feat(slide): rebuild PPT annotator on the pen-first canvas

PPT slides now annotate with the single performant inking engine
(PenCanvas) instead of the old ink_canvas, per "all note features on the
pen-first canvas".

- PenSlideScreen: per-slide normalized strokes over each slide image,
  prev/next + slider nav, undo/redo, shared M3 palette, and the pressure
  curve / eraser size+mode / palm rejection from the shared canvas.
- slide_export: pure, tested export geometry. Because strokes are now
  normalized to the page rect, the PDF exporter maps them straight into
  each slide's draw rect — fixing the old exporter's known ink
  misalignment (it guessed live-widget size).
- Route PPT import + open -> PenSlideScreen; delete the dead old
  ppt_annotator_screen. (ink_canvas/annotation_toolbar remain for
  split_view, the last old-canvas screen.)

Tests: slide_export geometry (4). flutter analyze: 0 issues. Suite: 269/269.

lib/editor/canvas/pen_slide_screen.dart

@@ -0,0 +1,544 @@
+// lib/editor/canvas/pen_slide_screen.dart
+//
+// Pen-first slide (PPT) annotator. Reuses the single performant inking engine
+// (PenCanvas) over each slide image, with per-slide normalized strokes and
+// prev/next navigation. Export to PDF maps the normalized strokes into each
+// slide's draw rect (slide_export.dart) — which also fixes the old exporter's
+// known ink-misalignment bug. In-memory only (PPT ink is not auto-saved; Export
+// to PDF is how annotations are kept), matching the previous behavior.
+
+import 'dart:io';
+import 'dart:typed_data';
+import 'dart:ui' as ui;
+
+import 'package:flutter/material.dart';
+import 'package:path/path.dart' as p;
+import 'package:syncfusion_flutter_pdf/pdf.dart';
+
+import '../input/pen_config.dart';
+import '../input/pen_input_service.dart';
+import '../input/pressure_curve.dart' show kNaturalPressureGamma;
+import '../layout/viewport_fit.dart';
+import '../pdf/slide_export.dart';
+import 'pen_canvas.dart';
+import 'pen_palette_widgets.dart';
+import 'pen_stroke.dart';
+
+class PenSlideScreen extends StatefulWidget {
+  const PenSlideScreen({
+    super.key,
+    required this.filePath,
+    required this.slideImagePaths,
+    this.extractedText,
+  });
+
+  final String filePath;
+  final List<String> slideImagePaths;
+  final String? extractedText;
+
+  @override
+  State<PenSlideScreen> createState() => _PenSlideScreenState();
+}
+
+class _PenSlideScreenState extends State<PenSlideScreen> {
+  int _slideIndex = 0;
+  final Map<int, List<PenStroke>> _strokesBySlide = {};
+  final Map<int, List<List<PenStroke>>> _undo = {};
+  final Map<int, List<List<PenStroke>>> _redo = {};
+
+  /// Intrinsic pixel size of each slide image, loaded async so the page rect
+  /// keeps the slide's aspect (no distortion). Null until loaded.
+  Map<int, Size>? _slideSizes;
+
+  CanvasTool _tool = CanvasTool.pen;
+  Color _color = Colors.black;
+  bool _allowFingerDrawing = false;
+  bool _needsCenter = true;
+  bool _showSlider = false;
+  double? _scrub;
+
+  PenConfigController? _penConfig;
+  final TransformationController _transform = TransformationController();
+
+  static const double _penWidthFraction = 0.006;
+  static const double _highlighterWidthFraction = 0.02;
+  static const Size _fallbackSlide = Size(1600, 900);
+
+  static const List<Color> _palette = [
+    Colors.black,
+    Colors.red,
+    Colors.blue,
+    Colors.green,
+    Colors.orange,
+  ];
+
+  int get _slideCount => widget.slideImagePaths.length;
+  List<PenStroke> get _currentStrokes => _strokesBySlide[_slideIndex] ?? const [];
+
+  @override
+  void initState() {
+    super.initState();
+    PenInputService.instance.start();
+    _loadSlideSizes();
+    _initPenConfig();
+  }
+
+  Future<void> _loadSlideSizes() async {
+    final sizes = <int, Size>{};
+    for (var i = 0; i < _slideCount; i++) {
+      try {
+        final bytes = await File(widget.slideImagePaths[i]).readAsBytes();
+        final codec = await ui.instantiateImageCodec(bytes);
+        final frame = await codec.getNextFrame();
+        sizes[i] = Size(
