components/Typography/src/MDCTypography.m

// Copyright 2015-present the Material Components for iOS authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#import "MDCTypography.h"

#import "private/UIFont+MaterialTypographyPrivate.h"
#import <MDFTextAccessibility/MDFTextAccessibility.h>

static id<MDCTypographyFontLoading> gFontLoader = nil;

@implementation MDCTypography

#pragma mark - Font loader access

+ (id<MDCTypographyFontLoading>)fontLoader {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    if (!gFontLoader) {
      gFontLoader = [self defaultFontLoader];
    }
  });
  return gFontLoader;
}

#pragma mark - Display fonts (extra large fonts)

+ (UIFont *)display4Font {
  return [[self fontLoader] lightFontOfSize:112];
}

+ (UIFont *)display3Font {
  return [[self fontLoader] regularFontOfSize:56];
}

+ (UIFont *)display2Font {
  return [[self fontLoader] regularFontOfSize:45];
}

+ (UIFont *)display1Font {
  return [[self fontLoader] regularFontOfSize:34];
}

#pragma mark - Common UI fonts.

+ (UIFont *)headlineFont {
  return [[self fontLoader] regularFontOfSize:24];
}

+ (UIFont *)titleFont {
  return [[self fontLoader] mediumFontOfSize:20];
}

+ (UIFont *)subheadFont {
  return [[self fontLoader] regularFontOfSize:16];
}

+ (UIFont *)body2Font {
  return [[self fontLoader] mediumFontOfSize:14];
}

+ (UIFont *)body1Font {
  return [[self fontLoader] regularFontOfSize:14];
}

+ (UIFont *)captionFont {
  return [[self fontLoader] regularFontOfSize:12];
}

+ (UIFont *)buttonFont {
  return [[self fontLoader] mediumFontOfSize:14];
}

+ (BOOL)isLargeForContrastRatios:(nonnull UIFont *)font {
  id<MDCTypographyFontLoading> fontLoader = [self fontLoader];

  if ([fontLoader respondsToSelector:@selector(isLargeForContrastRatios:)]) {
    return [fontLoader isLargeForContrastRatios:font];
  }

  return [MDFTextAccessibility isLargeForContrastRatios:font];
}

#pragma mark - Private

+ (id<MDCTypographyFontLoading>)defaultFontLoader {
  return [[MDCSystemFontLoader alloc] init];
}

@end

@interface MDCSystemFontLoader ()

/*
 In collectionView scrolling tests, manually caching UIFonts performs around 4.5 times better
 (e.g. 230 ms vs. 1,080 ms in one test) than calling [UIFont systemFontForSize:weight:] every time.
 */
@property(nonatomic, strong) NSCache *fontCache;

@end

@implementation MDCSystemFontLoader

- (instancetype)init {
  self = [super init];
  if (self) {
    _fontCache = [[NSCache alloc] init];
    [[NSNotificationCenter defaultCenter]
        addObserver:self
           selector:@selector(accessibilityFontAttributesDidChange)
               name:UIContentSizeCategoryDidChangeNotification
             object:nil];
    [[NSNotificationCenter defaultCenter]
        addObserver:self
           selector:@selector(accessibilityFontAttributesDidChange)
               name:UIAccessibilityBoldTextStatusDidChangeNotification
             object:nil];
  }
  return self;
}

- (void)accessibilityFontAttributesDidChange {
  [_fontCache removeAllObjects];
}

- (nullable UIFont *)lightFontOfSize:(CGFloat)fontSize {
  NSString *cacheKey = [NSString stringWithFormat:@"%@-%06f", NSStringFromSelector(_cmd), fontSize];
  UIFont *font = [self.fontCache objectForKey:cacheKey];
  if (font) {
    return font;
  }

  font = [UIFont systemFontOfSize:fontSize weight:UIFontWeightLight];
  if (font) {
    [self.fontCache setObject:font forKey:cacheKey];
  }
  return font;
}

- (UIFont *)regularFontOfSize:(CGFloat)fontSize {
  NSString *cacheKey = [NSString stringWithFormat:@"%@-%06f", NSStringFromSelector(_cmd), fontSize];
  UIFont *font = [self.fontCache objectForKey:cacheKey];
  if (font) {
    return font;
  }

  font = [UIFont systemFontOfSize:fontSize weight:UIFontWeightRegular];
  [self.fontCache setObject:font forKey:cacheKey];

  return (UIFont *)font;
}

- (nullable UIFont *)mediumFontOfSize:(CGFloat)fontSize {
  NSString *cacheKey = [NSString stringWithFormat:@"%@-%06f", NSStringFromSelector(_cmd), fontSize];
  UIFont *font = [self.fontCache objectForKey:cacheKey];
  if (font) {
    return font;
  }

  font = [UIFont systemFontOfSize:fontSize weight:UIFontWeightMedium];
  if (font) {
    [self.fontCache setObject:font forKey:cacheKey];
  }
  return font;
}

- (UIFont *)boldFontOfSize:(CGFloat)fontSize {
  NSString *cacheKey = [NSString stringWithFormat:@"%@-%06f", NSStringFromSelector(_cmd), fontSize];
  UIFont *font = [self.fontCache objectForKey:cacheKey];
  if (font) {
    return font;
  }

  font = [UIFont systemFontOfSize:fontSize weight:UIFontWeightSemibold];

  [self.fontCache setObject:font forKey:cacheKey];

  return font;
}

- (UIFont *)italicFontOfSize:(CGFloat)fontSize {
  NSString *cacheKey = [NSString stringWithFormat:@"%@-%06f", NSStringFromSelector(_cmd), fontSize];
  UIFont *font = [self.fontCache objectForKey:cacheKey];
  if (font) {
    return font;
  }

  font = [UIFont italicSystemFontOfSize:fontSize];

  [self.fontCache setObject:font forKey:cacheKey];

  return font;
}

- (nullable UIFont *)boldItalicFontOfSize:(CGFloat)fontSize {
  NSString *cacheKey = [NSString stringWithFormat:@"%@-%06f", NSStringFromSelector(_cmd), fontSize];
  UIFont *font = [self.fontCache objectForKey:cacheKey];
  if (font) {
    return font;
  }

  UIFont *regular = [self regularFontOfSize:fontSize];
  UIFontDescriptor *_Nullable descriptor = [regular.fontDescriptor
      fontDescriptorWithSymbolicTraits:UIFontDescriptorTraitBold | UIFontDescriptorTraitItalic];
  if (!descriptor) {
    return nil;
  }
  UIFontDescriptor *nonnullDescriptor = descriptor;
  font = [UIFont fontWithDescriptor:nonnullDescriptor size:fontSize];

  [self.fontCache setObject:font forKey:cacheKey];

  return font;
}

- (BOOL)isLargeForContrastRatios:(UIFont *)font {
  if (font.pointSize >= 18) {
    return YES;
  }
  if (font.pointSize < 14) {
    return NO;
  }

  UIFontDescriptor *fontDescriptor = font.fontDescriptor;
  if ((fontDescriptor.symbolicTraits & UIFontDescriptorTraitBold) == UIFontDescriptorTraitBold) {
    return YES;
  }

  // We treat system font medium as large for accessibility when larger than 14.
  if (font.mdc_weight >= UIFontWeightMedium) {
    return YES;
  }

  return NO;
}

@end