Akiba So
d346cc2670
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Make Surface remote debugging and classroom workflows viable: always-on structured logs with one-click zip export, a single AppShell chrome, OOXML PPTX/DOCX annotation without LibreOffice, and a first-class sticky board. Also drop spike/legacy ink widgets and tighten pen feel (predictor, PenInfoHistory, page-tile layer). Co-authored-by: Cursor <cursoragent@cursor.com>
57 lines
1.7 KiB
Dart
57 lines
1.7 KiB
Dart
// Lightweight stroke prediction — extrapolates the next point from recent
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// velocity so the live stroke tip leads the digitizer slightly (lower perceived
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// latency). Not a full ink-stroke-modeler; intentionally small and testable.
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import 'dart:ui';
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class PredictedPoint {
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const PredictedPoint(this.offset, this.pressure);
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final Offset offset;
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final double pressure;
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}
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class StrokePredictor {
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StrokePredictor({this.lookaheadMs = 12});
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/// How far ahead to project, in milliseconds of recent velocity.
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final double lookaheadMs;
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Offset? _prev;
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double? _prevPressure;
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DateTime? _prevAt;
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Offset _velocity = Offset.zero;
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void reset() {
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_prev = null;
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_prevPressure = null;
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_prevAt = null;
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_velocity = Offset.zero;
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}
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/// Feed a real sample; returns an optional predicted tip ahead of [point].
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PredictedPoint? observe(Offset point, double pressure, {DateTime? at}) {
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final now = at ?? DateTime.now();
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if (_prev != null && _prevAt != null) {
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final dtMs = now.difference(_prevAt!).inMicroseconds / 1000.0;
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if (dtMs > 0.5 && dtMs < 80) {
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final raw = (point - _prev!) * (1000.0 / dtMs);
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// EMA blend to avoid jerky predictions.
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_velocity = Offset(
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_velocity.dx * 0.55 + raw.dx * 0.45,
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_velocity.dy * 0.55 + raw.dy * 0.45,
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);
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}
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}
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_prev = point;
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_prevPressure = pressure;
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_prevAt = now;
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if (_velocity.distance < 40) return null; // idle / slow — no predict
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final tip = point + _velocity * (lookaheadMs / 1000.0);
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return PredictedPoint(tip, pressure);
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}
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/// Last known pressure (for predicted tip).
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double get lastPressure => _prevPressure ?? 0.5;
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}
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