iOS: Add a maxFontSizeMultiplier prop to <Text> and <TextInput>

Libraries/Components/TextInput/TextInput.js

@@ -177,6 +177,7 @@ type Props = $ReadOnly<{|
   autoCorrect?: ?boolean,
   autoFocus?: ?boolean,
   allowFontScaling?: ?boolean,
+  maxContentSizeMultiplier?: ?boolean,
   editable?: ?boolean,
   keyboardType?: ?KeyboardType,
   returnKeyType?: ?ReturnKeyType,
@@ -367,6 +368,14 @@ const TextInput = createReactClass({
      * default is `true`.
      */
     allowFontScaling: PropTypes.bool,
+    /**
+     * Specifies largest possible scale a font can reach when `allowFontScaling` is enabled.
+     * Possible values:
+     * `null/undefined` (default): inherit from the parent node or the global default (0)
+     * `0`: no max, ignore parent/global default
+     * `>= 1`: sets the maxContentSizeMultiplier of this node to this value
+     */
+    maxContentSizeMultiplier: PropTypes.number,
     /**
      * If `false`, text is not editable. The default value is `true`.
      */
@@ -933,7 +942,11 @@ const TextInput = createReactClass({
       );
       if (childCount >= 1) {
         children = (
-          <Text style={props.style} allowFontScaling={props.allowFontScaling}>
+          <Text
+            style={props.style}
+            allowFontScaling={props.allowFontScaling}
+            maxContentSizeMultiplier={props.maxContentSizeMultiplier}
+          >
             {children}
           </Text>
         );

Libraries/Text/BaseText/RCTBaseTextViewManager.m

@@ -36,6 +36,7 @@ - (RCTShadowView *)shadowView
 RCT_REMAP_SHADOW_PROPERTY(fontStyle, textAttributes.fontStyle, NSString)
 RCT_REMAP_SHADOW_PROPERTY(fontVariant, textAttributes.fontVariant, NSArray)
 RCT_REMAP_SHADOW_PROPERTY(allowFontScaling, textAttributes.allowFontScaling, BOOL)
+RCT_REMAP_SHADOW_PROPERTY(maxContentSizeMultiplier, textAttributes.maxContentSizeMultiplier, CGFloat)
 RCT_REMAP_SHADOW_PROPERTY(letterSpacing, textAttributes.letterSpacing, CGFloat)
 // Paragraph Styles
 RCT_REMAP_SHADOW_PROPERTY(lineHeight, textAttributes.lineHeight, CGFloat)

Libraries/Text/RCTTextAttributes.h

@@ -31,6 +31,7 @@ extern NSString *const RCTTextAttributesTagAttributeName;
 @property (nonatomic, copy, nullable) NSString *fontFamily;
 @property (nonatomic, assign) CGFloat fontSize;
 @property (nonatomic, assign) CGFloat fontSizeMultiplier;
+@property (nonatomic, assign) CGFloat maxContentSizeMultiplier;
 @property (nonatomic, copy, nullable) NSString *fontWeight;
 @property (nonatomic, copy, nullable) NSString *fontStyle;
 @property (nonatomic, copy, nullable) NSArray<NSString *> *fontVariant;
@@ -71,7 +72,7 @@ extern NSString *const RCTTextAttributesTagAttributeName;
 - (UIFont *)effectiveFont;
 
 /**
- * Font size multiplier reflects `allowFontScaling` and `fontSizeMultiplier`.
+ * Font size multiplier reflects `allowFontScaling`, `fontSizeMultiplier`, and `maxContentSizeMultiplier`.
  */
 - (CGFloat)effectiveFontSizeMultiplier;
 

Libraries/Text/RCTTextAttributes.m

@@ -14,6 +14,9 @@
 NSString *const RCTTextAttributesIsHighlightedAttributeName = @"RCTTextAttributesIsHighlightedAttributeName";
 NSString *const RCTTextAttributesTagAttributeName = @"RCTTextAttributesTagAttributeName";
 
+// Setting the default to 0 indicates that there is no max.
+static CGFloat defaultMaxContentSizeMultiplier = 0.0;
+
 @implementation RCTTextAttributes
 
