diff --git a/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift b/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift
index a770892c..a57d3bc3 100644
--- a/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift
@@ -37,341 +37,345 @@ extension KeyHandler {
   ) -> Bool {
     let inputText = input.inputText
     let charCode: UniChar = input.charCode
-    if let ctlCandidateCurrent = delegate?.ctlCandidate() {
-      // MARK: Cancel Candidate
+    guard let ctlCandidateCurrent = delegate?.ctlCandidate() else {
+      IME.prtDebugIntel("06661F6E")
+      errorCallback()
+      return true
+    }
 
-      let cancelCandidateKey =
-        input.isBackSpace || input.isESC || input.isDelete
-        || ((input.isCursorBackward || input.isCursorForward) && input.isShiftHold)
+    // MARK: Cancel Candidate
 
-      if cancelCandidateKey {
-        if (state is InputState.AssociatedPhrases)
-          || mgrPrefs.useSCPCTypingMode
-          || isBuilderEmpty
-        {
-          // 如果此時發現當前組字緩衝區為真空的情況的話，
-          // 就將當前的組字緩衝區析構處理、強制重設輸入狀態。
-          // 否則，一個本不該出現的真空組字緩衝區會使前後方向鍵與 BackSpace 鍵失靈。
-          // 所以這裡需要對 isBuilderEmpty 做判定。
-          clear()
-          stateCallback(InputState.EmptyIgnoringPreviousState())
-        } else {
-          stateCallback(buildInputtingState)
-        }
+    let cancelCandidateKey =
+      input.isBackSpace || input.isESC || input.isDelete
+      || ((input.isCursorBackward || input.isCursorForward) && input.isShiftHold)
+
+    if cancelCandidateKey {
+      if (state is InputState.AssociatedPhrases)
+        || mgrPrefs.useSCPCTypingMode
+        || isBuilderEmpty
+      {
+        // 如果此時發現當前組字緩衝區為真空的情況的話，
+        // 就將當前的組字緩衝區析構處理、強制重設輸入狀態。
+        // 否則，一個本不該出現的真空組字緩衝區會使前後方向鍵與 BackSpace 鍵失靈。
+        // 所以這裡需要對 isBuilderEmpty 做判定。
+        clear()
+        stateCallback(InputState.EmptyIgnoringPreviousState())
+      } else {
+        stateCallback(buildInputtingState)
+      }
+      return true
+    }
+
+    // MARK: Enter
+
+    if input.isEnter {
+      if state is InputState.AssociatedPhrases {
+        clear()
+        stateCallback(InputState.EmptyIgnoringPreviousState())
         return true
       }
+      delegate!.keyHandler(
+        self,
+        didSelectCandidateAt: ctlCandidateCurrent.selectedCandidateIndex,
+        ctlCandidate: ctlCandidateCurrent
+      )
+      return true
+    }
 
