BadNote/lib/editor/canvas/pen_stroke.dart

// lib/editor/canvas/pen_stroke.dart
//
// Pen-first canvas stroke model. Points are stored in NORMALIZED page
// coordinates ([0,1] x [0,1] relative to the page rectangle) so strokes stay
// pinned to the page regardless of zoom/pan or the on-screen page size.

import 'package:flutter/foundation.dart';

import '../engine/brush.dart';

/// A single captured sample of a stroke.
///
/// [x]/[y] are normalized to the page rectangle ([0,1]).
/// [pressure] is the normalized stylus pressure ([0,1]) or null when the
/// device reported no usable pressure (perfect_freehand then simulates it).
/// [tilt] is the pen tilt magnitude in degrees (0 = perpendicular), or null
/// when unavailable. On Windows it is sourced from the native pen plugin
/// (`badnote/pen`) since Flutter 3.44 does not surface tilt itself.
@immutable
class PenPoint {
  const PenPoint(this.x, this.y, this.pressure, {this.tilt});

  final double x;
  final double y;
  final double? pressure;
  final double? tilt;
}

/// Which kind of mark a stroke is.
enum PenStrokeKind { pen, highlighter }

/// A committed stroke for a single page, in normalized page coordinates.
@immutable
class PenStroke {
  const PenStroke({
    required this.points,
    required this.color,
    required this.width,
    required this.kind,
    this.brush = BrushKind.fountainPen,
  });

  /// Normalized points (see [PenPoint]).
  final List<PenPoint> points;

  /// ARGB color value.
  final int color;

  /// Stroke width expressed as a fraction of the page width, so it scales with
  /// the page when zoomed. Multiply by the on-screen page width to get pixels.
  final double width;

  final PenStrokeKind kind;

  /// The brush this stroke was drawn with — drives the perfect_freehand
  /// geometry (thinning/streamline/smoothing/caps) at render time via
  /// [brushProfileFor]. The pressure pre-warp ([BrushProfile.pressureGamma]) is
  /// applied at CAPTURE so it is already baked into [points]. Defaults to
  /// [BrushKind.fountainPen] (the legacy pen visual) so old/loaded strokes keep
  /// rendering as before.
  final BrushKind brush;
}