Preserve per-tab scroll and state across tab switches
epic-role-based-access-control-ui-and-navigation-task-009 — Ensure StatefulShellRoute correctly preserves scroll positions, form state, and list positions within each tab branch when navigating between tabs or switching roles. Implement tab state retention so navigating away and back does not reset in-progress flows. Validate with coordinator, peer mentor, and org admin role scenarios.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 4 - 323 tasks
Can start after Tier 3 completes
Implementation Notes
Use StatefulShellRoute.indexedStack (not the default StatefulShellRoute) to keep all branch widgets alive in the widget tree. Add AutomaticKeepAliveClientMixin to any StatefulWidget that needs to preserve scroll or form state — call super.build(context) and wantKeepAlive: true. Use PageStorageKey('
When handling role switches that remove a tab, call GoRouter.go('/home') before updating the tab permission matrix to avoid GoRouter route-not-found errors.
Testing Requirements
Widget tests: (1) navigate to tab with scrollable list, scroll down 200px, switch tab, return and assert scroll offset is preserved using ScrollController.offset, (2) partially fill a form on a tab, switch tabs, return and assert form fields retain values, (3) switch role while on a preserved tab and assert state retention where role still permits the tab. Integration test: simulate full coordinator workflow (scroll contacts list, switch to Work tab, return) and assert no resets. Manual validation required on physical device for all three role scenarios. Use Flutter DevTools to confirm no memory leaks from mounted branches.
Combining GoRouter's declarative redirect logic in the route guard with StatefulShellRoute's stateful branch management is known to produce subtle bugs where the shell rebuilds unnecessarily on role switches, losing tab state or causing double-navigation events.
Mitigation & Contingency
Mitigation: Implement the route guard as a GoRouter redirect callback that only evaluates role from an already-resolved Riverpod provider (not async). Use a dedicated ShellRoute navigator key per tab branch to anchor state independently of role-driven rebuilds. Write integration tests for the full navigation graph.
Contingency: If StatefulShellRoute state loss is confirmed during QA, fall back to a manual tab state preservation approach using a TabStateManager service that caches the last route per tab and restores it after role switches, decoupling tab state from the shell lifecycle.
The role-based home screen must render three significantly different layouts (coordinator dashboard, peer mentor activity summary, org admin overview). If these variants are implemented as a single widget with conditionals, the file will become unmaintainable and difficult to test in isolation, especially as each variant grows with downstream feature additions.
Mitigation & Contingency
Mitigation: Design the role-based home screen as a router/dispatcher widget that delegates to three separate variant widgets (CoordinatorHomeView, PeerMentorHomeView, OrgAdminHomeView). Each variant is independently testable and can be developed by separate team members in parallel.
Contingency: If variant coupling has already occurred before this risk is addressed, refactor to the dispatcher pattern in a dedicated cleanup task before feature handoff. The dispatcher pattern is a straightforward extraction that carries low refactoring risk.
The no-access screen must link global admin users to the correct admin portal URL, which may differ per organization (NHF, HLF, Blindeforbundet each have their own admin portals). Hardcoding a single URL will result in wrong or broken links for some global admin users.
Mitigation & Contingency
Mitigation: Source the admin portal URL from the organization's configuration record in Supabase rather than hardcoding it. The no-access screen reads the active org context and resolves the portal URL dynamically. Provide a safe fallback to a generic Norse Digital Products support page if the URL is not configured.
Contingency: If dynamic URL resolution is not ready when the no-access screen ships, display a static instruction to contact the organization's administrator along with a support email address as an interim measure, and track the URL configuration task as a follow-up.