fix(Android, Stack): don't add top inset to measured header height when it's disabled

android/src/main/java/com/swmansion/rnscreens/legacy/utils/ScreenDummyLayoutHelper.kt

@@ -176,13 +176,19 @@ internal class ScreenDummyLayoutHelper(
      * the cache while a measurement is in progress.
      *
      * @param fontSize font size value as passed from JS
+     * @param isTitleEmpty whether the header title is empty
+     * @param applyTopInset whether the native header applies the top inset (mirrors
+     * `legacyTopInsetBehavior || consumeTopInset` from [CustomToolbar]). When `false`
+     * (e.g. `disableTopInsetApplication`), the top inset must be excluded so the reported
+     * header height matches what actually renders.
      * @return header height in dp as consumed by Yoga
      */
     @DoNotStrip
     @Synchronized
     private fun computeDummyLayout(
         fontSize: Int,
         isTitleEmpty: Boolean,
+        applyTopInset: Boolean,
     ): Float {
         if (!isLayoutInitialized) {
             val reactContext =
@@ -198,7 +204,7 @@ internal class ScreenDummyLayoutHelper(
             }
         }
 
-        if (cache.hasKey(CacheKey(fontSize, isTitleEmpty))) {
+        if (cache.hasKey(CacheKey(fontSize, isTitleEmpty, applyTopInset))) {
             return cache.headerHeight
         }
 
@@ -212,7 +218,7 @@ internal class ScreenDummyLayoutHelper(
         }
 
         val topLevelDecorView = currentActivity.window.decorView
-        val topInset = getDecorViewTopInset(topLevelDecorView)
+        val topInset = if (applyTopInset) getDecorViewTopInset(topLevelDecorView) else 0
 
         // These dimensions are not accurate, as they do include navigation bar, however
         // it is ok for our purposes.
@@ -242,11 +248,13 @@ internal class ScreenDummyLayoutHelper(
         // scenarios when layout violates measured dimensions.
         currentCoordinatorLayout.layout(0, 0, decorViewWidth, decorViewHeight)
 
-        // Include the top inset to account for the extra padding manually applied to the CustomToolbar.
+        // Include the top inset to account for the extra padding manually applied to the
+        // CustomToolbar. When the header opts out of the top inset (`applyTopInset == false`),
+        // `topInset` is 0 here so the measured height matches the rendered header.
         val totalAppBarLayoutHeight = currentAppBarLayout.height.toFloat() + topInset
 
         val headerHeight = PixelUtil.toDIPFromPixel(totalAppBarLayoutHeight)
-        cache = CacheEntry(CacheKey(fontSize, isTitleEmpty), headerHeight)
+        cache = CacheEntry(CacheKey(fontSize, isTitleEmpty, applyTopInset), headerHeight)
         return headerHeight
     }
 
@@ -359,6 +367,7 @@ internal class ScreenDummyLayoutHelper(
 private data class CacheKey(
     val fontSize: Int,
     val isTitleEmpty: Boolean,
+    val applyTopInset: Boolean,
 )
 
 private class CacheEntry(
@@ -368,6 +377,6 @@ private class CacheEntry(
     fun hasKey(key: CacheKey) = cacheKey.fontSize != Int.MIN_VALUE && cacheKey == key
 
     companion object {
-        val EMPTY = CacheEntry(CacheKey(Int.MIN_VALUE, false), 0f)
+        val EMPTY = CacheEntry(CacheKey(Int.MIN_VALUE, false, true), 0f)
     }
 }

