73 lines
2.2 KiB
Dart
73 lines
2.2 KiB
Dart
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import 'dart:ui';
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/// Annotation tools available while presenting. Drawings live in a layer that
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/// is fully separate from the Marp content — they are never written to the
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/// markdown.
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enum InkTool { laser, pen, highlighter, eraser }
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/// A single freehand stroke on the annotation layer.
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///
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/// Coordinates are normalized (0..1) within the 16:9 slide rectangle and the
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/// width is a fraction of the slide width, so a stroke renders identically on
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/// the laptop preview and the beamer regardless of resolution or letterboxing.
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class InkStroke {
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final InkTool tool;
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final int color; // ARGB
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final double width; // fraction of the slide width
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final List<Offset> points; // normalized 0..1
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const InkStroke({
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required this.tool,
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required this.color,
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required this.width,
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required this.points,
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});
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InkStroke copyWith({List<Offset>? points}) => InkStroke(
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tool: tool,
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color: color,
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width: width,
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points: points ?? this.points,
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);
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/// Compact JSON: points are flattened to [x0, y0, x1, y1, …].
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Map<String, dynamic> toJson() => {
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'tool': tool.name,
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'color': color,
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'width': width,
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'points': [
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for (final p in points) ...[
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_round(p.dx),
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_round(p.dy),
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],
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],
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};
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static double _round(double v) => (v * 10000).roundToDouble() / 10000;
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factory InkStroke.fromJson(Map<String, dynamic> json) {
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final raw = (json['points'] as List?)?.cast<num>() ?? const [];
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final pts = <Offset>[];
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for (var i = 0; i + 1 < raw.length; i += 2) {
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pts.add(Offset(raw[i].toDouble(), raw[i + 1].toDouble()));
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}
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return InkStroke(
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tool: InkTool.values.firstWhere(
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(t) => t.name == json['tool'],
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orElse: () => InkTool.pen,
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),
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color: (json['color'] as num?)?.toInt() ?? 0xFFEF4444,
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width: (json['width'] as num?)?.toDouble() ?? 0.004,
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points: pts,
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);
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}
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}
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/// Encode/decode a per-slide map of strokes keyed by slide id.
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List<Map<String, dynamic>> encodeStrokes(List<InkStroke> strokes) =>
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[for (final s in strokes) s.toJson()];
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List<InkStroke> decodeStrokes(List<dynamic> raw) => [
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for (final e in raw) InkStroke.fromJson(Map<String, dynamic>.from(e as Map)),
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];
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