-      // MARK: Enter
+    // MARK: Tab
 
-      if input.isEnter {
-        if state is InputState.AssociatedPhrases {
-          clear()
-          stateCallback(InputState.EmptyIgnoringPreviousState())
-          return true
+    if input.isTab {
+      let updated: Bool =
+        mgrPrefs.specifyShiftTabKeyBehavior
+        ? (input.isShiftHold
+          ? ctlCandidateCurrent.showPreviousPage()
+          : ctlCandidateCurrent.showNextPage())
+        : (input.isShiftHold
+          ? ctlCandidateCurrent.highlightPreviousCandidate()
+          : ctlCandidateCurrent.highlightNextCandidate())
+      if !updated {
+        IME.prtDebugIntel("9B691919")
+        errorCallback()
+      }
+      return true
+    }
+
+    // MARK: Space
+
+    if input.isSpace {
+      let updated: Bool =
+        mgrPrefs.specifyShiftSpaceKeyBehavior
+        ? (input.isShiftHold
+          ? ctlCandidateCurrent.highlightNextCandidate()
+          : ctlCandidateCurrent.showNextPage())
+        : (input.isShiftHold
+          ? ctlCandidateCurrent.showNextPage()
+          : ctlCandidateCurrent.highlightNextCandidate())
+      if !updated {
+        IME.prtDebugIntel("A11C781F")
+        errorCallback()
+      }
+      return true
+    }
+
+    // MARK: PgDn
+
+    if input.isPageDown || input.emacsKey == vChewingEmacsKey.nextPage {
+      let updated: Bool = ctlCandidateCurrent.showNextPage()
+      if !updated {
+        IME.prtDebugIntel("9B691919")
+        errorCallback()
+      }
+      return true
+    }
+
+    // MARK: PgUp
+
+    if input.isPageUp {
+      let updated: Bool = ctlCandidateCurrent.showPreviousPage()
+      if !updated {
+        IME.prtDebugIntel("9569955D")
+        errorCallback()
+      }
+      return true
+    }
+
+    // MARK: Left Arrow
+
+    if input.isLeft {
+      switch ctlCandidateCurrent.currentLayout {
+        case .horizontal:
+          do {
+            if !ctlCandidateCurrent.highlightPreviousCandidate() {
+              IME.prtDebugIntel("1145148D")
+              errorCallback()
+            }
+          }
+        case .vertical:
+          do {
+            if !ctlCandidateCurrent.showPreviousPage() {
+              IME.prtDebugIntel("1919810D")
+              errorCallback()
+            }
+          }
+      }
+      return true
+    }
+
+    // MARK: EmacsKey Backward
+
+    if input.emacsKey == vChewingEmacsKey.backward {
+      let updated: Bool = ctlCandidateCurrent.highlightPreviousCandidate()
+      if !updated {
+        IME.prtDebugIntel("9B89308D")
+        errorCallback()
+      }
+      return true
+    }
+
+    // MARK: Right Arrow
+
+    if input.isRight {
+      switch ctlCandidateCurrent.currentLayout {
+        case .horizontal:
+          do {
+            if !ctlCandidateCurrent.highlightNextCandidate() {
+              IME.prtDebugIntel("9B65138D")
+              errorCallback()
+            }
+          }
+        case .vertical:
+          do {
+            if !ctlCandidateCurrent.showNextPage() {
+              IME.prtDebugIntel("9244908D")
+              errorCallback()
+            }
+          }
+      }
+      return true
+    }
+
+    // MARK: EmacsKey Forward
+
+    if input.emacsKey == vChewingEmacsKey.forward {
+      let updated: Bool = ctlCandidateCurrent.highlightNextCandidate()
+      if !updated {
+        IME.prtDebugIntel("9B2428D")
