NSTextField subclasses that grow/shrink their width or height to fit text content

RSDimensionHuggingTextField.swift

//
//  RSDimensionHuggingTextField.swift
//  RSUIKit
//
//  Created by Daniel Jalkut on 6/13/18.
//

import Cocoa

// You probably want to use one of RSHeightHuggingTextField or RSWidthHuggingTextField, below

open class RSDimensionHuggingTextField: NSTextField {

	public enum Dimension {
		case vertical
		case horizontal
	}

	var huggedDimension: Dimension

	init(frame frameRect: NSRect, huggedDimension: Dimension) {
		self.huggedDimension = huggedDimension

		super.init(frame: frameRect)
	}

	// For subclasses to pass in the dimension setting
	public init?(coder: NSCoder, huggedDimension: Dimension) {
		self.huggedDimension = huggedDimension
		super.init(coder: coder)
	}

	public required init?(coder: NSCoder) {
		// We don't yet support dimension being coded, just default to vertical
		self.huggedDimension = .vertical
		super.init(coder: coder)
	}

	open override var intrinsicContentSize: NSSize {
		get {
			let defaultCellSize = super.intrinsicContentSize
			guard let textCell = self.cell else {
				return defaultCellSize
			}

			// Set up the bounds to induce unlimited sizing in the desired dimension
			var cellSizeBounds = self.bounds
			switch self.huggedDimension {
			case .vertical: cellSizeBounds.size.height = CGFloat(Float.greatestFiniteMagnitude)
			case .horizontal: cellSizeBounds.size.width = CGFloat(Float.greatestFiniteMagnitude)
			}

			// Do the actual sizing
			var nativeCellSize = textCell.cellSize(forBounds: cellSizeBounds)

			// Special case - work around a bug in which cellSize(forBounds:) returns a width
			// greater than the supplied bounds. This only seems to occur when the string just
			// barely doesn't fit. Coerce it into computing a taller value by temporary setting
			// a slightly longer string... I'm limiting this to vertical hugging fields for now
			// because that's the only scenario where I know it causes a problem. FB7448962.
			if self.huggedDimension == .vertical && (nativeCellSize.width > cellSizeBounds.width) {
				// Use a copy of the cell to avoid sending the view into a life updateConstraints/loopfkdsj
				if
					let measuringCell = textCell.copy() as? NSTextFieldCell,
					let mutableString = measuringCell.attributedStringValue.mutableCopy() as? NSMutableAttributedString
				{
						mutableString.append(NSAttributedString(string: "X"))
						measuringCell.attributedStringValue = mutableString
						nativeCellSize = measuringCell.cellSize(forBounds: cellSizeBounds)
				}
			}

			// Return an intrinsic size that imposes calculated (hugged) dimensional size
			var intrinsicSize = NSSize(width: NSView.noIntrinsicMetric, height: NSView.noIntrinsicMetric)
			switch self.huggedDimension {
			case .vertical:
				intrinsicSize.height = nativeCellSize.height
			case .horizontal:
				intrinsicSize.width = nativeCellSize.width
			}
			return intrinsicSize
		}
	}

	open override func textDidChange(_ notification: Notification) {
		super.textDidChange(notification)
		self.invalidateIntrinsicContentSize()

		// It seems important to set the string from the cell on ourself to
		// get the change to be respected by the cell and to get the cellSize
		// computation to update!
		if let changedCell = self.cell {
			self.stringValue = changedCell.stringValue
		}
	}
}

open class RSHeightHuggingTextField: RSDimensionHuggingTextField {
	@objc init(frame frameRect: NSRect) {
		super.init(frame: frameRect, huggedDimension: .vertical)
	}

	public required init?(coder: NSCoder) {
		super.init(coder: coder, huggedDimension: .vertical)
	}

	public override init(frame frameRect: NSRect, huggedDimension: Dimension = .vertical) {
		super.init(frame: frameRect, huggedDimension: huggedDimension)
	}
}

open class RSWidthHuggingTextField: RSDimensionHuggingTextField {
	@objc init(frame frameRect: NSRect) {
		super.init(frame: frameRect, huggedDimension: .horizontal)
	}

	public required init?(coder: NSCoder) {
		super.init(coder: coder, huggedDimension: .horizontal)
	}

	public override init(frame frameRect: NSRect, huggedDimension: Dimension = .horizontal) {
		super.init(frame: frameRect, huggedDimension: huggedDimension)
	}
}

I found that setting the non-hugged dimension to .noIntrinsicMetric in line 56 looked too tight with an editable text field, so I instead used super.intrinsicContentSize to get the height when having the width grow to fix the content.

@michaeljtsai Thanks, I'll have to take a look and see if something similar would work well for my uses too.