widgets/clipboard: Add, to be used soon in lightbox

Author: chrisbobbe

lib/widgets/clipboard.dart

@@ -0,0 +1,42 @@
+import 'package:device_info_plus/device_info_plus.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+/// Copies [data] to the clipboard and shows a popup on success.
+///
+/// Must have a [Scaffold] ancestor.
+///
+/// On newer Android the popup is defined and shown by the platform. On older
+/// Android and on iOS, shows a [Snackbar] with [successContent].
+///
+/// In English, the text in [successContent] should be short, should start with
+/// a capital letter, and should have no ending punctuation: "{noun} copied".
+void copyWithPopup({
+  required BuildContext context,
+  required ClipboardData data,
+  required Widget successContent,
+}) async {
+  await Clipboard.setData(data);
+  final deviceInfo = await DeviceInfoPlugin().deviceInfo;
+
+  // Early return on !mounted would be better, but:
+  //   https://github.com/dart-lang/linter/issues/4007
+  if (context.mounted) {
+    final bool shouldShowSnackbar;
+    switch (deviceInfo) {
+      case AndroidDeviceInfo(:var version):
+        // Android 13+ shows its own popup on copying to the clipboard,
+        // so we suppress ours, following the advice at:
+        //   https://developer.android.com/develop/ui/views/touch-and-input/copy-paste#duplicate-notifications
+        // TODO(android-sdk-33): Simplify this and dartdoc
+        shouldShowSnackbar = version.sdkInt <= 32;
+      default:
+        shouldShowSnackbar = true;
+    }
+
+    if (shouldShowSnackbar) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(behavior: SnackBarBehavior.floating, content: successContent));
+    }
+  }
+}