Follow a native call into picture-in-picture from the app

supportsPictureInPicture and smallestScreenSize have to be declared here, because a library cannot change a host Activity's manifest entry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -53,9 +53,10 @@
         -->
         <activity
             android:name=".MainActivity"
-            android:configChanges="orientation|screenSize|screenLayout|keyboardHidden|uiMode"
+            android:configChanges="orientation|screenSize|smallestScreenSize|screenLayout|keyboardHidden|uiMode"
             android:exported="true"
             android:launchMode="singleTask"
+            android:supportsPictureInPicture="true"
             android:theme="@style/Theme.ElementX.Splash"
             android:windowSoftInputMode="adjustResize">
             <intent-filter>

app/src/main/kotlin/io/element/android/x/MainActivity.kt

@@ -70,6 +70,19 @@ class MainActivity : NodeActivity() {
         }
     }
 
+    /**
+     * The pre-Android 12 way into picture-in-picture for a native call.
+     *
+     * Everything else about it is installed where the call is drawn, which knows whose call it is.
+     * This cannot be: an Activity override has no session in scope. From Android 12 the system is told
+     * up front that this Activity would like to shrink, and the call handles it without ever coming
+     * through here.
+     */
+    override fun onUserLeaveHint() {
+        super.onUserLeaveHint()
+        appBindings.nativeCallPip().onUserLeaveHint(this)
+    }
+
     @Composable
     private fun MainContent(appBindings: AppBindings) {
         val migrationState = appBindings.migrationEntryPoint().present()

app/src/main/kotlin/io/element/android/x/di/AppBindings.kt

@@ -12,6 +12,7 @@ import dev.zacsweers.metro.AppScope
 import dev.zacsweers.metro.ContributesTo
 import dev.zacsweers.metro.Multibinds
 import io.element.android.features.api.MigrationEntryPoint
+import io.element.android.features.callnative.api.NativeCallPip
 import io.element.android.features.enterprise.api.AppStartupHook
 import io.element.android.features.enterprise.api.EnterpriseService
 import io.element.android.features.lockscreen.api.LockScreenEntryPoint
@@ -52,6 +53,13 @@ interface AppBindings {
 
     fun buildMeta(): BuildMeta
 
+    /**
+     * For picture-in-picture. Only an Activity is told it is being left, and only the call knows
+     * whether that is worth shrinking for, so `MainActivity` needs this much of the native call and
+     * no more.
+     */
+    fun nativeCallPip(): NativeCallPip
+
     fun sentrySdkDsn(): SentrySdkDsn?
 
     @Multibinds(allowEmpty = true)