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Calculate height of some text when width is fixed
public struct TextSize {
fileprivate struct CacheEntry: Hashable {
let text: String
let font: UIFont
let width: CGFloat
let insets: UIEdgeInsets
fileprivate var hashValue: Int {
return text.hashValue ^ Int(width) ^ Int(insets.top) ^ Int(insets.left) ^ Int(insets.bottom) ^ Int(insets.right)
}
}
fileprivate static var cache = [CacheEntry: CGRect]() {
didSet {
assert(Thread.isMainThread)
}
}
public static func size(_ text: String, font: UIFont, width: CGFloat, insets: UIEdgeInsets = UIEdgeInsets.zero) -> CGRect {
let key = CacheEntry(text: text, font: font, width: width, insets: insets)
if let hit = cache[key] {
return hit
}
let constrainedSize = CGSize(width: width - insets.left - insets.right, height: CGFloat.greatestFiniteMagnitude)
let attributes = [ NSFontAttributeName: font ]
let options: NSStringDrawingOptions = [.usesFontLeading, .usesLineFragmentOrigin]
var bounds = (text as NSString).boundingRect(with: constrainedSize, options: options, attributes: attributes, context: nil)
bounds.size.width = width
bounds.size.height = ceil(bounds.height + insets.top + insets.bottom)
cache[key] = bounds
return bounds
}
}
private func ==(lhs: TextSize.CacheEntry, rhs: TextSize.CacheEntry) -> Bool {
return lhs.width == rhs.width && lhs.insets == rhs.insets && lhs.text == rhs.text
}
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