Combine and simplify legacy ffi plugin pages (#13469)

Combine the 3 pages (iOS, macOS, Android) covering the legacy template
and mechanisms into a single, cleaned up page so we have a smaller
legacy surface to maintain while not confusing developers who already
used the template or are still using the mechanisms used by it. Also
completes some clean up, updates, and fixes to the consolidated content.

However, removes or updates the remaining links to the legacy pages to
their more up-to-date counterparts.

Contributes to #13313

Author: parlough

firebase.json

@@ -167,20 +167,23 @@
       { "source": "/learn/learning-resources", "destination": "/reference/learning-resources", "type": 301 },
       { "source": "/material-3-migration", "destination": "/release/breaking-changes/material-3-migration", "type": 301 },
       { "source": "/packages-and-plugins/androidx-compatibility", "destination": "/platform-integration/android/androidx-migration", "type": 301 },
-      { "source": "/packages-and-plugins/c-interop", "destination": "/platform-integration/android/c-interop", "type": 301 },
+      { "source": "/packages-and-plugins/c-interop", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/packages-and-plugins/plugins-in-tests", "destination": "/testing/plugins-in-tests", "type": 301 },
       { "source": "/packages-and-plugins/plugin-api-migration", "destination": "/release/breaking-changes/plugin-api-migration", "type": 301 },
       { "source": "/platform-integration/android/androidx-migration", "destination": "/release/breaking-changes/androidx-migration", "type": 301 },
+      { "source": "/platform-integration/android/c-interop", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/platform-integration/android/install-android", "destination": "/platform-integration/android/setup", "type": 301 },
       { "source": "/platform-integration/android/install-android/:rest*", "destination": "/platform-integration/android/setup", "type": 301 },
       { "source": "/platform-integration/android/splash-screen-migration", "destination": "/release/breaking-changes/splash-screen-migration", "type": 301 },
-      { "source": "/platform-integration/c-interop", "destination": "/platform-integration", "type": 301 },
+      { "source": "/platform-integration/c-interop", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/platform-integration/ios-app-clip", "destination": "/platform-integration/ios/ios-app-clip", "type": 301 },
+      { "source": "/platform-integration/ios/c-interop", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/platform-integration/ios/install-ios", "destination": "/platform-integration/ios/setup", "type": 301 },
       { "source": "/platform-integration/ios/install-ios/:rest*", "destination": "/platform-integration/ios/setup", "type": 301 },
       { "source": "/platform-integration/ios/splash-screen", "destination": "/platform-integration/ios/launch-screen", "type": 301 },
       { "source": "/platform-integration/linux/install-linux", "destination": "/platform-integration/linux/setup", "type": 301 },
       { "source": "/platform-integration/linux/install-linux/:rest*", "destination": "/platform-integration/linux/setup", "type": 301 },
+      { "source": "/platform-integration/macos/c-interop", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/platform-integration/macos/install-macos", "destination": "/platform-integration/macos/setup", "type": 301 },
       { "source": "/platform-integration/macos/install-macos/:rest*", "destination": "/platform-integration/macos/setup", "type": 301 },
       { "source": "/platform-integration/platform-adaptations", "destination": "/ui/adaptive-responsive/platform-adaptations", "type": 301 },
@@ -809,7 +812,7 @@
       { "source": "/to/add-to-app", "destination": "/add-to-app", "type": 301 },
       { "source": "/to/add-swift-package-manager-manually", "destination": "/packages-and-plugins/swift-package-manager/for-app-developers#add-to-a-flutter-app-manually", "type": 301 },
       { "source": "/to/add-web-support", "destination": "/platform-integration/web/building#add-web-support-to-an-existing-app", "type": 301 },
-      { "source": "/to/android-ffi", "destination": "/platform-integration/android/c-interop", "type": 301 },
+      { "source": "/to/android-ffi", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/to/android-setup", "destination": "/platform-integration/android/setup", "type": 301 },
       { "source": "/to/android-supported-architectures", "destination": "/deployment/android#what-are-the-supported-target-architectures", "type": 301 },
       { "source": "/to/asset-from-package", "destination": "/ui/assets/assets-and-images#from-packages", "type": 301 },
@@ -860,16 +863,15 @@
       { "source": "/to/ios-create-flutter-engine", "destination": "/add-to-app/ios/add-flutter-screen#create-a-flutterengine", "type": 301 },
       { "source": "/to/ios-deploy", "destination": "/deployment/ios", "type": 301 },
       { "source": "/to/ios-development-team", "destination": "/deployment/ios#review-xcode-project-settings", "type": 301 },
-      { "source": "/to/ios-ffi", "destination": "/platform-integration/ios/c-interop", "type": 301 },
-      { "source": "/platform-integration/ios/c-interop", "destination": "/platform-integration/bind-native-code", "type": 301 },
+      { "source": "/to/ios-ffi", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/to/ios-minimum-target", "destination": "/deployment/ios#review-xcode-project-settings", "type": 301 },
       { "source": "/to/to/java-gradle-incompatibility", "destination": "/release/breaking-changes/android-java-gradle-migration-guide", "type": 301 },
       { "source": "/to/java-gradle-incompatibility", "destination": "/release/breaking-changes/android-java-gradle-migration-guide", "type": 301 },
       { "source": "/to/linux-android-setup", "destination": "/platform-integration/android/setup", "type": 301 },
       { "source": "/to/macos-android-setup", "destination": "/platform-integration/android/setup", "type": 301 },
       { "source": "/to/macos-deploy", "destination": "/deployment/macos", "type": 301 },
       { "source": "/to/macos-entitlements", "destination": "/platform-integration/macos/building#entitlements-and-the-app-sandbox", "type": 301 },
-      { "source": "/to/macos-ffi", "destination": "/platform-integration/macos/c-interop", "type": 301 },
+      { "source": "/to/macos-ffi", "destination": "/platform-integration/legacy-ffi-plugin", "type": 301 },
       { "source": "/to/macos-ios-setup", "destination": "/platform-integration/ios/setup", "type": 301 },
       { "source": "/to/macos-minimum-target", "destination": "/deployment/ios#review-xcode-project-settings", "type": 301 },
       { "source": "/to/minimize-layout-passes", "destination": "/perf/best-practices#minimize-layout-passes-caused-by-intrinsic-operations", "type": 301 },

