From 6a96a9f65546cbe7e5c57a6005f6fa9b15f72b94 Mon Sep 17 00:00:00 2001
From: David Vacca <dvacca@fb.com>
Date: Sat, 16 May 2020 01:03:32 -0700
Subject: [PATCH] Use MC to Start Fabric surfaces using layoutMetrics or not

Summary:
This diff uses a new MC to Start Fabric surfaces using layoutMetrics or not.

The motivation is to verify if the new initialization of fabric surfaces is regressing in production

changelog: [Internal] Internal change in fabric

Reviewed By: JoshuaGross

Differential Revision: D21606971

fbshipit-source-id: ed1f6937ffd0f1e6c54e3ebc34595d75b6c5f6e1
---
 .../facebook/react/ReactInstanceManager.java  | 47 ++++++++++++++-----
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java b/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
index 83a0750f464..63ac2ec11df 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
@@ -1152,18 +1152,30 @@ public class ReactInstanceManager {
 
     final int rootTag;
 
-    if (reactRoot.getUIManagerType() == FABRIC) {
-      rootTag =
-          uiManager.startSurface(
-              reactRoot.getRootViewGroup(),
-              reactRoot.getJSModuleName(),
-              initialProperties == null
-                  ? new WritableNativeMap()
-                  : Arguments.fromBundle(initialProperties),
-              reactRoot.getWidthMeasureSpec(),
-              reactRoot.getHeightMeasureSpec());
-      reactRoot.setRootViewTag(rootTag);
-      reactRoot.setShouldLogContentAppeared(true);
+    if (ReactFeatureFlags.enableFabricStartSurfaceWithLayoutMetrics) {
+      if (reactRoot.getUIManagerType() == FABRIC) {
+        rootTag =
+            uiManager.startSurface(
+                reactRoot.getRootViewGroup(),
+                reactRoot.getJSModuleName(),
+                initialProperties == null
+                    ? new WritableNativeMap()
+                    : Arguments.fromBundle(initialProperties),
+                reactRoot.getWidthMeasureSpec(),
+                reactRoot.getHeightMeasureSpec());
+        reactRoot.setRootViewTag(rootTag);
+        reactRoot.setShouldLogContentAppeared(true);
+      } else {
+        rootTag =
+            uiManager.addRootView(
+                reactRoot.getRootViewGroup(),
+                initialProperties == null
+                    ? new WritableNativeMap()
+                    : Arguments.fromBundle(initialProperties),
+                reactRoot.getInitialUITemplate());
+        reactRoot.setRootViewTag(rootTag);
+        reactRoot.runApplication();
+      }
     } else {
       rootTag =
           uiManager.addRootView(
@@ -1173,8 +1185,17 @@ public class ReactInstanceManager {
                   : Arguments.fromBundle(initialProperties),
               reactRoot.getInitialUITemplate());
       reactRoot.setRootViewTag(rootTag);
-      reactRoot.runApplication();
+      if (reactRoot.getUIManagerType() == FABRIC) {
+        // Fabric requires to call updateRootLayoutSpecs before starting JS Application,
+        // this ensures the root will hace the correct pointScaleFactor.
+        uiManager.updateRootLayoutSpecs(
+            rootTag, reactRoot.getWidthMeasureSpec(), reactRoot.getHeightMeasureSpec());
+        reactRoot.setShouldLogContentAppeared(true);
+      } else {
+        reactRoot.runApplication();
+      }
     }
+
     Systrace.beginAsyncSection(
         TRACE_TAG_REACT_JAVA_BRIDGE, "pre_rootView.onAttachedToReactInstance", rootTag);
     UiThreadUtil.runOnUiThread(