UILable.h

import Foundation
import UIKit

//
//  UILabel.h
//  UIKit
//
//  Copyright (c) 2006-2016 Apple Inc. All rights reserved.
//

@available(iOS 2.0, *)
public class UILabel : UIView, NSCoding, UIContentSizeCategoryAdjusting {

    // lable 显示的 文本信息
    public var text: String? // default is nil

    // 文本的字体
    public var font: UIFont! // default is nil (system font 17 plain)

    // 文本的颜色
    public var textColor: UIColor! // default is nil (text draws black)

    // 文本的阴影
    public var shadowColor: UIColor? // default is nil (no shadow)

    // 文本的阴影偏移
    public var shadowOffset: CGSize // default is CGSizeMake(0, -1) -- a top shadow

    // 文本的排列 
    public var textAlignment: NSTextAlignment // default is NSTextAlignmentNatural (before iOS 9, the default was NSTextAlignmentLeft)

    // 文本的换行模式 
    public var lineBreakMode: NSLineBreakMode // default is NSLineBreakByTruncatingTail. used for single and multiple lines of text

    
    // the underlying attributed string drawn by the label, if set, the label ignores the properties above.
    @available(iOS 6.0, *)
    // 属性文本 （ TextKit 的主要内容 ）
    @NSCopying public var attributedText: AttributedString? // default is nil

    
    // the 'highlight' property is used by subclasses for such things as pressed states. it's useful to make it part of the base class as a user property
    
   // 高亮的文本颜色
    public var highlightedTextColor: UIColor? // default is nil

    // 是否高亮
    public var isHighlighted: Bool // default is NO

    // 是否响应用户事件（no ，用户事件将从事件队列中移除）
    public var isUserInteractionEnabled: Bool // default is NO

    public var isEnabled: Bool // default is YES. changes how the label is drawn

    
    // this determines the number of lines to draw and what to do when sizeToFit is called. default value is 1 (single line). A value of 0 means no limit
    // if the height of the text reaches the # of lines or the height of the view is less than the # of lines allowed, the text will be
    // truncated using the line break mode.
    // 文本的行数
    public var numberOfLines: Int

    
    // these next 3 property allow the label to be autosized to fit a certain width by scaling the font size(s) by a scaling factor >= the minimum scaling factor
    // and to specify how the text baseline moves when it needs to shrink the font.
    
    public var adjustsFontSizeToFitWidth: Bool // default is NO

    public var baselineAdjustment: UIBaselineAdjustment // default is UIBaselineAdjustmentAlignBaselines

    @available(iOS 6.0, *)
    public var minimumScaleFactor: CGFloat // default is 0.0

    
    // Tightens inter-character spacing in attempt to fit lines wider than the available space if the line break mode is one of the truncation modes before starting to truncate.
    // The maximum amount of tightening performed is determined by the system based on contexts such as font, line width, etc.
    @available(iOS 9.0, *)
    public var allowsDefaultTighteningForTruncation: Bool // default is NO

    
    // override points. can adjust rect before calling super.
    // label has default content mode of UIViewContentModeRedraw
    
    public func textRect(forBounds bounds: CGRect, limitedToNumberOfLines numberOfLines: Int) -> CGRect



    // 在指定的范围内进行文本绘制（或者绘制阴影）
    // 这个方法不能被直接调用，只有当子类需要修改默认的文本绘制行为的时候，才在子类中重写，这个方法只能被子类重写，
    public func drawText(in rect: CGRect)

    
    // Support for constraint-based layout (auto layout)  支持自动布局
    // If nonzero, this is used when determining -intrinsicContentSize for multiline labels
    // 如果为非零值，在多行文本下调用  -intrinsicContentSize 方法就会被调用
    @available(iOS 6.0, *)
   // 优先的多行文本布局最大宽度
   // 当使用 约束进行文本布局的时候，这个属性就会影响文本的尺寸，如果文本的扩展超过这个属性指定的值，
   // 文本就会另起一行，并增加 文本的高度 
    public var preferredMaxLayoutWidth: CGFloat
}