fix(ios): backport clear text background omission to 0.87

Author: kurohune538

packages/react-native/React/Tests/Text/RCTAttributedTextUtilsTest.mm

@@ -12,6 +12,7 @@
 
 #include <react/renderer/attributedstring/conversions.h>
 #include <react/renderer/core/RawValue.h>
+#include <react/renderer/graphics/Color.h>
 
 using namespace facebook::react;
 
@@ -45,6 +46,70 @@ - (void)testTextAlignmentStartAndEndResolveWithLayoutDirection
   XCTAssertEqual(NSTextAlignmentFromTextAlign(@"end", LayoutDirection::RightToLeft), NSTextAlignmentLeft);
 }
 
+- (void)testDefaultClearBackgroundIsOmitted
+{
+  TextAttributes textAttributes = TextAttributes::defaultTextAttributes();
+
+  NSDictionary<NSAttributedStringKey, id> *attributes = RCTNSTextAttributesFromTextAttributes(textAttributes);
+
+  XCTAssertNil(attributes[NSBackgroundColorAttributeName]);
+  XCTAssertEqualObjects(attributes[NSForegroundColorAttributeName], [UIColor colorWithRed:0 green:0 blue:0 alpha:1]);
+}
+
+- (void)testOpacityDoesNotAddBackgroundColor
+{
+  TextAttributes textAttributes;
+  textAttributes.opacity = 0.5;
+
+  NSDictionary<NSAttributedStringKey, id> *attributes = RCTNSTextAttributesFromTextAttributes(textAttributes);
+
+  XCTAssertNil(attributes[NSBackgroundColorAttributeName]);
+  XCTAssertEqualObjects(attributes[NSForegroundColorAttributeName], [UIColor colorWithWhite:0 alpha:0.5]);
+}
+
+- (void)testDefaultClearBackgroundWithOpacityIsOmitted
+{
+  TextAttributes textAttributes = TextAttributes::defaultTextAttributes();
+  textAttributes.opacity = 0.5;
+
+  NSDictionary<NSAttributedStringKey, id> *attributes = RCTNSTextAttributesFromTextAttributes(textAttributes);
+
+  XCTAssertNil(attributes[NSBackgroundColorAttributeName]);
+  XCTAssertEqualObjects(attributes[NSForegroundColorAttributeName], [UIColor colorWithRed:0 green:0 blue:0 alpha:0.5]);
+}
+
+- (void)testVisibleBackgroundColorPreservesAlphaWithOpacity
+{
+  TextAttributes textAttributes;
+  textAttributes.backgroundColor = colorFromComponents({.red = 1, .alpha = 0.5, .colorSpace = ColorSpace::sRGB});
+
+  NSDictionary<NSAttributedStringKey, id> *attributes = RCTNSTextAttributesFromTextAttributes(textAttributes);
+
+  XCTAssertEqualObjects(attributes[NSBackgroundColorAttributeName], [UIColor colorWithRed:1 green:0 blue:0 alpha:0.5]);
+
+  textAttributes.opacity = 0.5;
+  attributes = RCTNSTextAttributesFromTextAttributes(textAttributes);
+
+  XCTAssertEqualObjects(attributes[NSBackgroundColorAttributeName], [UIColor colorWithRed:1 green:0 blue:0 alpha:0.25]);
+}
+
+- (void)testForegroundColorPreservesAlphaWithOpacity
+{
+  TextAttributes textAttributes = TextAttributes::defaultTextAttributes();
+  textAttributes.foregroundColor = colorFromComponents({.blue = 1, .alpha = 0.5, .colorSpace = ColorSpace::sRGB});
+
+  NSDictionary<NSAttributedStringKey, id> *attributes = RCTNSTextAttributesFromTextAttributes(textAttributes);
+
+  XCTAssertNil(attributes[NSBackgroundColorAttributeName]);
+  XCTAssertEqualObjects(attributes[NSForegroundColorAttributeName], [UIColor colorWithRed:0 green:0 blue:1 alpha:0.5]);
+
+  textAttributes.opacity = 0.5;
+  attributes = RCTNSTextAttributesFromTextAttributes(textAttributes);
+
+  XCTAssertNil(attributes[NSBackgroundColorAttributeName]);
+  XCTAssertEqualObjects(attributes[NSForegroundColorAttributeName], [UIColor colorWithRed:0 green:0 blue:1 alpha:0.25]);
+}
+
 - (void)testSamenessOfEmptyAttributedStrings
 {
   NSAttributedString *attributedString1 = [[NSAttributedString alloc] initWithString:@""];

packages/react-native/ReactCommon/react/renderer/textlayoutmanager/platform/ios/react/renderer/textlayoutmanager/RCTAttributedTextUtils.mm

@@ -200,7 +200,8 @@ inline static CGFloat RCTEffectiveFontSizeMultiplierFromTextAttributes(const Tex
     attributes[NSForegroundColorAttributeName] = effectiveForegroundColor;
   }
 
-  if (textAttributes.backgroundColor || !isnan(textAttributes.opacity)) {
+  // A clear background draws nothing, but TextKit still computes and fills its rects on every draw.
+  if (textAttributes.backgroundColor && textAttributes.backgroundColor != clearColor()) {
     attributes[NSBackgroundColorAttributeName] = RCTEffectiveBackgroundColorFromTextAttributes(textAttributes);
   }