web.dart:136:11

Same underlying pattern ("geometry read on an unlaid-out / disposed SelectionContainer"), different code path: the web mousedown JS listener calls client.getTransformTo(null) on a stale static _activeClient during a route transition. Neither the _RouteAwareSelectionArea toggle nor framework PR #184900 cover this path.

Filed upstream as flutter/flutter#189575. Root-causing it there found three concrete lifecycle defects in PlatformSelectableRegionContextMenu's attach/detach pair and SelectableRegionState's focus/dispose handling — not just an unguarded read. Fix PR flutter/flutter#189587 corrects the three defects directly and is open, independent of #184900.

See the INVESTIGATION.md sibling-bug section for the full root-cause breakdown, the fix PR's approach, and why a narrower geometry-read guard (our original proposal here) would have been insufficient.