Restore window’s .level from last session

CHANGELOG.md

@@ -5,6 +5,10 @@ Change Log
 4.5.4 (unreleased)
 --------------------------
 
+### Improvements
+
+- Restore the “Keep on Top” state of windows from the last session.
+
 
 
 4.5.3 (564)

CotEditor/Sources/DocumentWindow.swift

@@ -73,6 +73,7 @@ final class DocumentWindow: NSWindow {
         super.encodeRestorableState(with: coder, backgroundQueue: queue)
         
         coder.encode(self.backgroundAlpha, forKey: #keyPath(backgroundAlpha))
+        coder.encode(self.level, forKey: #keyPath(level))
     }
     
     
@@ -83,6 +84,9 @@ final class DocumentWindow: NSWindow {
         if let alpha = coder.decodeObject(of: NSNumber.self, forKey: #keyPath(backgroundAlpha)) as? CGFloat, alpha != 1 {
             self.backgroundAlpha = alpha
         }
+        if let level = coder.decodeObject(of: NSNumber.self, forKey: #keyPath(level)) as? NSWindow.Level {
+            self.level = level
+        }
     }
     
     
@@ -128,6 +132,7 @@ final class DocumentWindow: NSWindow {
     @IBAction func toggleKeepOnTop(_ sender: Any?) {
         
         self.level = (self.level == .floating) ? .normal : .floating
+        self.invalidateRestorableState()
     }