macos - getting a NSTextField to grow with the text in auto layout?

Question

I'm trying to get my NSTextField to have its height grow (much like in iChat or Adium) once the user types enough text to overflow the width of the control (as asked on this post)

I've implimented the accepted answer yet I can't seem to get it to work. I have uploaded my attempt at http://scottyob.com/pub/autoGrowingExample.zip

Ideally, when the text grows, the containing window should grow with it, but I'm trying baby steps here.

Answer 1

Solved it! (Inspired by https://github.com/jerrykrinock/CategoriesObjC/blob/master/NS(Attributed)String%2BGeometrics/NS(Attributed)String%2BGeometrics.m )

Reading the Apple Documentation is usually helpful. Apple has engineered all this text layout stuff to be powerful enough to handle all sorts of complicated edge cases which is sometimes extremely helpful, and sometimes not.

Firstly, I set the text field to wrap lines on word break, so we actually get multiple lines. (Your example code even had an if statement so it did nothing at all when wrapping was turned off).

The trick to this one was to note that when text is being edited, it’s printed by a ‘field editor’ – a heavy weight NSTextView object, owned by an NSWindow, that’s reused by whatever NSTextField is currently the ‘first responder’ (selected). The NSTextView has a single NSTextContainer (rectangle where text goes), which has a NSLayoutManager to layout the text. We can ask the layout manager how much space it wants to use up, to get the new height of our text field.

The other trick was to override the NSText delegate method - (void)textDidChange:(NSNotification *)notification to invalidate the intrinsic content size when the text is changed (so it doesn’t just wait to update when you commit changed by pressing return).

The reason I didn’t use cellSizeForBounds as you originally suggested was I couldn’t solve your problem – even when invalidating the intrinsic content size of the cell, cellSizeForBounds: continued to return the old size.

Find the example project on GitHub.

@interface TSTTextGrowth()
{
    BOOL _hasLastIntrinsicSize;
    BOOL _isEditing;
    NSSize _lastIntrinsicSize;
}

@end

@implementation TSTTextGrowth

- (void)textDidBeginEditing:(NSNotification *)notification
{
    [super textDidBeginEditing:notification];
    _isEditing = YES;
}

- (void)textDidEndEditing:(NSNotification *)notification
{
    [super textDidEndEditing:notification];
    _isEditing = NO;
}

- (void)textDidChange:(NSNotification *)notification
{
    [super textDidChange:notification];
    [self invalidateIntrinsicContentSize];
}

-(NSSize)intrinsicContentSize
{
    NSSize intrinsicSize = _lastIntrinsicSize;

    // Only update the size if we’re editing the text, or if we’ve not set it yet
    // If we try and update it while another text field is selected, it may shrink back down to only the size of one line (for some reason?)
    if(_isEditing || !_hasLastIntrinsicSize)
    {
        intrinsicSize = [super intrinsicContentSize];

        // If we’re being edited, get the shared NSTextView field editor, so we can get more info
        NSText *fieldEditor = [self.window fieldEditor:NO forObject:self];
        if([fieldEditor isKindOfClass:[NSTextView class]])
        {
            NSTextView *textView = (NSTextView *)fieldEditor;
            NSRect usedRect = [textView.textContainer.layoutManager usedRectForTextContainer:textView.textContainer];

            usedRect.size.height += 5.0; // magic number! (the field editor TextView is offset within the NSTextField. It’s easy to get the space above (it’s origin), but it’s difficult to get the default spacing for the bottom, as we may be changing the height

            intrinsicSize.height = usedRect.size.height;
        }

        _lastIntrinsicSize = intrinsicSize;
        _hasLastIntrinsicSize = YES;
    }

    return intrinsicSize;
}

@end

As a last note, I’ve never actually used auto layout myself – the demos look amazing, but whenever I actually try it myself, I can’t get it to work quite right and it makes things more complicated. However, in this case, I think it actually did save a bunch of work – without it, -intrinsicContentSize wouldn’t exist, and you’d possibly have to set the frame yourself, calculating the new origin as well as the new size (not too difficult, but just more code).