diff --git a/Source/Modules/IMEState.swift b/Source/Modules/IMEState.swift
index bf810d6d..64a17112 100644
--- a/Source/Modules/IMEState.swift
+++ b/Source/Modules/IMEState.swift
@@ -96,7 +96,7 @@ extension IMEState {
   }
 
   public static func ofInputting(displayTextSegments: [String], cursor: Int) -> IMEState {
-    var result = IMEState.ofNotEmpty(displayTextSegments: displayTextSegments, cursor: cursor)
+    var result = Self.ofNotEmpty(displayTextSegments: displayTextSegments, cursor: cursor)
     result.type = .ofInputting
     return result
   }
@@ -106,7 +106,7 @@ extension IMEState {
   )
     -> IMEState
   {
-    var result = IMEState.ofNotEmpty(displayTextSegments: displayTextSegments, cursor: cursor)
+    var result = Self.ofNotEmpty(displayTextSegments: displayTextSegments, cursor: cursor)
     result.type = .ofMarking
     result.data.marker = marker
     result.data.markedReadings = markedReadings
@@ -117,7 +117,7 @@ extension IMEState {
   public static func ofCandidates(candidates: [(String, String)], displayTextSegments: [String], cursor: Int)
     -> IMEState
   {
-    var result = IMEState.ofNotEmpty(displayTextSegments: displayTextSegments, cursor: cursor)
+    var result = Self.ofNotEmpty(displayTextSegments: displayTextSegments, cursor: cursor)
     result.type = .ofCandidates
     result.data.candidates = candidates
     return result
@@ -154,7 +154,7 @@ extension IMEState {
 
   public var convertedToInputting: IMEStateProtocol {
     if type == .ofInputting { return self }
-    var result = IMEState.ofInputting(displayTextSegments: data.displayTextSegments, cursor: data.cursor)
+    var result = Self.ofInputting(displayTextSegments: data.displayTextSegments, cursor: data.cursor)
     result.tooltip = data.tooltipBackupForInputting
     result.isVerticalTyping = isVerticalTyping
     return result
diff --git a/Source/Modules/ctlInputMethod_Delegates.swift b/Source/Modules/ctlInputMethod_Delegates.swift
index 88c245ca..ac0173bb 100644
--- a/Source/Modules/ctlInputMethod_Delegates.swift
+++ b/Source/Modules/ctlInputMethod_Delegates.swift
@@ -18,7 +18,7 @@ extension ctlInputMethod: KeyHandlerDelegate {
     return client.bundleIdentifier() ?? ""
   }
 
-  func ctlCandidate() -> CtlCandidateProtocol { ctlInputMethod.ctlCandidateCurrent }
+  func ctlCandidate() -> CtlCandidateProtocol { Self.ctlCandidateCurrent }
 
   func candidateSelectionCalledByKeyHandler(at index: Int) {
     candidateSelected(at: index)
diff --git a/Source/Modules/ctlInputMethod_HandleDisplay.swift b/Source/Modules/ctlInputMethod_HandleDisplay.swift
index bb27fe89..67929c69 100644
--- a/Source/Modules/ctlInputMethod_HandleDisplay.swift
+++ b/Source/Modules/ctlInputMethod_HandleDisplay.swift
@@ -58,14 +58,14 @@ extension ctlInputMethod {
     }()
     // 強制重新初期化，因為 NSAttributedTextView 有顯示滯後性。
     do {
-      ctlInputMethod.tooltipInstance.hide()
-      ctlInputMethod.tooltipInstance = .init()
+      Self.tooltipInstance.hide()
+      Self.tooltipInstance = .init()
       if state.type == .ofMarking {
-        ctlInputMethod.tooltipInstance.setColor(state: state.data.tooltipColorState)
+        Self.tooltipInstance.setColor(state: state.data.tooltipColorState)
       }
     }
     // 再設定其文字顯示內容並顯示。
-    ctlInputMethod.tooltipInstance.show(
+    Self.tooltipInstance.show(
       tooltip: tooltip, at: finalOrigin,
       bottomOutOfScreenAdjustmentHeight: delta, direction: tooltipContentDirection
     )
@@ -80,7 +80,7 @@ extension ctlInputMethod {
       }
       if isVerticalTyping { return true }
       // 接下來的判斷並非適用於 IMK 選字窗，所以先插入排除語句。
-      guard ctlInputMethod.ctlCandidateCurrent is CtlCandidateUniversal else { return false }
+      guard Self.ctlCandidateCurrent is CtlCandidateUniversal else { return false }
       // 以上是通用情形。接下來決定橫排輸入時是否使用縱排選字窗。
       // 因為在拿候選字陣列時已經排序過了，所以這裡不用再多排序。
       // 測量每頁顯示候選字的累計總長度。如果太長的話就強制使用縱排候選字窗。
@@ -93,7 +93,7 @@ extension ctlInputMethod {
 
