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.