input: fix caret jumping to end of text on iOS keyboard switch

damus/Shared/Components/Text/TextViewWrapper.swift

@@ -49,7 +49,16 @@ struct TextViewWrapper: UIViewRepresentable {
         uiView.linkTextAttributes = linkAttributes
     }
 
+    /// Pushes the SwiftUI-side attributed text into the text view and restores the
+    /// caret position, which UIKit resets whenever `attributedText` is re-assigned.
+    ///
+    /// Every text/selection change made here is programmatic, so the coordinator's
+    /// selection tracking is suppressed for the duration of this update: the delegate
+    /// callbacks fired by these changes must not be recorded as user-driven caret moves.
     func updateUIView(_ uiView: UITextView, context: Context) {
+        context.coordinator.isApplyingProgrammaticChange = true
+        defer { context.coordinator.isApplyingProgrammaticChange = false }
+
         // Save the current selection BEFORE making any changes
         // This is critical because setting attributedText causes UITextView to reset the cursor position
         let savedRange = uiView.selectedRange
@@ -108,6 +117,11 @@ struct TextViewWrapper: UIViewRepresentable {
         let initialTextSuffix: String?
         var initialTextSuffixWasAdded: Bool = false
         var convertMentionRef: ((Pubkey) -> NSMutableAttributedString?)? = nil
+        /// True while `updateUIView` applies programmatic text/selection changes.
+        ///
+        /// `textViewDidChangeSelection` checks this flag so that delegate callbacks
+        /// fired by those changes are not recorded as user-driven caret moves.
+        var isApplyingProgrammaticChange: Bool = false
         static let ESCAPE_SEQUENCES = ["\n", "@", "  ", ", ", ". ", "! ", "? ", "; ", "#"]
 
         init(attributedText: Binding<NSMutableAttributedString>,
@@ -149,6 +163,20 @@ struct TextViewWrapper: UIViewRepresentable {
             updateCursorPosition(textView.selectedRange.location)
         }
 
+        /// Keeps the tracked cursor position in sync when the user moves the caret
+        /// without editing the text (e.g. by tapping mid-text).
+        ///
+        /// Without this, the position recorded at the last text change goes stale,
+        /// and the next view update (e.g. one triggered by an iOS keyboard switch)
+        /// would re-apply it, jumping the caret to the end of the text (issue #3545).
+        ///
+        /// Programmatic selection changes are ignored while `isApplyingProgrammaticChange`
+        /// is set, as are range selections, which a single index cannot represent.
+        func textViewDidChangeSelection(_ textView: UITextView) {
+            guard !isApplyingProgrammaticChange, textView.selectedRange.length == 0 else { return }
+            updateCursorPosition(textView.selectedRange.location)
+        }
+
         private func processFocusedWordForMention(textView: UITextView) {
             var val: (String?, NSRange?) = (nil, nil)
 

damusTests/PostViewTests.swift

@@ -319,6 +319,42 @@ final class PostViewTests: XCTestCase {
         XCTAssertTrue(shouldChange, "shouldChangeTextIn should return true for regular text")
     }
 
+    /// Tests that moving the caret without editing text updates the tracked cursor
+    /// position, so a later view update does not restore a stale position (issue #3545)
+    func testSelectionChangeUpdatesTrackedCursorPosition() {
+        let content = NSMutableAttributedString(string: "Hello world")
+        let bindingContent: Binding<NSMutableAttributedString> = Binding(get: { content }, set: { _ in })
+
+        var trackedCursorPosition: Int? = nil
+        let coordinator = TextViewWrapper.Coordinator(
+            attributedText: bindingContent,
+            getFocusWordForMention: nil,
+            updateCursorPosition: { trackedCursorPosition = $0 },
+            initialTextSuffix: nil,
+            convertMentionRef: nil
+        )
+
+        let textView = UITextView()
+        textView.attributedText = content
+
+        // Simulate the user tapping to place the caret mid-text
+        textView.selectedRange = NSRange(location: 5, length: 0)
+        coordinator.textViewDidChangeSelection(textView)
+        XCTAssertEqual(trackedCursorPosition, 5, "A user-driven caret move should update the tracked cursor position")
+
+        // Range selections cannot be represented by a single index, so they are not tracked
+        trackedCursorPosition = nil
+        textView.selectedRange = NSRange(location: 2, length: 3)
+        coordinator.textViewDidChangeSelection(textView)
+        XCTAssertNil(trackedCursorPosition, "Range selections should not update the tracked cursor position")
+
+        // Programmatic selection changes made by updateUIView should not be recorded
+        coordinator.isApplyingProgrammaticChange = true
+        textView.selectedRange = NSRange(location: 8, length: 0)
+        coordinator.textViewDidChangeSelection(textView)
+        XCTAssertNil(trackedCursorPosition, "Programmatic selection changes should not update the tracked cursor position")
+    }
+
     /// Tests that client tags are added to events when provided.
     func testToEventAddsClientTagWhenProvided() {
         let post = NostrPost(content: "gm")