Add <Text> shadow support

Summary:
Add three new TextStylePropTypes for \<Text>
- textShadowOffset
- textShadowRadius
- textShadowColor
Closes https://github.com/facebook/react-native/pull/4975

Reviewed By: svcscm

Differential Revision: D2796278

Pulled By: nicklockwood

fb-gh-sync-id: f8c3fa210e664428b029b9fba8eca4a8eb81c08d

Libraries/Text/RCTShadowText.h

@@ -33,6 +33,9 @@ extern NSString *const RCTReactTagAttributeName;
 @property (nonatomic, assign) CGFloat fontSizeMultiplier;
 @property (nonatomic, assign) BOOL allowFontScaling;
 @property (nonatomic, assign) CGFloat opacity;
+@property (nonatomic, assign) CGSize textShadowOffset;
+@property (nonatomic, assign) CGFloat textShadowRadius;
+@property (nonatomic, strong) UIColor *textShadowColor;
 
 - (void)recomputeText;
 

Libraries/Text/RCTShadowText.m

@@ -305,22 +305,31 @@ static css_dim_t RCTMeasure(void *context, float width, float height)
   }
 
   // Text decoration
-  if(_textDecorationLine == RCTTextDecorationLineTypeUnderline ||
-     _textDecorationLine == RCTTextDecorationLineTypeUnderlineStrikethrough) {
+  if (_textDecorationLine == RCTTextDecorationLineTypeUnderline ||
+      _textDecorationLine == RCTTextDecorationLineTypeUnderlineStrikethrough) {
     [self _addAttribute:NSUnderlineStyleAttributeName withValue:@(_textDecorationStyle)
      toAttributedString:attributedString];
   }
-  if(_textDecorationLine == RCTTextDecorationLineTypeStrikethrough ||
-     _textDecorationLine == RCTTextDecorationLineTypeUnderlineStrikethrough){
+  if (_textDecorationLine == RCTTextDecorationLineTypeStrikethrough ||
+      _textDecorationLine == RCTTextDecorationLineTypeUnderlineStrikethrough){
     [self _addAttribute:NSStrikethroughStyleAttributeName withValue:@(_textDecorationStyle)
      toAttributedString:attributedString];
   }
-  if(_textDecorationColor) {
+  if (_textDecorationColor) {
     [self _addAttribute:NSStrikethroughColorAttributeName withValue:_textDecorationColor
      toAttributedString:attributedString];
     [self _addAttribute:NSUnderlineColorAttributeName withValue:_textDecorationColor
      toAttributedString:attributedString];
   }
+
+  // Text shadow
+  if (!CGSizeEqualToSize(_textShadowOffset, CGSizeZero)) {
+    NSShadow *shadow = [NSShadow new];
+    shadow.shadowOffset = _textShadowOffset;
+    shadow.shadowBlurRadius = _textShadowRadius;
+    shadow.shadowColor = _textShadowColor;
+    [self _addAttribute:NSShadowAttributeName withValue:shadow toAttributedString:attributedString];
+  }
 }
 
 - (void)fillCSSNode:(css_node_t *)node
@@ -371,6 +380,9 @@ RCT_TEXT_PROPERTY(TextDecorationLine, _textDecorationLine, RCTTextDecorationLine
 RCT_TEXT_PROPERTY(TextDecorationStyle, _textDecorationStyle, NSUnderlineStyle);
 RCT_TEXT_PROPERTY(WritingDirection, _writingDirection, NSWritingDirection)
 RCT_TEXT_PROPERTY(Opacity, _opacity, CGFloat)
+RCT_TEXT_PROPERTY(TextShadowOffset, _textShadowOffset, CGSize);
+RCT_TEXT_PROPERTY(TextShadowRadius, _textShadowRadius, CGFloat);
+RCT_TEXT_PROPERTY(TextShadowColor, _textShadowColor, UIColor *);
 
 - (void)setAllowFontScaling:(BOOL)allowFontScaling
 {

Libraries/Text/RCTTextManager.m

@@ -59,6 +59,9 @@ RCT_EXPORT_SHADOW_PROPERTY(textDecorationLine, RCTTextDecorationLineType)
 RCT_EXPORT_SHADOW_PROPERTY(writingDirection, NSWritingDirection)
 RCT_EXPORT_SHADOW_PROPERTY(allowFontScaling, BOOL)
 RCT_EXPORT_SHADOW_PROPERTY(opacity, CGFloat)
+RCT_EXPORT_SHADOW_PROPERTY(textShadowOffset, CGSize)
+RCT_EXPORT_SHADOW_PROPERTY(textShadowRadius, CGFloat)
+RCT_EXPORT_SHADOW_PROPERTY(textShadowColor, UIColor)
 
 - (RCTViewManagerUIBlock)uiBlockToAmendWithShadowViewRegistry:(NSDictionary<NSNumber *, RCTShadowView *> *)shadowViewRegistry
 {

Libraries/Text/TextStylePropTypes.js

@@ -30,6 +30,11 @@ var TextStylePropTypes = Object.assign(Object.create(ViewStylePropTypes), {
     ['normal' /*default*/, 'bold',
      '100', '200', '300', '400', '500', '600', '700', '800', '900']
   ),
+  textShadowOffset: ReactPropTypes.shape(
+    {width: ReactPropTypes.number, height: ReactPropTypes.number}
+  ),
+  textShadowRadius: ReactPropTypes.number,
+  textShadowColor: ColorPropType,
   /**
    * @platform ios
    */