Compose Multiplatform Accessibility: A Comprehensive Guide

Accessibility is a crucial aspect of modern application development. Ensuring that your application is usable by people with disabilities not only broadens your audience but also enhances the overall user experience. Jetpack Compose, with its declarative UI paradigm, offers powerful tools to build accessible applications across multiple platforms.

Why Accessibility Matters

Accessibility involves designing and developing applications that are usable by people with disabilities. This includes visual, auditory, motor, and cognitive impairments. Making your app accessible ensures inclusivity and can also improve usability for all users, regardless of ability.

Compose Multiplatform and Accessibility

Compose Multiplatform extends the Jetpack Compose framework to enable building UIs for various platforms, including Android, iOS, desktop, and web, from a single codebase. Achieving accessibility across these platforms requires a unified approach and careful consideration of platform-specific accessibility features.

Accessibility Features in Jetpack Compose

Jetpack Compose provides several key features that facilitate accessibility:

• Semantic Properties: Allows you to convey the meaning of UI elements to accessibility services.
• Modifiers: Enables setting accessibility properties such as labels, roles, and state descriptions.
• Testing Tools: Offers utilities for testing and verifying the accessibility of your UI.

How to Implement Accessibility in Compose Multiplatform

Step 1: Set Up Your Compose Multiplatform Project

First, ensure you have a Compose Multiplatform project set up. This typically involves configuring your build.gradle.kts file to include necessary dependencies and plugins for multiple platforms.

plugins {
    kotlin("multiplatform") version "1.9.0"
    id("org.jetbrains.compose") version "1.5.1"
}

kotlin {
    jvm()
    iosX64()
    iosArm64()
    iosSimulatorArm64()

    sourceSets {
        val commonMain by getting {
            dependencies {
                implementation(compose.runtime)
                implementation(compose.foundation)
                implementation(compose.ui)
            }
        }
        val androidMain by getting {
            dependencies {
                implementation("androidx.appcompat:appcompat:1.6.1")
                implementation("androidx.core:core-ktx:1.12.0")
                implementation(compose.uiToolingPreview)
                debugImplementation(compose.uiTooling)
            }
        }
        val iosX64Main by getting
        val iosArm64Main by getting
        val iosSimulatorArm64Main by getting
        val iosMain by getting {
            dependsOn(commonMain)
        }
    }
}

android {
    namespace = "org.example.myproject"
    compileSdk = 34
    defaultConfig {
        minSdk = 24
        targetSdk = 34
    }
    buildFeatures {
        compose = true
    }
    composeOptions {
        kotlinCompilerExtensionVersion = "1.5.1"
    }
}

Step 2: Using Semantic Properties

Semantic properties help convey the meaning of UI elements to accessibility services, such as screen readers. These properties are set using the semantics modifier.

import androidx.compose.ui.semantics.*
import androidx.compose.ui.Modifier

@Composable
fun AccessibleButton(
    onClick: () -> Unit,
    text: String,
    modifier: Modifier = Modifier
) {
    Button(
        onClick = onClick,
        modifier = modifier.semantics {
            role = Role.Button
            contentDescription = text // Set the accessible label
            onClick(actionLabel = "Click $text") {
                onClick()
                true
            }
        }
    ) {
        Text(text = text)
    }
}

In this example:

• role = Role.Button indicates that the element is a button.
• contentDescription = text provides a text label for screen readers.
• onClick with actionLabel specifies the action that the button performs, improving the user experience for those using screen readers.

Step 3: Customizing Accessibility Actions

You can define custom accessibility actions using the customActions semantic property. This is particularly useful for complex components or interactions.

import androidx.compose.ui.semantics.*
import androidx.compose.ui.Modifier

@Composable
fun VolumeControl(
    volume: Float,
    onVolumeChange: (Float) -> Unit,
    modifier: Modifier = Modifier
) {
    Column(
        modifier = modifier.semantics {
            contentDescription = "Volume Control"
            customActions = listOf(
                AccessibilityAction("Increase Volume") {
                    onVolumeChange(volume + 0.1f)
                    true
                },
                AccessibilityAction("Decrease Volume") {
                    onVolumeChange(volume - 0.1f)
                    true
                }
            )
        }
    ) {
        Text("Volume: ${volume * 100}%")
        Slider(value = volume, onValueChange = onVolumeChange)
    }
}

Here, we provide custom actions to increase or decrease the volume, making it easier for users to control the volume via accessibility services.

Step 4: Managing Focus

Managing focus is critical for keyboard navigation and screen reader usability. Ensure that focus order is logical and predictable. Use the focusRequester and focusable modifiers to control focus behavior.

import androidx.compose.ui.focus.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.ExperimentalComposeUiApi

@OptIn(ExperimentalComposeUiApi::class)
@Composable
fun FocusableInputs() {
    val focusRequester1 = remember { FocusRequester() }
    val focusRequester2 = remember { FocusRequester() }

    Column {
        TextField(
            value = "",
            onValueChange = {},
            modifier = Modifier
                .focusRequester(focusRequester1)
                .focusable()
        )
        Button(
            onClick = { focusRequester2.requestFocus() },
            modifier = Modifier.padding(8.dp)
        ) {
            Text("Focus Next")
        }
        TextField(
            value = "",
            onValueChange = {},
            modifier = Modifier
                .focusRequester(focusRequester2)
                .focusable()
        )
    }

    LaunchedEffect(Unit) {
        focusRequester1.requestFocus()
    }
}

In this example, we use FocusRequester to programmatically manage focus between text fields, enhancing keyboard navigation.

Step 5: Handling Platform-Specific Accessibility

While Compose Multiplatform aims to provide a unified UI layer, platform-specific accessibility features may require additional handling. For instance, iOS and Android have different accessibility APIs, so you might need to write platform-specific code to fully leverage their capabilities.

For example, to ensure proper content labeling on iOS using VoiceOver, you may utilize the platformSpecific modifier block:

import androidx.compose.ui.platform.LocalView
import androidx.compose.ui.Modifier

@Composable
fun AccessibleText(text: String, modifier: Modifier = Modifier) {
    val view = LocalView.current
    Text(
        text = text,
        modifier = modifier.platformSpecific {
            if (view.context is CocoaViewConfiguration) {
                semantics {
                    contentDescription = text
                }
            }
        }
    )
}

Step 6: Testing for Accessibility

Regular testing is vital to ensure the accessibility of your Compose Multiplatform application. Utilize accessibility testing tools available on each platform, such as:

• Android: Accessibility Scanner, TalkBack.
• iOS: VoiceOver.
• Web: Accessibility Insights, WAVE.

Additionally, Compose provides ComposeTestRule and other testing APIs to programmatically verify accessibility properties.

Best Practices for Compose Multiplatform Accessibility

• Provide Clear Labels: Always use meaningful content descriptions and labels.
• Ensure Sufficient Contrast: Maintain adequate contrast ratios between text and background colors.
• Support Keyboard Navigation: Make sure users can navigate all interactive elements using the keyboard.
• Test on Real Devices: Test your application with actual accessibility tools and users.
• Stay Updated: Keep up with the latest accessibility guidelines and best practices.

Conclusion

Accessibility in Compose Multiplatform is an essential consideration for building inclusive applications. By leveraging semantic properties, managing focus, and addressing platform-specific requirements, you can create UIs that are usable by everyone. Regularly test your application with accessibility tools and users to ensure a high level of accessibility across all platforms. Investing in accessibility not only broadens your audience but also enhances the overall user experience, making your application more valuable and user-friendly.