Dynamic Text Sizes for Text component

Summary:
Dynamic Text Sizes for Text component.
Text gains new prop - allowFontScaling (false by default).
There is also AccessibilityManager module that allows you to tune multipliers per each content size category.

Libraries/ART/RCTConvert+ART.m

@@ -87,7 +87,7 @@ RCT_ENUM_CONVERTER(CTTextAlignment, (@{
   }
 
   NSDictionary *fontDict = dict[@"font"];
-  CTFontRef font = (__bridge CTFontRef)[self UIFont:nil withFamily:fontDict[@"fontFamily"] size:fontDict[@"fontSize"] weight:fontDict[@"fontWeight"] style:fontDict[@"fontStyle"]];
+  CTFontRef font = (__bridge CTFontRef)[self UIFont:nil withFamily:fontDict[@"fontFamily"] size:fontDict[@"fontSize"] weight:fontDict[@"fontWeight"] style:fontDict[@"fontStyle"] scaleMultiplier:1.0];
   if (!font) {
     return frame;
   }

Libraries/Text/RCTShadowRawText.m

@@ -9,8 +9,32 @@
 
 #import "RCTShadowRawText.h"
 
+#import "RCTUIManager.h"
+
 @implementation RCTShadowRawText
 
+- (instancetype)init
+{
+  if ((self = [super init])) {
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(contentSizeMultiplierDidChange:)
+                                                 name:RCTUIManagerWillUpdateViewsDueToContentSizeMultiplierChangeNotification
+                                               object:nil];
+  }
+  return self;
+}
+
+- (void)dealloc
+{
+  [[NSNotificationCenter defaultCenter] removeObserver:self];
+}
+
+- (void)contentSizeMultiplierDidChange:(NSNotification *)note
+{
+  [self dirtyLayout];
+  [self dirtyText];
+}
+
 - (void)setText:(NSString *)text
 {
   if (_text != text) {

Libraries/Text/RCTShadowText.h

@@ -30,6 +30,8 @@ extern NSString *const RCTReactTagAttributeName;
 @property (nonatomic, strong) UIColor *textDecorationColor;
 @property (nonatomic, assign) NSUnderlineStyle textDecorationStyle;
 @property (nonatomic, assign) RCTTextDecorationLineType textDecorationLine;
+@property (nonatomic, assign) CGFloat fontSizeMultiplier;
+@property (nonatomic, assign) BOOL allowFontScaling;
 
 - (void)recomputeText;
 

Libraries/Text/RCTShadowText.m

@@ -9,6 +9,9 @@
 
 #import "RCTShadowText.h"
 
+#import "RCTAccessibilityManager.h"
+#import "RCTUIManager.h"
+#import "RCTBridge.h"
 #import "RCTConvert.h"
 #import "RCTLog.h"
 #import "RCTShadowRawText.h"
@@ -51,16 +54,31 @@ static css_dim_t RCTMeasure(void *context, float width)
     _letterSpacing = NAN;
     _isHighlighted = NO;
     _textDecorationStyle = NSUnderlineStyleSingle;
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(contentSizeMultiplierDidChange:)
+                                                 name:RCTUIManagerWillUpdateViewsDueToContentSizeMultiplierChangeNotification
+                                               object:nil];
   }
   return self;
 }
 
+- (void)dealloc
+{
+  [[NSNotificationCenter defaultCenter] removeObserver:self];
+}
+
 - (NSString *)description
 {
   NSString *superDescription = super.description;
   return [[superDescription substringToIndex:superDescription.length - 1] stringByAppendingFormat:@"; text: %@>", [self attributedString].string];
 }
 
+- (void)contentSizeMultiplierDidChange:(NSNotification *)note
+{
+  [self dirtyLayout];
+  [self dirtyText];
+}
+
 - (NSDictionary *)processUpdatedProperties:(NSMutableSet *)applierBlocks
                           parentProperties:(NSDictionary *)parentProperties
 {
@@ -190,7 +208,9 @@ static css_dim_t RCTMeasure(void *context, float width)
     [self _addAttribute:NSBackgroundColorAttributeName withValue:self.backgroundColor toAttributedString:attributedString];
   }
 
