Using Autolayout with expanding NSTextViews

Question

My app consists of an NSScrollView whose document view contains a number of vertically stacked NSTextViews — each of which resizes in the vertical direction as text is added.

Currently, this is all managed in code. The NSTextViews resize automatically, but I observe their resizing with an NSViewFrameDidChangeNotification, recalc all their origins so that they don't overlap, and resize their superview (the scroll view's document view) so that they all fit and can be scrolled to.

This seems as though it would be the perfect candidate for autolayout! I set NSLayoutConstraints between the first text view and its container, the last text view and its container, and each text view between each other. Then, if any text view grows, it automatically "pushes down" the origins of the text views below it to satisfy contraints, ultimately growing the size of the document view, and everyone's happy!

Except, it seems there's no way to make an NSTextView automatically grow as text is added in a constraints-based layout? Using the exact same NSTextView that automatically expanded as text was entered before, if I don't specify a constraint for its height, it defautls to 0 and isn't shown. If I do specify a constraint, even an inequality such as >=20, it stays stuck at that size and doesn't grow as text is added.

I suspect this has to do with NSTextView's implementation of -intrinsicContentSize, which by default returns (NSViewNoInstrinsicMetric, NSViewNoInstrinsicMetric).

So my questions: if I subclasses NSTextView to return a more meaningful intrinsicContentSize based on the layout of my text, would my autolayout then work as expected?

Any pointers on implementing intrinsicContentSize for a vertically resizing NSTextView?

Answer 1

I am working on a very similar setup — a vertical stack of views containing text views that expand to fit their text contents and use autolayout.

So far I have had to subclass NSTextView, which is does not feel clean, but works superbly in practice:

- (NSSize) intrinsicContentSize {
    NSTextContainer* textContainer = [self textContainer];
    NSLayoutManager* layoutManager = [self layoutManager];
    [layoutManager ensureLayoutForTextContainer: textContainer];
    return [layoutManager usedRectForTextContainer: textContainer].size;
}

- (void) didChangeText {
    [super didChangeText];
    [self invalidateIntrinsicContentSize];
}

The initial size of the text view when added with addSubview is, curiously, not the intrinsic size; I have not yet figured out how to issue the first invalidation (hooking viewDidMoveToSuperview does not help), but I'm sure I will figure it out eventually.

Answer 2

I had a similar problem with an NSTextField, and it turned out that it was due to the view wanting to hug its text content tightly along the vertical orientation. So if you set the content hugging priority to something lower than the priorities of your other constraints, it may work. E.g.:

[textView setContentHuggingPriority:NSLayoutPriorityFittingSizeCompression-1.0 forOrientation:NSLayoutConstraintOrientationVertical];

And in Swift, this would be:

setContentHuggingPriority(NSLayoutConstraint.Priority.fittingSizeCompression, for:NSLayoutConstraint.Orientation.vertical)

Answer 3

Here is how to make an expanding NSTextView using Auto Layout, in Swift 3

• I used Anchors for Auto Layout
• Use textDidChange from NSTextDelegate. NSTextViewDelegate conforms to NSTextDelegate

• The idea is that textView has edges constraints, which means whenever its intrinsicContentSize changes, it will expand its parent, which is scrollView

  import Cocoa
  import Anchors
  
  class TextView: NSTextView {
    override var intrinsicContentSize: NSSize {
      guard let manager = textContainer?.layoutManager else {
        return .zero
      }
  
      manager.ensureLayout(for: textContainer!)
  
      return manager.usedRect(for: textContainer!).size
    }
  }
  
  class ViewController: NSViewController, NSTextViewDelegate {
  
    @IBOutlet var textView: NSTextView!
    @IBOutlet weak var scrollView: NSScrollView!
    override func viewDidLoad() {
      super.viewDidLoad()
  
      textView.delegate = self
  
      activate(
        scrollView.anchor.top.constant(100),
        scrollView.anchor.paddingHorizontally(30)
      )
  
      activate(
        textView.anchor.edges
      )
    }
  
    // MARK: - NSTextDelegate
    func textDidChange(_ notification: Notification) {
      guard let textView = notification.object as? NSTextView else { return }
  
      print(textView.intrinsicContentSize)
      textView.invalidateIntrinsicContentSize()
    }
  }