原生epub阅读

lib/pages/epub_reader/widgets/reader_scale_slider.dart

@@ -0,0 +1,66 @@
+import 'package:flutter/material.dart';
+
+/// A horizontal scale slider with small/large "A" tap targets on either side.
+///
+/// The slider range is fixed to [0.5, 2.5] with 0.1 increments.
+/// Tapping the letter glyphs nudges the value by 0.1 in the respective
+/// direction; the glyph is greyed-out when the limit is reached.
+class ReaderScaleSlider extends StatelessWidget {
+  const ReaderScaleSlider({
+    super.key,
+    required this.value,
+    required this.onChanged,
+  });
+
+  final double value;
+  final ValueChanged<double> onChanged;
+
+  static const double _min = 0.5;
+  static const double _max = 2.5;
+  static const double _nudge = 0.1;
+
+  @override
+  Widget build(BuildContext context) {
+    final color = Theme.of(context).colorScheme.onSurfaceVariant;
+    final disabledColor = Theme.of(context).colorScheme.outline;
+
+    return Row(
+      children: [
+        GestureDetector(
+          onTap: value > _min
+              ? () => onChanged((value - _nudge).clamp(_min, _max))
+              : null,
+          child: Text(
+            'A',
+            style: TextStyle(
+              fontSize: 12,
+              color: value > _min ? color : disabledColor,
+            ),
+          ),
+        ),
+        Expanded(
+          child: Slider(
+            value: value,
+            min: _min,
+            max: _max,
+            divisions: 20,
+            label: value.toStringAsFixed(1),
+            onChanged: onChanged,
+          ),
+        ),
+        GestureDetector(
+          onTap: value < _max
+              ? () => onChanged((value + _nudge).clamp(_min, _max))
+              : null,
+          child: Text(
+            'A',
+            style: TextStyle(
+              fontSize: 22,
+              color: value < _max ? color : disabledColor,
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}