UITextView cursor position with EnvironmentObject

Question

The Problem

I want a text editor in SwiftUI that styles any instance of certain keywords, in real time as the user types. Additionally, I want a button in the toolbar to add whatever text is selected in the text editor to this list of keywords.

This is my current attempt, UIViewControllerRepresentable and a Coordinator:


struct FormTextEditorBody: UIViewRepresentable {
    @EnvironmentObject var form: FormViewModel
    @Binding var text: String
    
    let highlightKeywords: Bool
    
    init(_ text: Binding<String>, _ highlightKeywords: Bool) {
        self._text = text
        self.highlightKeywords = highlightKeywords
    }
    
    func makeUIView(context: Context) -> UITextView {
        let textView = UITextView()
        textView.delegate = context.coordinator
        return textView
    }
    
    func updateUIView(_ uiView: UITextView, context: Context) {
        if !highlightKeywords {
            uiView.text = text; return
        }
        
        let attributed = NSMutableAttributedString(string: text)
        
        attributed.addAttribute(
            NSAttributedString.Key.font,
            value: UIFont.systemFont(ofSize: 16),
            range: NSRange(0..<NSString(string: text).length)
        )
        
        attributed.addAttribute(
            NSAttributedString.Key.foregroundColor,
            value: UIColor(Color.primary),
            range: NSRange(0..<NSString(string: text).length)
        )
        
        for word in form.keywords {
            for range in text.independentRangesOf(string: word.text) {
                attributed.addAttribute(
                    NSAttributedString.Key.foregroundColor,
                    value: UIColor(Color.secondaryAccent),
                    range: NSRange(range, in: text))
            }
        }
        
        uiView.attributedText = attributed
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    class Coordinator: NSObject, UITextViewDelegate {
        var parent: FormTextEditorBody
        
        init(_ parent: FormTextEditorBody) {
            self.parent = parent
        }
        
        func textViewDidChange(_ textView: UITextView) {
            parent.text = textView.text
        }
        
        func textViewDidChangeSelection(_ textView: UITextView) {
            if textView.selectedTextRange == nil {
                return
            }
            
            let selectedString = textView.text(in: textView.selectedTextRange!) ?? ""
            
            parent.form.selectedText = selectedString
        }
    }
}

A pure SwiftUI view higher up the stack accesses form.selectedText to add it to the highlight list.

This approach almost does everything I want, but it has a bug: if I type a character anywhere into the text editor, the character is inserted and then the cursor jumps to the end of the text.

What I've tried so far

I think the @EnvironmentObject is somehow involved. Removing it and the associated behaviour does fix the bug, but then I have nowhere to save the selected text that it can be accessed higher up the stack.
I tried stripping out all the attributed string stuff and just setting uiView.text, thinking that applying the styling might be a factor. The bug was unaffected.
I tried moving the @EnvironmentObject a view up the stack and passing the selected text as a binding. The bug was unaffected.
Manually retrieving the cursor position at the start of updateUIView and reapplying it after the style update. Causes janky, unpredictable typing behaviour.

UITextView cursor position with EnvironmentObject

The Problem

What I've tried so far

0 Answers0