+        errorCallback()
+      }
+      return true
+    }
+
+    // MARK: Up Arrow
+
+    if input.isUp {
+      switch ctlCandidateCurrent.currentLayout {
+        case .horizontal:
+          do {
+            if !ctlCandidateCurrent.showPreviousPage() {
+              IME.prtDebugIntel("9B614524")
+              errorCallback()
+            }
+          }
+        case .vertical:
+          do {
+            if !ctlCandidateCurrent.highlightPreviousCandidate() {
+              IME.prtDebugIntel("ASD9908D")
+              errorCallback()
+            }
+          }
+      }
+      return true
+    }
+
+    // MARK: Down Arrow
+
+    if input.isDown {
+      switch ctlCandidateCurrent.currentLayout {
+        case .horizontal:
+          do {
+            if !ctlCandidateCurrent.showNextPage() {
+              IME.prtDebugIntel("92B990DD")
+              errorCallback()
+            }
+          }
+        case .vertical:
+          do {
+            if !ctlCandidateCurrent.highlightNextCandidate() {
+              IME.prtDebugIntel("6B99908D")
+              errorCallback()
+            }
+          }
+      }
+      return true
+    }
+
+    // MARK: Home Key
+
+    if input.isHome || input.emacsKey == vChewingEmacsKey.home {
+      if ctlCandidateCurrent.selectedCandidateIndex == 0 {
+        IME.prtDebugIntel("9B6EDE8D")
+        errorCallback()
+      } else {
+        ctlCandidateCurrent.selectedCandidateIndex = 0
+      }
+
+      return true
+    }
+
+    // MARK: End Key
+
+    var candidates: [String]!
+
+    if let state = state as? InputState.ChoosingCandidate {
+      candidates = state.candidates
+    } else if let state = state as? InputState.AssociatedPhrases {
+      candidates = state.candidates
+    }
+
+    if candidates.isEmpty {
+      return false
+    } else {  // 這裡不用「count > 0」，因為該整數變數只要「!isEmpty」那就必定滿足這個條件。
+      if input.isEnd || input.emacsKey == vChewingEmacsKey.end {
+        if ctlCandidateCurrent.selectedCandidateIndex == candidates.count - 1 {
+          IME.prtDebugIntel("9B69AAAD")
+          errorCallback()
+        } else {
+          ctlCandidateCurrent.selectedCandidateIndex = candidates.count - 1
         }
+      }
+    }
+
+    // MARK: - Associated Phrases
+
+    if state is InputState.AssociatedPhrases {
+      if !input.isShiftHold { return false }
+    }
+
+    var index: Int = NSNotFound
+    var match: String!
+    if state is InputState.AssociatedPhrases {
+      match = input.inputTextIgnoringModifiers
+    } else {
+      match = inputText
+    }
+
+    var j = 0
+    while j < ctlCandidateCurrent.keyLabels.count {
+      let label: CandidateKeyLabel = ctlCandidateCurrent.keyLabels[j]
+      if match.compare(label.key, options: .caseInsensitive, range: nil, locale: .current) == .orderedSame {
+        index = j
+        break
+      }
+      j += 1
+    }
+
+    if index != NSNotFound {
+      let candidateIndex = ctlCandidateCurrent.candidateIndexAtKeyLabelIndex(index)
+      if candidateIndex != Int.max {
         delegate!.keyHandler(
-          self,
-          didSelectCandidateAt: ctlCandidateCurrent.selectedCandidateIndex,
-          ctlCandidate: ctlCandidateCurrent
+          self, didSelectCandidateAt: candidateIndex, ctlCandidate: ctlCandidateCurrent
         )
         return true
       }
+    }
 
