Implement loading skeleton states for all dashboard widgets
epic-coordinator-statistics-dashboard-ui-task-010 — Add shimmer/skeleton loading states to all dashboard widgets: StatsSummaryCards skeleton (4 grey card placeholders), chart skeleton (grey rectangle with label placeholders), and PeerMentorStatsList skeleton (6 row placeholders). Skeletons must be announced correctly by screen readers as 'Loading' to avoid confusing VoiceOver users with unlabelled elements.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 5 - 253 tasks
Can start after Tier 4 completes
Implementation Notes
Create a shared ShimmerContainer widget that accepts width, height, borderRadius, and an optional AnimationController. Instantiate one AnimationController at the dashboard screen level and pass it down via InheritedWidget or a simple constructor parameter to avoid multiple Tickers. For 'Reduce Motion' support, check MediaQuery.of(context).disableAnimations — when true, render static grey containers instead of animated shimmer. Use design token color values (e.g., colorSurface, colorOnSurface with low opacity) for skeleton fill colors, never hardcoded hex values.
Ensure all three skeleton widgets are co-located alongside their real widget counterparts (same file or nearby sibling file) to make side-by-side maintenance easy.
Testing Requirements
Write flutter_test widget tests for each skeleton widget: (1) verify correct number of placeholder children are rendered, (2) verify the root Semantics node has label 'Loading', (3) verify individual shimmer shapes are excluded from semantics tree via ExcludeSemantics, (4) use flutter_test's AccessibilityGuideline to confirm no spurious focusable nodes, (5) golden/snapshot tests for all three skeletons in loading state against approved baseline images. Tests should use a mock AnimationController to avoid flakiness from real animation timing.
PeerMentorStatsList must handle rosters of 40+ mentors efficiently. A naive ListView implementation that re-renders all rows on filter change may cause frame drops on mid-range devices, degrading the experience for coordinators managing large chapters.
Mitigation & Contingency
Mitigation: Use ListView.builder with const constructors for row widgets. Profile the list with Flutter DevTools on a release build against a 60-mentor dataset before submitting for review. Implement sort in the BLoC layer, not in the widget.
Contingency: If frame drops persist, introduce pagination (load 20 mentors, scroll to load more) and add a search filter to reduce visible row count in practice.
The ActivityTypeDonutChart must render org-configured activity type labels from the org-labels system. If the terminology provider is not available or returns stale labels, chart segments will display raw key strings instead of human-readable organisation-specific names, confusing coordinators.
Mitigation & Contingency
Mitigation: Always resolve labels through the OrganizationLabelsProvider before passing data to the donut chart widget. Implement a fallback that formats the raw key as a readable string (e.g., 'peer_support' → 'Peer Support') if the provider returns null.
Contingency: If the org-labels system is unavailable, display the formatted fallback label and log a warning. Do not block chart rendering on label resolution — render with fallbacks immediately.
fl_chart widgets do not natively expose semantic labels for individual bars and donut segments. Without explicit Semantics wrappers, VoiceOver and TalkBack users will receive no meaningful chart information, failing accessibility requirements critical for Blindeforbundet and NHF deployments.
Mitigation & Contingency
Mitigation: Wrap each fl_chart widget in a Semantics widget with a descriptive label summarising the chart data. Implement the data table fallback toggle from the start, not as an afterthought. Validate with VoiceOver on iOS and TalkBack on Android during development.
Contingency: If fl_chart's rendering pipeline prevents semantic overlay from working reliably, replace chart widgets with a custom Canvas-based implementation that has full semantic control, or use a different charting library with better accessibility support.
The period filter state must be preserved when navigating away from the dashboard (e.g., drilling into a mentor's detail screen and pressing back). If the BLoC is re-created on navigation, the filter resets to default, forcing coordinators to re-select their period every time they drill down, degrading operational workflow efficiency.
Mitigation & Contingency
Mitigation: Provide the StatsBloc at a route level above the dashboard screen using a BlocProvider scoped to the statistics navigation shell, not inside the screen widget itself. Verify persistence with a widget integration test that navigates away and back.
Contingency: If route-level scoping is not achievable within the current navigation architecture, persist the last-used filter to a local session store and restore it on screen re-entry.