Token Accessibility Enforcer
Component Detail
Description
Runtime service that applies non-overridable accessibility constraints from the design token layer when building the Flutter theme. Rejects any attempt to compose a color pair, text style, or sizing token that would violate WCAG 2.2 AA, throwing an assertion in debug mode and logging a warning in release builds.
token-accessibility-enforcer
Summaries
The Token Accessibility Enforcer directly protects the organization from accessibility-related legal liability and app store rejection by making WCAG 2.2 AA compliance physically impossible to bypass at the code level. Rather than relying on manual reviews or developer discipline, this component automatically rejects any color pair, text style, or touch target that would fail accessibility standards before it can reach users. This proactive enforcement reduces remediation costs, which historically run 10–100x higher when accessibility defects are caught post-launch. It also broadens the addressable market by ensuring the application is usable by people with visual or motor impairments — a segment that represents over 15% of the global population.
The result is a product that meets enterprise accessibility procurement requirements and signals a strong organizational commitment to inclusive design.
The Token Accessibility Enforcer is a medium-complexity service that integrates into the Flutter theme-building layer and runs at application startup and during widget composition. It has a hard dependency on both the contrast-ratio-validator and design-token-provider, meaning those two components must be stable before enforcement logic can be finalized and tested. Development effort is moderate — the core enforcement logic is straightforward, but thorough edge-case testing is required across light and dark mode palettes and across all semantic token roles. The component introduces a risk of false-positive assertion failures during debug builds if token pairs are not pre-validated, which could temporarily slow feature development.
Mitigation involves coordinating token validation with the CI lint runner early in the sprint. Deployment is mobile-only and requires no backend changes, but QA must include accessibility-specific test passes on both Android and iOS.
Token Accessibility Enforcer is a stateless runtime service operating in the mobile execution context. It intercepts theme composition calls and applies hard enforcement rules derived from WCAG 2.2 AA thresholds. The `enforceContrastPair(Color fg, Color bg) → Color` method delegates ratio computation to the contrast-ratio-validator dependency and throws an AssertionError in debug mode or emits a structured warning in release builds via `reportViolation(AccessibilityViolation)`. `enforceFontWeight(TextStyle, TextRole)` gates body-role styles against a minimum weight of w400, and `enforceTouchTarget(Size) → Size` clamps values to a minimum 44pt footprint.
`setStrictMode(bool)` controls whether violations hard-crash (debug default) or warn-and-continue (release default). The design-token-provider dependency supplies token keys and typed constants; this component never reads raw values directly. Engineers extending the token system must register new token roles through the enforcement layer to maintain coverage.
Responsibilities
- Block color compositions that violate contrast thresholds
- Reject text styles with font weight below w400 for body roles
- Enforce minimum sizing tokens for touch targets
- Log accessibility violations with token path and computed ratio
Interfaces
enforceContrastPair(Color fg, Color bg) → Color
enforceFontWeight(TextStyle style, TextRole role) → TextStyle
enforceTouchTarget(Size size) → Size
reportViolation(AccessibilityViolation violation)
isEnforcementActive() → bool
setStrictMode(bool strict)
Relationships
Dependencies (2)
Components this component depends on
Related Data Entities (1)
Data entities managed by this component