"given this many pixels and a string with these attributes, tell me the optimal places to do a line break" https://iosdevelopers.slack.com/archives/C1GPPBMHC/p1697470218613869?thread_ts=1697467894.270959&cid=C1GPPBMHC

LineBreakPropose.swift

import Cocoa

/// "given this many pixels and a string with these attributes, tell me the optimal places to do a line break"
class LineBreakPropose: NSObject, NSTextLayoutManagerDelegate {
    
    var lineBreaks: [NSTextLocation] = []
    
    init(_ attributedString: NSAttributedString, in size: CGSize, by lineBreakMode: NSLineBreakMode = .byWordWrapping) {
        super.init() 
        
        let textContentManager = NSTextContentStorage()
        
        // Layout
        let textLayoutManager = NSTextLayoutManager()
        textLayoutManager.delegate = self
        textContentManager.addTextLayoutManager(textLayoutManager)
        textContentManager.primaryTextLayoutManager = textLayoutManager
        
        let textContainer = NSTextContainer()
        textLayoutManager.textContainer = textContainer
        textContainer.lineFragmentPadding = 0
        textContainer.lineBreakMode = lineBreakMode
        
        textContainer.size = size
        
        textContentManager.attributedString = attributedString //NSAttributedString(string: "0123456789 0123456789 012")
        textLayoutManager.ensureLayout(for: textContentManager.documentRange)
    }
    
    func textLayoutManager(_ textLayoutManager: NSTextLayoutManager, shouldBreakLineBefore location: NSTextLocation, hyphenating: Bool) -> Bool {
        lineBreaks.append(location)
        return true
    }
}

let breakLocations = LineBreakPropose(NSAttributedString(string: "0123456789 0123456789 012"), in: CGSize(width: 40, height: 10000)).lineBreaks

print(breakLocations)