apps/src/tests/issue-tests/Test4357.tsx

@@ -0,0 +1,56 @@
+import React, { useState } from 'react';
+import { Button, StyleSheet, View } from 'react-native';
+import { NavigationContainer } from '@react-navigation/native';
+import { createNativeStackNavigator } from '@react-navigation/native-stack';
+import { Colors } from '@apps/shared/styling';
+
+const Stack = createNativeStackNavigator();
+
+const DummyContent = () => <View style={styles.contentContainer} />;
+
+function Screen1() {
+  return <DummyContent />;
+}
+
+function NavigationStack() {
+  return (
+    <NavigationContainer>
+      <Stack.Navigator>
+        <Stack.Screen
+          name="Screen1"
+          component={Screen1}
+          options={{ unstable_headerInsets: { top: false } }}
+        />
+      </Stack.Navigator>
+    </NavigationContainer>
+  );
+}
+
+export default function App() {
+  const [show, setShow] = useState(false);
+
+  if (show) {
+    return <NavigationStack />;
+  }
+
+  return (
+    <View style={styles.centerLayout}>
+      <Button title="Mount Navigation Stack" onPress={() => setShow(true)} />
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  centerLayout: {
+    flex: 1,
+    justifyContent: 'center',
+    alignItems: 'center',
+  },
+  screen: {
+    flex: 1,
+  },
+  contentContainer: {
+    flex: 1,
+    backgroundColor: Colors.NavyDark100,
+  },
+});

apps/src/tests/issue-tests/index.ts

@@ -204,6 +204,7 @@ export { default as Test4258 } from './Test4258';
 export { default as Test4264 } from './Test4264';
 export { default as Test4265 } from './Test4265';
 export { default as Test4276 } from './Test4276';
+export { default as Test4357 } from './Test4357';
 export { default as TestScreenAnimation } from './TestScreenAnimation';
 // The following test was meant to demo the "go back" gesture using Reanimated
 // but the associated PR in react-navigation is currently put on hold

common/cpp/react/renderer/components/rnscreens/legacy/RNSScreenShadowNode.cpp

@@ -32,7 +32,8 @@ static constexpr const char *kScreenDummyLayoutHelperClass =
 
 std::optional<float> findHeaderHeight(
     const int fontSize,
-    const bool isTitleEmpty) {
+    const bool isTitleEmpty,
+    const bool applyTopInset) {
   JNIEnv *env = facebook::jni::Environment::current();
 
   if (env == nullptr) {
@@ -49,7 +50,7 @@ std::optional<float> findHeaderHeight(
   }
 
   jmethodID computeDummyLayoutID =
-      env->GetMethodID(layoutHelperClass, "computeDummyLayout", "(IZ)F");
+      env->GetMethodID(layoutHelperClass, "computeDummyLayout", "(IZZ)F");
 
   if (computeDummyLayoutID == nullptr) {
     LOG(ERROR) << "[RNScreens] Failed to retrieve computeDummyLayout method ID";
@@ -76,7 +77,7 @@ std::optional<float> findHeaderHeight(
   }
 
   jfloat headerHeight = env->CallFloatMethod(
-      packageInstance, computeDummyLayoutID, fontSize, isTitleEmpty);
+      packageInstance, computeDummyLayoutID, fontSize, isTitleEmpty, applyTopInset);
 
   return {headerHeight};
 }
@@ -101,13 +102,23 @@ void RNSScreenShadowNode::appendChild(
           *std::static_pointer_cast<const RNSScreenStackHeaderConfigProps>(
               headerConfigChild->getProps());
 
+      // The native CustomToolbar only pads itself with the top inset when
+      // `legacyTopInsetBehavior || consumeTopInset` holds (see CustomToolbar.kt).
+      // The dummy measurement must mirror that condition, otherwise the header
+      // height is over-reported by the top inset whenever a header opts out via
+      // `disableTopInsetApplication` (consumeTopInset == false).
+      const bool applyTopInset =
+          headerProps.legacyTopInsetBehavior || headerProps.consumeTopInset;
+
       // Translucent headers do not reserve vertical space, so applying the
       // estimated header correction can expose the previous screen at the
       // bottom during the first Fabric layout.
       const auto headerHeight = (headerProps.hidden || headerProps.translucent)
           ? 0.f
           : findHeaderHeight(
-                headerProps.titleFontSize, headerProps.title.empty())
+                headerProps.titleFontSize,
+                headerProps.title.empty(),
+                applyTopInset)
                 .value_or(0.f);
 
       screenShadowNode.setPadding({0, 0, 0, headerHeight});