A Kotlin Multiplatform port of the HarfBuzz text-shaping library, packaged as two first-class artifacts:

• harfbuzz-core - pure Kotlin bindings over HarfBuzz. Headless shaping, font introspection, OpenType feature control, glyph metrics, glyph outline extraction, COLR v0/v1 paint trees, SVG-in-OT documents. No Compose dependency.
• harfbuzz-compose - Compose Multiplatform layer on top of harfbuzz-core. ArcText, ShapedText, MeasuredText, DrawScope.drawShapedText, rememberHbFont. Renders monochrome glyphs, COLR v0 layered colors, COLR v1 paint trees (gradients, transforms, composite layers), and SVG-in-OT - picking the highest-fidelity path the font supplies.

Compose's built-in text stack has known limitations rendering Arabic - cursive joining, tashkeel positioning, ligatures (لا LAM-ALEF, joined letterforms, mark stacks), bidi mixing with Latin/digits, OpenType feature control. It also can't render color fonts at all on most targets - no emoji, no inked Arabic, no flag glyphs. This library exposes HarfBuzz directly to KMP/Compose so:

• Arabic renders correctly out of the box.
• Color fonts render with their designed gradients, paint trees, and SVG artwork - same fidelity as hb-view and Google Fonts.
• Effects the built-in APIs don't support (arc text, path text, precise measurements) become available.

• Android (minSdk 24)
• iOS (iosArm64 + iosSimulatorArm64)
• Desktop JVM (Linux x86_64, macOS aarch64/x86_64, Windows x86_64)
• Web (Wasm-JS)

Snapshots of 0.1.0-SNAPSHOT are published to the Sonatype snapshots repo on every push to main. A first stable 0.1.0 release will follow once the API surface is locked.

// build.gradle.kts
dependencies {
    implementation("com.mohamedrejeb.harfbuzz:harfbuzz-core:0.1.0-SNAPSHOT")
    implementation("com.mohamedrejeb.harfbuzz:harfbuzz-compose:0.1.0-SNAPSHOT")
}

repositories {
    // for snapshots; remove once a stable release is published
    maven("https://central.sonatype.com/repository/maven-snapshots/")
}

@Composable
fun ArabicSample() {
    val state by rememberHbFont(
        bytesProvider = { Res.readBytes("font/NotoNaskhArabic-Regular.ttf") },
    )
    when (val s = state) {
        FontLoad.Loading   -> CircularProgressIndicator()
        is FontLoad.Failed -> Text("Failed: ${s.cause.message}")
        is FontLoad.Ready  -> ShapedText(
            text = "نَصٌّ عَرَبِيٌّ مُشَكَّلٌ لِلْاِخْتِبَارِ",
            font = s.font,
            sizePx = 32f,
            features = listOf(HbFeature("liga"), HbFeature("calt"), HbFeature("rlig")),
        )
    }
}

val state by rememberHbFont(
    bytesProvider = { Res.readBytes("font/NotoColorEmoji-Regular.ttf") },
)
(state as? FontLoad.Ready)?.let {
    ShapedText("😀🌍🎉⭐", font = it.font, sizePx = 64f)
}

drawShapedText automatically picks the best render path the face supplies, in priority order:

1. forceForegroundColor - every glyph paints with the caller's color only. Bypasses every color path.
2. SVG-in-OT bitmap - highest fidelity for fonts that ship hand-tuned SVG (Aref Ruqaa Ink, Noto Color Emoji, …). Skipped on Android (no skiko's SVGDOM available there); the COLR fallback covers it.
3. COLR v1 paint tree - gradients, transforms, composite layers.
4. COLR v0 layer stack - palette-colored layered glyphs.
5. Monochrome - fall-through.

See docs/guides/color-glyphs.md for a deeper walk through what each table looks like and how the renderer chooses.

ArcText(
    text = "نص عربي تجريبي للاختبار",
    font = arabicFont,
    sizePx = 32f,
    radius = 120.dp,
    sweep = ArcSweep.Auto,
    color = MaterialTheme.colorScheme.primary,
)

Paint specific characters or character ranges with different colors or brushes inside a single ShapedText / ShapedParagraphText, without disturbing shaping. The shape pass runs once - per-glyph paint is resolved at draw time via a cluster-position heuristic so an Arabic base letter and its combining mark inside the same HarfBuzz cluster can each take a different color.

@Composable
fun TashkeelSample() {
    val state by rememberHbFont(
        bytesProvider = { Res.readBytes("font/NotoNaskhArabic-Regular.ttf") },
    )
    val font = (state as? FontLoad.Ready)?.font ?: return

    val styled = StyledText("بِسْمِ اللَّهِ الرَّحْمَٰنِ الرَّحِيمِ")
        .withTashkeelColor(Color.Red)

    ShapedText(
        text = styled,
        font = font,
        sizePx = 36f,
        color = Color.Black,    // default for un-spanned chars
    )
}

For more general styling (multi-color phrases, gradient-painted words, etc.) build a StyledText with the DSL:

val styled = buildStyledText {
    append("Hello ", SpanStyle(color = Color.Red))
    append("World", SpanStyle(brush = Brush.linearGradient(listOf(Color.Magenta, Color.Cyan))))
}
ShapedText(text = styled, font = font, sizePx = 32f, color = Color.Black)

harfbuzz-compose depends on harfbuzz-core. The core has zero Compose dependencies - server-side and CLI consumers can use it for headless shaping.

Native bindings:

HarfBuzz pinned at 14.2.0.

• docs/guides/arabic.md - Arabic cookbook (BiDi, OT features, common fonts, caveats).
• docs/guides/color-glyphs.md - Color font cookbook (COLR v0/v1, SVG-in-OT, render priority, platform support).
• docs/guides/arc-text.md - Arc-text cookbook.
• docs/guides/perf.md - Performance and zero-copy contracts at platform boundaries.

./gradlew :harfbuzz-core:jvmTest          # 18 core tests + Arabic gate
./gradlew :sample:jvmTest                 # 44 screenshot tests covering
                                          # paint, SVG, emoji, Arabic, …
./gradlew :sample:run                     # Desktop demo
./gradlew :sample:wasmJsBrowserDevelopmentRun   # Browser demo
./gradlew :harfbuzz-core:assembleRelease  # Android AAR

For the Wasm target, the committed native/harfbuzzjs/hb.{js,wasm} are known-good builds that work without Emscripten installed. To rebuild after touching config-override.h, hb.symbols, or the HarfBuzz submodule:

./gradlew :harfbuzz-core:buildHarfBuzzJs   # requires `em++` (emsdk) on PATH

The first full build pulls Gradle, the Kotlin/Native distribution, and (on macOS) runs Xcode's CMake plumbing to cross-compile HarfBuzz for iOS - typical clean build is ~5 min the first time, ~10 s on incremental.

Apache 2.0. HarfBuzz itself is under the Old MIT license, which is compatible.