+            frame.image.width.toDouble(), frame.image.height.toDouble());
+        frame.image.dispose();
+      } catch (_) {
+        sizes[i] = _fallbackSlide;
+      }
+    }
+    if (mounted) setState(() => _slideSizes = sizes);
+  }
+
+  Future<void> _initPenConfig() async {
+    final controller = await PenConfigController.load();
+    if (!mounted) {
+      controller.dispose();
+      return;
+    }
+    controller.addListener(_onPenConfigChanged);
+    setState(() {
+      _penConfig = controller;
+      _allowFingerDrawing = controller.value.fingerDrawing;
+    });
+  }
+
+  void _onPenConfigChanged() {
+    if (mounted) setState(() {});
+  }
+
+  @override
+  void dispose() {
+    _penConfig?.removeListener(_onPenConfigChanged);
+    _penConfig?.dispose();
+    _transform.dispose();
+    super.dispose();
+  }
+
+  // ── Mutations ──────────────────────────────────────────────────────────────
+
+  void _pushUndo() {
+    (_undo[_slideIndex] ??= []).add(List<PenStroke>.from(_currentStrokes));
+    _redo[_slideIndex]?.clear();
+  }
+
+  void _commitStroke(PenStroke stroke) {
+    setState(() {
+      _pushUndo();
+      _strokesBySlide[_slideIndex] = [..._currentStrokes, stroke];
+    });
+  }
+
+  void _eraseStroke(int index, List<PenStroke> replacements) {
+    final strokes = _currentStrokes;
+    if (index < 0 || index >= strokes.length) return;
+    setState(() {
+      _pushUndo();
+      _strokesBySlide[_slideIndex] = [
+        ...strokes.sublist(0, index),
+        ...replacements,
+        ...strokes.sublist(index + 1),
+      ];
+    });
+  }
+
+  void _performUndo() {
+    final stack = _undo[_slideIndex];
+    if (stack == null || stack.isEmpty) return;
+    setState(() {
+      (_redo[_slideIndex] ??= []).add(List<PenStroke>.from(_currentStrokes));
+      _strokesBySlide[_slideIndex] = stack.removeLast();
+    });
+  }
+
+  void _performRedo() {
+    final stack = _redo[_slideIndex];
+    if (stack == null || stack.isEmpty) return;
+    setState(() {
+      (_undo[_slideIndex] ??= []).add(List<PenStroke>.from(_currentStrokes));
+      _strokesBySlide[_slideIndex] = stack.removeLast();
+    });
+  }
+
+  void _toggleFingerDrawing() {
+    final next = !_allowFingerDrawing;
+    setState(() => _allowFingerDrawing = next);
+    _penConfig?.setFingerDrawing(next);
+  }
+
+  void _goToSlide(int i) {
+    final clamped = i.clamp(0, _slideCount - 1);
+    if (clamped == _slideIndex) return;
+    setState(() {
+      _slideIndex = clamped;
+      _needsCenter = true;
+    });
+  }
+
+  // ── Export ──────────────────────────────────────────────────────────────────
+
+  Future<void> _exportPdf() async {
+    final messenger = ScaffoldMessenger.of(context);
+    messenger.showSnackBar(
+        const SnackBar(content: Text('Exporting PDF...')));
+    try {
+      final bytes = await _buildPdfBytes();
+      final dir = await _exportDir();
+      final base = p.basenameWithoutExtension(widget.filePath);
+      final outPath = p.join(dir.path, '${base}_annotated.pdf');
+      await File(outPath).writeAsBytes(bytes);
+      if (!mounted) return;
+      messenger.showSnackBar(SnackBar(content: Text('PDF saved: $outPath')));
+    } catch (e) {
+      if (!mounted) return;
+      messenger.showSnackBar(SnackBar(content: Text('Export failed: $e')));
+    }
+  }
+
+  Future<Directory> _exportDir() async {
+    try {
+      final home = Platform.environment['HOME'];
+      if (home != null) {
+        final dir = Directory(p.join(home, 'Documents', 'BadNote'));
+        if (!await dir.exists()) await dir.create(recursive: true);
+        return dir;
+      }
+    } catch (_) {}
+    return Directory.current;
+  }
+
+  Future<Uint8List> _buildPdfBytes() async {
+    final doc = PdfDocument();
+    doc.pageSettings.margins.all = 0;
+    final sizes = _slideSizes ?? const {};
+    for (var i = 0; i < _slideCount; i++) {
+      final page = doc.pages.add();
+      final pageSize = page.getClientSize();
+      try {
+        final imgBytes = await File(widget.slideImagePaths[i]).readAsBytes();
+        final bitmap = PdfBitmap(imgBytes);
+        final imageSize = sizes[i] ??