-      // MARK: Tab
+    if state is InputState.AssociatedPhrases { return false }
 
-      if input.isTab {
-        let updated: Bool =
-          mgrPrefs.specifyShiftTabKeyBehavior
-          ? (input.isShiftHold
-            ? ctlCandidateCurrent.showPreviousPage()
-            : ctlCandidateCurrent.showNextPage())
-          : (input.isShiftHold
-            ? ctlCandidateCurrent.highlightPreviousCandidate()
-            : ctlCandidateCurrent.highlightNextCandidate())
-        if !updated {
-          IME.prtDebugIntel("9B691919")
-          errorCallback()
-        }
-        return true
-      }
+    // MARK: SCPC Mode Processing
 
-      // MARK: Space
+    if mgrPrefs.useSCPCTypingMode {
+      var punctuationNamePrefix = ""
 
-      if input.isSpace {
-        let updated: Bool =
-          mgrPrefs.specifyShiftSpaceKeyBehavior
-          ? (input.isShiftHold
-            ? ctlCandidateCurrent.highlightNextCandidate()
-            : ctlCandidateCurrent.showNextPage())
-          : (input.isShiftHold
-            ? ctlCandidateCurrent.showNextPage()
-            : ctlCandidateCurrent.highlightNextCandidate())
-        if !updated {
-          IME.prtDebugIntel("A11C781F")
-          errorCallback()
-        }
-        return true
-      }
-
-      // MARK: PgDn
-
-      if input.isPageDown || input.emacsKey == vChewingEmacsKey.nextPage {
-        let updated: Bool = ctlCandidateCurrent.showNextPage()
-        if !updated {
-          IME.prtDebugIntel("9B691919")
-          errorCallback()
-        }
-        return true
-      }
-
-      // MARK: PgUp
-
-      if input.isPageUp {
-        let updated: Bool = ctlCandidateCurrent.showPreviousPage()
-        if !updated {
-          IME.prtDebugIntel("9569955D")
-          errorCallback()
-        }
-        return true
-      }
-
-      // MARK: Left Arrow
-
-      if input.isLeft {
-        switch ctlCandidateCurrent.currentLayout {
-          case .horizontal:
-            do {
-              if !ctlCandidateCurrent.highlightPreviousCandidate() {
-                IME.prtDebugIntel("1145148D")
-                errorCallback()
-              }
-            }
-          case .vertical:
-            do {
-              if !ctlCandidateCurrent.showPreviousPage() {
-                IME.prtDebugIntel("1919810D")
-                errorCallback()
-              }
-            }
-        }
-        return true
-      }
-
-      // MARK: EmacsKey Backward
-
-      if input.emacsKey == vChewingEmacsKey.backward {
-        let updated: Bool = ctlCandidateCurrent.highlightPreviousCandidate()
-        if !updated {
-          IME.prtDebugIntel("9B89308D")
-          errorCallback()
-        }
-        return true
-      }
-
-      // MARK: Right Arrow
-
-      if input.isRight {
-        switch ctlCandidateCurrent.currentLayout {
-          case .horizontal:
-            do {
-              if !ctlCandidateCurrent.highlightNextCandidate() {
-                IME.prtDebugIntel("9B65138D")
-                errorCallback()
-              }
-            }
-          case .vertical:
-            do {
-              if !ctlCandidateCurrent.showNextPage() {
-                IME.prtDebugIntel("9244908D")
-                errorCallback()
-              }
-            }
-        }
-        return true
-      }
-
-      // MARK: EmacsKey Forward
-
-      if input.emacsKey == vChewingEmacsKey.forward {
-        let updated: Bool = ctlCandidateCurrent.highlightNextCandidate()
-        if !updated {
-          IME.prtDebugIntel("9B2428D")
-          errorCallback()
-        }
-        return true
-      }
-
-      // MARK: Up Arrow
-
-      if input.isUp {
-        switch ctlCandidateCurrent.currentLayout {
-          case .horizontal:
-            do {
-              if !ctlCandidateCurrent.showPreviousPage() {
-                IME.prtDebugIntel("9B614524")
-                errorCallback()
-              }
-            }
-          case .vertical:
-            do {
-              if !ctlCandidateCurrent.highlightPreviousCandidate() {
-                IME.prtDebugIntel("ASD9908D")
-                errorCallback()
-              }
-            }
-        }
-        return true
-      }
-
-      // MARK: Down Arrow
-
-      if input.isDown {
-        switch ctlCandidateCurrent.currentLayout {
-          case .horizontal:
-            do {
-              if !ctlCandidateCurrent.showNextPage() {
-                IME.prtDebugIntel("92B990DD")
-                errorCallback()
-              }
-            }
-          case .vertical:
-            do {
-              if !ctlCandidateCurrent.highlightNextCandidate() {
-                IME.prtDebugIntel("6B99908D")
-                errorCallback()
-              }
-            }
-        }
-        return true
-      }
-
-      // MARK: Home Key
-
-      if input.isHome || input.emacsKey == vChewingEmacsKey.home {
-        if ctlCandidateCurrent.selectedCandidateIndex == 0 {
-          IME.prtDebugIntel("9B6EDE8D")
-          errorCallback()
-        } else {
-          ctlCandidateCurrent.selectedCandidateIndex = 0
-        }
-
-        return true
-      }
-
-      // MARK: End Key
-
-      var candidates: [String]!
-
-      if let state = state as? InputState.ChoosingCandidate {
-        candidates = state.candidates
-      } else if let state = state as? InputState.AssociatedPhrases {
-        candidates = state.candidates
-      }
-
-      if candidates.isEmpty {
-        return false
-      } else {  // 這裡不用「count > 0」，因為該整數變數只要「!isEmpty」那就必定滿足這個條件。
-        if input.isEnd || input.emacsKey == vChewingEmacsKey.end {
-          if ctlCandidateCurrent.selectedCandidateIndex == candidates.count - 1 {
-            IME.prtDebugIntel("9B69AAAD")
-            errorCallback()
-          } else {
-            ctlCandidateCurrent.selectedCandidateIndex = candidates.count - 1
-          }
-        }
-      }
-
-      // MARK: - Associated Phrases
-
-      if state is InputState.AssociatedPhrases {
-        if !input.isShiftHold { return false }
-      }
-
-      var index: Int = NSNotFound
-      var match: String!
-      if state is InputState.AssociatedPhrases {
-        match = input.inputTextIgnoringModifiers
+      if input.isOptionHold && !input.isControlHold {
+        punctuationNamePrefix = "_alt_punctuation_"
+      } else if input.isControlHold && !input.isOptionHold {
+        punctuationNamePrefix = "_ctrl_punctuation_"
+      } else if input.isControlHold && input.isOptionHold {
+        punctuationNamePrefix = "_alt_ctrl_punctuation_"
+      } else if mgrPrefs.halfWidthPunctuationEnabled {
+        punctuationNamePrefix = "_half_punctuation_"
       } else {
-        match = inputText
+        punctuationNamePrefix = "_punctuation_"
       }
 
