actions [nfc]: Add PlatformActions, alongside ZulipActions

And bring over one function that fits well here.

This seems like a good place to put a function for opening a link;
we'll do that next.

Author: chrisbobbe

lib/model/binding.dart

@@ -32,7 +32,7 @@ typedef FirebaseRemoteMessage = firebase_messaging.RemoteMessage;
 ///
 /// Most code should not interact with the bindings directly.
 /// Instead, use the corresponding higher-level APIs that expose the bindings'
-/// functionality in a widget-oriented way.
+/// functionality in a widget-oriented way; see [PlatformActions] for some.
 ///
 /// This piece of architecture is modelled on the "binding" classes in Flutter
 /// itself.  For discussion, see [BindingBase], [WidgetsFlutterBinding], and

lib/widgets/action_sheet.dart

@@ -15,7 +15,6 @@ import '../model/emoji.dart';
 import '../model/internal_link.dart';
 import '../model/narrow.dart';
 import 'actions.dart';
-import 'clipboard.dart';
 import 'color.dart';
 import 'compose_box.dart';
 import 'dialog.dart';
@@ -910,7 +909,7 @@ class CopyMessageTextButton extends MessageActionSheetMenuItemButton {
 
     if (!pageContext.mounted) return;
 
-    copyWithPopup(context: pageContext,
+    PlatformActions.copyWithPopup(context: pageContext,
       successContent: Text(zulipLocalizations.successMessageTextCopied),
       data: ClipboardData(text: rawContent));
   }
@@ -936,7 +935,7 @@ class CopyMessageLinkButton extends MessageActionSheetMenuItemButton {
       nearMessageId: message.id,
     );
 
-    copyWithPopup(context: pageContext,
+    PlatformActions.copyWithPopup(context: pageContext,
       successContent: Text(zulipLocalizations.successMessageLinkCopied),
       data: ClipboardData(text: messageLink.toString()));
   }

lib/widgets/actions.dart

@@ -1,12 +1,14 @@
 import 'dart:async';
 
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 
 import '../api/exception.dart';
 import '../api/model/model.dart';
 import '../api/model/narrow.dart';
 import '../api/route/messages.dart';
 import '../generated/l10n/zulip_localizations.dart';
+import '../model/binding.dart';
 import '../model/narrow.dart';
 import 'dialog.dart';
 import 'store.dart';
@@ -239,3 +241,44 @@ abstract final class ZulipAction {
     }
   }
 }
+
+/// Methods that act through platform APIs and show feedback in the UI.
+///
+/// The static methods on this class can be thought of as higher-level wrappers
+/// for some of the platform binding methods in [ZulipBinding].
+/// But they don't belong there, because they also interact with widgets
+/// in order to present success or error feedback to the user through the UI.
+abstract final class PlatformActions {
+  /// 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".
+  static void copyWithPopup({
+    required BuildContext context,
+    required ClipboardData data,
+    required Widget successContent,
+  }) async {
+    await Clipboard.setData(data);
+    final deviceInfo = await ZulipBinding.instance.deviceInfo;
+
+    if (!context.mounted) return;
+
+    final shouldShowSnackbar = switch (deviceInfo) {
+      // 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
+      AndroidDeviceInfo(:var sdkInt) => sdkInt <= 32,
+      _                              => true,
+    };
+    if (shouldShowSnackbar) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(behavior: SnackBarBehavior.floating, content: successContent));
+    }
+  }
+}

lib/widgets/clipboard.dart

@@ -9,10 +9,10 @@ import '../api/model/model.dart';
 import '../generated/l10n/zulip_localizations.dart';
 import '../log.dart';
 import '../model/binding.dart';
+import 'actions.dart';
 import 'content.dart';
 import 'dialog.dart';
 import 'page.dart';
-import 'clipboard.dart';
 import 'store.dart';
 