+            Size(bitmap.width.toDouble(), bitmap.height.toDouble());
+        final draw = slideDrawRect(
+            Size(pageSize.width, pageSize.height), imageSize);
+        page.graphics.drawImage(bitmap, draw);
+
+        for (final stroke in _strokesBySlide[i] ?? const <PenStroke>[]) {
+          if (stroke.points.length < 2) continue;
+          final r = (stroke.color >> 16) & 0xFF;
+          final g = (stroke.color >> 8) & 0xFF;
+          final b = stroke.color & 0xFF;
+          final path = PdfPath();
+          path.startFigure();
+          for (var j = 0; j < stroke.points.length - 1; j++) {
+            final p1 = stroke.points[j];
+            final p2 = stroke.points[j + 1];
+            path.addLine(
+              normToSlide(p1.x, p1.y, draw),
+              normToSlide(p2.x, p2.y, draw),
+            );
+          }
+          page.graphics.drawPath(
+            path,
+            pen: PdfPen(PdfColor(r, g, b),
+                width: slideStrokeWidth(stroke.width, draw)),
+          );
+        }
+      } catch (_) {
+        page.graphics.drawRectangle(
+          brush: PdfSolidBrush(PdfColor(230, 230, 230)),
+          bounds: Rect.fromLTWH(0, 0, pageSize.width, pageSize.height),
+        );
+      }
+    }
+    final bytes = await doc.save();
+    doc.dispose();
+    return Uint8List.fromList(bytes);
+  }
+
+  // ── Layout ────────────────────────────────────────────────────────────────
+
+  void _centerPage(Size viewport, Size pageSize) {
+    final o = centerOffset(pageSize, viewport, 1.0);
+    _transform.value = Matrix4.identity()..translateByDouble(o.dx, o.dy, 0, 1);
+  }
+
+  double get _strokeWidth => _tool == CanvasTool.highlighter
+      ? (_penConfig?.value.highlighterWidth ?? _highlighterWidthFraction)
+      : (_penConfig?.value.penWidth ?? _penWidthFraction);
+
+  @override
+  Widget build(BuildContext context) {
+    final cs = Theme.of(context).colorScheme;
+    return Scaffold(
+      body: Stack(
+        children: [
+          Positioned.fill(child: _buildCanvas()),
+          SafeArea(
+            child: Align(
+              alignment: Alignment.topCenter,
+              child: Padding(
+                padding: const EdgeInsets.only(top: 8),
+                child: _buildToolPalette(cs),
+              ),
+            ),
+          ),
+          SafeArea(
+            child: Padding(
+              padding: const EdgeInsets.all(8),
+              child: RoundIconButton(
+                icon: Icons.arrow_back,
+                tooltip: 'Back',
+                onPressed: () => Navigator.of(context).maybePop(),
+              ),
+            ),
+          ),
+          SafeArea(
+            child: Align(
+              alignment: Alignment.topRight,
+              child: Padding(
+                padding: const EdgeInsets.all(8),
+                child: RoundIconButton(
+                  icon: Icons.picture_as_pdf_outlined,
+                  tooltip: 'Export to PDF',
+                  onPressed: _exportPdf,
+                ),
+              ),
+            ),
+          ),
+          if (_slideCount > 0)
+            SafeArea(
+              child: Align(
+                alignment: Alignment.bottomCenter,
+                child: Padding(
+                  padding: const EdgeInsets.only(bottom: 16),
+                  child: _buildSlidePill(cs),
+                ),
+              ),
+            ),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildCanvas() {
+    final sizes = _slideSizes;
+    if (sizes == null) {
+      return const Center(child: CircularProgressIndicator());
+    }
+    if (_slideCount == 0) {
+      return const Center(child: Text('No slides.'));
+    }
+    final slide = sizes[_slideIndex] ?? _fallbackSlide;
+    return LayoutBuilder(
+      builder: (context, constraints) {
+        final fitW = constraints.maxWidth / slide.width;
+        final fitH = constraints.maxHeight / slide.height;
+        final scale = fitW < fitH ? fitW : fitH;
+        final pageSize = Size(slide.width * scale, slide.height * scale);
+
+        if (_needsCenter) {
+          WidgetsBinding.instance.addPostFrameCallback((_) {
+            if (!mounted) return;
+            _centerPage(
+                Size(constraints.maxWidth, constraints.maxHeight), pageSize);
+            setState(() => _needsCenter = false);
+          });
+        }
+
+        return PenCanvas(
+          key: ValueKey(_slideIndex),
+          pageSize: pageSize,
+          strokes: _currentStrokes,
+          transformationController: _transform,
+          tool: _tool,
+          color: _color,
+          strokeWidth: _strokeWidth,
+          pressureGamma:
+              _penConfig?.value.pressureGamma ?? kNaturalPressureGamma,
+          eraserRadius: _penConfig?.value.eraserRadius ?? kDefaultEraserRadius,
+          eraserWholeStroke: _penConfig?.value.eraserWholeStroke ?? false,
+          sideButtonAction:
+              _penConfig?.value.sideButton ?? PenButtonAction.eraser,
+          eraserEndAction:
+              _penConfig?.value.eraserEnd ?? PenButtonAction.eraser,
+          allowFingerDrawing: _allowFingerDrawing,
+          onStrokeComplete: _commitStroke,
+          onEraseStroke: _eraseStroke,
+          pageWidget: Image.file(
+            File(widget.slideImagePaths[_slideIndex]),
+            fit: BoxFit.fill,
+            gaplessPlayback: true,
+          ),
+        );
+      },
+    );
+  }
+
+  Widget _buildToolPalette(ColorScheme cs) {
+    return Material(
+      color: cs.surfaceContainerHigh,
+      elevation: 3,
+      borderRadius: BorderRadius.circular(28),
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            ToolButton(
+              icon: Icons.edit_outlined,
+              selected: _tool == CanvasTool.pen,
+              tooltip: 'Pen',
+              onPressed: () => setState(() => _tool = CanvasTool.pen),
+            ),
+            ToolButton(
+              icon: Icons.brush_outlined,
+              selected: _tool == CanvasTool.highlighter,
+              tooltip: 'Highlighter',
