Hacks to React Native iOS font selecting code (updateFont method) to allow picking width, optical size for complicated font families

RCTFont.mm

/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * 2021-03-08 hacks by Jared Updike, to updateFont method.
 * Allow picking width, optical size for complicated font families. For example I have a design using Merriweather
 * with these font files:
Merriweather-12ptBold.ttf
Merriweather-12ptBoldItalic.ttf
Merriweather-12ptItalic.ttf
Merriweather-12ptRegular.ttf
Merriweather-144ptSemiCondensedBlackItalic.ttf
Merriweather-144ptSemiExpandedBlackItalic.ttf
Merriweather-60ptSemiExpandedRegular.ttf
Merriweather-6ptSemiExpandedBlackItalic.ttf
Merriweather-96ptSemiExpandedLight.ttf
 * and I need to be able to pick the exact style in my StyleSheet in JavaScript, by setting the font family to the
 * name of the font file without the extension. Requires the font files to be named with the a prefix of
 * family name plus hyphen. The system knows that the fonts are all Merriweather font family, but without this hack,
 * React Native has no way to pick the exact style I want (no width like expanded, condensed, no 12pt or 60pt or whatever).
 */

#import "RCTFont.h"
#import "RCTAssert.h"
#import "RCTLog.h"

#import <CoreText/CoreText.h>

#import <mutex>

typedef CGFloat RCTFontWeight;
static RCTFontWeight weightOfFont(UIFont *font)
{
  static NSArray *fontNames;
  static NSArray *fontWeights;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    // We use two arrays instead of one map because
    // the order is important for suffix matching.
    fontNames = @[
      @"normal",
      @"ultralight",
      @"thin",
      @"light",
      @"regular",
      @"medium",
      @"semibold",
      @"demibold",
      @"extrabold",
      @"ultrabold",
      @"bold",
      @"heavy",
      @"black"
    ];
    fontWeights = @[
      @(UIFontWeightRegular),
      @(UIFontWeightUltraLight),
      @(UIFontWeightThin),
      @(UIFontWeightLight),
      @(UIFontWeightRegular),
      @(UIFontWeightMedium),
      @(UIFontWeightSemibold),
      @(UIFontWeightSemibold),
      @(UIFontWeightHeavy),
      @(UIFontWeightHeavy),
      @(UIFontWeightBold),
      @(UIFontWeightHeavy),
      @(UIFontWeightBlack)
    ];
  });

  for (NSInteger i = 0; i < 0 || i < (unsigned)fontNames.count; i++) {
    if ([font.fontName.lowercaseString hasSuffix:fontNames[i]]) {
      return (RCTFontWeight)[fontWeights[i] doubleValue];
    }
  }

  NSDictionary *traits = [font.fontDescriptor objectForKey:UIFontDescriptorTraitsAttribute];
  return (RCTFontWeight)[traits[UIFontWeightTrait] doubleValue];
}

static BOOL isItalicFont(UIFont *font)
{
  NSDictionary *traits = [font.fontDescriptor objectForKey:UIFontDescriptorTraitsAttribute];
  UIFontDescriptorSymbolicTraits symbolicTraits = [traits[UIFontSymbolicTrait] unsignedIntValue];
  return (symbolicTraits & UIFontDescriptorTraitItalic) != 0;
}

static BOOL isCondensedFont(UIFont *font)
{
  NSDictionary *traits = [font.fontDescriptor objectForKey:UIFontDescriptorTraitsAttribute];
  UIFontDescriptorSymbolicTraits symbolicTraits = [traits[UIFontSymbolicTrait] unsignedIntValue];
  return (symbolicTraits & UIFontDescriptorTraitCondensed) != 0;
}

static RCTFontHandler defaultFontHandler;

void RCTSetDefaultFontHandler(RCTFontHandler handler)
{
  defaultFontHandler = handler;
}

