setting [nfc]: Make in-app explicitly the browser preference on Android

The url_launcher documentation warns that the meaning of
platformDefault may change at any time.  We've chosen
particular behaviors we want on different platforms, so
express those choices explicitly.

This change is NFC given the current behavior of url_launcher,
which appears to be that platformDefault means an in-app browser
for at least HTTP links.

Co-authored-by: Greg Price <[email protected]>
Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/model/settings.dart

@@ -1,4 +1,8 @@
+import 'package:flutter/foundation.dart';
+
 import '../generated/l10n/zulip_localizations.dart';
+import 'binding.dart';
+import 'database.dart';
 
 /// The user's choice of visual theme for the app.
 ///
@@ -34,8 +38,46 @@ enum ThemeSetting {
 /// Write a migration if such a change is necessary.
 enum BrowserPreference {
   /// Use the in-app browser for HTTP links.
+  ///
+  /// For other types of links (e.g. mailto) where a browser won't work,
+  /// this falls back to [UrlLaunchMode.platformDefault].
   inApp,
 
   /// Use the user's default browser app.
   external,
 }
+
+extension GlobalSettingsHelpers on GlobalSettingsData {
+  BrowserPreference get defaultBrowserPreference {
+    return switch (defaultTargetPlatform) {
+      // On iOS we prefer UrlLaunchMode.externalApplication because (for
+      // HTTP URLs) UrlLaunchMode.platformDefault uses SFSafariViewController,
+      // which gives an awkward UX as described here:
+      //  https://chat.zulip.org/#narrow/stream/48-mobile/topic/in-app.20browser/near/1169118
+      TargetPlatform.iOS => BrowserPreference.external,
+
+      // On Android we prefer an in-app browser.  See discussion from 2021:
+      //   https://chat.zulip.org/#narrow/channel/48-mobile/topic/in-app.20browser/near/1169095
+      // That's also the `url_launcher` default (at least as of 2025).
+      _ => BrowserPreference.inApp,
+    };
+  }
+
+  UrlLaunchMode getUrlLaunchMode(Uri url) {
+    switch (defaultBrowserPreference) {
+      case BrowserPreference.inApp:
+        if (!(url.scheme == 'https' || url.scheme == 'http')) {
+          // For URLs on non-HTTP schemes such as `mailto`,
+          // `url_launcher.launchUrl` rejects `inAppBrowserView` with an error:
+          //   https://github.com/flutter/packages/blob/9cc6f370/packages/url_launcher/url_launcher/lib/src/url_launcher_uri.dart#L46-L51
+          // TODO(upstream/url_launcher): should fall back in this case instead
+          //   (as the `launchUrl` doc already says it may do).
+          return UrlLaunchMode.platformDefault;
+        }
+        return UrlLaunchMode.inAppBrowserView;
+
+      case BrowserPreference.external:
+        return UrlLaunchMode.externalApplication;
+    }
+  }
+}

lib/widgets/content.dart

@@ -1,7 +1,6 @@
 import 'dart:async';
 
 import 'package:flutter/cupertino.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
@@ -16,6 +15,7 @@ import '../model/avatar_url.dart';
 import '../model/binding.dart';
 import '../model/content.dart';
 import '../model/internal_link.dart';
+import '../model/settings.dart';
 import 'code_block.dart';
 import 'dialog.dart';
 import 'icons.dart';
@@ -1439,18 +1439,12 @@ void _launchUrl(BuildContext context, String urlString) async {
     return;
   }
 
+  final globalSettings = GlobalStoreWidget.of(context).globalSettings;
   bool launched = false;
   String? errorMessage;
   try {
     launched = await ZulipBinding.instance.launchUrl(url,
-      mode: switch (defaultTargetPlatform) {
-        // On iOS we prefer LaunchMode.externalApplication because (for
-        // HTTP URLs) LaunchMode.platformDefault uses SFSafariViewController,
-        // which gives an awkward UX as described here:
-        //  https://chat.zulip.org/#narrow/stream/48-mobile/topic/in-app.20browser/near/1169118
-        TargetPlatform.iOS => UrlLaunchMode.externalApplication,
-        _ => UrlLaunchMode.platformDefault,
-      });
+      mode: globalSettings.getUrlLaunchMode(url));
   } on PlatformException catch (e) {
     errorMessage = e.message;
   }

