Pressure, tilt and source on Wacom tablets, Surface Pen and Apple Pencil sidecar — same Compose API on every OS.

Drawing apps need more than (x, y). The Tao backend forwards pressure, tilt and pointer source — Wacom, Surface Pen, Apple Pencil over Sidecar — into Compose pointer events. Same API on every OS.

TL;DR

PointerInputChange.type == PointerType.Stylus identifies pen input.
PointerInputChange.pressure is normalised to [0f, 1f].
Tilt and rotation arrive via PointerInputChange.orientation when the device supports it.
Wacom (USB/Bluetooth), Microsoft Surface Pen and Apple Pencil via macOS Sidecar all surface through the same event stream.
PointerType.Eraser reports the eraser end of supported pens.

Quickstart

import androidx.compose.foundation.Canvas
import androidx.compose.foundation.gestures.*
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.drawscope.Stroke
import androidx.compose.ui.input.pointer.*
import androidx.compose.ui.unit.dp

@Composable
fun InkSurface() {
    val strokes = remember { mutableStateListOf<Triple<Offset, Offset, Float>>() }
    var last: Offset? by remember { mutableStateOf(null) }

    Canvas(
        Modifier
            .fillMaxSize()
            .pointerInput(Unit) {
                awaitPointerEventScope {
                    while (true) {
                        val event = awaitPointerEvent()
                        val c = event.changes.first()
                        if (c.type != PointerType.Stylus) { last = null; continue }
                        val start = last ?: c.position
                        strokes += Triple(start, c.position, c.pressure)
                        last = if (c.pressed) c.position else null
                        c.consume()
                    }
                }
            }
    ) {
        strokes.forEach { (a, b, p) ->
            drawLine(Color.Black, a, b, strokeWidth = (1f + p * 6f))
        }
    }
}

Tao taps each OS's native pen API: NSEvent.pressure and tangentialPressure on macOS, WM_POINTER with POINTER_PEN_INFO on Windows, and the wp_tablet_v2 Wayland protocol on Linux. The Rust JNI bridge normalises pressure to [0f, 1f], sets PointerType.Stylus (or PointerType.Eraser) on the change, and dispatches through Compose's input pipeline.

Tilt and orientation come through PointerInputChange.orientation when the device exposes them. Wacom Intuos and Surface Pro pens report both; entry-level tablets often report pressure only.

Apple Pencil reaches Compose two ways: when the host is a macOS Mac with Sidecar, pen events arrive from the iPad as PointerType.Stylus with pressure. When the host is iOS proper, you'd run on a different Compose target — Tao is desktop-only.

Reference

Stylus-aware event reading

val change = event.changes.first()
val source: PointerType = change.type          // Stylus | Eraser | Touch | Mouse
val pressure: Float = change.pressure          // 0f if unsupported
val tilt = change.orientation                  // optional, device-dependent

Supported devices (verified)

Device	Pressure	Tilt	Notes
Wacom Intuos / Cintiq	Yes	Yes	USB and Bluetooth.
Microsoft Surface Pen	Yes	Yes	Windows Ink; surface-style hover.
Apple Pencil via Sidecar (macOS)	Yes	Yes	Mac must be a Sidecar host.
XP-Pen / Huion (driver-mode)	Yes	Varies	Depends on vendor driver.

Linux pen support requires Wayland and a compositor that implements wp_tablet_v2 (GNOME 45+, KDE Plasma 5.27+). On X11, pen events arrive as plain mouse moves — no pressure. See Wayland.

Pen & stylus input

TL;DR

Install

Quickstart

How it works

Reference

Stylus-aware event reading

Supported devices (verified)

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