 // TODO(#44): Add index of the image preview in the message, to not break if
@@ -82,7 +82,7 @@ class _CopyLinkButton extends StatelessWidget {
       tooltip: zulipLocalizations.lightboxCopyLinkTooltip,
       icon: const Icon(Icons.copy),
       onPressed: () async {
-        copyWithPopup(context: context,
+        PlatformActions.copyWithPopup(context: context,
           successContent: Text(zulipLocalizations.successLinkCopied),
           data: ClipboardData(text: url.toString()));
       });

lib/widgets/lightbox.dart

@@ -2,22 +2,26 @@ import 'dart:convert';
 
 import 'package:checks/checks.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
 import 'package:zulip/api/model/initial_snapshot.dart';
 import 'package:zulip/api/model/model.dart';
 import 'package:zulip/api/model/narrow.dart';
 import 'package:zulip/api/route/messages.dart';
+import 'package:zulip/model/binding.dart';
 import 'package:zulip/model/localizations.dart';
 import 'package:zulip/model/narrow.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/widgets/actions.dart';
 
 import '../api/fake_api.dart';
 import '../example_data.dart' as eg;
+import '../flutter_checks.dart';
 import '../model/binding.dart';
 import '../model/unreads_checks.dart';
 import '../stdlib_checks.dart';
+import '../test_clipboard.dart';
 import 'dialog_checks.dart';
 import 'test_app.dart';
 
@@ -340,4 +344,75 @@ void main() {
       });
     });
   });
+
+  group('PlatformActions', () {
+    TestZulipBinding.ensureInitialized();
+    TestWidgetsFlutterBinding.ensureInitialized();
+
+    tearDown(() async {
+      testBinding.reset();
+    });
+
+    group('copyWithPopup', () {
+      setUp(() async {
+        TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.setMockMethodCallHandler(
+          SystemChannels.platform,
+          MockClipboard().handleMethodCall,
+        );
+      });
+
+      Future<void> call(WidgetTester tester, {required String text}) async {
+        await tester.pumpWidget(TestZulipApp(
+          child: Scaffold(
+            body: Builder(builder: (context) => Center(
+              child: ElevatedButton(
+                onPressed: () async {
+                  PlatformActions.copyWithPopup(context: context,
+                    successContent: const Text('Text copied'),
+                    data: ClipboardData(text: text));
+                },
+                child: const Text('Copy')))))));
+        await tester.pump();
+        await tester.tap(find.text('Copy'));
+        await tester.pump(); // copy
+        await tester.pump(Duration.zero); // await platform info (awkwardly async)
+      }
+
+      Future<void> checkSnackBar(WidgetTester tester, {required bool expected}) async {
+        if (!expected) {
+          check(tester.widgetList(find.byType(SnackBar))).isEmpty();
+          return;
+        }
+        final snackBar = tester.widget<SnackBar>(find.byType(SnackBar));
+        check(snackBar.behavior).equals(SnackBarBehavior.floating);
+        tester.widget(find.descendant(matchRoot: true,
+          of: find.byWidget(snackBar.content), matching: find.text('Text copied')));
+      }
+
+      Future<void> checkClipboardText(String expected) async {
+        check(await Clipboard.getData('text/plain')).isNotNull().text.equals(expected);
+      }
+
+      testWidgets('iOS', (tester) async {
+        testBinding.deviceInfoResult = const IosDeviceInfo(systemVersion: '16.0');
+        await call(tester, text: 'asdf');
+        await checkClipboardText('asdf');
+        await checkSnackBar(tester, expected: true);
+      });
+
+      testWidgets('Android', (tester) async {
+        testBinding.deviceInfoResult = const AndroidDeviceInfo(sdkInt: 33, release: '13');
+        await call(tester, text: 'asdf');
+        await checkClipboardText('asdf');
+        await checkSnackBar(tester, expected: false);
+      });
+
+      testWidgets('Android <13', (tester) async {
+        testBinding.deviceInfoResult = const AndroidDeviceInfo(sdkInt: 32, release: '12');
+        await call(tester, text: 'asdf');
+        await checkClipboardText('asdf');
+        await checkSnackBar(tester, expected: true);
+      });
+    });
+  });
 }