Implement focus management for wizard step transitions
epic-screen-reader-support-complex-widgets-task-004 — Within ActivityWizardStepSemantics, implement per-step focus management so that when the wizard advances to a new step, focus is programmatically placed on the step's primary input or heading. On step regression (back navigation), restore focus to the relevant field. Use FocusManagementService to manage FocusNode lifecycles and ensure no orphaned focus nodes leak across steps.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
Create FocusNodes in FocusManagementService.registerStep(stepIndex, primaryNodeKey) during the wizard's initState, not in build(). Use a Map
Before disposing, call FocusScope.of(context).unfocus() to cleanly release focus from the tree. For the back-navigation restoration: the popped step index from the history stack gives you the FocusNode to request. Important: on the Summary step, the 'primary focus target' is a Semantics widget with a heading role, not a TextField — use a FocusNode attached via Focus(focusNode: ..., child: Semantics(header: true, ...)).
Testing Requirements
Unit tests: verify FocusManagementService.registerStep() creates and returns a FocusNode; verify .disposeStep() calls FocusNode.dispose() and removes the node from the registry; verify .focusPrimaryNodeForStep(stepIndex) calls requestFocus on the correct node. Widget tests: mount the full 5-step wizard; simulate tapping 'Next' and assert that the primary input FocusNode of each step has hasFocus==true after transition. Simulate 'Back' and assert focus restoration. Memory test: step through all 5 steps and back, then check FocusManager.instance.debugGetActiveScopeChain() contains no wizard-owned nodes after the wizard is popped.
Run on flutter_test with semanticsEnabled: true. Coverage target: 85%.
Flutter does not natively enforce a focus trap within a bottom sheet or modal dialog in the semantic tree — VoiceOver and TalkBack can navigate outside the sheet to background content. Implementing a reliable focus trap requires overriding the semantic tree, which may conflict with the existing modal helper infrastructure in the app and require changes to shared components beyond this feature's scope.
Mitigation & Contingency
Mitigation: Prototype the focus trap on the first modal sheet implementation before building the remaining sheets. Evaluate Flutter's ExcludeSemantics and BlockSemantics widgets as the trap mechanism, and coordinate with the team owning the shared modal helpers to agree on a non-breaking integration point before writing production code.
Contingency: If a complete semantic focus trap cannot be implemented without breaking existing modal patterns, implement a partial solution using FocusScope with autofocus on the modal's first element and a prominent 'Return to main content' semantic action, documenting the deviation from WCAG 2.4.3 with a scheduled remediation item.
The activity wizard uses BLoC state management and the UI rebuilds the entire step widget subtree on transition. If the semantic tree is traversed by VoiceOver before the build cycle settles, focus may land on a stale or partially rendered step, causing the wrong step label or progress value to be announced. This is particularly problematic for blind users who cannot visually verify the announcement against the screen.
Mitigation & Contingency
Mitigation: Coordinate ActivityWizardStepSemantics with FocusManagementService (from the core services epic) to delay focus placement until the post-build callback confirms the new step's semantic tree is complete. Write integration tests using the AccessibilityTestHarness that assert the full announcement sequence across all five wizard steps.
Contingency: If post-build focus delay is insufficient due to async BLoC emission timing, add an explicit semantic notification barrier in the wizard cubit that emits a 'step ready' event only after the new widget tree has been marked as built, decoupling the announcement trigger from the raw state transition.
Automated WCAG contrast ratio checking on widget tree snapshots may produce false positives for gradient backgrounds, dark-mode overrides, or design token overrides that are resolved at runtime but appear as unresolvable colours at static analysis time. Excessive false positives would erode team trust in the CI gate, leading to suppression rules that also mask real violations.
Mitigation & Contingency
Mitigation: Scope the WCAGComplianceChecker to check only solid-colour backgrounds in the first iteration, explicitly excluding gradients from contrast checks with documented rationale. Design the check output to distinguish 'undetermined' (gradient/unknown) from 'fail' (solid colour below threshold) so the team can take targeted action on genuine failures only.
Contingency: If false positive rates exceed 20% of reported violations during initial CI runs, switch the CI gate from a hard build failure to a warning annotation on the pull request, combined with a mandatory manual review step, until the checker's rule set has been tuned to match actual design token values.