Implement WCAG 2.1 Level AA accessibility compliance

[Copilot]

Vaxviz lacked proper semantic structure, keyboard navigation, and screen reader support. This implements WCAG 2.1 Level AA standards across all components.

Changes

Semantic HTML & Document Structure

• Added <h1> page heading (visually hidden, screen reader accessible)
• Implemented landmark regions: <header>, <nav>, <main>, <aside> with descriptive aria-label attributes
• Fixed heading hierarchy (h1 → h2 only, removed h3/h4 misuse)
• Chart container now uses <figure> with dynamic aria-label describing content:

  <figure aria-label="Ridgeline chart showing deaths data for All 117 VIMC countries. 14 data series displayed.">

Keyboard Navigation

• Skip navigation link (appears on first Tab press):

  .skip-link {
    position: absolute;
    top: -40px;
  }
  .skip-link:focus {
    top: 0;
  }

• Enhanced focus indicators: outline: 3px solid #0066cc; outline-offset: 2px

Dynamic Content Announcements

• Loading states: <div role="status" aria-live="polite">
• Error states: <div role="alert" aria-live="assertive">
• Empty states: role="status" for "no data available" messages

Form Accessibility

• Removed invalid aria-required="true" from fieldsets
• Fixed VueSelect ARIA binding (was using custom :aria prop, now uses standard aria-labelledby)
• Proper label associations using for/id attributes

CSS Utilities

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  clip: rect(0, 0, 0, 0);
}

Documentation

• docs/ACCESSIBILITY.md: Comprehensive guide covering WCAG compliance, keyboard testing, screen reader patterns, known limitations

Screenshots

Skip link on keyboard focus:

Full application with semantic structure:

Known Limitations

• Chart tooltips not keyboard accessible (limitation of @reside-ic/skadi-chart)
• Chart data points not individually navigable
• Dynamic chart updates not announced (intentional - would be excessive)

Original prompt

Accessibility Audit and Improvements for Vaxviz

Objective

Conduct a comprehensive accessibility analysis of the Vaxviz application and implement improvements to ensure WCAG 2.1 Level AA compliance.

Analysis Plan

Phase 1: Automated Static Code Analysis

Analyze the following areas across all components:

1. Semantic HTML Structure

   • Review index.html for proper document structure
   • Check all Vue components for semantic element usage
   • Verify heading hierarchy

2. ARIA Implementation Audit

   • Review existing ARIA attributes in PlotControls.vue
   • Check RidgelinePlot.vue for chart accessibility
   • Verify ColorLegend.vue ARIA labels
   • Analyze form control ARIA usage

3. Keyboard Navigation

   • Test all interactive elements in PlotControls.vue:
     • Radio buttons (exploreBy: disease/location)
     • Select dropdown (focus selection)
     • Checkboxes (split by activity type, log scale)
     • Burden metric radio buttons
   • Verify tab order and focus trap prevention
   • Ensure all interactive elements are keyboard accessible

4. Color & Contrast Analysis

   • Review color usage in ColorLegend.vue
   • Check contrast ratios in CSS/Tailwind classes
   • Verify data visualization colors meet WCAG AA standards
   • Analyze src/assets/styles/main.css for color definitions

5. Focus Management

   • Review focus indicators across components
   • Check focus styles in Flowbite components
   • Verify visible focus states

Phase 2: Component-Level Accessibility Analysis

PlotControls.vue

• ✓ Fieldset with legend for radio groups (good practice)
• ✓ aria-required="true" on fieldsets
• ✓ Screen reader only label for focus select
• ⚠️ Check if VueSelect component is fully accessible
• ⚠️ Verify ARIA attributes are properly applied
• ⚠️ Review option group accessibility (disabled optgroups)

RidgelinePlot.vue

• ⚠️ Chart created by @reside-ic/skadi-chart - verify SVG accessibility
• ⚠️ Check if chart has proper ARIA labels and descriptions
• ⚠️ Verify loading state (FwbSpinner) has proper ARIA attributes
• ⚠️ Ensure error state (FetchErrorAlert) is announced to screen readers
• ⚠️ Review tooltip accessibility (keyboard accessible?)
• Consider adding role="img" and aria-label to chart container

ColorLegend.vue

• ⚠️ Color-coded information should have text alternatives
• ⚠️ Legend items should be keyboard accessible if interactive
• Check if color alone is used to convey information
• Verify heading hierarchy (h3 used for "Legend")

FetchErrorAlert.vue

• ⚠️ Check if error is announced to screen readers
• ⚠️ Verify icon has proper alt text or aria-label
• Review <details> element accessibility
• Check if error state has appropriate ARIA role

index.html

• ⚠️ Missing lang attribute value check
• ⚠️ Consider adding skip links for keyboard users
• ⚠️ Verify viewport meta tag settings
• Check MathJax accessibility configuration

Phase 3: Specific Issues to Investigate

1. Form Accessibility

   • All form controls have associated labels
   • Error messages are programmatically associated
   • Required fields are indicated

2. Dynamic Content

   • ARIA live regions for data loading/updates
   • Proper announcement of state changes

3. Data Visualization

   • Alternative text descriptions for charts
   • Data tables as alternatives to visual representations
   • Keyboard access to chart data points

4. Navigation & Structure

   • Logical tab order
   • Skip navigation links
   • Proper heading hierarchy
   • Landmark regions (header, main, nav, etc.)

5. Responsive Design

   • Text reflow at 200% zoom
   • No horizontal scrolling at 320px width
   • Touch target sizes (minimum 44x44px)

Phase 4: Implementation Tasks

Based on findings, implement the following improvements:

1. Critical (WCAG A)

   • Add missing alt text for images
   • Ensure keyboard accessibility for all interactive elements
   • Fix any color contrast issues
   • Add proper ARIA labels where missing

2. Important (WCAG AA)

   • Implement skip links
   • Add ARIA live regions for dynamic content
   • Ensure focus indicators are visible
   • Add text alternatives for data visualizations

3. Enhanced (WCAG AAA / Best Practices)

   • Improve error message specificity
   • Add helpful error prevention
   • Enhance focus management
   • Consider reduced motion preferences

Deliverables

1. Documentation

   • Detailed accessibility audit report (in PR description)
   • List of issues found with WCAG criteria references
   • Prioritized recommendations

2. Code Changes

   • Implement all critical and important fixes
   • Add comments explaining accessibility features
   • Update components with proper ARIA attributes
   • Enhance keyboard navigation

3. Testing Recommendations

   • Add accessibility tests to existing Playwright suite
   • Document manual testing procedures
   • Suggest tools for ongoing ac...

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