+              onPressed: () => setState(() => _tool = CanvasTool.highlighter),
+            ),
+            ToolButton(
+              icon: Icons.cleaning_services_outlined,
+              selected: _tool == CanvasTool.eraser,
+              tooltip: 'Eraser',
+              onPressed: () => setState(() => _tool = CanvasTool.eraser),
+            ),
+            PaletteDivider(cs: cs),
+            ToolButton(
+              icon: Icons.undo,
+              selected: false,
+              tooltip: 'Undo',
+              onPressed:
+                  (_undo[_slideIndex]?.isNotEmpty ?? false) ? _performUndo : null,
+            ),
+            ToolButton(
+              icon: Icons.redo,
+              selected: false,
+              tooltip: 'Redo',
+              onPressed:
+                  (_redo[_slideIndex]?.isNotEmpty ?? false) ? _performRedo : null,
+            ),
+            PaletteDivider(cs: cs),
+            for (final c in _palette) _colorDot(c, cs),
+            PaletteDivider(cs: cs),
+            ToolButton(
+              icon: _allowFingerDrawing ? Icons.touch_app : Icons.do_not_touch,
+              selected: _allowFingerDrawing,
+              tooltip: _allowFingerDrawing
+                  ? 'Finger drawing ON'
+                  : 'Finger drawing OFF (pen only)',
+              onPressed: _toggleFingerDrawing,
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _colorDot(Color c, ColorScheme cs) {
+    final selected =
+        _color.toARGB32() == c.toARGB32() && _tool != CanvasTool.eraser;
+    return GestureDetector(
+      onTap: () => setState(() {
+        _color = c;
+        if (_tool == CanvasTool.eraser) _tool = CanvasTool.pen;
+      }),
+      child: AnimatedContainer(
+        duration: const Duration(milliseconds: 150),
+        margin: const EdgeInsets.symmetric(horizontal: 3),
+        width: 24,
+        height: 24,
+        decoration: BoxDecoration(
+          color: c,
+          shape: BoxShape.circle,
+          border: Border.all(
+            color: selected ? cs.onSurface : cs.outlineVariant,
+            width: selected ? 3 : 1,
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildSlidePill(ColorScheme cs) {
+    final shown = (_scrub ?? (_slideIndex + 1).toDouble()).round();
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        if (_showSlider && _slideCount > 1)
+          Container(
+            margin: const EdgeInsets.only(bottom: 8),
+            constraints: const BoxConstraints(maxWidth: 420),
+            child: Material(
+              color: cs.surfaceContainerHigh,
+              elevation: 3,
+              borderRadius: BorderRadius.circular(28),
+              child: Padding(
+                padding: const EdgeInsets.symmetric(horizontal: 12),
+                child: Slider(
+                  min: 1,
+                  max: _slideCount.toDouble(),
+                  value: (_scrub ?? (_slideIndex + 1).toDouble())
+                      .clamp(1, _slideCount.toDouble()),
+                  divisions: _slideCount > 1 ? _slideCount - 1 : null,
+                  onChanged: (v) => setState(() => _scrub = v),
+                  onChangeEnd: (v) {
+                    setState(() => _scrub = null);
+                    _goToSlide(v.round() - 1);
+                  },
+                ),
+              ),
+            ),
+          ),
+        Material(
+          color: cs.surfaceContainerHigh,
+          elevation: 3,
+          borderRadius: BorderRadius.circular(28),
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
+            child: Row(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                IconButton(
+                  tooltip: 'Previous slide',
+                  icon: const Icon(Icons.chevron_left),
+                  onPressed:
+                      _slideIndex > 0 ? () => _goToSlide(_slideIndex - 1) : null,
+                ),
+                TextButton(
+                  onPressed: _slideCount > 1
+                      ? () => setState(() => _showSlider = !_showSlider)
+                      : null,
+                  child: Text(
+                    '$shown / $_slideCount',
+                    style: TextStyle(
+                      color: cs.onSurface,
+                      fontWeight: FontWeight.w600,
+                    ),
+                  ),
+                ),
+                IconButton(
+                  tooltip: 'Next slide',
+                  icon: const Icon(Icons.chevron_right),
+                  onPressed: _slideIndex < _slideCount - 1
+                      ? () => _goToSlide(_slideIndex + 1)
+                      : null,
+                ),
+              ],
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}

lib/editor/pdf/slide_export.dart

@@ -0,0 +1,36 @@
+// lib/editor/pdf/slide_export.dart
+//
+// Pure geometry for exporting pen-first slide annotations to PDF. Because the
+// pen canvas captures strokes NORMALIZED to the page rect ([0,1]), the export
+// just maps each normalized point into the slide image's draw rectangle on the
+// PDF page — no live-widget-size guessing, which is what made the old PPT
+// exporter misalign ink (see the removed ppt_annotator_screen comment).
+
+import 'dart:ui' show Offset, Rect, Size;
+
+/// The rectangle a slide [image] occupies when drawn "contain"-fit and centered
+/// on a PDF page of size [page]. Mirrors the live canvas's fit-to-view so the
+/// exported ink lands exactly where it was drawn.
+Rect slideDrawRect(Size page, Size image) {
+  final iw = image.width <= 0 ? 1.0 : image.width;
+  final ih = image.height <= 0 ? 1.0 : image.height;
+  final scale = (page.width / iw) < (page.height / ih)
+      ? page.width / iw
+      : page.height / ih;
+  final drawW = iw * scale;
+  final drawH = ih * scale;
+  final offX = (page.width - drawW) / 2;
+  final offY = (page.height - drawH) / 2;
+  return Rect.fromLTWH(offX, offY, drawW, drawH);
+}
+
+/// Map a normalized stroke point ([0,1] of the page rect) to an absolute point
+/// inside the slide's [drawRect] on the PDF page.
