feat(widgets): let the platform drive caption button hover and press

lib/src/widgets/window_caption_button.dart

@@ -277,6 +277,8 @@ class WindowCaptionButton extends StatefulWidget {
     super.key,
     this.brightness,
     this.icon,
+    this.hovered = false,
+    this.pressed = false,
     this.iconName,
     required this.onPressed,
   });
@@ -285,27 +287,35 @@ class WindowCaptionButton extends StatefulWidget {
     super.key,
     this.brightness,
     this.icon,
+    this.hovered = false,
+    this.pressed = false,
     this.onPressed,
   }) : iconName = _kIconChromeMinimize;
 
   WindowCaptionButton.maximize({
     super.key,
     this.brightness,
     this.icon,
+    this.hovered = false,
+    this.pressed = false,
     this.onPressed,
   }) : iconName = _kIconChromeMaximize;
 
   WindowCaptionButton.unmaximize({
     super.key,
     this.brightness,
     this.icon,
+    this.hovered = false,
+    this.pressed = false,
     this.onPressed,
   }) : iconName = _kIconChromeUnmaximize;
 
   WindowCaptionButton.close({
     super.key,
     this.brightness,
     this.icon,
+    this.hovered = false,
+    this.pressed = false,
     this.onPressed,
   }) : iconName = _kIconChromeClose,
        _lightButtonBgColorScheme = _ButtonBgColorScheme(
@@ -336,6 +346,16 @@ class WindowCaptionButton extends StatefulWidget {
   final String? iconName;
   final VoidCallback? onPressed;
 
+  /// Shows the hovered look even when Flutter does not see the pointer.
+  ///
+  /// For input the platform handles over the button, such as a Windows 11
+  /// maximize button that reports `HTMAXBUTTON` to open Snap Layouts.
+  final bool hovered;
+
+  /// Shows the pressed look even when Flutter does not see the pointer.
+  /// See [hovered].
+  final bool pressed;
+
   _ButtonBgColorScheme _lightButtonBgColorScheme = _ButtonBgColorScheme(
     normal: Colors.transparent,
     hovered: Colors.black.withValues(alpha: 0.0373),
@@ -389,11 +409,11 @@ class _WindowCaptionButtonState extends State<WindowCaptionButton> {
     Color bgColor = widget.buttonBgColorScheme.normal;
     Color iconColor = widget.buttonIconColorScheme.normal;
 
-    if (_isHovering) {
+    if (_isHovering || widget.hovered) {
       bgColor = widget.buttonBgColorScheme.hovered;
       iconColor = widget.buttonIconColorScheme.hovered;
     }
-    if (_isPressed) {
+    if (_isPressed || widget.pressed) {
       bgColor = widget.buttonBgColorScheme.pressed;
       iconColor = widget.buttonIconColorScheme.pressed;
     }

test/window_caption_button_test.dart

@@ -0,0 +1,61 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:window_manager/window_manager.dart';
+
+Color? _background(WidgetTester tester) {
+  final container = tester.widget<Container>(
+    find.descendant(
+      of: find.byType(WindowCaptionButton),
+      matching: find.byType(Container),
+    ),
+  );
+  return (container.decoration as BoxDecoration?)?.color;
+}
+
+Future<void> _pump(WidgetTester tester, WindowCaptionButton button) {
+  return tester.pumpWidget(
+    Directionality(
+      textDirection: TextDirection.ltr,
+      child: Center(child: button),
+    ),
+  );
+}
+
+void main() {
+  testWidgets('idle button has the normal background', (tester) async {
+    await _pump(tester, WindowCaptionButton.maximize(onPressed: () {}));
+    expect(_background(tester), Colors.transparent);
+  });
+
+  testWidgets('hovered shows the hover look without a pointer', (tester) async {
+    await _pump(
+      tester,
+      WindowCaptionButton.maximize(onPressed: () {}, hovered: true),
+    );
+    expect(_background(tester), Colors.black.withValues(alpha: 0.0373));
+  });
+
+  testWidgets('pressed wins over hovered', (tester) async {
+    await _pump(
+      tester,
+      WindowCaptionButton.unmaximize(
+        onPressed: () {},
+        hovered: true,
+        pressed: true,
+      ),
+    );
+    expect(_background(tester), Colors.black.withValues(alpha: 0.0241));
+  });
+
+  testWidgets('dark close button uses its own hover color', (tester) async {
+    await _pump(
+      tester,
+      WindowCaptionButton.close(
+        brightness: Brightness.dark,
+        onPressed: () {},
+        hovered: true,
+      ),
+    );
+    expect(_background(tester), const Color(0xffC42B1C));
+  });
+}