 - (instancetype)init
@@ -24,6 +27,7 @@ - (instancetype)init
     _lineHeight = NAN;
     _textDecorationStyle = NSUnderlineStyleSingle;
     _fontSizeMultiplier = NAN;
+    _maxContentSizeMultiplier = NAN;
     _alignment = NSTextAlignmentNatural;
     _baseWritingDirection = NSWritingDirectionNatural;
     _textShadowRadius = NAN;
@@ -49,6 +53,7 @@ - (void)applyTextAttributes:(RCTTextAttributes *)textAttributes
   _fontFamily = textAttributes->_fontFamily ?: _fontFamily;
   _fontSize = !isnan(textAttributes->_fontSize) ? textAttributes->_fontSize : _fontSize;
   _fontSizeMultiplier = !isnan(textAttributes->_fontSizeMultiplier) ? textAttributes->_fontSizeMultiplier : _fontSizeMultiplier;
+  _maxContentSizeMultiplier = !isnan(textAttributes->_maxContentSizeMultiplier) ? textAttributes->_maxContentSizeMultiplier : _maxContentSizeMultiplier;
   _fontWeight = textAttributes->_fontWeight ?: _fontWeight;
   _fontStyle = textAttributes->_fontStyle ?: _fontStyle;
   _fontVariant = textAttributes->_fontVariant ?: _fontVariant;
@@ -191,7 +196,15 @@ - (UIFont *)effectiveFont
 
 - (CGFloat)effectiveFontSizeMultiplier
 {
-  return !RCTHasFontHandlerSet() && _allowFontScaling && !isnan(_fontSizeMultiplier) ? _fontSizeMultiplier : 1.0;
+  bool fontScalingEnabled = !RCTHasFontHandlerSet() && _allowFontScaling;
+
+  if (fontScalingEnabled) {
+    CGFloat fontSizeMultiplier = !isnan(_fontSizeMultiplier) ? _fontSizeMultiplier : 1.0;
+    CGFloat maxContentSizeMultiplier = !isnan(_maxContentSizeMultiplier) ? _maxContentSizeMultiplier : defaultMaxContentSizeMultiplier;
+    return maxContentSizeMultiplier >= 1.0 ? fminf(maxContentSizeMultiplier, fontSizeMultiplier) : fontSizeMultiplier;
+  } else {
+    return 1.0;
+  }
 }
 
 - (UIColor *)effectiveForegroundColor
@@ -260,6 +273,7 @@ - (BOOL)isEqual:(RCTTextAttributes *)textAttributes
     RCTTextAttributesCompareObjects(_fontFamily) &&
     RCTTextAttributesCompareFloats(_fontSize) &&
     RCTTextAttributesCompareFloats(_fontSizeMultiplier) &&
+    RCTTextAttributesCompareFloats(_maxContentSizeMultiplier) &&
     RCTTextAttributesCompareStrings(_fontWeight) &&
     RCTTextAttributesCompareObjects(_fontStyle) &&
     RCTTextAttributesCompareObjects(_fontVariant) &&

Libraries/Text/Text.js

@@ -58,6 +58,7 @@ const viewConfig = {
     numberOfLines: true,
     ellipsizeMode: true,
     allowFontScaling: true,
+    maxContentSizeMultiplier: true,
     disabled: true,
     selectable: true,
     selectionColor: true,
@@ -257,6 +258,7 @@ const RCTVirtualText =
         validAttributes: {
           ...ReactNativeViewAttributes.UIView,
           isHighlighted: true,
+          maxContentSizeMultiplier: true,
         },
         uiViewClassName: 'RCTVirtualText',
       }));

Libraries/Text/Text/RCTTextViewManager.m

@@ -24,7 +24,6 @@ @interface RCTTextViewManager () <RCTUIManagerObserver>
 @implementation RCTTextViewManager
 {
   NSHashTable<RCTTextShadowView *> *_shadowViews;
-  CGFloat _fontSizeMultiplier;
 }
 
 RCT_EXPORT_MODULE(RCTText)

Libraries/Text/TextPropTypes.js

@@ -100,6 +100,14 @@ module.exports = {
    * See https://facebook.github.io/react-native/docs/text.html#allowfontscaling
    */
   allowFontScaling: PropTypes.bool,
+  /**
+   * Specifies largest possible scale a font can reach when `allowFontScaling` is enabled.
+   * Possible values:
+   * `null/undefined` (default): inherit from the parent node or the global default (0)
+   * `0`: no max, ignore parent/global default
+   * `>= 1`: sets the maxContentSizeMultiplier of this node to this value
+   */
+  maxContentSizeMultiplier: PropTypes.number,
   /**
    * Indicates whether the view is an accessibility element.
    *