form-accessibility

What this skill does

# Form Accessibility

WCAG 2.2 AA compliance patterns for forms. Ensures forms work for keyboard users, screen reader users, and users with cognitive or motor disabilities.

## Quick Start

```tsx
// Accessible form field pattern
<div className="form-field">
  {/* 1. Visible label (never placeholder-only) */}
  <label htmlFor="email">
    Email
    <span className="required" aria-hidden="true">*</span>
  </label>
  
  {/* 2. Hint text (separate from label) */}
  <span id="email-hint" className="hint">
    We'll send your confirmation here
  </span>
  
  {/* 3. Input with full ARIA binding */}
  <input
    id="email"
    type="email"
    autoComplete="email"
    aria-required="true"
    aria-invalid={hasError}
    aria-describedby={hasError ? "email-error email-hint" : "email-hint"}
  />
  
  {/* 4. Error message (announced by screen readers) */}
  {hasError && (
    <span id="email-error" className="error" role="alert">
      Please enter a valid email address
    </span>
  )}
</div>
```

## WCAG 2.2 Form Requirements

### Critical Criteria

| Criterion | Level | Requirement | Implementation |
|-----------|-------|-------------|----------------|
| 1.3.1 Info & Relationships | A | Structure conveyed programmatically | `<label>`, `<fieldset>`, `aria-describedby` |
| 1.3.5 Identify Input Purpose | AA | Input purpose identifiable | `autocomplete` attributes |
| 2.1.1 Keyboard | A | All functionality via keyboard | Tab order, focus management |
| 2.4.6 Headings & Labels | AA | Labels describe purpose | Descriptive, visible labels |
| 2.4.11 Focus Not Obscured | AA | Focus not hidden by other content | Scroll behavior, sticky elements |
| 2.5.8 Target Size | AA | 24×24px minimum touch target | Button/input sizing |
| 3.3.1 Error Identification | A | Errors identified and described | `aria-invalid`, error messages |
| 3.3.2 Labels or Instructions | A | Labels provided | Visible labels, not just placeholders |
| 3.3.3 Error Suggestion | AA | Suggestions for fixing errors | Actionable error messages |
| 3.3.7 Redundant Entry | A | Don't re-ask for info already provided | Form state management |
| 3.3.8 Accessible Authentication | AA | No cognitive function tests | No CAPTCHAs requiring text recognition |

### New in WCAG 2.2 (October 2023)

**2.4.11 Focus Not Obscured (AA)**
```css
/* Ensure focus is never hidden by sticky headers */
.sticky-header {
  position: sticky;
  top: 0;
}

input:focus {
  /* Browser should scroll input into view above sticky elements */
  scroll-margin-top: 80px; /* Height of sticky header */
}
```

**2.5.8 Target Size (AA)**
```css
/* Minimum 24×24px touch targets */
button,
input[type="submit"],
input[type="checkbox"],
input[type="radio"] {
  min-width: 24px;
  min-height: 24px;
}

/* Better: 44×44px for comfortable touch */
.touch-friendly {
  min-width: 44px;
  min-height: 44px;
}
```

**3.3.7 Redundant Entry (A)**
```tsx
// ❌ BAD: Asking for email twice
<input name="email" />
<input name="confirmEmail" />

// ✅ GOOD: Ask once, show confirmation
<input name="email" />
<p>Confirmation will be sent to: {email}</p>
```

**3.3.8 Accessible Authentication (AA)**
```tsx
// ❌ BAD: CAPTCHA requiring text recognition
<img src="captcha.png" alt="Enter the text shown" />

// ✅ GOOD: Alternative verification methods
<button type="button" onClick={sendVerificationEmail}>
  Send verification code to email
</button>
```

## ARIA Patterns

### Error Message Binding

```tsx
// Pattern: aria-describedby links input to error
<input
  id="email"
  aria-invalid={hasError ? "true" : "false"}
  aria-describedby={hasError ? "email-error" : undefined}
/>

{hasError && (
  <span id="email-error" role="alert">
    {errorMessage}
  </span>
)}
```

### Multiple Descriptions

```tsx
// Pattern: Combine hint + error in aria-describedby
<input
  id="password"
  aria-describedby={[
    "password-hint",
    hasError && "password-error"
  ].filter(Boolean).join(" ")}
/>

<span id="password-hint">Must be at least 8 characters</span>
{hasError && <span id="password-error" role="alert">{error}</span>}
```

