所有文本的 attributes 枚举，NSAttributedString

// Predefined character attributes for text. If the key is not in the dictionary, then use the default values as described below.
UIKIT_EXTERN NSString * const NSFontAttributeName NS_AVAILABLE(10_0, 6_0);                // UIFont, default Helvetica(Neue) 12
UIKIT_EXTERN NSString * const NSParagraphStyleAttributeName NS_AVAILABLE(10_0, 6_0);      // NSParagraphStyle, default defaultParagraphStyle
UIKIT_EXTERN NSString * const NSForegroundColorAttributeName NS_AVAILABLE(10_0, 6_0);     // UIColor, default blackColor
UIKIT_EXTERN NSString * const NSBackgroundColorAttributeName NS_AVAILABLE(10_0, 6_0);     // UIColor, default nil: no background
UIKIT_EXTERN NSString * const NSLigatureAttributeName NS_AVAILABLE(10_0, 6_0);            // NSNumber containing integer, default 1: default ligatures, 0: no ligatures
UIKIT_EXTERN NSString * const NSKernAttributeName NS_AVAILABLE(10_0, 6_0);                // NSNumber containing floating point value, in points; amount to modify default kerning. 0 means kerning is disabled.
UIKIT_EXTERN NSString * const NSStrikethroughStyleAttributeName NS_AVAILABLE(10_0, 6_0);  // NSNumber containing integer, default 0: no strikethrough
UIKIT_EXTERN NSString * const NSUnderlineStyleAttributeName NS_AVAILABLE(10_0, 6_0);      // NSNumber containing integer, default 0: no underline
UIKIT_EXTERN NSString * const NSStrokeColorAttributeName NS_AVAILABLE(10_0, 6_0);         // UIColor, default nil: same as foreground color
UIKIT_EXTERN NSString * const NSStrokeWidthAttributeName NS_AVAILABLE(10_0, 6_0);         // NSNumber containing floating point value, in percent of font point size, default 0: no stroke; positive for stroke alone, negative for stroke and fill (a typical value for outlined text would be 3.0)
UIKIT_EXTERN NSString * const NSShadowAttributeName NS_AVAILABLE(10_0, 6_0);              // NSShadow, default nil: no shadow
UIKIT_EXTERN NSString *const NSTextEffectAttributeName NS_AVAILABLE(10_10, 7_0);          // NSString, default nil: no text effect

UIKIT_EXTERN NSString * const NSAttachmentAttributeName NS_AVAILABLE(10_0, 7_0);          // NSTextAttachment, default nil
UIKIT_EXTERN NSString * const NSLinkAttributeName NS_AVAILABLE(10_0, 7_0);                // NSURL (preferred) or NSString
UIKIT_EXTERN NSString * const NSBaselineOffsetAttributeName NS_AVAILABLE(10_0, 7_0);      // NSNumber containing floating point value, in points; offset from baseline, default 0
UIKIT_EXTERN NSString * const NSUnderlineColorAttributeName NS_AVAILABLE(10_0, 7_0);      // UIColor, default nil: same as foreground color
UIKIT_EXTERN NSString * const NSStrikethroughColorAttributeName NS_AVAILABLE(10_0, 7_0);  // UIColor, default nil: same as foreground color
UIKIT_EXTERN NSString * const NSObliquenessAttributeName NS_AVAILABLE(10_0, 7_0);         // NSNumber containing floating point value; skew to be applied to glyphs, default 0: no skew
UIKIT_EXTERN NSString * const NSExpansionAttributeName NS_AVAILABLE(10_0, 7_0);           // NSNumber containing floating point value; log of expansion factor to be applied to glyphs, default 0: no expansion

UIKIT_EXTERN NSString * const NSWritingDirectionAttributeName NS_AVAILABLE(10_6, 7_0);    // NSArray of NSNumbers representing the nested levels of writing direction overrides as defined by Unicode LRE, RLE, LRO, and RLO characters.  The control characters can be obtained by masking NSWritingDirection and NSTextWritingDirection values.  LRE: NSWritingDirectionLeftToRight|NSWritingDirectionEmbedding, RLE: NSWritingDirectionRightToLeft|NSWritingDirectionEmbedding, LRO: NSWritingDirectionLeftToRight|NSWritingDirectionOverride, RLO: NSWritingDirectionRightToLeft|NSWritingDirectionOverride,

UIKIT_EXTERN NSString * const NSVerticalGlyphFormAttributeName NS_AVAILABLE(10_7, 6_0);   // An NSNumber containing an integer value.  0 means horizontal text.  1 indicates vertical text.  If not specified, it could follow higher-level vertical orientation settings.  Currently on iOS, it‘s always horizontal.  The behavior for any other value is undefined.