+Offset normToSlide(double nx, double ny, Rect drawRect) =>
+    Offset(drawRect.left + nx * drawRect.width,
+        drawRect.top + ny * drawRect.height);
+
+/// Absolute pen width (PDF units) for a stroke whose width is a fraction of the
+/// page width, scaled into [drawRect].
+double slideStrokeWidth(double normalizedWidth, Rect drawRect) =>
+    normalizedWidth * drawRect.width;

lib/screens/home_screen.dart

@@ -10,7 +10,7 @@ import '../editor/canvas/pen_editor_screen.dart';
 import '../services/pdf_service.dart';
 import '../services/pptx_service.dart';
 import '../editor/canvas/pen_note_screen.dart';
-import 'ppt_annotator_screen.dart';
+import '../editor/canvas/pen_slide_screen.dart';
 import 'search_screen.dart';
 import 'settings_screen.dart';
 import 'split_view_screen.dart';
@@ -222,7 +222,7 @@ class HomeScreen extends ConsumerWidget {
     if (context.mounted) {
       Navigator.of(context).push(
         MaterialPageRoute(
-          builder: (_) => PptAnnotatorScreen(
+          builder: (_) => PenSlideScreen(
             filePath: filePath,
             slideImagePaths: slideImages,
             extractedText: extractedText.isEmpty ? null : extractedText,
@@ -527,7 +527,7 @@ class _DocumentTileState extends ConsumerState<_DocumentTile> {
     );
   }
 
-  // [L2] Route by docType: pdf → PenEditorScreen (pen-first), ppt/pptx → PptAnnotatorScreen
+  // [L2] Route by docType: pdf → PenEditorScreen (pen-first), ppt/pptx → PenSlideScreen
   Future<void> _openDocument(BuildContext context) async {
     final document = widget.document;
     final isPdf = document.docType == 'pdf';
@@ -539,7 +539,7 @@ class _DocumentTileState extends ConsumerState<_DocumentTile> {
         ),
       );
     } else {
-      // PPT/PPTX: convert to images then push PptAnnotatorScreen
+      // PPT/PPTX: convert to images then push PenSlideScreen
       if (mounted) {
         ScaffoldMessenger.of(this.context).showSnackBar(
           const SnackBar(content: Text('Processing presentation...')),
@@ -557,7 +557,7 @@ class _DocumentTileState extends ConsumerState<_DocumentTile> {
       }
       Navigator.of(this.context).push(
         MaterialPageRoute(
-          builder: (_) => PptAnnotatorScreen(
+          builder: (_) => PenSlideScreen(
             filePath: document.filePath,
             slideImagePaths: slideImages,
             extractedText: extractedText.isEmpty ? null : extractedText,

lib/screens/ppt_annotator_screen.dart

@@ -1,528 +0,0 @@
-import 'dart:io';
-import 'dart:math';
-import 'dart:typed_data';
-
-import 'package:flutter/material.dart';
-import 'package:path/path.dart' as p;
-import 'package:syncfusion_flutter_pdf/pdf.dart';
-
-import '../models/ink_stroke.dart';
-import '../models/pen_tool.dart';
-import '../models/pressure_curve.dart';
-import '../services/undo_manager.dart';
-import '../utils/stroke_stabilizer.dart';
-import '../widgets/annotation_toolbar.dart';
-import '../widgets/ink_canvas.dart';
-
-/// Per-slide annotation state. The [UndoManager] is the single source of
-/// truth for a slide's strokes; [strokes] reflects its current contents so
-/// the live canvas and the PDF export always render what was actually drawn.
-class _SlideAnnotations {
-  final UndoManager undoManager = UndoManager();
-  List<InkStroke> get strokes => undoManager.currentStrokes;
-}
-
-/// Screen that displays PPTX slides with an ink annotation overlay.
-///
-/// Each slide is shown as an image in a [PageView]. A transparent [InkCanvas]
-/// sits on top of each slide so the user can annotate freely. Annotations are
-/// stored per-slide and can be exported as a PDF.
-class PptAnnotatorScreen extends StatefulWidget {
-  final String filePath;
-  final List<String> slideImagePaths;
-  final String? extractedText;
-
-  const PptAnnotatorScreen({
-    super.key,
-    required this.filePath,
-    required this.slideImagePaths,
-    this.extractedText,
-  });
-
-  @override
-  State<PptAnnotatorScreen> createState() => _PptAnnotatorScreenState();
-}
-
-class _PptAnnotatorScreenState extends State<PptAnnotatorScreen> {
-  late final PageController _pageController;
-  late final Map<int, _SlideAnnotations> _annotations;
-  int _currentPage = 0;
-  bool _isDrawing = false;
-  bool _showTextPanel = false;
-  // Set to true once the unsaved-annotations warning SnackBar has been shown.