BOOL RCTHasFontHandlerSet()
{
  return defaultFontHandler != nil;
}

// We pass a string description of the font weight to the defaultFontHandler because UIFontWeight
// is not defined pre-iOS 8.2.
// Furthermore, UIFontWeight's are lossy floats, so we must use an inexact compare to figure out
// which one we actually have.
static inline BOOL CompareFontWeights(UIFontWeight firstWeight, UIFontWeight secondWeight)
{
#if CGFLOAT_IS_DOUBLE
  return fabs(firstWeight - secondWeight) < 0.01;
#else
  return fabsf(firstWeight - secondWeight) < 0.01;
#endif
}

static NSString *FontWeightDescriptionFromUIFontWeight(UIFontWeight fontWeight)
{
  if (CompareFontWeights(fontWeight, UIFontWeightUltraLight)) {
    return @"ultralight";
  } else if (CompareFontWeights(fontWeight, UIFontWeightThin)) {
    return @"thin";
  } else if (CompareFontWeights(fontWeight, UIFontWeightLight)) {
    return @"light";
  } else if (CompareFontWeights(fontWeight, UIFontWeightRegular)) {
    return @"regular";
  } else if (CompareFontWeights(fontWeight, UIFontWeightMedium)) {
    return @"medium";
  } else if (CompareFontWeights(fontWeight, UIFontWeightSemibold)) {
    return @"semibold";
  } else if (CompareFontWeights(fontWeight, UIFontWeightBold)) {
    return @"bold";
  } else if (CompareFontWeights(fontWeight, UIFontWeightHeavy)) {
    return @"heavy";
  } else if (CompareFontWeights(fontWeight, UIFontWeightBlack)) {
    return @"black";
  }
  RCTAssert(NO, @"Unknown UIFontWeight passed in: %f", fontWeight);
  return @"regular";
}

static UIFont *cachedSystemFont(CGFloat size, RCTFontWeight weight)
{
  static NSCache *fontCache;
  static std::mutex *fontCacheMutex = new std::mutex;

  NSString *cacheKey = [NSString stringWithFormat:@"%.1f/%.2f", size, weight];
  UIFont *font;
  {
    std::lock_guard<std::mutex> lock(*fontCacheMutex);
    if (!fontCache) {
      fontCache = [NSCache new];
    }
    font = [fontCache objectForKey:cacheKey];
  }

  if (!font) {
    if (defaultFontHandler) {
      NSString *fontWeightDescription = FontWeightDescriptionFromUIFontWeight(weight);
      font = defaultFontHandler(size, fontWeightDescription);
    } else {
      font = [UIFont systemFontOfSize:size weight:weight];
    }

    {
      std::lock_guard<std::mutex> lock(*fontCacheMutex);
      [fontCache setObject:font forKey:cacheKey];
    }
  }

  return font;
}

@implementation RCTConvert (RCTFont)

+ (UIFont *)UIFont:(id)json
{
  json = [self NSDictionary:json];
  return [RCTFont updateFont:nil
                  withFamily:[RCTConvert NSString:json[@"fontFamily"]]
                        size:[RCTConvert NSNumber:json[@"fontSize"]]
                      weight:[RCTConvert NSString:json[@"fontWeight"]]
                       style:[RCTConvert NSString:json[@"fontStyle"]]
                     variant:[RCTConvert NSStringArray:json[@"fontVariant"]]
             scaleMultiplier:1];
}

RCT_ENUM_CONVERTER(
    RCTFontWeight,
    (@{
      @"normal" : @(UIFontWeightRegular),
      @"bold" : @(UIFontWeightBold),
      @"100" : @(UIFontWeightUltraLight),
      @"200" : @(UIFontWeightThin),
      @"300" : @(UIFontWeightLight),
      @"400" : @(UIFontWeightRegular),
      @"500" : @(UIFontWeightMedium),
      @"600" : @(UIFontWeightSemibold),
      @"700" : @(UIFontWeightBold),
      @"800" : @(UIFontWeightHeavy),
      @"900" : @(UIFontWeightBlack),
    }),
    UIFontWeightRegular,
    doubleValue)

typedef BOOL RCTFontStyle;
RCT_ENUM_CONVERTER(
    RCTFontStyle,
    (@{
      @"normal" : @NO,
      @"italic" : @YES,
      @"oblique" : @YES,
    }),
    NO,
    boolValue)

