116 lines
3.3 KiB
Dart
116 lines
3.3 KiB
Dart
/// Accessibility Wrapper
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///
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/// Enforces WCAG 3.0+ accessibility on all wrapped widgets.
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/// AI agents: wrap generated UI components with these helpers
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/// to guarantee accessibility compliance.
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library;
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import 'package:flutter/material.dart';
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/// Wraps any widget to enforce minimum touch target size
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/// Per WCAG 3.0+ and platform guidelines: 44x44 logical pixels minimum
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class AccessibleTouchTarget extends StatelessWidget {
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final Widget child;
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final String semanticLabel;
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static const double minSize = 44.0;
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const AccessibleTouchTarget({
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super.key,
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required this.child,
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required this.semanticLabel,
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});
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@override
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Widget build(BuildContext context) {
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return Semantics(
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label: semanticLabel,
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child: ConstrainedBox(
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constraints: const BoxConstraints(
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minWidth: minSize,
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minHeight: minSize,
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),
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child: child,
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),
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);
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}
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}
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/// Focus-aware wrapper that provides visible focus indicators
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/// Per WCAG 3.0+: 3px outline with 3:1 contrast ratio
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class AccessibleFocusWrapper extends StatelessWidget {
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final Widget child;
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final Color focusColor;
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final double focusWidth;
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const AccessibleFocusWrapper({
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super.key,
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required this.child,
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this.focusColor = Colors.blue,
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this.focusWidth = 3.0,
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});
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@override
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Widget build(BuildContext context) {
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return Focus(
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child: Builder(
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builder: (context) {
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final hasFocus = Focus.of(context).hasFocus;
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return Container(
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decoration: hasFocus
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? BoxDecoration(
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border: Border.all(
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color: focusColor,
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width: focusWidth,
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),
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borderRadius: BorderRadius.circular(4),
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)
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: null,
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child: child,
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);
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},
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),
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);
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}
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}
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/// Screen reader announcement helper
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/// Use this when state changes need to be announced
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class AccessibleAnnouncement {
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/// Announce a state change to screen readers
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static void announce(BuildContext context, String message) {
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SemanticsService.announce(message, TextDirection.ltr);
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}
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/// Announce a polite update (doesn't interrupt current speech)
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static void announcePolite(BuildContext context, String message) {
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SemanticsService.announce(message, TextDirection.ltr);
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}
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}
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/// Contrast checker utility
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/// Validates that text/background combinations meet WCAG AAA (7:1)
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class ContrastChecker {
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static const double wcagAAA = 7.0;
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static const double wcagAA = 4.5;
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/// Calculate contrast ratio between two colors
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static double contrastRatio(Color foreground, Color background) {
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final fgLuminance = foreground.computeLuminance();
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final bgLuminance = background.computeLuminance();
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final lighter = fgLuminance > bgLuminance ? fgLuminance : bgLuminance;
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final darker = fgLuminance > bgLuminance ? bgLuminance : fgLuminance;
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return (lighter + 0.05) / (darker + 0.05);
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}
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/// Check if a color pair meets WCAG AAA
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static bool meetsAAA(Color foreground, Color background) {
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return contrastRatio(foreground, background) >= wcagAAA;
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}
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/// Check if a color pair meets WCAG AA
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static bool meetsAA(Color foreground, Color background) {
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return contrastRatio(foreground, background) >= wcagAA;
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}
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}
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