-  bool _hasShownUnsavedWarning = false;
-
-  // Toolbar state
-  PenTool _currentTool = PenTool.pen;
-  Color _currentColor = Colors.black;
-  double _currentStrokeWidth = 2.0;
-  bool _filled = false;
-  PressureCurveType _pressureCurveType = PressureCurveType.linear;
-  StabilizationLevel _stabilizationLevel = StabilizationLevel.none;
-
-  // Derived
-  late final String _fileName;
-  late final int _slideCount;
-  late final String _extractedText;
-
-  PressureCurve get _pressureCurve {
-    switch (_pressureCurveType) {
-      case PressureCurveType.linear:
-        return PressureCurve.linear;
-      case PressureCurveType.soft:
-        return PressureCurve.soft;
-      case PressureCurveType.hard:
-        return PressureCurve.hard;
-      case PressureCurveType.custom:
-        return const PressureCurve(type: PressureCurveType.custom);
-    }
-  }
-
-  UndoManager get _currentUndoManager =>
-      _annotations.putIfAbsent(_currentPage, _SlideAnnotations.new).undoManager;
-
-  @override
-  void initState() {
-    super.initState();
-    _fileName = p.basename(widget.filePath);
-    _slideCount = widget.slideImagePaths.length;
-    _extractedText = widget.extractedText ?? '';
-
-    _pageController = PageController();
-    _annotations = {};
-    for (var i = 0; i < _slideCount; i++) {
-      _annotations[i] = _SlideAnnotations();
-    }
-  }
-
-  @override
-  void dispose() {
-    _pageController.dispose();
-    super.dispose();
-  }
-
-  // -- Drawing callbacks --
-
-  void _onStrokeComplete(InkStroke stroke) {
-    setState(() {
-      _currentUndoManager.addStroke(stroke);
-    });
-    // Warn once per session that PPT annotations are not auto-saved.
-    if (!_hasShownUnsavedWarning) {
-      _hasShownUnsavedWarning = true;
-      WidgetsBinding.instance.addPostFrameCallback((_) {
-        if (!mounted) return;
-        ScaffoldMessenger.of(context).showSnackBar(
-          const SnackBar(
-            content: Text(
-              "PPT ink isn't saved automatically — use Export to PDF to keep your annotations.",
-            ),
-            duration: Duration(seconds: 5),
-          ),
-        );
-      });
-    }
-  }
-
-  void _onErase(String strokeId, List<InkStroke> replacements) {
-    setState(() {
-      final original = _currentUndoManager.currentStrokes
-          .where((s) => s.id == strokeId)
-          .firstOrNull;
-      if (original != null) {
-        _currentUndoManager.removeStroke(original, replacements: replacements);
-      }
-    });
-  }
-
-  // -- Export --
-
-  Future<void> _exportPdf() async {
-    if (!mounted) return;
-
-    ScaffoldMessenger.of(
-      context,
-    ).showSnackBar(const SnackBar(content: Text('Exporting PDF...')));
-
-    try {
-      final bytes = await _buildPdfBytes();
-      if (!mounted) return;
-
-      final dir = await _getExportDir();
-      final baseName = p.basenameWithoutExtension(_fileName);
-      final outPath = p.join(dir.path, '${baseName}_annotated.pdf');
-      await File(outPath).writeAsBytes(bytes);
-
-      if (!mounted) return;
-      ScaffoldMessenger.of(
-        context,
-      ).showSnackBar(SnackBar(content: Text('PDF saved: $outPath')));
-    } catch (e) {
-      if (!mounted) return;
-      ScaffoldMessenger.of(
-        context,
-      ).showSnackBar(SnackBar(content: Text('Export failed: $e')));
-    }
-  }
-
-  Future<Directory> _getExportDir() async {
-    try {
-      final home = Platform.environment['HOME'];
-      if (home != null) {
-        final dir = Directory(p.join(home, 'Documents', 'BadNote'));
-        if (!await dir.exists()) {
-          await dir.create(recursive: true);
-        }
-        return dir;
-      }
-    } catch (_) {}
-    return Directory.current;
-  }
-
-  Future<Uint8List> _buildPdfBytes() async {
-    final doc = PdfDocument();
-    doc.pageSettings.margins.all = 0;
-
-    for (var i = 0; i < _slideCount; i++) {
-      final page = doc.pages.add();
-      final pageSize = page.getClientSize();
-
-      // Draw slide image
-      final imgPath = widget.slideImagePaths[i];
-      try {
-        final imgBytes = await File(imgPath).readAsBytes();
-        final bitmap = PdfBitmap(imgBytes);
-
-        final imgW = bitmap.width.toDouble();
-        final imgH = bitmap.height.toDouble();
-        final scale = min(pageSize.width / imgW, pageSize.height / imgH);
-        final drawW = imgW * scale;
-        final drawH = imgH * scale;
-        final offX = (pageSize.width - drawW) / 2;
-        final offY = (pageSize.height - drawH) / 2;
-        final imgRect = Rect.fromLTWH(offX, offY, drawW, drawH);
-
-        page.graphics.drawImage(bitmap, imgRect);
-
-        // Draw ink strokes
-        final annots = _annotations[i];
-        if (annots != null && annots.strokes.isNotEmpty) {
-          // KNOWN LIMITATION: strokes are captured in the live viewer's
-          // full-fill pixel space (the InkCanvas is Positioned.fill over the
-          // whole slide area, while the slide image is BoxFit.contain inside
-          // it). The scale below is derived from the PDF page layout, not the
-          // live widget size, so exported ink can be misaligned/scaled wrong.