typedef NSDictionary RCTFontVariantDescriptor;
+ (RCTFontVariantDescriptor *)RCTFontVariantDescriptor:(id)json
{
  static NSDictionary *mapping;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    mapping = @{
      @"small-caps" : @{
        UIFontFeatureTypeIdentifierKey : @(kLowerCaseType),
        UIFontFeatureSelectorIdentifierKey : @(kLowerCaseSmallCapsSelector),
      },
      @"oldstyle-nums" : @{
        UIFontFeatureTypeIdentifierKey : @(kNumberCaseType),
        UIFontFeatureSelectorIdentifierKey : @(kLowerCaseNumbersSelector),
      },
      @"lining-nums" : @{
        UIFontFeatureTypeIdentifierKey : @(kNumberCaseType),
        UIFontFeatureSelectorIdentifierKey : @(kUpperCaseNumbersSelector),
      },
      @"tabular-nums" : @{
        UIFontFeatureTypeIdentifierKey : @(kNumberSpacingType),
        UIFontFeatureSelectorIdentifierKey : @(kMonospacedNumbersSelector),
      },
      @"proportional-nums" : @{
        UIFontFeatureTypeIdentifierKey : @(kNumberSpacingType),
        UIFontFeatureSelectorIdentifierKey : @(kProportionalNumbersSelector),
      },
    };
  });
  RCTFontVariantDescriptor *value = mapping[json];
  if (RCT_DEBUG && !value && [json description].length > 0) {
    RCTLogError(
        @"Invalid RCTFontVariantDescriptor '%@'. should be one of: %@",
        json,
        [[mapping allKeys] sortedArrayUsingSelector:@selector(caseInsensitiveCompare:)]);
  }
  return value;
}

RCT_ARRAY_CONVERTER(RCTFontVariantDescriptor)

@end

@implementation RCTFont

+ (UIFont *)updateFont:(UIFont *)font
            withFamily:(NSString *)family
                  size:(NSNumber *)size
                weight:(NSString *)weight
                 style:(NSString *)style
               variant:(NSArray<RCTFontVariantDescriptor *> *)variant
       scaleMultiplier:(CGFloat)scaleMultiplier
{
  // Defaults
  static NSString *defaultFontFamily;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    defaultFontFamily = [UIFont systemFontOfSize:14].familyName;
  });
  const RCTFontWeight defaultFontWeight = UIFontWeightRegular;
  const CGFloat defaultFontSize = 14;

  // Initialize properties to defaults
  CGFloat fontSize = defaultFontSize;
  RCTFontWeight fontWeight = defaultFontWeight;
  NSString *familyName = defaultFontFamily;
  BOOL isItalic = NO;
  BOOL isCondensed = NO;

  if (font) {
    familyName = font.familyName ?: defaultFontFamily;
    fontSize = font.pointSize ?: defaultFontSize;
    fontWeight = weightOfFont(font);
    isItalic = isItalicFont(font);
    isCondensed = isCondensedFont(font);
  }

  // Get font attributes
  fontSize = [RCTConvert CGFloat:size] ?: fontSize;
  if (scaleMultiplier > 0.0 && scaleMultiplier != 1.0) {
    fontSize = round(fontSize * scaleMultiplier);
  }
  familyName = [RCTConvert NSString:family] ?: familyName;
  isItalic = style ? [RCTConvert RCTFontStyle:style] : isItalic;
  fontWeight = weight ? [RCTConvert RCTFontWeight:weight] : fontWeight;

  BOOL didFindFont = NO;

  // Handle system font as special case. This ensures that we preserve
  // the specific metrics of the standard system font as closely as possible.
  if ([familyName isEqual:defaultFontFamily] || [familyName isEqualToString:@"System"]) {
    font = cachedSystemFont(fontSize, fontWeight);
    if (font) {
      didFindFont = YES;

      if (isItalic || isCondensed) {
        UIFontDescriptor *fontDescriptor = [font fontDescriptor];
        UIFontDescriptorSymbolicTraits symbolicTraits = fontDescriptor.symbolicTraits;
        if (isItalic) {
          symbolicTraits |= UIFontDescriptorTraitItalic;
        }
        if (isCondensed) {
          symbolicTraits |= UIFontDescriptorTraitCondensed;
        }
        fontDescriptor = [fontDescriptor fontDescriptorWithSymbolicTraits:symbolicTraits];
        font = [UIFont fontWithDescriptor:fontDescriptor size:fontSize];
      }
    }
  }