sites/docs/src/_includes/docs/resource-links/ffi-video-resources.md

@@ -1026,8 +1026,6 @@ file, like any other Dart package.
 [Effective Dart Documentation]: {{site.dart-site}}/guides/language/effective-dart/documentation
 [federated plugins]: #federated-plugins
 [ffigen docs]: {{site.pub-pkg}}/ffigen/install
-[Android]: /platform-integration/android/c-interop
-[macOS]: /platform-integration/macos/c-interop
 [`fluro`]: {{site.pub}}/packages/fluro
 [Flutter editor]: /tools/editors
 [Flutter Favorites]: {{site.pub}}/flutter/favorites

sites/docs/src/content/packages-and-plugins/developing-packages.md

@@ -377,7 +377,7 @@ or begin improving integration with Android.
           <a class="text-button" href="/deployment/android">Build and deploy to Android</a>
         </li>
         <li>
-          <a class="text-button" href="/platform-integration/android/c-interop">Bind to native Android code</a>
+          <a class="text-button" href="/platform-integration/bind-native-code">Bind to native Android code</a>
         </li>
         <li>
           <a class="text-button" href="/platform-integration/android/splash-screen">Add a splash screen</a>

sites/docs/src/content/platform-integration/android/c-interop.md

@@ -17,6 +17,12 @@ If you need to use the Flutter Plugin API, or if you need to configure a Google
 Play services runtime on Android, use the standard plugin template (`flutter create
 --template=plugin`).
 
