Kotlin Multiplatform library for Skia and window management

Skiko (short for Skia for Kotlin) is the graphical library exposing significant part of Skia library APIs to Kotlin, along with the gluing code for rendering context.

Supported platforms:

• Kotlin/JVM on Linux(x86_64 and arm64)
• Kotlin/JVM on Windows(x86_64)
• Kotlin/JVM on macOS(x86_64 and arm64)
• Kotlin/JVM on Android(x86_64 and arm64), starting with API version 24
• Kotlin/JS + WebAssembly in browsers
• Kotlin/Native on iOS(arm64 and x64)
• Kotlin/Native on macOS (arm64 and x64)

API documentation

See autogenerated API docs at https://jetbrains.github.io/skiko/

Using as dependency

To use in build scripts one has to compute appropriate target platform and version, i.e. something like this

    repositories {
        mavenCentral()
        maven("https://redirector.kotlinlang.org/maven/compose-dev")
    }

    val osName = System.getProperty("os.name")
    val targetOs = when {
        osName == "Mac OS X" -> "macos"
        osName.startsWith("Win") -> "windows"
        osName.startsWith("Linux") -> "linux"
        else -> error("Unsupported OS: $osName")
    }

    val osArch = System.getProperty("os.arch")
    val targetArch = when (osArch) {
        "x86_64", "amd64" -> "x64"
        "aarch64" -> "arm64"
        else -> error("Unsupported arch: $osArch")
    }

    val version = "0.8.9" // or any more recent version
    val target = "${targetOs}-${targetArch}"
    dependencies {
        implementation("org.jetbrains.skiko:skiko-awt-runtime-$target:$version")
    }

Simple example for Kotlin/JVM

fun main() {
    val skiaLayer = SkiaLayer()
    skiaLayer.renderDelegate = SkiaLayerRenderDelegate(skiaLayer, object : SkikoRenderDelegate {
        val paint = Paint().apply {
            color = Color.RED
        }
        override fun onRender(canvas: Canvas, width: Int, height: Int, nanoTime: Long) {
            canvas.clear(Color.CYAN)
            val ts = nanoTime / 5_000_000
            canvas.drawCircle( (ts % width).toFloat(), (ts % height).toFloat(), 20f, paint )
        }
    })
    SwingUtilities.invokeLater {
        val window = JFrame("Skiko example").apply {
            defaultCloseOperation = WindowConstants.EXIT_ON_CLOSE
            preferredSize = Dimension(800, 600)
        }
        skiaLayer.attachTo(window.contentPane)
        skiaLayer.needRedraw()
        window.pack()
        window.isVisible = true
    }
}

Simple example for iOS

fun main() {
    val args = emptyArray<String>()
    memScoped {
        val argc = args.size + 1
        val argv = (arrayOf("skikoApp") + args).map { it.cstr.ptr }.toCValues()
        autoreleasepool {
            UIApplicationMain(argc, argv, null, NSStringFromClass(SkikoAppDelegate))
        }
    }
}

class SkikoAppDelegate : UIResponder, UIApplicationDelegateProtocol {
    companion object : UIResponderMeta(), UIApplicationDelegateProtocolMeta

    @ObjCObjectBase.OverrideInit
    constructor() : super()

    private var _window: UIWindow? = null
    override fun window() = _window
    override fun setWindow(window: UIWindow?) {
        _window = window
    }

    override fun application(application: UIApplication, didFinishLaunchingWithOptions: Map<Any?, *>?): Boolean {
        window = UIWindow(frame = UIScreen.mainScreen.bounds)
        window!!.rootViewController = SkikoViewController(
            SkikoUIView(
                SkiaLayer().apply {
                    renderDelegate = SkiaLayerRenderDelegate(skiaLayer, object : SkikoRenderDelegate {
                      val paint = Paint().apply { color = Color.RED }
                      override fun onRender(canvas: Canvas, width: Int, height: Int, nanoTime: Long) {
                        canvas.clear(Color.CYAN)
                        val ts = nanoTime / 5_000_000
                        canvas.drawCircle( (ts % width).toFloat(), (ts % height).toFloat(), 20f, paint )
                      }
                    })
                }
            )
        )
        window!!.makeKeyAndVisible()
        return true
    }
}

See this sample for complete example.