The flagship leg of design/pen-tablet-input.md §7: against a HOST_CAP_PEN host
the Pencil splits out of the finger path (independent of touch-input mode) into
PencilStream — state-full samples with force→pressure, altitude→polar tilt,
azimuth (+90° to the wire's north-clockwise convention), Pencil Pro rollAngle→
barrel roll (17.5+), coalesced touches batched ≤8/send for full 240Hz fidelity,
and Pencil hover (zOffset>0 distinguishes it from trackpad hover) as in-range
samples with distance. Squeeze holds barrel 1, double-tap clicks barrel 2 (the
Pencil has no hardware buttons/eraser — these are how host apps get those
affordances). Implements the ≤100ms heartbeat wire contract (80ms timer) so a
stationary held stroke survives the host's 200ms dead-client failsafe. Toward a
pen-less host nothing changes (Pencil stays a finger).
Also fixes hostSupportsCursor testing the STALE 0x04 bit — HOST_CAP_CURSOR
moved to 0x08 when TEXT_INPUT claimed 0x04; the old test would mistake a
text-input host (e.g. Windows) for a cursor grant and double-render the pointer.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehlerandClaude Fable 5
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