-      var j = 0
-      while j < ctlCandidateCurrent.keyLabels.count {
-        let label: CandidateKeyLabel = ctlCandidateCurrent.keyLabels[j]
-        if match.compare(label.key, options: .caseInsensitive, range: nil, locale: .current) == .orderedSame {
-          index = j
-          break
-        }
-        j += 1
+      let parser = currentMandarinParser
+
+      let arrCustomPunctuations: [String] = [
+        punctuationNamePrefix, parser, String(format: "%c", CChar(charCode)),
+      ]
+      let customPunctuation: String = arrCustomPunctuations.joined(separator: "")
+
+      let arrPunctuations: [String] = [punctuationNamePrefix, String(format: "%c", CChar(charCode))]
+      let punctuation: String = arrPunctuations.joined(separator: "")
+
+      var shouldAutoSelectCandidate: Bool =
+        _composer.inputValidityCheck(key: charCode) || ifLangModelHasUnigrams(forKey: customPunctuation)
+        || ifLangModelHasUnigrams(forKey: punctuation)
+
+      if !shouldAutoSelectCandidate, input.isUpperCaseASCIILetterKey {
+        let letter: String! = String(format: "%@%c", "_letter_", CChar(charCode))
+        if ifLangModelHasUnigrams(forKey: letter) { shouldAutoSelectCandidate = true }
       }
 
-      if index != NSNotFound {
-        let candidateIndex = ctlCandidateCurrent.candidateIndexAtKeyLabelIndex(index)
+      if shouldAutoSelectCandidate {
+        let candidateIndex = ctlCandidateCurrent.candidateIndexAtKeyLabelIndex(0)
         if candidateIndex != Int.max {
           delegate!.keyHandler(
-            self, didSelectCandidateAt: candidateIndex, ctlCandidate: ctlCandidateCurrent
+            self,
+            didSelectCandidateAt: candidateIndex,
+            ctlCandidate: ctlCandidateCurrent
+          )
+          clear()
+          let empty = InputState.EmptyIgnoringPreviousState()
+          stateCallback(empty)
+          return handle(
+            input: input, state: empty, stateCallback: stateCallback, errorCallback: errorCallback
           )
-          return true
         }
+        return true
       }
-
-      if state is InputState.AssociatedPhrases { return false }
-
-      // MARK: SCPC Mode Processing
-
-      if mgrPrefs.useSCPCTypingMode {
-        var punctuationNamePrefix = ""
-
-        if input.isOptionHold && !input.isControlHold {
-          punctuationNamePrefix = "_alt_punctuation_"
-        } else if input.isControlHold && !input.isOptionHold {
-          punctuationNamePrefix = "_ctrl_punctuation_"
-        } else if input.isControlHold && input.isOptionHold {
-          punctuationNamePrefix = "_alt_ctrl_punctuation_"
-        } else if mgrPrefs.halfWidthPunctuationEnabled {
-          punctuationNamePrefix = "_half_punctuation_"
-        } else {
-          punctuationNamePrefix = "_punctuation_"
-        }
-
-        let parser = currentMandarinParser
-
-        let arrCustomPunctuations: [String] = [
-          punctuationNamePrefix, parser, String(format: "%c", CChar(charCode)),
-        ]
-        let customPunctuation: String = arrCustomPunctuations.joined(separator: "")
-
-        let arrPunctuations: [String] = [punctuationNamePrefix, String(format: "%c", CChar(charCode))]
-        let punctuation: String = arrPunctuations.joined(separator: "")
-
-        var shouldAutoSelectCandidate: Bool =
-          _composer.inputValidityCheck(key: charCode) || ifLangModelHasUnigrams(forKey: customPunctuation)
-          || ifLangModelHasUnigrams(forKey: punctuation)
-
-        if !shouldAutoSelectCandidate, input.isUpperCaseASCIILetterKey {
-          let letter: String! = String(format: "%@%c", "_letter_", CChar(charCode))
-          if ifLangModelHasUnigrams(forKey: letter) { shouldAutoSelectCandidate = true }
-        }
-
-        if shouldAutoSelectCandidate {
-          let candidateIndex = ctlCandidateCurrent.candidateIndexAtKeyLabelIndex(0)
-          if candidateIndex != Int.max {
-            delegate!.keyHandler(
-              self,
-              didSelectCandidateAt: candidateIndex,
-              ctlCandidate: ctlCandidateCurrent
-            )
-            clear()
-            let empty = InputState.EmptyIgnoringPreviousState()
-            stateCallback(empty)
-            return handle(
-              input: input, state: empty, stateCallback: stateCallback, errorCallback: errorCallback
-            )
-          }
-          return true
-        }
-      }
-    }  // END: "if let ctlCandidateCurrent"
+    }
 
     IME.prtDebugIntel("172A0F81")
     errorCallback()