feat(ui_shared): pass platform-specific icons and colors explicitly

packages/firebase_ui_auth/lib/src/screens/profile_screen.dart

@@ -417,7 +417,8 @@ class _EmailVerificationBadgeState extends State<_EmailVerificationBadge> {
                     state != EmailVerificationState.sending)
                   UniversalButton(
                     variant: ButtonVariant.text,
-                    color: Theme.of(context).colorScheme.error,
+                    materialColor: Theme.of(context).colorScheme.error,
+                    cupertinoColor: CupertinoColors.destructiveRed,
                     text: 'Dismiss',
                     onPressed: () {
                       setState(service.dismiss);

packages/firebase_ui_auth/lib/src/widgets/delete_account_button.dart

@@ -78,15 +78,16 @@ class _DeleteAccountButtonState extends State<DeleteAccountButton> {
   @override
   Widget build(BuildContext context) {
     final l = FirebaseUILocalizations.labelsOf(context);
-    bool isCupertino = CupertinoUserInterfaceLevel.maybeOf(context) != null;
 
     final themeData = Theme.of(context);
     final colorScheme = themeData.colorScheme;
 
     return LoadingButton(
       isLoading: _isLoading,
-      color: isCupertino ? CupertinoColors.destructiveRed : colorScheme.error,
-      icon: isCupertino ? CupertinoIcons.delete : Icons.delete,
+      cupertinoColor: CupertinoColors.destructiveRed,
+      materialColor: colorScheme.error,
+      cupertinoIcon: CupertinoIcons.delete,
+      materialIcon: Icons.delete,
       label: l.deleteAccount,
       labelColor: colorScheme.onError,
       onTap: _deleteAccount,

packages/firebase_ui_auth/lib/src/widgets/email_link_sign_in_button.dart

@@ -35,12 +35,12 @@ class EmailLinkSignInButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final isCupertino = CupertinoUserInterfaceLevel.maybeOf(context) != null;
     final l = FirebaseUILocalizations.labelsOf(context);
 
     return UniversalButton(
       text: l.emailLinkSignInButtonLabel,
-      icon: isCupertino ? CupertinoIcons.link : Icons.link,
+      cupertinoIcon: CupertinoIcons.link,
+      materialIcon: Icons.link,
       onPressed: () {
         final action = FirebaseUIAction.ofType<EmailLinkSignInAction>(context);
         if (action != null) {

packages/firebase_ui_auth/lib/src/widgets/sign_out_button.dart

@@ -29,15 +29,15 @@ class SignOutButton extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final l = FirebaseUILocalizations.labelsOf(context);
-    final isCupertino = CupertinoUserInterfaceLevel.maybeOf(context) != null;
 
     return UniversalButton(
       text: l.signOutButtonText,
       onPressed: () => FirebaseUIAuth.signOut(
         context: context,
         auth: auth,
       ),
-      icon: isCupertino ? CupertinoIcons.arrow_right_circle : Icons.logout,
+      cupertinoIcon: CupertinoIcons.arrow_right_circle,
+      materialIcon: Icons.logout,
       variant: variant,
     );
   }

packages/firebase_ui_shared/lib/src/loading_button.dart

@@ -55,11 +55,17 @@ class LoadingButton extends StatelessWidget {
   /// The text to display in the button.
   final String label;
 
-  /// The icon to display in the button.
-  final IconData? icon;
+  /// The icon to display in the button under [MaterialApp].
+  final IconData? materialIcon;
 
-  /// The color of the button background.
-  final Color? color;
+  /// The icon to display in the button under [CupertinoApp].
+  final IconData? cupertinoIcon;
+
+  /// The color of the button background under [MaterialApp].
+  final Color? materialColor;
+
+  /// The color of the button background under [CupertinoApp].
+  final Color? cupertinoColor;
 
   /// The color of the button content.
   final Color? labelColor;
@@ -75,8 +81,10 @@ class LoadingButton extends StatelessWidget {
     required this.label,
     required this.onTap,
     this.isLoading = false,
-    this.icon,
-    this.color,
+    this.materialIcon,
+    this.cupertinoIcon,
+    this.materialColor,
+    this.cupertinoColor,
     this.labelColor,
     this.variant = ButtonVariant.outlined,
   }) : super(key: key);
@@ -99,8 +107,10 @@ class LoadingButton extends StatelessWidget {
     );
 
     return UniversalButton(
-      color: color,
-      icon: icon,
+      materialColor: materialColor,
+      cupertinoColor: cupertinoColor,
+      materialIcon: materialIcon,
+      cupertinoIcon: cupertinoIcon,
       contentColor: contentColor,
       onPressed: onTap,
       variant: variant,

packages/firebase_ui_shared/lib/src/universal_button.dart

@@ -34,8 +34,11 @@ class UniversalButton extends PlatformWidget {
   /// The child to display in the button.
   final Widget? child;
 