-  UIFont *font = [RCTConvert UIFont:nil withFamily:fontFamily size:fontSize weight:fontWeight style:fontStyle];
+  UIFont *font = [RCTConvert UIFont:nil withFamily:fontFamily
+                               size:fontSize weight:fontWeight style:fontStyle
+                    scaleMultiplier:(_allowFontScaling && _fontSizeMultiplier > 0.0 ? _fontSizeMultiplier : 1.0)];
   [self _addAttribute:NSFontAttributeName withValue:font toAttributedString:attributedString];
   [self _addAttribute:NSKernAttributeName withValue:letterSpacing toAttributedString:attributedString];
   [self _addAttribute:RCTReactTagAttributeName withValue:self.reactTag toAttributedString:attributedString];
@@ -232,8 +252,9 @@ static css_dim_t RCTMeasure(void *context, float width)
   [attributedString enumerateAttribute:NSParagraphStyleAttributeName inRange:NSMakeRange(0, [attributedString length]) options:0 usingBlock:^(id value, NSRange range, BOOL *stop) {
     if (value) {
       NSParagraphStyle *paragraphStyle = (NSParagraphStyle *)value;
-      if ([paragraphStyle maximumLineHeight] > _lineHeight) {
-        self.lineHeight = [paragraphStyle maximumLineHeight];
+      CGFloat maximumLineHeight = round([paragraphStyle maximumLineHeight] / self.fontSizeMultiplier);
+      if (maximumLineHeight > self.lineHeight) {
+        self.lineHeight = maximumLineHeight;
       }
       hasParagraphStyle = YES;
     }
@@ -247,8 +268,9 @@ static css_dim_t RCTMeasure(void *context, float width)
     NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
     paragraphStyle.alignment = _textAlign;
     paragraphStyle.baseWritingDirection = _writingDirection;
-    paragraphStyle.minimumLineHeight = _lineHeight;
-    paragraphStyle.maximumLineHeight = _lineHeight;
+    CGFloat lineHeight = round(_lineHeight * self.fontSizeMultiplier);
+    paragraphStyle.minimumLineHeight = lineHeight;
+    paragraphStyle.maximumLineHeight = lineHeight;
     [attributedString addAttribute:NSParagraphStyleAttributeName
                              value:paragraphStyle
                              range:(NSRange){0, attributedString.length}];
@@ -321,4 +343,26 @@ RCT_TEXT_PROPERTY(TextDecorationLine, _textDecorationLine, RCTTextDecorationLine
 RCT_TEXT_PROPERTY(TextDecorationStyle, _textDecorationStyle, NSUnderlineStyle);
 RCT_TEXT_PROPERTY(WritingDirection, _writingDirection, NSWritingDirection)
 
+- (void)setAllowFontScaling:(BOOL)allowFontScaling
+{
+  _allowFontScaling = allowFontScaling;
+  for (RCTShadowView *child in [self reactSubviews]) {
+    if ([child isKindOfClass:[RCTShadowText class]]) {
+      [(RCTShadowText *)child setAllowFontScaling:allowFontScaling];
+    }
+  }
+  [self dirtyText];
+}
+
+- (void)setFontSizeMultiplier:(CGFloat)fontSizeMultiplier
+{
+  _fontSizeMultiplier = fontSizeMultiplier;
+  for (RCTShadowView *child in [self reactSubviews]) {
+    if ([child isKindOfClass:[RCTShadowText class]]) {
+      [(RCTShadowText *)child setFontSizeMultiplier:fontSizeMultiplier];
+    }
+  }
+  [self dirtyText];
+}
+
 @end

Libraries/Text/RCTTextManager.m

@@ -9,6 +9,7 @@
 
 #import "RCTTextManager.h"
 
+#import "RCTAccessibilityManager.h"
 #import "RCTAssert.h"
 #import "RCTConvert.h"
 #import "RCTLog.h"
@@ -49,6 +50,7 @@ RCT_EXPORT_SHADOW_PROPERTY(textDecorationStyle, NSUnderlineStyle)
 RCT_EXPORT_SHADOW_PROPERTY(textDecorationColor, UIColor)
 RCT_EXPORT_SHADOW_PROPERTY(textDecorationLine, RCTTextDecorationLineType)
 RCT_EXPORT_SHADOW_PROPERTY(writingDirection, NSWritingDirection)
+RCT_EXPORT_SHADOW_PROPERTY(allowFontScaling, BOOL)
 
 - (RCTViewManagerUIBlock)uiBlockToAmendWithShadowViewRegistry:(RCTSparseArray *)shadowViewRegistry
 {
@@ -69,6 +71,7 @@ RCT_EXPORT_SHADOW_PROPERTY(writingDirection, NSWritingDirection)
       RCTAssert([shadowView isTextDirty], @"Don't process any nodes that don't have dirty text");
 
       if ([shadowView isKindOfClass:[RCTShadowText class]]) {
+        [(RCTShadowText *)shadowView setFontSizeMultiplier:self.bridge.accessibilityManager.multiplier];
         [(RCTShadowText *)shadowView recomputeText];
       } else if ([shadowView isKindOfClass:[RCTShadowRawText class]]) {
         RCTLogError(@"Raw text cannot be used outside of a <Text> tag. Not rendering string: '%@'",

Libraries/Text/Text.js

@@ -30,6 +30,7 @@ var viewConfig = {
   validAttributes: merge(ReactNativeViewAttributes.UIView, {
     isHighlighted: true,
     numberOfLines: true,
+    allowFontScaling: true,
   }),
   uiViewClassName: 'RCTText',
 };
@@ -99,15 +100,25 @@ var Text = React.createClass({
      * Used to locate this view in end-to-end tests.
      */
     testID: React.PropTypes.string,
+    /**
+     * Specifies should fonts scale to respect Text Size accessibility setting on iOS.
+     */
+    allowFontScaling: React.PropTypes.bool,
   },
 
   viewConfig: viewConfig,
 
-  getInitialState: function() {
+  getInitialState: function(): Object {
     return merge(this.touchableGetInitialState(), {
       isHighlighted: false,
     });
   },
+  
+  getDefaultProps: function(): Object {
+    return {
+      allowFontScaling: true,
+    };
+  },
 
   onStartShouldSetResponder: function(): bool {
     var shouldSetFromProps = this.props.onStartShouldSetResponder &&