### Required Fields

```tsx
// Pattern: Announce required status
<label htmlFor="name">
  Name
  <span className="required" aria-hidden="true">*</span>
  {/* Visual indicator hidden from SR, aria-required announces it */}
</label>

<input
  id="name"
  aria-required="true"
/>

// Alternative: Required in label (simpler)
<label htmlFor="name">Name (required)</label>
<input id="name" required />
```

### Field Groups

```tsx
// Pattern: fieldset + legend for related fields
<fieldset>
  <legend>Shipping Address</legend>
  
  <label htmlFor="street">Street</label>
  <input id="street" autoComplete="street-address" />
  
  <label htmlFor="city">City</label>
  <input id="city" autoComplete="address-level2" />
</fieldset>
```

### Radio/Checkbox Groups

```tsx
// Pattern: fieldset groups options, legend is the question
<fieldset>
  <legend>Preferred contact method</legend>
  
  <label>
    <input type="radio" name="contact" value="email" />
    Email
  </label>
  
  <label>
    <input type="radio" name="contact" value="phone" />
    Phone
  </label>
</fieldset>
```

## Focus Management

### Focus on First Error

```tsx
// On form submit with errors, focus first invalid field
function handleSubmit(e: FormEvent) {
  e.preventDefault();
  
  const firstError = formRef.current?.querySelector('[aria-invalid="true"]');
  if (firstError) {
    (firstError as HTMLElement).focus();
    return;
  }
  
  // Submit if valid
  submitForm();
}
```

### Focus on Step Change (Multi-step)

```tsx
// Move focus to step heading when changing steps
function goToStep(stepNumber: number) {
  setCurrentStep(stepNumber);
  
  // Wait for render, then focus
  requestAnimationFrame(() => {
    const heading = document.getElementById(`step-${stepNumber}-heading`);
    heading?.focus();
  });
}

// Heading must be focusable
<h2 id="step-2-heading" tabIndex={-1}>Shipping Address</h2>
```

### Skip Links

```tsx
// Allow skipping to form
<a href="#main-form" className="skip-link">
  Skip to form
</a>

<form id="main-form">
  {/* Form content */}
</form>

// CSS for skip link
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  z-index: 100;
}

.skip-link:focus {
  top: 0;
}
```

### Focus Trap (Modals)

```tsx
// Keep focus within modal form
function FocusTrap({ children }) {
  const trapRef = useRef<HTMLDivElement>(null);
  
  useEffect(() => {
    const trap = trapRef.current;
    if (!trap) return;
    
    const focusableElements = trap.querySelectorAll(
      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
    );
    const firstElement = focusableElements[0] as HTMLElement;
    const lastElement = focusableElements[focusableElements.length - 1] as HTMLElement;
    
    function handleKeyDown(e: KeyboardEvent) {
      if (e.key !== 'Tab') return;
      
      if (e.shiftKey && document.activeElement === firstElement) {
        e.preventDefault();
        lastElement.focus();
      } else if (!e.shiftKey && document.activeElement === lastElement) {
        e.preventDefault();
        firstElement.focus();
      }
    }
    
    trap.addEventListener('keydown', handleKeyDown);
    firstElement?.focus();
    
    return () => trap.removeEventListener('keydown', handleKeyDown);
  }, []);
  
  return <div ref={trapRef}>{children}</div>;
}
```

## Color & Contrast

### Error States (Colorblind-Safe)

```css
/* ❌ BAD: Color only */
.error {
  border-color: red;
}

/* ✅ GOOD: Color + icon + text */
.field-error {
  border-color: #dc2626;
  border-width: 2px;
}

.field-error::after {
  content: "";
  background-image: url("data:image/svg+xml,..."); /* Error icon */
}

.error-message {
  color: #dc2626;
  font-weight: 500;
}

.error-message::before {
  content: "⚠ "; /* Text indicator */
}
```

### Focus Indicators

```css
/* Focus must have 3:1 contrast ratio */
input:focus {
  outline: 2px solid #2563eb;
  outline-offset: 2px;
}

/* For dark backgrounds */
input:foc