react-native/ReactCommon/react/renderer/textlayoutmanager/platform/ios/RCTFontUtils.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.
 */

#import "RCTFontUtils.h"

#import <algorithm>
#import <cmath>
#import <limits>
#import <mutex>

static RCTFontProperties RCTDefaultFontProperties()
{
  static RCTFontProperties defaultFontProperties;
  static dispatch_once_t onceToken;

  dispatch_once(&onceToken, ^{
    defaultFontProperties.family = [UIFont systemFontOfSize:defaultFontProperties.size].familyName;
    defaultFontProperties.size = 14;
    defaultFontProperties.weight = UIFontWeightRegular;
    defaultFontProperties.style = RCTFontStyleNormal;
    defaultFontProperties.variant = RCTFontVariantDefault;
    defaultFontProperties.sizeMultiplier = 1.0;
  });

  return defaultFontProperties;
}

static RCTFontProperties RCTResolveFontProperties(
    RCTFontProperties fontProperties,
    RCTFontProperties baseFontProperties)
{
  fontProperties.family = fontProperties.family.length ? fontProperties.family : baseFontProperties.family;
  fontProperties.size = !isnan(fontProperties.size) ? fontProperties.size : baseFontProperties.size;
  fontProperties.weight = !isnan(fontProperties.weight) ? fontProperties.weight : baseFontProperties.weight;
  fontProperties.style =
      fontProperties.style != RCTFontStyleUndefined ? fontProperties.style : baseFontProperties.style;
  fontProperties.variant =
      fontProperties.variant != RCTFontVariantUndefined ? fontProperties.variant : baseFontProperties.variant;
  return fontProperties;
}

static UIFontWeight RCTGetFontWeight(UIFont *font)
{
  NSDictionary *traits = [font.fontDescriptor objectForKey:UIFontDescriptorTraitsAttribute];
  return [traits[UIFontWeightTrait] doubleValue];
}

static RCTFontStyle RCTGetFontStyle(UIFont *font)
{
  NSDictionary *traits = [font.fontDescriptor objectForKey:UIFontDescriptorTraitsAttribute];
  UIFontDescriptorSymbolicTraits symbolicTraits = [traits[UIFontSymbolicTrait] unsignedIntValue];
  if (symbolicTraits & UIFontDescriptorTraitItalic) {
    return RCTFontStyleItalic;
  }

  return RCTFontStyleNormal;
}

static NSArray *RCTFontFeatures(RCTFontVariant fontVariant)
{
  // FIXME:
  return @[];
}

static UIFont *RCTDefaultFontWithFontProperties(RCTFontProperties fontProperties)
{
  static NSCache *fontCache;
  static std::mutex fontCacheMutex;

  CGFloat effectiveFontSize = fontProperties.sizeMultiplier * fontProperties.size;
  NSString *cacheKey = [NSString stringWithFormat:@"%.1f/%.2f", effectiveFontSize, fontProperties.weight];
  UIFont *font;

  {
    std::lock_guard<std::mutex> lock(fontCacheMutex);
    if (!fontCache) {
      fontCache = [NSCache new];
    }
    font = [fontCache objectForKey:cacheKey];
  }

  if (!font) {
    font = [UIFont systemFontOfSize:effectiveFontSize weight:fontProperties.weight];

    if (fontProperties.variant == RCTFontStyleItalic) {
      UIFontDescriptor *fontDescriptor = [font fontDescriptor];
      UIFontDescriptorSymbolicTraits symbolicTraits = fontDescriptor.symbolicTraits;

      symbolicTraits |= UIFontDescriptorTraitItalic;

      fontDescriptor = [fontDescriptor fontDescriptorWithSymbolicTraits:symbolicTraits];
      font = [UIFont fontWithDescriptor:fontDescriptor size:effectiveFontSize];
    }

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

  return font;
}

UIFont *RCTFontWithFontProperties(RCTFontProperties fontProperties)
{
  RCTFontProperties defaultFontProperties = RCTDefaultFontProperties();
  fontProperties = RCTResolveFontProperties(fontProperties, defaultFontProperties);

  assert(!isnan(fontProperties.sizeMultiplier));
  CGFloat effectiveFontSize = fontProperties.sizeMultiplier * fontProperties.size;
  UIFont *font;
  if ([fontProperties.family isEqualToString:defaultFontProperties.family]) {
    // Handle system font as special case. This ensures that we preserve
    // the specific metrics of the standard system font as closely as possible.
    font = RCTDefaultFontWithFontProperties(fontProperties);
  } else {
    NSArray<NSString *> *fontNames = [UIFont fontNamesForFamilyName:fontProperties.family];

    if (fontNames.count == 0) {
      // Gracefully handle being given a font name rather than font family, for
      // example: "Helvetica Light Oblique" rather than just "Helvetica".
      font = [UIFont fontWithName:fontProperties.family size:effectiveFontSize];

      if (!font) {
        // Failback to system font.
        font = [UIFont systemFontOfSize:effectiveFontSize weight:fontProperties.weight];
      }
    } else {
      // Get the closest font that matches the given weight for the fontFamily
      CGFloat closestWeight = INFINITY;
      for (NSString *name in fontNames) {
        UIFont *fontMatch = [UIFont fontWithName:name size:effectiveFontSize];

        if (RCTGetFontStyle(fontMatch) != fontProperties.style) {
          continue;
        }

        CGFloat testWeight = RCTGetFontWeight(fontMatch);
        if (ABS(testWeight - fontProperties.weight) < ABS(closestWeight - fontProperties.weight)) {
          font = fontMatch;
          closestWeight = testWeight;
        }
      }

      if (!font) {
        // 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
        font = [UIFont fontWithName:fontNames[0] size:effectiveFontSize];
      }
    }
  }

  // Apply font variants to font object.
  if (fontProperties.variant != RCTFontVariantDefault) {
    NSArray *fontFeatures = RCTFontFeatures(fontProperties.variant);
    UIFontDescriptor *fontDescriptor = [font.fontDescriptor
        fontDescriptorByAddingAttributes:@{UIFontDescriptorFeatureSettingsAttribute : fontFeatures}];
    font = [UIFont fontWithDescriptor:fontDescriptor size:effectiveFontSize];
  }

  return font;
}