[HunterAhlquist]

Apple Pencil pressure and tilt, as discussed in #81. Built on pencil-pressure-rebased, @Saffsanity's merge of my branch into main, with one more commit of mine on top and main at 125be9d merged in.

A Pencil on the stream now draws as a tablet pen in Mac apps that read pressure and tilt, and stays the mouse everywhere else. Double tap and barrel roll will come in a second pull request.

What's in it

• 593cc12: the stale hover that drew a straight line back to each stroke's start. It also fixes the Pencil-as-mouse path everyone has today, so it is first and can land on its own.
• My five commits (38fc2f6 … a85fba7), unchanged, merged by @Saffsanity:
  • wire kind 45 pen;
  • PenTablet and PenEvents on the Mac;
  • PenStrokes on the iPad, with palm rejection;
  • the This iPad › Pencil Pressure switch;
  • the Sidecar-matched edge cases.
• @Saffsanity's fixes after the merge: kind 45, PenStrokes' project IDs, the workspace file out, the docs.
• 5065289, the hover cursor (new since the review): while a Pencil hovers as a pen, the iPad shows the Mac's cursor only when it is an app's own, such as a drawing app's brush outline. It never shows a standard arrow, I-beam or hand, and it hides as the tip lands.
  • New wire kind 46 cursorKind (CursorKind {standard}), host → device, sent just before each kind 14. Older devices skip it, and a device that gets none treats the cursor as standard.
  • The Mac's CursorClass decides by comparing the cursor's pixels with AppKit's standard cursors. The arrow and I-beam are also recognised by the window server's 1×–10× images, because the CLI has no NSApplication to compare against.
  • The kind was 30 on my branch. Sill Viewer: a Mac controlling another Mac #66 holds 30, and 46 is in no open pull request's head (checked 2026-10-19).
• Merges of main at 68e880e (iPad: Shift+Return and Shift+Tab reach the Mac with the shift #110) and 125be9d (VirtualDisplay: the BOOL return's encoding follows the architecture #87): CI's mutants matrix keeps both new checks, pen and virtual-display-api; nothing else conflicted.

Checked

• swift build -c release and the iOS app for the simulator and for a device: only the known warnings.
• Tests/checks/run-all.sh: all pass.
• Mutants of the checks this pull request touches, every one caught: pen 97, pointer-presence 48, compatibility 43, protocol 24, pointer-control 33, clipboard 72. One clipboard mutant no longer applied once WindowList's init gained pencil: after clipboard:; its pattern is fixed in the last commit.
• On my iPad Pro (M4, iPadOS 27.0.1) with a Pencil:
  • Pressure and tilt: pressure in Affinity. Pressure and tilt in PenProbe --canvas, run through Sill on this build: every stroke arrived as tablet points, pressure finer than 8 bits, and tilt from −0.67 to +0.59, the same sign as Sidecar's for the same grip.
  • Hover: on this build, Affinity's brush outline shows under the hovering Pencil, and nothing shows over standard cursors (the toolbar, text, the canvas app's arrow). While building the rule, the arrow, I-beam, pointing hand and window-resize cursors all matched AppKit's; Affinity's outline and another app's tool cursor matched none.
  • The fix: the line back to the start is gone.
• Sidecar's own behaviour was recorded and is followed for hover, a held button and mouse input during a stroke (docs/pencil-pressure-plan.md §13).

Still open

The plan's device tests P1–P10 beyond those above:

• other drawing apps;
• a resting palm;
• a stroke cut by a rotation, a pick or Wi-Fi;
• mixed builds.

Known gaps:

• a palm resting before the Pencil's first touch gives a right-click;
• with a custom pointer size or colour in Accessibility, standard cursors may read as an app's own and show under a hovering Pencil.

Disclosure, as in #81: Claude Code wrote most of the code; I designed the behaviour with it and tested it on my devices.

🤖 Generated with Claude Code

[anurag1212]

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