Fix slow animation mode on Android

packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/NodesManager.java

@@ -3,6 +3,7 @@
 import static java.lang.Float.NaN;
 
 import android.graphics.drawable.Drawable;
+import android.os.SystemClock;
 import android.view.View;
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.GuardedRunnable;
@@ -50,6 +51,10 @@
 
 public class NodesManager implements EventDispatcherListener {
 
+  private Long mFirstUptime = SystemClock.uptimeMillis();
+  private boolean mSlowAnimationsEnabled = false;
+  private int mAnimationsDragFactor;
+
   public void scrollTo(int viewTag, double x, double y, boolean animated) {
     View view;
     try {
@@ -268,6 +273,10 @@ private void onAnimationFrame(long frameTimeNanos) {
     // Systrace.beginSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, "onAnimationFrame");
 
     double currentFrameTimeMs = frameTimeNanos / 1000000.;
+    if (mSlowAnimationsEnabled) {
+      currentFrameTimeMs =
+          mFirstUptime + (currentFrameTimeMs - mFirstUptime) / mAnimationsDragFactor;
+    }
 
     if (currentFrameTimeMs > lastFrameTimeMs) {
       // It is possible for ChoreographerCallback to be executed twice within the same frame
@@ -523,4 +532,12 @@ private static void addProp(WritableMap propMap, String key, Object value) {
       throw new IllegalStateException("[Reanimated] Unknown type of animated value.");
     }
   }
+
+  public void enableSlowAnimations(boolean slowAnimationsEnabled, int animationsDragFactor) {
+    mSlowAnimationsEnabled = slowAnimationsEnabled;
+    mAnimationsDragFactor = animationsDragFactor;
+    if (slowAnimationsEnabled) {
+      mFirstUptime = SystemClock.uptimeMillis();
+    }
+  }
 }

packages/react-native-reanimated/android/src/main/java/com/swmansion/reanimated/nativeProxy/NativeProxyCommon.java

@@ -45,6 +45,7 @@ public abstract class NativeProxyCommon {
   private KeyboardAnimationManager keyboardAnimationManager;
   private Long firstUptime = SystemClock.uptimeMillis();
   private boolean slowAnimationsEnabled = false;
+  private final int ANIMATIONS_DRAG_FACTOR = 10;
   protected String cppVersion = null;
 
   protected NativeProxyCommon(ReactApplicationContext context) {
@@ -78,6 +79,7 @@ private void toggleSlowAnimations() {
     if (slowAnimationsEnabled) {
       firstUptime = SystemClock.uptimeMillis();
     }
+    mNodesManager.enableSlowAnimations(slowAnimationsEnabled, ANIMATIONS_DRAG_FACTOR);
   }
 
   private void addDevMenuOption() {
@@ -156,7 +158,6 @@ public void setGestureState(int handlerTag, int newState) {
   @DoNotStrip
   public long getAnimationTimestamp() {
     if (slowAnimationsEnabled) {
-      final long ANIMATIONS_DRAG_FACTOR = 10;
       return this.firstUptime
           + (SystemClock.uptimeMillis() - this.firstUptime) / ANIMATIONS_DRAG_FACTOR;
     } else {

packages/react-native-reanimated/cspell.json

@@ -15,6 +15,7 @@
     "collapsable",
     "devs",
     "easings",
+    "gesturehandler",
     "inout",
     "ispreview",
     "layoutable",