test/model/settings_test.dart

@@ -0,0 +1,31 @@
+import 'package:checks/checks.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:zulip/model/binding.dart';
+
+import '../example_data.dart' as eg;
+import 'store_checks.dart';
+import 'store_test.dart';
+
+void main() {
+  final httpLink = Uri.parse('http://chat.zulip.org');
+  final nonHttpLink = Uri.parse('mailto:[email protected]');
+
+  group('getUrlLaunchMode', () {
+    testAndroidIos('use our per-platform defaults for HTTP links', () {
+      final globalStore = eg.globalStore(globalSettings: eg.globalSettings(
+        browserPreference: null));
+      check(globalStore).globalSettings.getUrlLaunchMode(httpLink).equals(
+        defaultTargetPlatform == TargetPlatform.iOS
+          ? UrlLaunchMode.externalApplication : UrlLaunchMode.inAppBrowserView);
+    });
+
+    testAndroidIos('use our per-platform defaults for non-HTTP links', () {
+      final globalStore = eg.globalStore(globalSettings: eg.globalSettings(
+        browserPreference: null));
+      check(globalStore).globalSettings.getUrlLaunchMode(nonHttpLink).equals(
+        defaultTargetPlatform == TargetPlatform.android
+          ? UrlLaunchMode.platformDefault : UrlLaunchMode.externalApplication);
+    });
+  });
+}

test/model/store_checks.dart

@@ -3,6 +3,7 @@ import 'package:zulip/api/core.dart';
 import 'package:zulip/api/model/initial_snapshot.dart';
 import 'package:zulip/api/model/model.dart';
 import 'package:zulip/model/autocomplete.dart';
+import 'package:zulip/model/binding.dart';
 import 'package:zulip/model/database.dart';
 import 'package:zulip/model/recent_dm_conversations.dart';
 import 'package:zulip/model/settings.dart';
@@ -32,6 +33,8 @@ extension GlobalStoreChecks on Subject<GlobalStore> {
 extension GlobalSettingsDataChecks on Subject<GlobalSettingsData> {
   Subject<ThemeSetting?> get themeSetting => has((x) => x.themeSetting, 'themeSetting');
   Subject<BrowserPreference?> get browserPreference => has((x) => x.browserPreference, 'browserPreference');
+  Subject<BrowserPreference> get defaultBrowserPreference => has((x) => x.defaultBrowserPreference, 'defaultBrowserPreference');
+  Subject<UrlLaunchMode> getUrlLaunchMode(Uri url) => has((x) => x.getUrlLaunchMode(url), 'getUrlLaunchMode');
 }
 
 extension PerAccountStoreChecks on Subject<PerAccountStore> {

test/widgets/content_test.dart

@@ -521,7 +521,7 @@ void main() {
       final expectedLaunchUrl = expectedVideo.hrefUrl;
       await tester.tap(find.byIcon(Icons.play_arrow_rounded));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse(expectedLaunchUrl), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse(expectedLaunchUrl), mode: LaunchMode.inAppBrowserView));
     }
 
     testWidgets('video preview for youtube embed', (tester) async {
@@ -793,7 +793,7 @@ void main() {
       await tapText(tester, find.text('hello'));
 
       final expectedLaunchMode = defaultTargetPlatform == TargetPlatform.iOS ?
-        LaunchMode.externalApplication : LaunchMode.platformDefault;
+        LaunchMode.externalApplication : LaunchMode.inAppBrowserView;
       check(testBinding.takeLaunchUrlCalls())
         .single.equals((url: Uri.parse('https://example/'), mode: expectedLaunchMode));
     }, variant: const TargetPlatformVariant({TargetPlatform.android, TargetPlatform.iOS}));
@@ -811,19 +811,19 @@ void main() {
 
       await tester.tapAt(base.translate(1*fontSize, 0)); // "fXo bar baz"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.inAppBrowserView));
 
       await tester.tapAt(base.translate(9*fontSize, 0)); // "foo bar bXz"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://b/'), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse('https://b/'), mode: LaunchMode.inAppBrowserView));
     });
 