     state.isVerticalCandidateWindow = (isCandidateWindowVertical || !PrefMgr.shared.useHorizontalCandidateList)
 
-    ctlInputMethod.ctlCandidateCurrent.delegate = nil
+    Self.ctlCandidateCurrent.delegate = nil
 
     /// 下面這一段本可直接指定 currentLayout，但這樣的話翻頁按鈕位置無法精準地重新繪製。
     /// 所以只能重新初期化。壞處就是得在 ctlCandidate() 當中與 SymbolTable 控制有關的地方
@@ -106,7 +106,7 @@ extension ctlInputMethod {
         ? CandidateLayout.vertical
         : CandidateLayout.horizontal)
 
-    ctlInputMethod.ctlCandidateCurrent =
+    Self.ctlCandidateCurrent =
       PrefMgr.shared.useIMKCandidateWindow
       ? CtlCandidateIMK(candidateLayout) : CtlCandidateUniversal(candidateLayout)
 
@@ -122,10 +122,10 @@ extension ctlInputMethod {
       return NSFont.systemFont(ofSize: size)
     }
 
-    ctlInputMethod.ctlCandidateCurrent.keyLabelFont = labelFont(
+    Self.ctlCandidateCurrent.keyLabelFont = labelFont(
       name: PrefMgr.shared.candidateKeyLabelFontName, size: keyLabelSize
     )
-    ctlInputMethod.ctlCandidateCurrent.candidateFont = ctlInputMethod.candidateFont(
+    Self.ctlCandidateCurrent.candidateFont = Self.candidateFont(
       name: PrefMgr.shared.candidateTextFontName, size: textSize
     )
 
@@ -133,14 +133,14 @@ extension ctlInputMethod {
     let keyLabels =
       candidateKeys.count > 4 ? Array(candidateKeys) : Array(CandidateKey.defaultKeys)
     let keyLabelSuffix = state.type == .ofAssociates ? "^" : ""
-    ctlInputMethod.ctlCandidateCurrent.keyLabels = keyLabels.map {
+    Self.ctlCandidateCurrent.keyLabels = keyLabels.map {
       CandidateKeyLabel(key: String($0), displayedText: String($0) + keyLabelSuffix)
     }
 
-    ctlInputMethod.ctlCandidateCurrent.delegate = self
-    ctlInputMethod.ctlCandidateCurrent.showPageButtons = PrefMgr.shared.showPageButtonsInCandidateWindow
-    ctlInputMethod.ctlCandidateCurrent.useLangIdentifier = PrefMgr.shared.handleDefaultCandidateFontsByLangIdentifier
-    ctlInputMethod.ctlCandidateCurrent.locale = {
+    Self.ctlCandidateCurrent.delegate = self
+    Self.ctlCandidateCurrent.showPageButtons = PrefMgr.shared.showPageButtonsInCandidateWindow
+    Self.ctlCandidateCurrent.useLangIdentifier = PrefMgr.shared.handleDefaultCandidateFontsByLangIdentifier
+    Self.ctlCandidateCurrent.locale = {
       switch inputMode {
         case .imeModeCHS: return "zh-Hans"
         case .imeModeCHT:
@@ -151,28 +151,28 @@ extension ctlInputMethod {
         default: return ""
       }
     }()
-    ctlInputMethod.ctlCandidateCurrent.reloadData()
+    Self.ctlCandidateCurrent.reloadData()
 
