Fix cursor jumping when pressing return

Changelog-Fixed: Fix cursor jumping when pressing return
Closes: #775

damus/Views/PostView.swift

@@ -15,6 +15,10 @@ enum NostrPostResult {
 
 let POST_PLACEHOLDER = NSLocalizedString("Type your post here...", comment: "Text box prompt to ask user to type their post.")
 
+class TagModel: ObservableObject {
+    var diff = 0
+}
+
 enum PostAction {
     case replying_to(NostrEvent)
     case quoting(NostrEvent)
@@ -50,6 +54,7 @@ struct PostView: View {
     @State var mediaToUpload: MediaUpload? = nil
     
     @StateObject var image_upload: ImageUploadModel = ImageUploadModel()
+    @StateObject var tagModel: TagModel = TagModel()
 
     let action: PostAction
     let damus_state: DamusState
@@ -208,6 +213,7 @@ struct PostView: View {
                 focusWordAttributes = (word, range)
                 self.newCursorIndex = nil
             })
+                .environmentObject(tagModel)
                 .focused($focus)
                 .textInputAutocapitalization(.sentences)
                 .onChange(of: post) { p in
@@ -338,6 +344,7 @@ struct PostView: View {
                 if let searching {
                     UserSearch(damus_state: damus_state, search: searching, focusWordAttributes: $focusWordAttributes, newCursorIndex: $newCursorIndex, postTextViewCanScroll: $postTextViewCanScroll, post: $post)
                         .frame(maxHeight: .infinity)
+                        .environmentObject(tagModel)
                 } else {
                     Divider()
                     VStack(alignment: .leading) {

damus/Views/Posting/UserSearch.swift

@@ -25,6 +25,7 @@ struct UserSearch: View {
     @Binding var postTextViewCanScroll: Bool
 
     @Binding var post: NSMutableAttributedString
+    @EnvironmentObject var tagModel: TagModel
     
     var users: [SearchedUser] {
         guard let contacts = damus_state.contacts.event else {
@@ -48,6 +49,9 @@ struct UserSearch: View {
         }
         let mutableString = NSMutableAttributedString(attributedString: post)
         mutableString.replaceCharacters(in: wordRange, with: tagAttributedString)
+        ///adjust cursor position appropriately: ('diff' used in TextViewWrapper / updateUIView after below update of 'post')
+        tagModel.diff = tagAttributedString.length - wordRange.length
+        
         post = mutableString
         focusWordAttributes = (nil, nil)
         newCursorIndex = wordRange.location + tagAttributedString.string.count

damus/Views/TextViewWrapper.swift

@@ -10,6 +10,8 @@ import SwiftUI
 struct TextViewWrapper: UIViewRepresentable {
     @Binding var attributedText: NSMutableAttributedString
     @Binding var postTextViewCanScroll: Bool
+    @EnvironmentObject var tagModel: TagModel
+    
     let cursorIndex: Int?
     var getFocusWordForMention: ((String?, NSRange?) -> Void)? = nil
     
@@ -32,9 +34,14 @@ struct TextViewWrapper: UIViewRepresentable {
 
     func updateUIView(_ uiView: UITextView, context: Context) {
         uiView.isScrollEnabled = postTextViewCanScroll
+        let range = uiView.selectedRange
         uiView.attributedText = attributedText
+
         TextViewWrapper.setTextProperties(uiView)
         setCursorPosition(textView: uiView)
+
+        uiView.selectedRange = NSRange(location: range.location + tagModel.diff, length: range.length)
+        tagModel.diff = 0
     }
 
     private func setCursorPosition(textView: UITextView) {