react-native/Libraries/Text/RCTTextAttributes.h
Adam Comella 01d5eff425 iOS: Add a maxFontSizeMultiplier prop to <Text> and <TextInput> (#20915)
Summary:
**Motivation**

Whenever a user changes the system font size to its maximum allowable setting, React Native apps that allow font scaling can become unusable because the text gets too big. Experimenting with a native app like iMessage on iOS, the font size used for non-body text (e.g. header, navigational elements) is capped while the body text (e.g. text in the message bubbles) is allowed to grow.

This PR introduces a new prop on `<Text>` and `<TextInput>` called `maxFontSizeMultiplier`. This enables devs to set the maximum allowed text scale factor on a Text/TextInput. The default is 0 which means no limit.

Another PR will add this feature to Android.

**Test Plan**

I created a test app which utilizes all categories of values of `maxFontSizeMultiplier`:
  - `undefined`: inherit from parent
  - `0`: no limit
  - `1`, `1.2`: fixed limits

I tried this with `Text`, `TextInput` with `value`, and `TextInput` with children. For `Text`, I also verified that nesting works properly (if a child `Text` doesn't specify `maxFontSizeMultiplier`, it inherits it from its parent).

Lastly, we've been using a version of this in Skype for several months.

**Release Notes**

[GENERAL] [ENHANCEMENT] [Text/TextInput] - Added maxFontSizeMultiplier prop to prevent some text from getting unusably large as user increases OS's font scale setting (iOS)

Adam Comella
Microsoft Corp.
Pull Request resolved: https://github.com/facebook/react-native/pull/20915

Differential Revision: D9646739

Pulled By: shergin

fbshipit-source-id: c823f59c1e342c22d6297b88b2cb11c5a1f10310
2018-09-04 17:50:42 -07:00

93 lines
2.9 KiB
Objective-C

/**
* Copyright (c) 2015-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
#import <UIKit/UIKit.h>
#import <React/RCTTextDecorationLineType.h>
#import "RCTTextTransform.h"
NS_ASSUME_NONNULL_BEGIN
extern NSString *const RCTTextAttributesIsHighlightedAttributeName;
extern NSString *const RCTTextAttributesTagAttributeName;
/**
* Represents knowledge about all supported *text* attributes
* assigned to some text component such as <Text>, <VirtualText>,
* and <TextInput>.
*/
@interface RCTTextAttributes : NSObject <NSCopying>
// Color
@property (nonatomic, strong, nullable) UIColor *foregroundColor;
@property (nonatomic, strong, nullable) UIColor *backgroundColor;
@property (nonatomic, assign) CGFloat opacity;
// Font
@property (nonatomic, copy, nullable) NSString *fontFamily;
@property (nonatomic, assign) CGFloat fontSize;
@property (nonatomic, assign) CGFloat fontSizeMultiplier;
@property (nonatomic, assign) CGFloat maxFontSizeMultiplier;
@property (nonatomic, copy, nullable) NSString *fontWeight;
@property (nonatomic, copy, nullable) NSString *fontStyle;
@property (nonatomic, copy, nullable) NSArray<NSString *> *fontVariant;
@property (nonatomic, assign) BOOL allowFontScaling;
@property (nonatomic, assign) CGFloat letterSpacing;
// Paragraph Styles
@property (nonatomic, assign) CGFloat lineHeight;
@property (nonatomic, assign) NSTextAlignment alignment;
@property (nonatomic, assign) NSWritingDirection baseWritingDirection;
// Decoration
@property (nonatomic, strong, nullable) UIColor *textDecorationColor;
@property (nonatomic, assign) NSUnderlineStyle textDecorationStyle;
@property (nonatomic, assign) RCTTextDecorationLineType textDecorationLine;
// Shadow
@property (nonatomic, assign) CGSize textShadowOffset;
@property (nonatomic, assign) CGFloat textShadowRadius;
@property (nonatomic, strong, nullable) UIColor *textShadowColor;
// Special
@property (nonatomic, assign) BOOL isHighlighted;
@property (nonatomic, strong, nullable) NSNumber *tag;
@property (nonatomic, assign) UIUserInterfaceLayoutDirection layoutDirection;
@property (nonatomic, assign) RCTTextTransform textTransform;
#pragma mark - Inheritance
- (void)applyTextAttributes:(RCTTextAttributes *)textAttributes;
#pragma mark - Adapters
/**
* Text attributes in NSAttributedString terms.
*/
- (NSDictionary<NSAttributedStringKey, id> *)effectiveTextAttributes;
/**
* Constructed font.
*/
- (UIFont *)effectiveFont;
/**
* Font size multiplier reflects `allowFontScaling`, `fontSizeMultiplier`, and `maxFontSizeMultiplier`.
*/
- (CGFloat)effectiveFontSizeMultiplier;
/**
* Foreground and background colors with opacity and right defaults.
*/
- (UIColor *)effectiveForegroundColor;
- (UIColor *)effectiveBackgroundColor;
/**
* Text transformed per 'none', 'uppercase', 'lowercase', 'capitalize'
*/
- (NSString *)applyTextAttributesToText:(NSString *)text;
@end
NS_ASSUME_NONNULL_END