feat: Automatically call FullyDrawnReporter to improve production PGOs

Author: mrousavy

packages/react-native/ReactAndroid/api/ReactAndroid.api

@@ -102,6 +102,7 @@ public class com/facebook/react/ReactActivityDelegate {
 	public fun getReactInstanceManager ()Lcom/facebook/react/ReactInstanceManager;
 	protected fun getReactNativeHost ()Lcom/facebook/react/ReactNativeHost;
 	protected fun isFabricEnabled ()Z
+	protected fun isFullyDrawnReportingEnabled ()Z
 	protected fun isWideColorGamutEnabled ()Z
 	protected fun loadApp (Ljava/lang/String;)V
 	public fun onActivityResult (IILandroid/content/Intent;)V
@@ -138,6 +139,7 @@ public class com/facebook/react/ReactDelegate {
 	public final fun getReactInstanceManager ()Lcom/facebook/react/ReactInstanceManager;
 	public final fun getReactRootView ()Lcom/facebook/react/ReactRootView;
 	protected final fun isFabricEnabled ()Z
+	public final fun isFullyDrawnReportingEnabled ()Z
 	public final fun loadApp ()V
 	public final fun loadApp (Ljava/lang/String;)V
 	public final fun onActivityResult (IILandroid/content/Intent;Z)V
@@ -152,6 +154,7 @@ public class com/facebook/react/ReactDelegate {
 	public final fun onUserLeaveHint ()V
 	public final fun onWindowFocusChanged (Z)V
 	public final fun reload ()V
+	public final fun setFullyDrawnReportingEnabled (Z)V
 	public final fun setReactRootView (Lcom/facebook/react/ReactRootView;)V
 	public final fun setReactSurface (Lcom/facebook/react/interfaces/fabric/ReactSurface;)V
 	public final fun shouldShowDevMenuOrReload (ILandroid/view/KeyEvent;)Z

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactActivityDelegate.java

@@ -168,6 +168,7 @@ protected ReactRootView createRootView() {
                   }
                 };
           }
+          mReactDelegate.setFullyDrawnReportingEnabled(isFullyDrawnReportingEnabled());
           if (mainComponentName != null) {
             LocalNetworkPermissionUtil.requestLocalNetworkAccessIfNeeded(
                 getPlainActivity(), () -> loadApp(mainComponentName));
@@ -322,4 +323,21 @@ protected boolean isFabricEnabled() {
   protected boolean isWideColorGamutEnabled() {
     return false;
   }
+
+  /**
+   * Controls whether {@link Activity#reportFullyDrawn()} is automatically triggered once the
+   * initial content of the React surface has appeared, via the activity's {@code
+   * androidx.activity.FullyDrawnReporter}. Android uses this signal to bound the startup window for
+   * profile guided compilation (Android 12+) and to report time-to-fully-drawn in Android vitals.
+   *
+   * <p>Apps that consider themselves fully drawn only later (e.g. once their initial data has been
+   * rendered) can keep this enabled and additionally register their own reporter on the activity's
+   * {@code FullyDrawnReporter} before the content appears, or override this method to return false
+   * to opt out entirely.
+   *
+   * @return true if fully drawn reporting is enabled for this Activity, false otherwise.
+   */
+  protected boolean isFullyDrawnReportingEnabled() {
+    return true;
+  }
 }

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactDelegate.kt

@@ -12,7 +12,10 @@ import android.content.Intent
 import android.content.res.Configuration
 import android.os.Bundle
 import android.view.KeyEvent
+import androidx.activity.ComponentActivity
 import com.facebook.react.bridge.ReactContext
+import com.facebook.react.bridge.ReactMarker
+import com.facebook.react.bridge.ReactMarkerConstants
 import com.facebook.react.bridge.UiThreadUtil.runOnUiThread
 import com.facebook.react.devsupport.DoubleTapReloadRecognizer
 import com.facebook.react.devsupport.ReleaseDevSupportManager
@@ -51,6 +54,27 @@ public open class ReactDelegate {
    */
   protected val isFabricEnabled: Boolean = true
 
