From 70cc27c901aeb447910e30ac3ceac85990d3c16d Mon Sep 17 00:00:00 2001
From: Samuel Susla <samuelsusla@meta.com>
Date: Fri, 14 Oct 2022 10:32:50 -0700
Subject: [PATCH] Center text if line height isn't 0

Summary: changelog: Fix vertical text alignment in new architecture when line height is not 0.

Reviewed By: javache

Differential Revision: D40346225

fbshipit-source-id: f6282cb8df80e9a543e5602fddcca1a1a82377e3
---
 .../platform/ios/RCTAttributedTextUtils.mm    | 46 ++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/ReactCommon/react/renderer/textlayoutmanager/platform/ios/RCTAttributedTextUtils.mm b/ReactCommon/react/renderer/textlayoutmanager/platform/ios/RCTAttributedTextUtils.mm
index 0a5828ab7f5dbd..1e2343cde80193 100644
--- a/ReactCommon/react/renderer/textlayoutmanager/platform/ios/RCTAttributedTextUtils.mm
+++ b/ReactCommon/react/renderer/textlayoutmanager/platform/ios/RCTAttributedTextUtils.mm
@@ -305,6 +305,50 @@ inline static CGFloat RCTEffectiveFontSizeMultiplierFromTextAttributes(const Tex
   return [attributes copy];
 }
 
+static void RCTApplyBaselineOffset(NSMutableAttributedString *attributedText)
+{
+  __block CGFloat maximumLineHeight = 0;
+
+  [attributedText enumerateAttribute:NSParagraphStyleAttributeName
+                             inRange:NSMakeRange(0, attributedText.length)
+                             options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired
+                          usingBlock:^(NSParagraphStyle *paragraphStyle, __unused NSRange range, __unused BOOL *stop) {
+                            if (!paragraphStyle) {
+                              return;
+                            }
+
+                            maximumLineHeight = MAX(paragraphStyle.maximumLineHeight, maximumLineHeight);
+                          }];
+
+  if (maximumLineHeight == 0) {
+    // `lineHeight` was not specified, nothing to do.
+    return;
+  }
+
+  __block CGFloat maximumFontLineHeight = 0;
+
+  [attributedText enumerateAttribute:NSFontAttributeName
+                             inRange:NSMakeRange(0, attributedText.length)
+                             options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired
+                          usingBlock:^(UIFont *font, NSRange range, __unused BOOL *stop) {
+                            if (!font) {
+                              return;
+                            }
+
+                            maximumFontLineHeight = MAX(font.lineHeight, maximumFontLineHeight);
+                          }];
+
+  if (maximumLineHeight < maximumFontLineHeight) {
+    return;
+  }
+
+  CGFloat baseLineOffset = (maximumLineHeight - maximumFontLineHeight) / 2.0;
+
+  [attributedText addAttribute:NSBaselineOffsetAttributeName
+                         value:@(baseLineOffset)
+                         range:NSMakeRange(0, attributedText.length)];
+}
+
 NSAttributedString *RCTNSAttributedStringFromAttributedString(const AttributedString &attributedString)
 {
   static UIImage *placeholderImage;
@@ -357,7 +401,7 @@ inline static CGFloat RCTEffectiveFontSizeMultiplierFromTextAttributes(const Tex
 
     [nsAttributedString appendAttributedString:nsAttributedStringFragment];
   }
-
+  RCTApplyBaselineOffset(nsAttributedString);
   [nsAttributedString endEditing];
 
   return nsAttributedString;