-          // A correct fix normalizes strokes to [0,1] of the *rendered image
-          // rect* at capture time (mirroring PdfAnnotationLayer) and maps that
-          // to the PDF draw rect here. Requires on-device visual verification.
-          final imgAspect = imgW / imgH;
-          final pageAspect = pageSize.width / pageSize.height;
-          double widgetW, widgetH;
-          if (imgAspect > pageAspect) {
-            widgetW = pageSize.width;
-            widgetH = pageSize.width / imgAspect;
-          } else {
-            widgetH = pageSize.height;
-            widgetW = pageSize.height * imgAspect;
-          }
-          final scaleX = drawW / widgetW;
-          final scaleY = drawH / widgetH;
-
-          for (final stroke in annots.strokes) {
-            if (stroke.tool == PenTool.eraser) continue;
-            if (stroke.points.length < 2) continue;
-
-            final r = (stroke.color >> 16) & 0xFF;
-            final g = (stroke.color >> 8) & 0xFF;
-            final b = stroke.color & 0xFF;
-            final pdfColor = PdfColor(r, g, b);
-
-            final path = PdfPath();
-            path.startFigure();
-            for (var j = 0; j < stroke.points.length - 1; j++) {
-              final pt1 = stroke.points[j];
-              final pt2 = stroke.points[j + 1];
-              path.addLine(
-                Offset(offX + pt1.x * scaleX, offY + pt1.y * scaleY),
-                Offset(offX + pt2.x * scaleX, offY + pt2.y * scaleY),
-              );
-            }
-
-            page.graphics.drawPath(
-              path,
-              pen: PdfPen(pdfColor, width: stroke.strokeWidth),
-            );
-          }
-        }
-      } catch (_) {
-        page.graphics.drawRectangle(
-          brush: PdfSolidBrush(PdfColor(230, 230, 230)),
-          bounds: Rect.fromLTWH(0, 0, pageSize.width, pageSize.height),
-        );
-      }
-    }
-
-    final bytes = await doc.save();
-    doc.dispose();
-    return Uint8List.fromList(bytes);
-  }
-
-  // -- UI --
-
-  @override
-  Widget build(BuildContext context) {
-    // No slides to annotate: show an empty state and skip the toolbar, which
-    // would otherwise dereference a non-existent slide's annotation state.
-    if (_slideCount == 0) {
-      return Scaffold(
-        appBar: AppBar(
-          title: Text(_fileName, style: const TextStyle(fontSize: 16)),
-        ),
-        body: const Center(child: Text('No slides to display')),
-      );
-    }
-
-    return Scaffold(
-      appBar: AppBar(
-        title: Text(_fileName, style: const TextStyle(fontSize: 16)),
-        actions: [
-          if (_extractedText.isNotEmpty)
-            IconButton(
-              icon: Icon(
-                _showTextPanel
-                    ? Icons.text_snippet
-                    : Icons.text_snippet_outlined,
-              ),
-              tooltip: 'Toggle extracted text',
-              onPressed: () => setState(() => _showTextPanel = !_showTextPanel),
-            ),
-          IconButton(
-            icon: const Icon(Icons.picture_as_pdf),
-            tooltip: 'Export as PDF',
-            onPressed: _exportPdf,
-          ),
-        ],
-      ),
-      body: Column(
-        children: [
-          AnnotationToolbar(
-            currentTool: _currentTool,
-            currentColor: _currentColor,
-            currentStrokeWidth: _currentStrokeWidth,
-            filled: _filled,
-            pressureCurveType: _pressureCurveType,
-            stabilizationLevel: _stabilizationLevel,
-            canUndo: _currentUndoManager.canUndo,
-            canRedo: _currentUndoManager.canRedo,
-            onToolChanged: (tool) => setState(() => _currentTool = tool),
-            onColorChanged: (color) => setState(() => _currentColor = color),
-            onStrokeWidthChanged: (w) =>
-                setState(() => _currentStrokeWidth = w),
-            onFilledChanged: (f) => setState(() => _filled = f),
-            onPressureCurveChanged: (v) =>
-                setState(() => _pressureCurveType = v),
-            onStabilizationChanged: (v) =>
-                setState(() => _stabilizationLevel = v),
-            onUndo: _undo,
-            onRedo: _redo,
-          ),
-          Expanded(
-            child: Row(
-              children: [
-                Expanded(child: _buildSlideViewer()),
-                if (_showTextPanel) _buildTextPanel(),
-              ],
-            ),
-          ),
-          _buildPageIndicator(),
-        ],
-      ),
-    );
-  }
-
-  Widget _buildSlideViewer() {
-    if (_slideCount == 0) {
-      return const Center(child: Text('No slides to display'));
-    }
-
-    return Listener(
-      onPointerDown: (_) => setState(() => _isDrawing = true),
-      onPointerUp: (_) => setState(() => _isDrawing = false),
-      child: PageView.builder(
-        controller: _pageController,
-        physics: _isDrawing ? const NeverScrollableScrollPhysics() : null,
-        itemCount: _slideCount,
-        onPageChanged: (page) => setState(() => _currentPage = page),
-        itemBuilder: (context, index) {
-          return Padding(
-            padding: const EdgeInsets.all(8),
-            child: Stack(
-              children: [
-                // Slide image (background)
-                Positioned.fill(
-                  child: Image.file(
-                    File(widget.slideImagePaths[index]),
-                    fit: BoxFit.contain,
-                    errorBuilder: (context, error, stackTrace) => Container(
-                      color: Colors.grey.shade200,