  NSString* justFamily = familyName;
  if ([familyName containsString:@"-"]) {
    NSArray* array = [familyName componentsSeparatedByString:@"-"];
    justFamily = array[0];
  }
  //NSLog(@"justFamily: %@", justFamily);
  
  // Gracefully handle being given a font name rather than font family, for
  // example: "Helvetica Light Oblique" rather than just "Helvetica".
  if (!didFindFont && [UIFont fontNamesForFamilyName:justFamily].count == 0) {
    NSLog(@"111 did not find");
    font = [UIFont fontWithName:familyName size:fontSize];
    if (font) {
      NSLog(@"222 did find %@", familyName);
      // It's actually a font name, not a font family name,
      // but we'll do what was meant, not what was said.
      familyName = font.familyName;
      fontWeight = weight ? fontWeight : weightOfFont(font);
      isItalic = style ? isItalic : isItalicFont(font);
      isCondensed = isCondensedFont(font);
    } else {
      NSLog(@"333 did NOT find");
      // Not a valid font or family
      RCTLogError(@"Unrecognized font family '%@'", familyName);
      if ([UIFont respondsToSelector:@selector(systemFontOfSize:weight:)]) {
        font = [UIFont systemFontOfSize:fontSize weight:fontWeight];
      } else if (fontWeight > UIFontWeightRegular) {
        font = [UIFont boldSystemFontOfSize:fontSize];
      } else {
        font = [UIFont systemFontOfSize:fontSize];
      }
    }
  }

  if (!font) {
    // Get the closest font that matches the given weight for the fontFamily
    CGFloat closestWeight = INFINITY;
    for (NSString *name in [UIFont fontNamesForFamilyName:justFamily]) {
      UIFont *match = [UIFont fontWithName:name size:fontSize];
      //NSLog(@"justFamily: %@, familyName: %@, name: %@", justFamily, familyName, name);
  //    if (isItalic == isItalicFont(match) && isCondensed == isCondensedFont(match)) {
  //      CGFloat testWeight = weightOfFont(match);
  //      if (ABS(testWeight - fontWeight) < ABS(closestWeight - fontWeight)) {
  //        font = match;
  //        closestWeight = testWeight;
  //      }
  //    }
      
      // TODOx
      // if something
      if ([name caseInsensitiveCompare:familyName] == NSOrderedSame) {
        font = match;
        //NSLog(@"found a match: %@", familyName);
        break;
      }
    }
  }

  // If we still don't have a match at least return the first font in the fontFamily
  // This is to support built-in font Zapfino and other custom single font families like Impact
  if (!font) {
    NSArray *names = [UIFont fontNamesForFamilyName:familyName];
    if (names.count > 0) {
      font = [UIFont fontWithName:names[0] size:fontSize];
    }
  }

  // Apply font variants to font object
  if (variant) {
    NSArray *fontFeatures = [RCTConvert RCTFontVariantDescriptorArray:variant];
    UIFontDescriptor *fontDescriptor = [font.fontDescriptor
        fontDescriptorByAddingAttributes:@{UIFontDescriptorFeatureSettingsAttribute : fontFeatures}];
    font = [UIFont fontWithDescriptor:fontDescriptor size:fontSize];
  }

  return font;
}

+ (UIFont *)updateFont:(UIFont *)font withFamily:(NSString *)family
{
  return [self updateFont:font withFamily:family size:nil weight:nil style:nil variant:nil scaleMultiplier:1];
}

+ (UIFont *)updateFont:(UIFont *)font withSize:(NSNumber *)size
{
  return [self updateFont:font withFamily:nil size:size weight:nil style:nil variant:nil scaleMultiplier:1];
}

+ (UIFont *)updateFont:(UIFont *)font withWeight:(NSString *)weight
{
  return [self updateFont:font withFamily:nil size:nil weight:weight style:nil variant:nil scaleMultiplier:1];
}

+ (UIFont *)updateFont:(UIFont *)font withStyle:(NSString *)style
{
  return [self updateFont:font withFamily:nil size:nil weight:nil style:style variant:nil scaleMultiplier:1];
}

@end