+  /**
+   * Controls whether this delegate reports the host [Activity] as fully drawn once the initial
+   * content of the React surface has appeared.
+   *
+   * When enabled (the default) and the host [Activity] is a [ComponentActivity], a reporter is
+   * added to the activity's [androidx.activity.FullyDrawnReporter] when the surface starts loading
+   * and removed once the first view of the surface is mounted, which calls
+   * [Activity.reportFullyDrawn] after the next frame is drawn. Android uses this signal to bound
+   * the startup window for profile guided compilation (Android 12+) and to report
+   * time-to-fully-drawn in Android vitals.
+   *
+   * Apps that consider themselves fully drawn only later (e.g. once their initial data has been
+   * rendered) can keep this enabled and additionally register their own reporter on the activity's
+   * [androidx.activity.FullyDrawnReporter] before the content appears.
+   *
+   * Must be set before [loadApp] to take effect.
+   */
+  public var isFullyDrawnReportingEnabled: Boolean = true
+
+  private var fullyDrawnMarkerListener: ReactMarker.MarkerListener? = null
+
   /**
    * Do not use this constructor as it's not accounting for New Architecture at all. You should use
    * [ReactDelegate(Activity, ReactNativeHost, String, Bundle, boolean)] as it's the constructor
@@ -318,6 +342,9 @@ public open class ReactDelegate {
    * @param appKey The ID of the app to load into the surface.
    */
   public fun loadApp(appKey: String) {
+    if (isFullyDrawnReportingEnabled) {
+      reportFullyDrawnWhenContentAppears(appKey)
+    }
     // With Bridgeless enabled, create and start the surface
     if (ReactNativeNewArchitectureFeatureFlags.enableBridgelessArchitecture()) {
       val reactHost = reactHost
@@ -340,6 +367,7 @@ public open class ReactDelegate {
 
   /** Stop the React surface started with [ReactDelegate.loadApp]. */
   public fun unloadApp() {
+    cancelFullyDrawnReporting()
     if (ReactNativeNewArchitectureFeatureFlags.enableBridgelessArchitecture()) {
       reactSurface?.stop()
       reactSurface = null
@@ -351,6 +379,41 @@ public open class ReactDelegate {
     }
   }
 
+  private fun reportFullyDrawnWhenContentAppears(appKey: String) {
+    if (fullyDrawnMarkerListener != null) {
+      return
+    }
+    val fullyDrawnReporter = (activity as? ComponentActivity)?.fullyDrawnReporter ?: return
+    if (fullyDrawnReporter.isFullyDrawnReported) {
+      return
+    }
+    fullyDrawnReporter.addReporter()
+    val listener =
+        object : ReactMarker.MarkerListener {
+          override fun logMarker(name: ReactMarkerConstants, tag: String?, instanceKey: Int) {
+            if (name == ReactMarkerConstants.CONTENT_APPEARED && tag == appKey) {
+              // CONTENT_APPEARED is logged on the UI thread, so this cannot race with
+              // cancelFullyDrawnReporting or a second loadApp.
+              if (fullyDrawnMarkerListener !== this) {
+                return
+              }
+              fullyDrawnMarkerListener = null
+              ReactMarker.removeListener(this)
+              fullyDrawnReporter.removeReporter()
+            }
+          }
+        }
+    fullyDrawnMarkerListener = listener
+    ReactMarker.addListener(listener)
+  }
+
+  private fun cancelFullyDrawnReporting() {
+    val listener = fullyDrawnMarkerListener ?: return
+    fullyDrawnMarkerListener = null
+    ReactMarker.removeListener(listener)
+    (activity as? ComponentActivity)?.fullyDrawnReporter?.removeReporter()
+  }
+
   public fun setReactSurface(reactSurface: ReactSurface?) {
     this.reactSurface = reactSurface
   }