From bd323929dc5be5666ee36043babec7d981a095dc Mon Sep 17 00:00:00 2001
From: Jakub Piasecki <jakubpiasecki67@gmail.com>
Date: Sat, 21 Sep 2024 06:34:21 -0700
Subject: [PATCH] Add a workaround for text being measured incorrectly when
 ending with an empty line (#42331)

Summary:
It looks like `StaticLayout` used for measuring multiline text on the new architecture returns wrong metrics for the last line if it's empty, however, if it contains anything, then the returned values are correct.

Similar approach with measuring `I` was already used in `ReactEditText`: https://github.com/facebook/react-native/blob/258d8e51b451b221e557dad4647cbd210fe37392/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/textinput/ReactEditText.java#L1203-L1213

## Changelog:

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[ANDROID] [FIXED] - Fixed text being measured incorrectly when ending with an empty line on the new architecture

Pull Request resolved: https://github.com/facebook/react-native/pull/42331

Test Plan:
<details>
<summary>I tested the change on this simple code on React Native 0.73.2 (with the new arch enabled)</summary>

```jsx
import React from 'react';
import {useState} from 'react';
import {SafeAreaView, TextInput} from 'react-native';

export default function App() {
  const [text, setText] = useState('ABC\nDEF\nGHI\n');

  return (
    <SafeAreaView style={{flex: 1}}>
      <TextInput
        value={text}
        onChangeText={setText}
        style={{borderWidth: 1, margin: 20, padding: 30}}
        multiline
      />
    </SafeAreaView>
  );
}
```

</details>

Before:

https://github.com/facebook/react-native/assets/21055725/0787cc86-70c6-4238-b93a-87984e527a83

After:

https://github.com/facebook/react-native/assets/21055725/2acf619f-5cb4-4869-9576-cb8cc081c15b

Reviewed By: cipolleschi

Differential Revision: D62873674

Pulled By: cortinico

fbshipit-source-id: cc2481b1924a13af7326cfc16c59b9390f0d06d8
---
 .../com/facebook/react/views/text/TextLayoutManager.java | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.java b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.java
index 706b77825eb..03303089ca3 100644
--- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.java
+++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.java
@@ -355,6 +355,15 @@ public class TextLayoutManager {
       int hyphenationFrequency,
       Layout.Alignment alignment) {
     Layout layout;
+    // StaticLayout returns wrong metrics for the last line if it's empty, add something to the
+    // last line so it's measured correctly
+    if (text.toString().endsWith("\n")) {
+      SpannableStringBuilder sb = new SpannableStringBuilder(text);
+      sb.append("I");
+
+      text = sb;
+    }
+
     int spanLength = text.length();
     boolean unconstrainedWidth = widthYogaMeasureMode == YogaMeasureMode.UNDEFINED || width < 0;
     float desiredWidth =