-                      child: Center(
-                        child: Text(
-                          'Slide ${index + 1}',
-                          style: TextStyle(
-                            fontSize: 24,
-                            color: Colors.grey.shade500,
-                          ),
-                        ),
-                      ),
-                    ),
-                  ),
-                ),
-                // Ink annotation overlay (foreground)
-                Positioned.fill(
-                  child: InkCanvas(
-                    strokes: _annotations[index]?.strokes ?? [],
-                    onStrokeComplete: _onStrokeComplete,
-                    onErase: _onErase,
-                    tool: _currentTool,
-                    color: _currentColor,
-                    strokeWidth: _currentStrokeWidth,
-                    pressureCurve: _pressureCurve,
-                    stabilizationLevel: _stabilizationLevel,
-                    filled: _filled,
-                  ),
-                ),
-              ],
-            ),
-          );
-        },
-      ),
-    );
-  }
-
-  Widget _buildPageIndicator() {
-    if (_slideCount == 0) return const SizedBox.shrink();
-
-    return Container(
-      padding: const EdgeInsets.symmetric(vertical: 8, horizontal: 16),
-      color: Theme.of(context).colorScheme.surface,
-      child: Row(
-        mainAxisAlignment: MainAxisAlignment.center,
-        children: [
-          // Previous button — always present for both modes.
-          IconButton(
-            icon: const Icon(Icons.chevron_left),
-            onPressed: _currentPage > 0
-                ? () => _pageController.previousPage(
-                    duration: const Duration(milliseconds: 300),
-                    curve: Curves.easeInOut,
-                  )
-                : null,
-          ),
-          // Dot row for small decks; compact text counter for large decks.
-          if (_slideCount <= 12)
-            ...List.generate(_slideCount, (i) {
-              final isActive = i == _currentPage;
-              return GestureDetector(
-                onTap: () => _pageController.animateToPage(
-                  i,
-                  duration: const Duration(milliseconds: 300),
-                  curve: Curves.easeInOut,
-                ),
-                child: Container(
-                  width: isActive ? 12 : 8,
-                  height: isActive ? 12 : 8,
-                  margin: const EdgeInsets.symmetric(horizontal: 4),
-                  decoration: BoxDecoration(
-                    shape: BoxShape.circle,
-                    color: isActive
-                        ? Theme.of(context).colorScheme.primary
-                        : Colors.grey.shade400,
-                  ),
-                ),
-              );
-            })
-          else
-            Text(
-              '${_currentPage + 1} / $_slideCount',
-              style: TextStyle(fontSize: 13, color: Colors.grey.shade600),
-            ),
-          // Next button — always present for both modes.
-          IconButton(
-            icon: const Icon(Icons.chevron_right),
-            onPressed: _currentPage < _slideCount - 1
-                ? () => _pageController.nextPage(
-                    duration: const Duration(milliseconds: 300),
-                    curve: Curves.easeInOut,
-                  )
-                : null,
-          ),
-          const Spacer(),
-          // Slide counter is always shown at the trailing end for dot mode;
-          // the compact text above already serves this role for large decks.
-          if (_slideCount <= 12)
-            Text(
-              '${_currentPage + 1} / $_slideCount',
-              style: TextStyle(fontSize: 13, color: Colors.grey.shade600),
-            ),
-        ],
-      ),
-    );
-  }
-
-  Widget _buildTextPanel() {
-    return SizedBox(
-      width: 280,
-      child: Card(
-        margin: const EdgeInsets.all(8),
-        child: Column(
-          crossAxisAlignment: CrossAxisAlignment.stretch,
-          children: [
-            Container(
-              padding: const EdgeInsets.all(12),
-              decoration: BoxDecoration(
-                color: Theme.of(context).colorScheme.surfaceContainerHighest,
-                borderRadius: const BorderRadius.vertical(
-                  top: Radius.circular(12),
-                ),
-              ),
-              child: Row(
-                children: [
-                  const Icon(Icons.text_fields, size: 18),
-                  const SizedBox(width: 8),
-                  Text(
-                    'Extracted Text',
-                    style: Theme.of(context).textTheme.titleSmall,
-                  ),
-                  const Spacer(),
-                  IconButton(
-                    icon: const Icon(Icons.close, size: 18),
-                    onPressed: () => setState(() => _showTextPanel = false),
-                  ),
-                ],
-              ),
-            ),
-            Expanded(
-              child: SingleChildScrollView(
-                padding: const EdgeInsets.all(12),
-                child: SelectableText(
-                  _extractedText,
-                  style: Theme.of(context).textTheme.bodySmall,
-                ),
-              ),
-            ),
-          ],
-        ),
-      ),
-    );
-  }
-
-  // -- Dialogs --
-
-  void _undo() {
-    setState(() => _currentUndoManager.undo());
-  }
-
-  void _redo() {
-    setState(() => _currentUndoManager.redo());
-  }
-}