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lib/pages/epub_reader/mixins/theme_mixin.dart

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+part of '../reader_screen.dart';
+
+mixin _ThemeMixin on State<ReaderScreen> {
+  // === Borrowed state (provided by _ReaderScreenState fields) ===
+  ReaderRendererController get rendererController;
+
+  ReaderSettings get readerSettings;
+
+  ThemeData? get currentTheme;
+  set currentTheme(ThemeData? v);
+
+  bool get updatingTheme;
+  set updatingTheme(bool v);
+
+  Timer? get themeUpdateDebouncer;
+  set themeUpdateDebouncer(Timer? v);
+
+  EpubTheme getEpubTheme() {
+    return readerSettings.toEpubTheme(context);
+  }
+
+  void updateWebViewThemeWithDebounce() {
+    themeUpdateDebouncer?.cancel();
+    themeUpdateDebouncer = Timer(const Duration(milliseconds: 50), () {
+      updateWebViewTheme();
+    });
+  }
+
+  Future<void> updateWebViewTheme() async {
+    final newTheme = getEpubTheme();
+    final currentWebViewTheme = rendererController.currentTheme;
+    if (currentWebViewTheme != null && currentWebViewTheme == newTheme) {
+      return;
+    }
+
+    setState(() {
+      updatingTheme = true;
+    });
+
+    await rendererController.updateTheme(getEpubTheme());
+
+    setState(() {
+      updatingTheme = false;
+    });
+  }
+}