-  /// The icon to display in the button.
-  final IconData? icon;
+  /// The icon to display in the button under [MaterialApp].
+  final IconData? materialIcon;
+
+  /// The icon to display in the button under [CupertinoApp].
+  final IconData? cupertinoIcon;
 
   /// Defines the order of the icon and the label.
   /// Icon will be placed on the left if [TextDirection.ltr] and on the right
@@ -46,8 +49,11 @@ class UniversalButton extends PlatformWidget {
   /// If not provided, [ButtonVariant.filled] will be used.
   final ButtonVariant variant;
 
-  /// The color of the button background.
-  final Color? color;
+  /// The color of the button background under [MaterialApp].
+  final Color? materialColor;
+
+  /// The color of the button background under [CupertinoApp].
+  final Color? cupertinoColor;
 
   /// The color of the button content.
   final Color? contentColor;
@@ -57,10 +63,12 @@ class UniversalButton extends PlatformWidget {
     this.text,
     this.child,
     this.onPressed,
-    this.icon,
+    this.materialIcon,
+    this.cupertinoIcon,
     this.direction = TextDirection.ltr,
     this.variant = ButtonVariant.filled,
-    this.color,
+    this.materialColor,
+    this.cupertinoColor,
     this.contentColor,
   })  : assert(text != null || child != null),
         super(key: key);
@@ -73,9 +81,9 @@ class UniversalButton extends PlatformWidget {
       textDirection: direction,
       mainAxisAlignment: MainAxisAlignment.center,
       children: [
-        if (icon != null) ...[
+        if (cupertinoIcon != null) ...[
           if (direction == TextDirection.rtl) const SizedBox(width: 8),
-          Icon(icon, size: 20, color: contentColor),
+          Icon(cupertinoIcon, size: 20, color: contentColor),
           if (direction == TextDirection.ltr) const SizedBox(width: 8),
         ],
         this.child ?? Text(text!),
@@ -95,9 +103,9 @@ class UniversalButton extends PlatformWidget {
       );
     }
 
-    if (color != null) {
+    if (cupertinoColor != null) {
       return CupertinoTheme(
-        data: CupertinoTheme.of(context).copyWith(primaryColor: color),
+        data: CupertinoTheme.of(context).copyWith(primaryColor: cupertinoColor),
         child: button,
       );
     } else {
@@ -111,46 +119,46 @@ class UniversalButton extends PlatformWidget {
 
     ButtonStyle? style;
 
-    if (color != null) {
+    if (materialColor != null) {
       MaterialStateColor? foregroundColor;
       MaterialStateColor? backgroundColor;
 
       if (variant == ButtonVariant.text) {
-        foregroundColor = MaterialStateColor.resolveWith((_) => color!);
+        foregroundColor = MaterialStateColor.resolveWith((_) => materialColor!);
       } else {
         foregroundColor = MaterialStateColor.resolveWith((_) => contentColor!);
-        backgroundColor = MaterialStateColor.resolveWith((_) => color!);
+        backgroundColor = MaterialStateColor.resolveWith((_) => materialColor!);
       }
 
       style = ButtonStyle(
         foregroundColor: foregroundColor,
         backgroundColor: backgroundColor,
         overlayColor: MaterialStateColor.resolveWith(
-          (states) => color!.withAlpha(20),
+          (states) => materialColor!.withAlpha(20),
         ),
       );
     }
 
-    if (icon != null) {
+    if (materialIcon != null) {
       switch (variant) {
         case ButtonVariant.text:
           return TextButton.icon(
-            icon: Icon(icon, color: contentColor),
+            icon: Icon(materialIcon, color: contentColor),
             onPressed: onPressed,
             label: child,
             style: style,
           );
         case ButtonVariant.filled:
           return ElevatedButton.icon(
             onPressed: onPressed,
-            icon: Icon(icon, color: contentColor),
+            icon: Icon(materialIcon, color: contentColor),
             label: child,
             style: style,
           );
         case ButtonVariant.outlined:
           return OutlinedButton.icon(
             onPressed: onPressed,
-            icon: Icon(icon, color: contentColor),
+            icon: Icon(materialIcon, color: contentColor),
             label: child,
             style: style,
           );