     testWidgets('link nested in other spans', (tester) async {
       await prepare(tester,
         '<p><strong><em><a href="https://a/">word</a></em></strong></p>');
       await tapText(tester, find.text('word'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.inAppBrowserView));
     });
 
     testWidgets('link containing other spans', (tester) async {
@@ -836,27 +836,27 @@ void main() {
 
       await tester.tapAt(base.translate(1*fontSize, 0)); // "tXo words"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.inAppBrowserView));
 
       await tester.tapAt(base.translate(6*fontSize, 0)); // "two woXds"
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.inAppBrowserView));
     });
 
     testWidgets('relative links are resolved', (tester) async {
       await prepare(tester,
         '<p><a href="/a/b?c#d">word</a></p>');
       await tapText(tester, find.text('word'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('${eg.realmUrl}a/b?c#d'), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse('${eg.realmUrl}a/b?c#d'), mode: LaunchMode.inAppBrowserView));
     });
 
     testWidgets('link inside HeadingNode', (tester) async {
       await prepare(tester,
         '<h6><a href="https://a/">word</a></h6>');
       await tapText(tester, find.text('word'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.platformDefault));
+        .single.equals((url: Uri.parse('https://a/'), mode: LaunchMode.inAppBrowserView));
     });
 
     testWidgets('error dialog if invalid link', (tester) async {
@@ -910,7 +910,7 @@ void main() {
       await tapText(tester, find.text('invalid'));
       final expectedUrl = eg.realmUrl.resolve('/#narrow/stream/1-check/topic');
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: expectedUrl, mode: LaunchMode.platformDefault));
+        .single.equals((url: expectedUrl, mode: LaunchMode.inAppBrowserView));
       check(pushedRoutes).isEmpty();
     });
   });
@@ -1060,11 +1060,11 @@ void main() {
 
       await tester.tap(find.text('Zulip — organized team chat'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: url, mode: LaunchMode.platformDefault));
+        .single.equals((url: url, mode: LaunchMode.inAppBrowserView));
 
       await tester.tap(find.byType(RealmContentNetworkImage));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: url, mode: LaunchMode.platformDefault));
+        .single.equals((url: url, mode: LaunchMode.inAppBrowserView));
       debugNetworkImageHttpClientProvider = null;
     });
 
@@ -1078,7 +1078,7 @@ void main() {
 
       await tester.tap(find.byType(RealmContentNetworkImage));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: url, mode: LaunchMode.platformDefault));
+        .single.equals((url: url, mode: LaunchMode.inAppBrowserView));
       debugNetworkImageHttpClientProvider = null;
     });
 
@@ -1088,11 +1088,11 @@ void main() {
 
       await tester.tap(find.text('Zulip — organized team chat'));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: url, mode: LaunchMode.platformDefault));
+        .single.equals((url: url, mode: LaunchMode.inAppBrowserView));
 
       await tester.tap(find.byType(RealmContentNetworkImage));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: url, mode: LaunchMode.platformDefault));
+        .single.equals((url: url, mode: LaunchMode.inAppBrowserView));
       debugNetworkImageHttpClientProvider = null;
     });
 
@@ -1102,7 +1102,7 @@ void main() {
 
       await tester.tap(find.byType(RealmContentNetworkImage));
       check(testBinding.takeLaunchUrlCalls())
-        .single.equals((url: url, mode: LaunchMode.platformDefault));
+        .single.equals((url: url, mode: LaunchMode.inAppBrowserView));
       debugNetworkImageHttpClientProvider = null;
     });
   });

test/widgets/profile_test.dart

@@ -164,7 +164,7 @@ void main() {
       await tester.tap(find.text(testUrl));
       check(testBinding.takeLaunchUrlCalls()).single.equals((
         url: Uri.parse(testUrl),
-        mode: LaunchMode.platformDefault,
+        mode: LaunchMode.inAppBrowserView,
       ));
     });
 
@@ -191,7 +191,7 @@ void main() {
       await tester.tap(find.text('externalValue'));
       check(testBinding.takeLaunchUrlCalls()).single.equals((
         url: Uri.parse('http://example/externalValue'),
-        mode: LaunchMode.platformDefault,
+        mode: LaunchMode.inAppBrowserView,
       ));
     });