IGListKit/Example/IGListKitExamples/Views/LabelCell.swift

/**
 Copyright (c) 2016-present, Facebook, Inc. All rights reserved.

 The examples provided by Facebook are for non-commercial testing and evaluation
 purposes only. Facebook reserves all rights not expressly granted.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

import UIKit

class LabelCell: UICollectionViewCell {

    fileprivate static let insets = UIEdgeInsets(top: 8, left: 15, bottom: 8, right: 15)
    fileprivate static let font = UIFont.systemFont(ofSize: 17)

    static var singleLineHeight: CGFloat {
        return font.lineHeight + insets.top + insets.bottom
    }

    static func textHeight(_ text: String, width: CGFloat) -> CGFloat {
        let constrainedSize = CGSize(width: width - insets.left - insets.right, height: CGFloat.greatestFiniteMagnitude)
        let attributes = [ NSFontAttributeName: font ]
        let options: NSStringDrawingOptions = [.usesFontLeading, .usesLineFragmentOrigin]
        let bounds = (text as NSString).boundingRect(with: constrainedSize, options: options, attributes: attributes, context: nil)
        return ceil(bounds.height) + insets.top + insets.bottom
    }

    lazy var label: UILabel = {
        let label = UILabel()
        label.backgroundColor = .clear
        label.numberOfLines = 1
        label.font = LabelCell.font
        self.contentView.addSubview(label)
        return label
    }()

    lazy var separator: CALayer = {
        let layer = CALayer()
        layer.backgroundColor = UIColor(red: 200/255.0, green: 199/255.0, blue: 204/255.0, alpha: 1).cgColor
        self.contentView.layer.addSublayer(layer)
        return layer
    }()

    override func layoutSubviews() {
        super.layoutSubviews()
        let bounds = contentView.bounds
        label.frame = UIEdgeInsetsInsetRect(bounds, LabelCell.insets)
        let height: CGFloat = 0.5
        let left = LabelCell.insets.left
        separator.frame = CGRect(x: left, y: bounds.height - height, width: bounds.width - left, height: height)
    }

    override var isHighlighted: Bool {
        didSet {
            contentView.backgroundColor = UIColor(white: isHighlighted ? 0.9 : 1, alpha: 1)
        }
    }
    
}