Updated TableViewDiffCalculator to run processChanges on main thread

Dwifft/Dwifft+AppKit.swift

@@ -51,16 +51,26 @@ public final class TableViewDiffCalculator<Value: Equatable>: AbstractDiffCalcul
 
     override internal func processChanges(newState: SectionedValues<Int, Value>, diff: [SectionedDiffStep<Int, Value>]) {
         guard let tableView = self.tableView else { return }
-        tableView.beginUpdates()
-        self._sectionedValues = newState
-        for result in diff {
-            switch result {
-            case let .delete(_, row, _): tableView.removeRows(at: [row], withAnimation: self.deletionAnimation)
-            case let .insert(_, row, _): tableView.insertRows(at: [row], withAnimation: self.insertionAnimation)
-            default: fatalError("NSTableViews do not have sections")
+        let updateAction = {
+            tableView.beginUpdates()
+            self._sectionedValues = newState
+            for result in diff {
+                switch result {
+                case let .delete(_, row, _): tableView.removeRows(at: [row], withAnimation: self.deletionAnimation)
+                case let .insert(_, row, _): tableView.insertRows(at: [row], withAnimation: self.insertionAnimation)
+                default: fatalError("NSTableViews do not have sections")
+                }
+            }
+            tableView.endUpdates()
+        }
+        if Thread.current.isMainThread {
+            updateAction()
+        } else {
+            DispatchQueue.main.sync {
+                updateAction()
             }
         }
-        tableView.endUpdates()
+
     }
 
 }