Text.swift

// Copyright 2016 LinkedIn Corp.
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

import UIKit

/// An attributed or unattributed string.
public enum Text {
    case unattributed(String)
    case attributed(NSAttributedString)

    /// Calculate the text size within `maxSize` by given `UIFont`
    func textSize(within maxSize: CGSize,
                  font: UIFont) -> CGSize {
        let options: NSStringDrawingOptions = [
            .usesLineFragmentOrigin
        ]

        let size: CGSize
        switch self {
        case .attributed(let attributedText):
            if attributedText.length == 0 {
                return .zero
            }

            // UILabel/UITextView uses a default font if one is not specified in the attributed string.
            // boundingRect(with:options:attributes:) does not appear to have the same logic,
            // so we need to ensure that our attributed string has a default font.
            // We do this by creating a new attributed string with the default font and then
            // applying all of the attributes from the provided attributed string.
            let fontAppliedAttributeString = attributedText.with(font: font)

            size = fontAppliedAttributeString.boundingRect(with: maxSize, options: options, context: nil).size
        case .unattributed(let text):
            if text.isEmpty {
                return .zero
            }
            size = text.boundingRect(with: maxSize, options: options, attributes: [NSAttributedStringKey.font: font], context: nil).size
        }
        // boundingRect(with:options:attributes:) returns size to a precision of hundredths of a point,
        // but UILabel only returns sizes with a point precision of 1/screenDensity.
        return CGSize(width: size.width.roundedUpToFractionalPoint, height: size.height.roundedUpToFractionalPoint)
    }
}