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//
// MultilineTextFieldSizer.swift
// NetNewsWire
//
// Created by Brent Simmons on 2/19/18.
// Copyright © 2018 Ranchero Software. All rights reserved.
//
import AppKit
// Get the height of an NSTextField given a string, font, and width.
// Uses a cache. Avoids actually measuring text as much as possible.
// Main thread only.
typealias WidthHeightCache = [Int: Int] // width: height
private struct TextFieldSizerSpecifier: Hashable {
let numberOfLines: Int
let font: NSFont
}
struct TextFieldSizeInfo {
let size: NSSize // Integral size (ceiled)
let numberOfLinesUsed: Int // A two-line text field may only use one line, for instance. This would equal 1, then.
}
final class MultilineTextFieldSizer {
private let numberOfLines: Int
private let font: NSFont
private let textField:NSTextField
private let singleLineHeightEstimate: Int
private let doubleLineHeightEstimate: Int
private var cache = [String: WidthHeightCache]() // Each string has a cache.
private static var sizers = [TextFieldSizerSpecifier: MultilineTextFieldSizer]()
private init(numberOfLines: Int, font: NSFont) {
self.numberOfLines = numberOfLines
self.font = font
self.textField = MultilineTextFieldSizer.createTextField(numberOfLines, font)
self.singleLineHeightEstimate = MultilineTextFieldSizer.calculateHeight("AqLjJ0/y", 200, self.textField)
self.doubleLineHeightEstimate = MultilineTextFieldSizer.calculateHeight("AqLjJ0/y\nAqLjJ0/y", 200, self.textField)
}
static func size(for string: String, font: NSFont, numberOfLines: Int, width: Int) -> TextFieldSizeInfo {
return sizer(numberOfLines: numberOfLines, font: font).sizeInfo(for: string, width: width)
}
static func emptyCache() {
sizers = [TextFieldSizerSpecifier: MultilineTextFieldSizer]()
}
}
// MARK: - Private
private extension MultilineTextFieldSizer {
static func sizer(numberOfLines: Int, font: NSFont) -> MultilineTextFieldSizer {
let specifier = TextFieldSizerSpecifier(numberOfLines: numberOfLines, font: font)
if let cachedSizer = sizers[specifier] {
return cachedSizer
}
let newSizer = MultilineTextFieldSizer(numberOfLines: numberOfLines, font: font)
sizers[specifier] = newSizer
return newSizer
}
func sizeInfo(for string: String, width: Int) -> TextFieldSizeInfo {
let textFieldHeight = height(for: string, width: width)
let numberOfLinesUsed = numberOfLines(for: textFieldHeight)
let size = NSSize(width: width, height: textFieldHeight)
let sizeInfo = TextFieldSizeInfo(size: size, numberOfLinesUsed: numberOfLinesUsed)
return sizeInfo
}
func height(for string: String, width: Int) -> Int {
if cache[string] == nil {
cache[string] = WidthHeightCache()
}
if let height = cache[string]![width] {
return height
}
if let height = heightConsideringNeighbors(cache[string]!, width) {
return height
}
let height = calculateHeight(string, width)
cache[string]![width] = height
return height
}
static func createTextField(_ numberOfLines: Int, _ font: NSFont) -> NSTextField {
let textField = NSTextField(wrappingLabelWithString: "")
textField.usesSingleLineMode = false
textField.maximumNumberOfLines = numberOfLines
textField.isEditable = false
textField.font = font
textField.allowsDefaultTighteningForTruncation = false
return textField
}
func calculateHeight(_ string: String, _ width: Int) -> Int {
return MultilineTextFieldSizer.calculateHeight(string, width, textField)
}
static func calculateHeight(_ string: String, _ width: Int, _ textField: NSTextField) -> Int {
textField.stringValue = string
textField.preferredMaxLayoutWidth = CGFloat(width)
let size = textField.fittingSize
return Int(ceil(size.height))
}
func numberOfLines(for height: Int) -> Int {
// We’ll have to see if this really works reliably.
let averageHeight = CGFloat(doubleLineHeightEstimate) / 2.0
let lines = Int(round(CGFloat(height) / averageHeight))
return lines
}
func heightIsProbablySingleLineHeight(_ height: Int) -> Bool {
return heightIsProbablyEqualToEstimate(height, singleLineHeightEstimate)
}
func heightIsProbablyDoubleLineHeight(_ height: Int) -> Bool {
return heightIsProbablyEqualToEstimate(height, doubleLineHeightEstimate)
}
func heightIsProbablyEqualToEstimate(_ height: Int, _ estimate: Int) -> Bool {
let slop = 4
let minimum = estimate - slop
let maximum = estimate + slop
return height >= minimum && height <= maximum
}
func heightConsideringNeighbors(_ heightCache: WidthHeightCache, _ width: Int) -> Int? {
// Given width, if the height at width - something and width + something is equal,
// then that height must be correct for the given width.
// Also:
// If a narrower neighbor’s height is single line height, then this wider width must also be single-line height.
// If a wider neighbor’s height is double line height, and numberOfLines == 2, then this narrower width must able be double-line height.
var smallNeighbor = (width: 0, height: 0)
var largeNeighbor = (width: 0, height: 0)
for (oneWidth, oneHeight) in heightCache {
if oneWidth < width && heightIsProbablySingleLineHeight(oneHeight) {
return oneHeight
}
if numberOfLines == 2 && oneWidth > width && heightIsProbablyDoubleLineHeight(oneHeight) {
return oneHeight
}
if oneWidth < width && (oneWidth > smallNeighbor.width || smallNeighbor.width == 0) {
smallNeighbor = (oneWidth, oneHeight)
}
else if oneWidth > width && (oneWidth < largeNeighbor.width || largeNeighbor.width == 0) {
largeNeighbor = (oneWidth, oneHeight)
}
if smallNeighbor.width != 0 && smallNeighbor.height == largeNeighbor.height {
return smallNeighbor.height
}
}
return nil
}
}
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