Add ButtonGroupM3E component with overflow handling and update API to use actions

packages/button_m3e/CHANGELOG.md

@@ -1,2 +1,7 @@
+## 0.1.2
+- Add optional `cornerRadiusOverride` to allow per-corner radii when using square shapes (enables grouped buttons with rounded outer and square inner corners).
+- Shape resolution updated to honor `cornerRadiusOverride` for square/pressed-square states; no breaking API changes.
+- Internal: minor style resolution refactors, no behavior changes for existing usages.
+
 ## 0.1.0
 - Changelog initialized.

packages/button_m3e/lib/src/button_m3e.dart

@@ -19,6 +19,7 @@ class ButtonM3E extends StatefulWidget {
     this.smallPaddingDeprecated24 = false,
     this.enabled = true,
     this.statesController,
+    this.cornerRadiusOverride, // new optional per-corner override for square shapes
   });
 
   final VoidCallback? onPressed;
@@ -33,6 +34,7 @@ class ButtonM3E extends StatefulWidget {
   final bool smallPaddingDeprecated24;
   final bool enabled;
   final WidgetStatesController? statesController;
+  final BorderRadius? cornerRadiusOverride;
 
   @override
   State<ButtonM3E> createState() => _ButtonM3EState();
@@ -165,12 +167,17 @@ class _ButtonM3EState extends State<ButtonM3E> {
     final selected = states.contains(WidgetState.selected) || widget.selected;
     final pressed = states.contains(WidgetState.pressed);
 
+    final BorderRadius squareBaseRadius = widget.cornerRadiusOverride ??
+        BorderRadius.circular(tokens.squareRadius(widget.size));
+    final BorderRadius pressedSquareRadius = widget.cornerRadiusOverride ??
+        BorderRadius.circular(tokens.pressedRadius(widget.size));
+
     OutlinedBorder round = const StadiumBorder();
     OutlinedBorder square = RoundedRectangleBorder(
-      borderRadius: BorderRadius.circular(tokens.squareRadius(widget.size)),
+      borderRadius: squareBaseRadius,
     );
     OutlinedBorder pressedSquare = RoundedRectangleBorder(
-      borderRadius: BorderRadius.circular(tokens.pressedRadius(widget.size)),
+      borderRadius: pressedSquareRadius,
     );
 
     OutlinedBorder base = widget.shape == ButtonM3EShape.round ? round : square;

packages/button_m3e/pubspec.yaml

@@ -1,7 +1,6 @@
-
 name: button_m3e
 description: Material 3 Expressive Buttons for Flutter with 5 styles, 5 sizes, round/square shapes, and toggle selection.
-version: 0.1.1
+version: 0.1.2
 repository: https://github.com/EmilyMoonstone/material_3_expressive/tree/main/packages/button_m3e
 issue_tracker: https://github.com/EmilyMonestone/material_3_expressive/issues