[Formula Android] Track first render.

formula-android-compose/src/main/java/com/instacart/formula/android/compose/ComposeViewFactory.kt

@@ -14,19 +14,28 @@ abstract class ComposeViewFactory<RenderModel> : ViewFactory<RenderModel> {
 
     override fun create(inflater: LayoutInflater, container: ViewGroup?): FeatureView<RenderModel> {
         val view = ComposeView(inflater.context)
+        var firstRender = true
         return FeatureView(
             view = view,
-            bind = {
+            bind = { state ->
                 view.setContent {
-                    val model = it.observable.subscribeAsState(null).value
+                    val model = state.observable.subscribeAsState(null).value
                     if (model != null) {
                         val start = SystemClock.uptimeMillis()
                         Content(model)
                         val end = SystemClock.uptimeMillis()
-                        it.environment.eventListener?.onRendered(
-                            fragmentId = it.fragmentId,
+                        state.environment.eventListener?.onRendered(
+                            fragmentId = state.fragmentId,
                             durationInMillis = end - start,
                         )
+
+                        if (firstRender) {
+                            firstRender = false
+                            state.environment.eventListener?.onFirstModelRendered(
+                                fragmentId = state.fragmentId,
+                                durationInMillis = end - state.initializedAtMillis,
+                            )
+                        }
                     }
                 }
                 null

formula-android/src/main/java/com/instacart/formula/android/FeatureView.kt

@@ -22,6 +22,7 @@ class FeatureView<RenderModel>(
     val lifecycleCallbacks: FragmentLifecycleCallback? = null,
 ) {
     class State<RenderModel>(
+        val initializedAtMillis: Long,
         val fragmentId: FragmentId,
         val environment: FragmentEnvironment,
         val observable: Observable<RenderModel>,

formula-android/src/main/java/com/instacart/formula/android/FormulaFragment.kt

@@ -1,6 +1,7 @@
 package com.instacart.formula.android
 
 import android.os.Bundle
+import android.os.SystemClock
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
@@ -29,6 +30,8 @@ class FormulaFragment : Fragment(), BaseFormulaFragment<Any> {
         requireArguments().getParcelable<FragmentKey>(ARG_CONTRACT)!!
     }
 
+    private val initializedAtMillis = SystemClock.uptimeMillis()
+
     private var featureView: FeatureView<Any>? = null
     private val stateRelay: BehaviorRelay<Any> = BehaviorRelay.create()
     private var cancelable: Cancelable? = null
@@ -50,6 +53,7 @@ class FormulaFragment : Fragment(), BaseFormulaFragment<Any> {
         super.onViewCreated(view, savedInstanceState)
         featureView?.let { value ->
             val state = FeatureView.State(
+                initializedAtMillis = initializedAtMillis,
                 fragmentId = getFormulaFragmentId(),
                 environment = FormulaFragmentDelegate.fragmentEnvironment(),
                 observable = stateRelay,

formula-android/src/main/java/com/instacart/formula/android/FragmentEnvironment.kt

@@ -25,5 +25,11 @@ data class FragmentEnvironment(
          * Called after render model was applied to the [FeatureView].
          */
         fun onRendered(fragmentId: FragmentId, durationInMillis: Long)
+
+        /**
+         * Called after first render model is rendered. The [durationInMillis] starts
+         * when formula fragment is initialized and ends after first render model is applied.
+         */
+        fun onFirstModelRendered(fragmentId: FragmentId, durationInMillis: Long)
     }
 }

formula-android/src/main/java/com/instacart/formula/android/views/FeatureViewBindFunction.kt

@@ -14,6 +14,7 @@ internal class FeatureViewBindFunction<RenderModel>(
 ) : (FeatureView.State<RenderModel>) -> Cancelable? {
     override fun invoke(state: FeatureView.State<RenderModel>): Cancelable {
         val environment = state.environment
+        var firstRender = true
         val disposable = state.observable.subscribe {
             try {
                 val start = SystemClock.uptimeMillis()
@@ -23,6 +24,13 @@ internal class FeatureViewBindFunction<RenderModel>(
                     fragmentId = state.fragmentId,
                     durationInMillis = end - start,
                 )
+                if (firstRender) {
+                    firstRender = false
+                    environment.eventListener?.onFirstModelRendered(
+                        fragmentId = state.fragmentId,
+                        durationInMillis = end - state.initializedAtMillis,
+                    )
+                }
             } catch (exception: Exception) {
                 environment.onScreenError(state.fragmentId.key, exception)
             }