Add YaruBackButtonTheme & YaruBackButtonStyle (rounded vs. square)

lib/src/controls/yaru_back_button.dart

@@ -1,24 +1,36 @@
 import 'package:flutter/material.dart';
 import 'package:yaru_icons/yaru_icons.dart';
 
+import 'yaru_back_button_theme.dart';
 import 'yaru_icon_button.dart';
 
 /// A Yaru style back button.
 class YaruBackButton extends StatelessWidget {
   /// Creates a [YaruBackButton].
-  const YaruBackButton({super.key, this.onPressed});
+  const YaruBackButton({
+    super.key,
+    this.onPressed,
+    this.style,
+  });
 
   /// An optional callback that is called when the button is pressed.
   ///
   /// By default, [Navigator.maybePop] is called.
   final VoidCallback? onPressed;
 
+  /// The style of the button. Overrides [YaruBackButtonThemeData.style] and
+  /// defaults to [YaruBackButtonStyle.square].
+  final YaruBackButtonStyle? style;
+
   @override
   Widget build(BuildContext context) {
-    return YaruIconButton(
+    final theme = YaruBackButtonTheme.of(context);
+    final round = (style ?? theme?.style) == YaruBackButtonStyle.rounded;
+    final shape = round ? const CircleBorder() : const BeveledRectangleBorder();
+    final button = YaruIconButton(
       icon: const Icon(YaruIcons.go_previous),
       style: ButtonStyle(
-        shape: ButtonStyleButton.allOrNull(const BeveledRectangleBorder()),
+        shape: ButtonStyleButton.allOrNull(shape),
       ),
       onPressed: () {
         if (onPressed != null) {
@@ -28,5 +40,6 @@ class YaruBackButton extends StatelessWidget {
         }
       },
     );
+    return round ? Center(child: button) : button;
   }
 }

lib/src/controls/yaru_back_button_theme.dart

@@ -0,0 +1,80 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+
+enum YaruBackButtonStyle { rounded, square }
+
+@immutable
+class YaruBackButtonThemeData extends ThemeExtension<YaruBackButtonThemeData>
+    with Diagnosticable {
+  /// Creates a theme that can be used with [YaruBackButton].
+  const YaruBackButtonThemeData({
+    this.style,
+  });
+
+  /// The button style to use.
+  final YaruBackButtonStyle? style;
+
+  /// Creates a copy of this object but with the given fields replaced with the
+  /// new values.
+  @override
+  YaruBackButtonThemeData copyWith({
+    YaruBackButtonStyle? style,
+  }) {
+    return YaruBackButtonThemeData(
+      style: style ?? this.style,
+    );
+  }
+
+  @override
+  ThemeExtension<YaruBackButtonThemeData> lerp(
+    ThemeExtension<YaruBackButtonThemeData>? other,
+    double t,
+  ) {
+    final o = other as YaruBackButtonThemeData?;
+    return YaruBackButtonThemeData(
+      style: t < 0.5 ? style : o?.style,
+    );
+  }
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(EnumProperty('style', style));
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+    return other is YaruBackButtonThemeData && other.style == style;
+  }
+
+  @override
+  int get hashCode => style.hashCode;
+}
+
+class YaruBackButtonTheme extends InheritedTheme {
+  const YaruBackButtonTheme({
+    super.key,
+    required this.data,
+    required super.child,
+  });
+
+  final YaruBackButtonThemeData data;
+
+  static YaruBackButtonThemeData? of(BuildContext context) {
+    final theme =
+        context.dependOnInheritedWidgetOfExactType<YaruBackButtonTheme>();
+    return theme?.data ??
+        Theme.of(context).extension<YaruBackButtonThemeData>();
+  }
+
+  @override
+  Widget wrap(BuildContext context, Widget child) {
+    return YaruBackButtonTheme(data: data, child: child);
+  }
+
+  @override
+  bool updateShouldNotify(YaruBackButtonTheme oldWidget) {
+    return data != oldWidget.data;
+  }
+}

lib/yaru_widgets.dart

@@ -4,6 +4,7 @@ library yaru_widgets;
 export 'src/constants.dart';
 // Controls
 export 'src/controls/yaru_back_button.dart';
+export 'src/controls/yaru_back_button_theme.dart';
 export 'src/controls/yaru_check_button.dart';
 export 'src/controls/yaru_checkbox.dart';
 export 'src/controls/yaru_checkbox_list_tile.dart';