     if #available(macOS 10.14, *) {
       // Spotlight 視窗會擋住 IMK 選字窗，所以需要特殊處理。
-      if let ctlCandidateCurrent = ctlInputMethod.ctlCandidateCurrent as? CtlCandidateIMK {
+      if let ctlCandidateCurrent = Self.ctlCandidateCurrent as? CtlCandidateIMK {
         while ctlCandidateCurrent.windowLevel() <= client.windowLevel() {
           ctlCandidateCurrent.setWindowLevel(UInt64(max(0, client.windowLevel() + 1000)))
         }
       }
     }
 
-    ctlInputMethod.ctlCandidateCurrent.visible = true
+    Self.ctlCandidateCurrent.visible = true
 
     if isVerticalTyping {
-      ctlInputMethod.ctlCandidateCurrent.set(
+      Self.ctlCandidateCurrent.set(
         windowTopLeftPoint: NSPoint(
           x: lineHeightRect().origin.x + lineHeightRect().size.width + 4.0, y: lineHeightRect().origin.y - 4.0
         ),
         bottomOutOfScreenAdjustmentHeight: lineHeightRect().size.height + 4.0
       )
     } else {
-      ctlInputMethod.ctlCandidateCurrent.set(
+      Self.ctlCandidateCurrent.set(
         windowTopLeftPoint: NSPoint(x: lineHeightRect().origin.x, y: lineHeightRect().origin.y - 4.0),
         bottomOutOfScreenAdjustmentHeight: lineHeightRect().size.height + 4.0
       )
diff --git a/Source/Modules/ctlInputMethod_HandleEvent.swift b/Source/Modules/ctlInputMethod_HandleEvent.swift
index a3e3218d..b79b80ec 100644
--- a/Source/Modules/ctlInputMethod_HandleEvent.swift
+++ b/Source/Modules/ctlInputMethod_HandleEvent.swift
@@ -143,7 +143,7 @@ extension ctlInputMethod {
     // 這樣可以讓 interpretKeyEvents() 函式自行判斷：
     // - 是就地交給 imkCandidates.interpretKeyEvents() 處理？
     // - 還是藉由 delegate 扔回 ctlInputMethod 給 KeyHandler 處理？
-    if let imkCandidates = ctlInputMethod.ctlCandidateCurrent as? CtlCandidateIMK, imkCandidates.visible {
+    if let imkCandidates = Self.ctlCandidateCurrent as? CtlCandidateIMK, imkCandidates.visible {
       let event: NSEvent = CtlCandidateIMK.replaceNumPadKeyCodes(target: eventToDeal) ?? eventToDeal
 
