Add @mainactor annotations to improve thread safety in completion han…

…dling

This commit applies the @mainactor attribute to methods associated with
autocomplete functionality in STTextView. This ensures that operations
that involve UI updates occur on the main thread, preventing potential
threading issues. Additionally, it improves the handling of completion
window visibility and closing logic.

Sources/STTextViewAppKit/STTextView+Complete.swift

@@ -9,6 +9,7 @@ extension STTextView {
     /// Supporting Autocomplete
     ///
     /// see NSStandardKeyBindingResponding
+    @MainActor
     open override func complete(_ sender: Any?) {
         if let completionWindowController, completionWindowController.isVisible {
             completionWindowController.close()
@@ -17,29 +18,29 @@ extension STTextView {
         }
     }
 
+    @MainActor
     open override func cancelOperation(_ sender: Any?) {
         self.complete(sender)
     }
 
     @MainActor
     private func performCompletion() {
+        dispatchPrecondition(condition: .onQueue(.main))
+
         guard let insertionPointLocation = textLayoutManager.insertionPointLocations.first,
-              let textCharacterSegmentRect = textLayoutManager.textSegmentFrame(at: insertionPointLocation, type: .standard)
+              let textCharacterSegmentRect = textLayoutManager.textSegmentFrame(at: insertionPointLocation, type: .standard),
+              let completionItems = delegateProxy.textView(self, completionItemsAtLocation: insertionPointLocation),
+              completionItems.isEmpty == false
         else {
-            self.completionWindowController?.close()
+            if let completionWindowController, completionWindowController.isVisible {
+                self.completionWindowController?.close()
+            }
             return
         }
 
-        // move left by arbitrary 14px
-        let characterSegmentFrame = textCharacterSegmentRect.moved(dx: -14, dy: textCharacterSegmentRect.height)
-
-        let completionItems = delegateProxy.textView(self, completionItemsAtLocation: insertionPointLocation) ?? []
-
-        dispatchPrecondition(condition: .onQueue(.main))
-
-        if completionItems.isEmpty {
-            self.completionWindowController?.close()
-        } else if let window = self.window {
+        if let window = self.window {
+            // move left by arbitrary 14px
+            let characterSegmentFrame = textCharacterSegmentRect.moved(dx: -14, dy: textCharacterSegmentRect.height)
             let completionWindowOrigin = window.convertPoint(toScreen: contentView.convert(characterSegmentFrame.origin, to: nil))
             completionWindowController?.showWindow(at: completionWindowOrigin, items: completionItems, parent: window)
             completionWindowController?.delegate = self