Akiba So
299b9546a8
"手写笔就是一个带压感的手指，没有特殊适配" — correct. The new editor fed RAW LINEAR stylus pressure into perfect_freehand, and the pressureGamma config (a slider in pen-settings) was read ONLY by that slider's UI and NEVER applied to a stroke. Dead wiring, like the rest. Wire it for real: - PenCanvas applies PressureCurve(floor, gamma) at capture, so stored pressure carries the feel and live + PDF export replay identically. - Natural defaults: gamma 0.7 (light touches register more width, rnote/ OneNote-like) + floor 0.12 (thin strokes keep body, not scratchy). - pen_editor threads PenConfig.pressureGamma into the canvas — the slider now actually changes stroke width. - pen_config: natural default + one-time migration of the legacy inert gamma 1.0, guarded by a marker so a deliberate 1.0 still sticks. Tests: pen_config_gamma_migration (4) + pressure_curve (6) pass; pen widget regressions green. flutter analyze: 0 issues. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
50 lines
2.1 KiB
Dart
50 lines
2.1 KiB
Dart
// lib/editor/input/pressure_curve.dart
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//
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// Configurable pen-pressure response (F5 — the user's repeated "可配置笔" ask).
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// Raw normalized stylus pressure [0,1] is pre-shaped here before it reaches
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// perfect_freehand, giving two user-facing knobs:
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// - [floor]: a minimum output (the plan's marker "min-width floor" — a fixed-
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// pressure marker uses floor≈1.0; a pen uses 0.0).
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// - [gamma]: the response exponent — γ<1 makes light touches register more
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// width (more sensitive), γ>1 requires firmer pressure (less sensitive).
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//
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// Pure value type (widget-free, storage-free) so the full mapping is unit
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// tested; PenConfig / the canvas wire it later (the wiring touches the live
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// draw path and is validated on-device).
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import 'dart:math' as math;
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/// Default pressure-response exponent. <1 so light-to-medium pressure registers
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/// more width — the responsive, rnote/OneNote-like feel — instead of the raw
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/// linear mapping that made the pen feel like a pressure-sensitive finger.
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const double kNaturalPressureGamma = 0.7;
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/// Default minimum shaped pressure: even the lightest touch keeps ~12% of the
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/// dynamic range so thin strokes have body instead of scratchy near-zero width.
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const double kNaturalPressureFloor = 0.12;
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/// Maps raw normalized pressure to a shaped response in `[floor, 1]`.
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class PressureCurve {
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const PressureCurve({this.floor = 0.0, this.gamma = 1.0})
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: assert(floor >= 0.0 && floor < 1.0),
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assert(gamma > 0.0);
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/// Minimum output (>=0, <1). 0 = full dynamic range; raise toward 1 for a
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/// fixed-pressure feel (marker).
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final double floor;
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/// Response exponent (>0). 1 = linear; <1 = more sensitive at light pressure;
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/// >1 = firmer.
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final double gamma;
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/// Linear, full-range pen response (identity).
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static const PressureCurve linear = PressureCurve();
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/// Shape [pressure] (clamped to [0,1]) into `[floor, 1]`.
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double apply(double pressure) {
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final p = pressure.isNaN ? 0.0 : pressure.clamp(0.0, 1.0);
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final shaped = gamma == 1.0 ? p : math.pow(p, gamma).toDouble();
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return floor + (1.0 - floor) * shaped;
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}
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}
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