Expense Type Selector — accessibility semantics
epic-travel-expense-registration-ui-task-002 — Augment the expense type selector with full screen-reader support: each type chip must have a descriptive Semantics label including its current enabled/disabled/selected state. Implement live-region announcements when a conflict warning appears or is dismissed. Validate contrast ratios against design token palette and ensure touch targets meet the 44×44dp minimum.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Build chip Semantics labels dynamically in a helper function buildChipSemanticLabel(ExpenseType type, ExpenseTypeSelectionState state) → String. Use Semantics(onTap: ..., label: label, button: true, enabled: isEnabled, excludeSemantics: true) wrapping the FilterChip to prevent double-announcement of the chip's own internal semantics. For the live region, use a ValueKey on the Semantics widget and swap the label string when the warning changes — Flutter will re-announce when the key or label changes. Contrast validation: write a dart test that reads design token hex values and computes the W3C contrast ratio formula; fail the test if any pair is below 4.5:1.
This keeps contrast checks in CI rather than requiring manual audits.
Testing Requirements
Widget tests (flutter_test): assert SemanticsData.label for each chip in selected, unselected, and disabled states. Assert SemanticsData.hasFlag(SemanticsFlag.isEnabled) is false for disabled chips. Use tester.getSize() to verify touch targets ≥ 44×44. Integration accessibility test: call tester.ensureSemantics() and run SemanticsController.find() for each chip.
Manual test checklist: VoiceOver on iOS 17 Simulator and TalkBack on Android 14 Emulator — navigate all chips, trigger conflict, confirm announcement, resolve conflict, confirm dismissal announcement.
The image_picker Flutter plugin requires platform-specific permissions (NSPhotoLibraryUsageDescription, camera permission) and behaves differently across iOS and Android versions. Permission denial or plugin misconfiguration can silently prevent receipt attachment.
Mitigation & Contingency
Mitigation: Configure all required permission strings in Info.plist and AndroidManifest.xml during initial plugin setup. Use the permission_handler package to check and request permissions before launching the picker, with clear user-facing explanations. Test on both platforms across at least two OS versions.
Contingency: If image_picker proves unreliable on a specific platform version, fall back to file_picker as an alternative that uses the OS document picker interface, which requires fewer permissions on some Android versions.
The expense form BLoC manages interconnected state across expense type selection, field visibility, receipt requirement, threshold evaluation, and submission flow. Incorrect state transitions can cause UI inconsistencies such as required receipt indicator not updating after amount change, or form appearing valid when mutual exclusion is violated.
Mitigation & Contingency
Mitigation: Model BLoC states as sealed classes with exhaustive pattern matching. Write state transition unit tests covering every combination of: type selection change, amount field change above/below threshold, receipt attachment/removal, and offline mode toggle. Use bloc_test for comprehensive state sequence assertions.
Contingency: If BLoC complexity becomes unmanageable, split into two BLoCs — one for type selection/exclusion state and one for field values/submission — coordinating via a parent provider, accepting the small overhead of inter-BLoC communication.
The expense type selector must enforce mutual exclusion visually by disabling options and showing conflict tooltips, while remaining fully accessible to screen reader users who cannot perceive visual disable states. Incorrect semantics labelling will fail WCAG 2.2 AA requirements critical for Blindeforbundet and HLF users.
Mitigation & Contingency
Mitigation: Use Flutter Semantics widgets to explicitly set disabled state and provide conflict explanations as semanticLabel strings on disabled options. Run accessibility audits with TalkBack and VoiceOver during widget development, not post-completion. Reference the project's accessibility test harness for required test coverage.
Contingency: If custom widget accessibility is difficult to certify, implement the selector as a standard Flutter Radio/Checkbox group with built-in accessibility semantics and an explanatory Text widget below each conflicting option, sacrificing visual elegance for guaranteed WCAG compliance.