Nib

Turn an iPad and Apple Pencil into a pressure-sensitive drawing tablet for your Mac.

Nib works like a Wacom Intuos: the iPad screen stays dark, the Pencil maps absolutely onto a Mac display, and Mac drawing apps — Krita, Photoshop, Affinity — receive real tablet events with pressure and tilt. Fingers handle the canvas: scroll, pinch to zoom, twist to rotate, tap to undo.

Developer preview. Usable daily, but there are no downloadable builds yet: you build both apps from source with Xcode (below). Built and tested on an iPad mini (A17 Pro) with Apple Pencil Pro and an Apple Silicon Mac. Roadmap: PLAN.md.

Features

• Real tablet pressure and tilt — injected as macOS tablet events, so apps treat Nib like a hardware tablet, not a mouse.
• Screen-off drawing — the iPad stays black (or faintly lit for edge buttons); you look at the Mac, not the iPad.
• USB-C or Wi-Fi — plug in for the lowest jitter; Nib switches to USB automatically and falls back to Wi-Fi when you unplug.
• Trackpad-style gestures — two-finger scroll, pinch to zoom and twist to rotate the canvas (sent as native macOS magnify/rotate gestures), two-finger tap to undo, three-finger tap to redo.
• Shortcut buttons and a slide strip — ExpressKeys-style buttons on one edge (tap or hold, e.g. hold Space to pan) and a strip on the other for scroll, zoom or brush size.
• Per-app profiles — the Mac reports the frontmost app and the iPad switches buttons and gestures to match. Presets for Krita, Photoshop and Affinity; edit everything on the iPad.
• Pressure curve on the iPad — soft/linear/firm presets, min/max thresholds, and a test strip that shows what the Mac receives.
• Choose where you draw — one display or all of them, the whole screen or a region, keep the iPad's proportions or stretch. An edge margin lets the Pencil reach the screen's edges (and an auto-hidden Dock) without touching the iPad's edge.
• Paired and encrypted — the iPad and Mac pair once by comparing a 6-digit code; after that every Pencil sample and command is encrypted, over Wi-Fi and USB.

Requirements

• Mac with Apple Silicon, macOS 14 or later.
• iPad with Apple Pencil support (developed on iPad mini 6/7), iPadOS 18 or later.
• Xcode, XcodeGen (brew install xcodegen), and an Apple ID signed in to Xcode (a free account works for personal installs).

Build and install

There are no prebuilt downloads yet; build both apps from source.

git clone <this repo> nib && cd nib
xcodegen generate
open Nib.xcodeproj

1. In Xcode, select each target (NibMac, NibPad) → Signing & Capabilities, choose your team. If signing complains about the bundle identifier, change bundleIdPrefix and the two PRODUCT_BUNDLE_IDENTIFIERs in project.yml to your own reverse-DNS prefix and run xcodegen generate again.
2. Run NibMac on the Mac. It lives in the menu bar (no Dock icon).
3. Connect the iPad, select it as the run destination, and run NibPad. The first time, trust the developer profile on the iPad (Settings → General → VPN & Device Management).

First run

Both apps walk you through setup on screen; this is the short version.

1. Accessibility — NibMac's setup window asks for Accessibility permission (it posts input events) and restarts itself once you grant it.
2. Connect — open Nib on the iPad and choose your Mac. Over Wi-Fi, both devices must be on the same network; allow Local Network access when asked. Over USB-C, plug in and accept "Trust This Computer".
3. Pair — tap Pair on the iPad and check that both screens show the same 6-digit code, then confirm on both. You only do this once; the keys are kept in the Keychain on each device.
4. Draw — the Mac's setup window has a test canvas: a light-to-heavy stroke should go from thin to thick.

Settings

• On the iPad (four-finger tap): Connection, Pen (pressure curve and test strip), Profiles, Gestures, Display (edge brightness) and Advanced (debug HUD, reset).
• On the Mac (menu → Settings…): which display, the drawing area, proportions, edge margin, smoothing, launch at login and paired iPads.

Using Nib

On the iPad	On the Mac
Pencil	Tablet pen with pressure and tilt; double-tap / squeeze toggles eraser
Two-finger slide	Scroll / pan the canvas
Pinch / twist	Zoom / rotate the canvas
Two-finger tap / three-finger tap	Undo / redo
Edge buttons and strip	Keyboard shortcuts from the active profile
Four-finger tap	Opens the companion panel

The companion panel holds the pressure curve, profiles (buttons, strip, gesture options per app), edge-button brightness, and a debug HUD that shows pressure, angles, sample rate and link state.

Each two-finger gesture decides once whether it is a scroll or a zoom/rotate, so a twist does not turn into a scroll; a deliberate twist during a scroll still switches to rotating.

Troubleshooting

• The cursor does not move — Accessibility was probably granted while NibMac was running. Quit and reopen NibMac.
• Stays on Wi-Fi with the cable plugged in — bring Nib to the front on the iPad once (iPadOS closes its USB listener while suspended) and make sure the iPad trusts this Mac.
• The Pencil stops for a few seconds every so often, in every app — check Settings → Bluetooth. A Pencil that disconnects on a regular cycle (we saw every 30 s) is an iPadOS/Pencil pairing problem: forget the Pencil, restart the iPad, and pair again.
• An app ignores pinch or rotate — in that app's profile, set the zoom method to Modifier + scroll. Native gestures use undocumented macOS event fields (see decision 0007).
• Logs: log stream --info --predicate 'subsystem == "dev.yukai.nib"'.

How it works

The iPad captures Pencil samples (position, force, altitude, azimuth) and sends fixed 40-byte packets over UDP on Wi-Fi or a framed stream over USB (usbmuxd); finger gestures, keys and settings-driven events travel on a reliable control channel. NibMac maps samples onto the chosen display and posts CoreGraphics tablet-proximity and tablet-point events. Details: docs/architecture.md and the decision records in docs/decisions/.

Development

scripts/verify.sh                              # the gate: format, tests, both app builds
swift test --package-path Packages/NibCore     # unit tests only
swift run --package-path Packages/NibCore nib-inject-demo    # pressure stroke, no iPad needed
swift run --package-path Packages/NibCore nib-gesture-demo   # zoom/rotate the front app

Contributor and agent workflow: AGENTS.md.

Security note

The iPad and Mac pair by comparing a 6-digit code (commit-then-reveal, so a device in the middle can't force matching codes). Every session after that is authenticated and encrypted with ChaCha20-Poly1305, over Wi-Fi and USB. The cable is not trusted on its own: USB pairs the same way. Details: decision 0011 and docs/protocol.md. The handshake is ours and has been reviewed, not audited; please report issues privately.

License

MIT