UITextView does not adjust size when used in SwiftUI - ios

Question

My ultimate goal is to display html content in SwiftUI.
For that I am using UIKit's UITextView (I can't use web view, because I need to control font and text color).
This is the entire code of the view representable:
struct HTMLTextView: UIViewRepresentable {
private var htmlString: String
private var maxWidth: CGFloat = 0
private var font: UIFont = .systemFont(ofSize: 14)
private var textColor: UIColor = .darkText
init(htmlString: String) {
self.htmlString = htmlString
}
func makeUIView(context: UIViewRepresentableContext<HTMLTextView>) -> UITextView {
let textView = UITextView()
textView.isScrollEnabled = false
textView.isEditable = false
textView.backgroundColor = .clear
update(textView: textView)
return textView
}
func updateUIView(_ textView: UITextView, context: UIViewRepresentableContext<HTMLTextView>) {
update(textView: textView)
}
func sizeToFit(width: CGFloat) -> Self {
var textView = self
textView.maxWidth = width
return textView
}
func font(_ font: UIFont) -> Self {
var textView = self
textView.font = font
return textView
}
func textColor(_ textColor: UIColor) -> Self {
var textView = self
textView.textColor = textColor
return textView
}
// MARK: - Private
private func update(textView: UITextView) {
textView.attributedText = buildAttributedString(fromHTML: htmlString)
// this is one of the options that don't work
let size = textView.sizeThatFits(CGSize(width: width, height: .greatestFiniteMagnitude))
textView.frame.size = size
}
private func buildAttributedString(fromHTML htmlString: String) -> NSAttributedString {
let htmlData = Data(htmlString.utf8)
let options = [NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.html]
let attributedString = try? NSMutableAttributedString(data: htmlData, options: options, documentAttributes: nil)
let range = NSRange(location: 0, length: attributedString?.length ?? 0)
attributedString?.addAttributes([.font: font,
.foregroundColor: textColor],
range: range)
return attributedString ?? NSAttributedString(string: "")
}
}
It is called from the SwiftUI code like this:
HTMLTextView(htmlString: "some string with html tags")
.font(.systemFont(ofSize: 15))
.textColor(descriptionTextColor)
.sizeToFit(width: 200)
The idea is that the HTMLTextView would stick to the width (here 200, but in practice - the screen width) and grow vertically when the text is multiline.
The problem is whatever I do (see below), it is always displayed as a one line of text stretching outside of screen on the left and right. And it never grows vertically.
The stuff I tried:
calculating the size and setting the frame (you can see that in the code snippet)
doing the above + fixedSize() on the SwiftUI side
setting frame(width: ...) on the SwiftUI side
setting translatesAutoresizingMaskIntoConstraints to false
setting hugging priorities to required
setting ideal width on the SwiftUI side
Nothing helped. Any advice on how could I solve this will be very welcome!
P.S. I can't use SwiftUI's AttributedString, because I need to support iOS 14.
UPDATE:
I have removed all the code with maxWidth and calculating size. And added textView.setContentCompressionResistancePriority(.defaultLow, for: .horizontal) when creating the textView in makeUIView(context:). This kind of solved the problem, except for this: even though the height of the text view is correct, the last line is not visible; if I rotate to landscape, it becomes visible; rotate to portrait - not visible again.
UPDATE 2:
After some trial and error I figured out that it is ScrollView to blame. HTMLTextView is inside VStack, which is inside ScrollView. When I remove scroll view, everything sizes correctly.
The problem is, I need scrolling when the content is too long.

Answer 1

So, in the end, I had to move calculating the size that the attributed string would take in the text view with the given font/size etc into the view model, and then set .frame(width:, height:) to those values.
Not ideal, as the pre-calculated height seems a little bit larger than the actual text's height, but could not find better solution for now.
Update (for readability):
I calculate the actual size in view model (calculateDescriptionSize(limitedToWidth maxWidth:), and then I use the result on the Swift UI view:
HTMLTextView(htmlString: viewModel.attributedDescription)
.frame(width: maxWidth, height: viewModel.calculateDescriptionSize(limitedToWidth: maxWidth).height)
where HTMLTextView is my custom view wrapping the UIKit text view.
And this is the size calculation:
func calculateDescriptionSize(limitedToWidth maxWidth: CGFloat) -> CGSize {
// source: https://stackoverflow.com/questions/54497598/nsattributedstring-boundingrect-returns-wrong-height
let textStorage = NSTextStorage(attributedString: attributedDescription)
let size = CGSize(width: maxWidth, height: CGFloat.greatestFiniteMagnitude)
let boundingRect = CGRect(origin: .zero, size: size)
let textContainer = NSTextContainer(size: size)
textContainer.lineFragmentPadding = 0
let layoutManager = NSLayoutManager()
layoutManager.addTextContainer(textContainer)
textStorage.addLayoutManager(layoutManager)
layoutManager.glyphRange(forBoundingRect: boundingRect, in: textContainer)
let rect = layoutManager.usedRect(for: textContainer)
return rect.integral.size
}