47 lines
2.0 KiB
Dart
47 lines
2.0 KiB
Dart
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// lib/editor/input/input_arbiter.dart
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//
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// Pure draw-vs-pan/zoom arbitration for the pen-first canvas (P0 step 4 —
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// extracted verbatim from `pen_canvas.dart` so the make-or-break gesture rules
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// are decided by ONE testable place rather than inline in a StatefulWidget).
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//
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// The model (clean-room from Saber, proven live):
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// - A DRAW gesture is exactly ONE active pointer that is a stylus / inverted
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// stylus / mouse, OR (when the finger-drawing toggle is on) a single finger.
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// - >= 2 active pointers ALWAYS means pan/zoom (pinch); never draw.
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// - Palm rejection: a finger never draws unless the user explicitly enabled
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// finger-drawing — so a resting palm pans (or is ignored) instead of marking.
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// - A hardware pen button mapped to `pan` suppresses drawing so the shared
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// InteractiveViewer pans instead.
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//
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// These are PURE functions (no widget/IO state) so the whole truth table is
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// unit-tested; `pen_canvas.dart` owns the live pointer map and delegates the
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// decisions here.
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import 'package:flutter/gestures.dart' show PointerDeviceKind;
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/// Whether [kind] is a pen (tip or flipped eraser end).
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bool isStylusKind(PointerDeviceKind kind) =>
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kind == PointerDeviceKind.stylus ||
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kind == PointerDeviceKind.invertedStylus;
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/// Decide whether the gesture currently forming should DRAW.
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///
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/// True iff there is exactly one active pointer, drawing is not suppressed by a
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/// hardware pan button, and the pointer is a draw device:
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/// - stylus / inverted stylus → always draws,
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/// - mouse → always draws (desktop authoring),
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/// - touch → draws only when [fingerDrawingEnabled] (else it pans / is palm).
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bool shouldDraw({
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required int activePointerCount,
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required PointerDeviceKind kind,
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required bool fingerDrawingEnabled,
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required bool hwPanActive,
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}) {
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if (activePointerCount != 1) return false;
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if (hwPanActive) return false;
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if (isStylusKind(kind)) return true;
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if (kind == PointerDeviceKind.mouse) return true;
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if (kind == PointerDeviceKind.touch) return fingerDrawingEnabled;
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return false;
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}
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