       // Shift+Enter 是個特殊情形，不提前攔截處理的話、會有垃圾參數傳給 delegate 的 keyHandler 從而崩潰。
@@ -206,7 +206,7 @@ extension ctlInputMethod {
         let newEvent = event.reinitiate(characters: newChar)
         if let newEvent = newEvent {
           if PrefMgr.shared.useSCPCTypingMode, state.type == .ofAssociates {
-            // 註：input.isShiftHold 已經在 ctlInputMethod.handle() 內處理，因為在那邊處理才有效。
+            // 註：input.isShiftHold 已經在 Self.handle() 內處理，因為在那邊處理才有效。
             return event.isShiftHold ? true : commonEventHandler(event)
           } else {
             if #available(macOS 10.14, *) {
diff --git a/Source/Modules/ctlInputMethod_HandleStates.swift b/Source/Modules/ctlInputMethod_HandleStates.swift
index b390d376..72ca16ac 100644
--- a/Source/Modules/ctlInputMethod_HandleStates.swift
+++ b/Source/Modules/ctlInputMethod_HandleStates.swift
@@ -24,9 +24,9 @@ extension ctlInputMethod {
     state = newState
     switch state.type {
       case .ofDeactivated:
-        ctlInputMethod.ctlCandidateCurrent.delegate = nil
-        ctlInputMethod.ctlCandidateCurrent.visible = false
-        ctlInputMethod.tooltipInstance.hide()
+        Self.ctlCandidateCurrent.delegate = nil
+        Self.ctlCandidateCurrent.visible = false
+        Self.tooltipInstance.hide()
         if previous.hasComposition {
           commit(text: previous.displayedText)
         }
@@ -39,29 +39,29 @@ extension ctlInputMethod {
           state = IMEState.ofEmpty()
           previous = state
         }
-        ctlInputMethod.ctlCandidateCurrent.visible = false
-        ctlInputMethod.tooltipInstance.hide()
+        Self.ctlCandidateCurrent.visible = false
+        Self.tooltipInstance.hide()
         // 全專案用以判斷「.Abortion」的地方僅此一處。
         if previous.hasComposition, state.type != .ofAbortion {
           commit(text: previous.displayedText)
         }
         // 在這裡手動再取消一次選字窗與工具提示的顯示，可謂雙重保險。
-        ctlInputMethod.ctlCandidateCurrent.visible = false
-        ctlInputMethod.tooltipInstance.hide()
+        Self.ctlCandidateCurrent.visible = false
+        Self.tooltipInstance.hide()
         clearInlineDisplay()
         // 最後一道保險
         keyHandler.clear()
       case .ofCommitting:
-        ctlInputMethod.ctlCandidateCurrent.visible = false
-        ctlInputMethod.tooltipInstance.hide()
+        Self.ctlCandidateCurrent.visible = false
+        Self.tooltipInstance.hide()
         let textToCommit = state.textToCommit
         if !textToCommit.isEmpty { commit(text: textToCommit) }
         clearInlineDisplay()
         // 最後一道保險
         keyHandler.clear()
       case .ofInputting:
-        ctlInputMethod.ctlCandidateCurrent.visible = false
-        ctlInputMethod.tooltipInstance.hide()
+        Self.ctlCandidateCurrent.visible = false
+        Self.tooltipInstance.hide()
         let textToCommit = state.textToCommit
         if !textToCommit.isEmpty { commit(text: textToCommit) }
         setInlineDisplayWithCursor()
@@ -69,27 +69,27 @@ extension ctlInputMethod {
           show(tooltip: state.tooltip)
         }
       case .ofMarking:
-        ctlInputMethod.ctlCandidateCurrent.visible = false
+        Self.ctlCandidateCurrent.visible = false
         setInlineDisplayWithCursor()
         if state.tooltip.isEmpty {
-          ctlInputMethod.tooltipInstance.hide()
+          Self.tooltipInstance.hide()
         } else {
           show(tooltip: state.tooltip)
         }
       case .ofCandidates, .ofAssociates, .ofSymbolTable:
-        ctlInputMethod.tooltipInstance.hide()
+        Self.tooltipInstance.hide()
         setInlineDisplayWithCursor()
         showCandidates()
       default: break
     }
     // 浮動組字窗的顯示判定
     if state.hasComposition, PrefMgr.shared.clientsIMKTextInputIncapable.contains(clientBundleIdentifier) {
-      ctlInputMethod.popupCompositionBuffer.isTypingDirectionVertical = isVerticalTyping
-      ctlInputMethod.popupCompositionBuffer.show(
+      Self.popupCompositionBuffer.isTypingDirectionVertical = isVerticalTyping
+      Self.popupCompositionBuffer.show(
         state: state, at: lineHeightRect(zeroCursor: true).origin
       )
     } else {
-      ctlInputMethod.popupCompositionBuffer.hide()
+      Self.popupCompositionBuffer.hide()
     }
   }