+:::note
+Looking for the previous FFI plugin workflow? See
+[Bind to native code using the legacy FFI plugin template](/platform-integration/legacy-ffi-plugin),
+which documents the `plugin_ffi` template and OS-specific build files.
+:::
+
 [build hooks]: https://dart.dev/tools/hooks
 [dart:ffi]: {{site.dart.api}}/dart-ffi/dart-ffi-library.html
 [FFI]: https://en.wikipedia.org/wiki/Foreign_function_interface
@@ -107,6 +113,14 @@ For many system libraries on Android, iOS, Linux, and macOS, you can use
 For Windows, you often use `DynamicLoadingSystem()` and provide the name of the
 DLL.
 
+:::note
+For desktop-specific guidance on calling system APIs—including wrapper
+packages like [`package:win32`]({{site.pub-pkg}}/win32) and
+[Canonical's Linux packages]({{site.pub}}/publishers/canonical.com/packages)—see
+[Integrating with Windows](/platform-integration/windows/building#integrating-with-windows)
+and [Integrate with Linux](/platform-integration/linux/building#integrate-with-linux).
+:::
+
 Here is an example `build.dart` that links against system libraries to get the
 host name:
 

sites/docs/src/content/platform-integration/android/setup.md

@@ -141,12 +141,12 @@ Learn how to add custom integrations with Android to your Flutter app.
       <p>Learn how the latest Android APIs in your app from Dart.</p>
     </div>
   </a>
-  <a class="card outlined-card" href="/platform-integration/android/c-interop">
+  <a class="card outlined-card" href="/platform-integration/bind-native-code">
     <div class="card-header">
       <span class="card-title">Bind to native code</span>
     </div>
     <div class="card-content">
-      <p>Learn how to bind to native C code from your app on Android.</p>
+      <p>Learn how to bind to native code from your app on Android.</p>
     </div>
   </a>
   <a class="card outlined-card" href="/platform-integration/android/platform-views">
@@ -188,6 +188,14 @@ Learn how to add custom integrations with iOS to your Flutter app.
       <p>Learn about plugins that support functionality from native iOS frameworks.</p>
     </div>
   </a>
+  <a class="card outlined-card" href="/platform-integration/bind-native-code">
+    <div class="card-header">
+      <span class="card-title">Bind to native code</span>
+    </div>
+    <div class="card-content">
+      <p>Learn how to bind to native code from your app on iOS.</p>
+    </div>
+  </a>
   <a class="card outlined-card" href="/platform-integration/ios/platform-views">
     <div class="card-header">
       <span class="card-title">Embed an iOS view</span>
@@ -228,14 +236,6 @@ web platform to your Flutter app.
       <p>Customize how your Flutter app is initialized on the web.</p>
     </div>
   </a>
-  <a class="card outlined-card" href="/platform-integration/android/c-interop">
-    <div class="card-header">
-      <span class="card-title">Bind to native code</span>
-    </div>
-    <div class="card-content">
-      <p>Learn how to bind to native C code from your app on Android.</p>
-    </div>
-  </a>
   <a class="card outlined-card" href="/platform-integration/web/web-content-in-flutter">
     <div class="card-header">
       <span class="card-title">Embed web content</span>
@@ -309,12 +309,12 @@ Learn how to add custom integrations with Windows to your Flutter app.
 Learn how to add custom integrations with macOS to your Flutter app.
 
 <div class="card-grid">
-  <a class="card outlined-card" href="/platform-integration/macos/c-interop">
+  <a class="card outlined-card" href="/platform-integration/bind-native-code">
     <div class="card-header">
       <span class="card-title">Bind to native code</span>
     </div>
     <div class="card-content">
-      <p>Learn how to bind to native C, Objective-C, and Swift code from your app.</p>
+      <p>Learn how to bind to native code from your app on macOS.</p>
     </div>
   </a>
   <a class="card outlined-card" href="/platform-integration/macos/platform-views">

sites/docs/src/content/platform-integration/bind-native-code.md

@@ -251,6 +251,9 @@ or begin improving integration with iOS.
         <li>
           <a class="text-button" href="/deployment/ios">Build and deploy to iOS</a>
         </li>
+        <li>
+          <a class="text-button" href="/platform-integration/bind-native-code">Bind to native iOS code</a>
+        </li>
         <li>
           <a class="text-button" href="/platform-integration/ios/apple-frameworks">Leverage system frameworks</a>
         </li>