vnidrop/.codex/skills/compose-skill/references/accessibility.md

Accessibility

Content Descriptions

Every Image and Icon composable must have an explicit contentDescription:

• Decorative (no information conveyed): contentDescription = null
• Meaningful (conveys information): localized string via stringResource()

// Decorative — purely visual, screen reader skips it
Icon(Icons.Default.Star, contentDescription = null)

// Meaningful — screen reader announces it
Image(
    painter = painterResource(Res.drawable.profile_avatar),
    contentDescription = stringResource(Res.string.user_avatar_description)
)

Flag any Image with a non-obvious resource name and contentDescription = null that lacks a comment explaining why it is decorative.

Semantics API

Use Modifier.semantics { } to add or override accessibility information.

Property	Purpose	Example values
contentDescription	Override screen reader announcement	"Profile picture of $name"
role	Declare interactive role	Role.Button, Role.Image, Role.Switch, Role.Tab, Role.RadioButton, Role.Checkbox
stateDescription	Describe current state	"Expanded", "Selected", "3 of 5"
heading	Mark as section heading	heading()

Box(
    modifier = Modifier.semantics {
        contentDescription = "Profile picture of ${user.name}"
        role = Role.Image
    }
)

Prefer built-in Material components (Button, Switch, Checkbox) over manual role assignment — they include correct semantics automatically.

Grouping and Overriding Semantics

mergeDescendants

Groups a composable's children into a single screen reader announcement. Use when children together form one logical unit.

// GOOD — screen reader announces "4.5 stars, 128 reviews" as one item
Row(modifier = Modifier.semantics(mergeDescendants = true) { }) {
    Icon(Icons.Default.Star, contentDescription = null)
    Text("4.5 stars")
    Text("(128 reviews)")
}

// BAD — screen reader stops on each child separately, fragmenting the meaning
Row {
    Icon(Icons.Default.Star, contentDescription = "Star icon")
    Text("4.5 stars")
    Text("(128 reviews)")
}

clearAndSetSemantics

Replaces all auto-generated and child semantics with a single custom description. Use when the auto-generated text is verbose or misleading.

Row(modifier = Modifier.clearAndSetSemantics {
    contentDescription = "Rating: 4.5 stars from 128 reviews"
}) {
    StarRating(4.5f)
    Text("(128 reviews)")
}

Need	Use
Group children into one announcement, keep their text	semantics(mergeDescendants = true)
Replace all child semantics with a custom string	clearAndSetSemantics { }

Touch Targets

Minimum interactive size: 48 x 48 dp.

• Use Modifier.minimumInteractiveComponentSize() on custom interactive elements to enforce this automatically.
• Material components (Button, IconButton, Switch, etc.) handle this internally — do not add redundant padding.

// Custom clickable element — enforce minimum touch target
Box(
    modifier = Modifier
        .minimumInteractiveComponentSize()
        .clickable { onAction() }
) {
    Icon(Icons.Default.Add, contentDescription = "Add item")
}

Color and Contrast

WCAG AA minimum contrast ratios:

Text type	Minimum ratio
Normal text (<18sp)	4.5 : 1
Large text (18sp+ or 14sp bold+)	3 : 1

Never use color as the only way to convey information. Always pair with an icon, text label, or pattern.

// BAD — only color differentiates status
Box(modifier = Modifier.background(if (isOnline) Color.Green else Color.Red))

// GOOD — icon + text + color
Row {
    Icon(
        imageVector = if (isOnline) Icons.Default.CheckCircle else Icons.Default.Cancel,
        contentDescription = null,
    )
    Text(if (isOnline) "Online" else "Offline")
}

Use theme tokens (MaterialTheme.colorScheme) rather than hardcoded colors — theme tokens are designed to meet contrast requirements across light/dark modes.

Custom Interactive Elements

When using Modifier.clickable on a non-Button composable, add semantic role and click label:

Card(
    modifier = Modifier
        .clickable(onClickLabel = "Open book details") { onBookClick(book.id) }
        .semantics { role = Role.Button }
) {
    Text(book.title)
}

Prefer Button / IconButton / TextButton over custom clickable elements when possible — they include correct semantics, touch targets, and visual feedback out of the box.

Custom Accessibility Actions

For composables with multiple actions (e.g., a list item with favorite, share, delete), expose named accessibility actions so screen reader users can discover and invoke them without navigating to individual buttons:

Modifier.semantics {
    customActions = listOf(
        CustomAccessibilityAction("Add to favorites") { onFavorite(); true },
        CustomAccessibilityAction("Share") { onShare(); true },
    )
}

The lambda returns true if the action was handled successfully.

MVI Integration

Accessibility does not change the MVI architecture. Key placement rules:

Concern	Where	Why
Semantic descriptions (contentDescription, stateDescription)	Screen / Leaf composables	These are UI-layer concerns — resolve from state close to rendering
Semantic keys/enums for dynamic descriptions	State data class	e.g., statusLabel: StringKey — the UI resolves to a localized string
Modifier.semantics	Composable modifier chains	Applied in the UI layer, never in ViewModel
Accessibility-triggered actions (e.g., custom action callbacks)	onEvent callbacks → ViewModel	Same as any user interaction — goes through the event pipeline

Keep accessibility descriptions in the UI layer, not in state. State holds semantic keys (enums, string resource keys); the Screen/Leaf composable resolves them to localized strings via stringResource().

Do / Don't

Do

• Provide contentDescription for every meaningful Image and Icon
• Use mergeDescendants for logically grouped content
• Use clearAndSetSemantics when auto-generated text is misleading
• Enforce 48dp minimum touch targets on custom interactive elements
• Pair color with icons/text for status indicators
• Use MaterialTheme.colorScheme tokens for contrast-safe colors
• Test with a screen reader on each target platform

Don't

• Leave contentDescription = null on meaningful images without a comment
• Apply role manually when a Material component already provides it
• Add extra padding on Material components that already meet touch target requirements
• Rely on color alone to communicate state changes
• Put localized accessibility strings in ViewModel state — use semantic keys and resolve in UI
• Hardcode accessibility text — use stringResource() for localization