diff --git a/Source/Modules/ControllerModules/KeyHandler_Core.swift b/Source/Modules/ControllerModules/KeyHandler_Core.swift
index 531c2213..40b33e51 100644
--- a/Source/Modules/ControllerModules/KeyHandler_Core.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_Core.swift
@@ -392,10 +392,10 @@ public class KeyHandler {
   /// 檢測某個傳入的按鍵訊號是否為聲調鍵。
   /// - Parameter input: 傳入的按鍵訊號。
   /// - Returns: 判斷結果：是否為聲調鍵。
-  func isIntonationKey(_ input: InputSignal) -> Bool {
+  func isIntonationKey(_ input: InputSignalProtocol) -> Bool {
     var theComposer = composer  // 複製一份用來做實驗。
     theComposer.clear()  // 清空各種槽的內容。
-    theComposer.receiveKey(fromCharCode: input.charCode)
+    theComposer.receiveKey(fromString: input.text)
     return theComposer.hasToneMarker(withNothingElse: true)
   }
 
@@ -417,7 +417,7 @@ public class KeyHandler {
   /// 生成標點符號索引鍵。
   /// - Parameter input: 輸入的按鍵訊號。
   /// - Returns: 生成的標點符號索引鍵。
-  func generatePunctuationNamePrefix(withKeyCondition input: InputSignal) -> String {
+  func generatePunctuationNamePrefix(withKeyCondition input: InputSignalProtocol) -> String {
     if mgrPrefs.halfWidthPunctuationEnabled {
       return "_half_punctuation_"
     }
diff --git a/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift b/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift
index 895dc668..ff6b89ed 100644
--- a/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_HandleCandidate.swift
@@ -24,12 +24,10 @@ extension KeyHandler {
   /// - Returns: 告知 IMK「該按鍵是否已經被輸入法攔截處理」。
   func handleCandidate(
     state: InputStateProtocol,
-    input: InputSignal,
+    input: InputSignalProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool {
-    let inputText = input.inputText
-    let charCode: UniChar = input.charCode
     guard var ctlCandidateCurrent = delegate?.ctlCandidate() else {
       IME.prtDebugIntel("06661F6E")
       errorCallback()
@@ -275,7 +273,7 @@ extension KeyHandler {
 
     var index: Int = NSNotFound
     let match: String =
-      (state is InputState.AssociatedPhrases) ? input.inputTextIgnoringModifiers ?? "" : inputText
+      (state is InputState.AssociatedPhrases) ? input.inputTextIgnoringModifiers ?? "" : input.text
 
     for j in 0..<ctlCandidateCurrent.keyLabels.count {
       let label: CandidateKeyLabel = ctlCandidateCurrent.keyLabels[j]
@@ -307,25 +305,23 @@ extension KeyHandler {
       let punctuationNamePrefix: String = generatePunctuationNamePrefix(withKeyCondition: input)
       let parser = currentMandarinParser
       let arrCustomPunctuations: [String] = [
-        punctuationNamePrefix, parser, String(format: "%c", charCode.isPrintableASCII ? CChar(charCode) : inputText),
+        punctuationNamePrefix, parser, input.text,
       ]
       let customPunctuation: String = arrCustomPunctuations.joined(separator: "")
 
       /// 看看這個輸入是否是不需要修飾鍵的那種標點鍵輸入。
 
       let arrPunctuations: [String] = [
-        punctuationNamePrefix, String(format: "%c", charCode.isPrintableASCII ? CChar(charCode) : inputText),
+        punctuationNamePrefix, input.text,
       ]
       let punctuation: String = arrPunctuations.joined(separator: "")
 
       var shouldAutoSelectCandidate: Bool =
-        composer.inputValidityCheck(key: charCode) || currentLM.hasUnigramsFor(key: customPunctuation)
+        composer.inputValidityCheck(key: input.charCode) || currentLM.hasUnigramsFor(key: customPunctuation)
         || currentLM.hasUnigramsFor(key: punctuation)
 
       if !shouldAutoSelectCandidate, input.isUpperCaseASCIILetterKey {
-        let letter: String! = String(
-          format: "%@%c", "_letter_", charCode.isPrintableASCII ? CChar(charCode) : inputText
-        )
+        let letter = "_letter_\(input.text)"
         if currentLM.hasUnigramsFor(key: letter) { shouldAutoSelectCandidate = true }
       }
 
diff --git a/Source/Modules/ControllerModules/KeyHandler_HandleComposition.swift b/Source/Modules/ControllerModules/KeyHandler_HandleComposition.swift
index 3e637372..001f7683 100644
--- a/Source/Modules/ControllerModules/KeyHandler_HandleComposition.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_HandleComposition.swift
@@ -18,7 +18,7 @@ extension KeyHandler {
   ///   - errorCallback: 錯誤回呼。
   /// - Returns: 告知 IMK「該按鍵是否已經被輸入法攔截處理」。
   func handleComposition(
-    input: InputSignal,
+    input: InputSignalProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool? {
@@ -42,7 +42,7 @@ extension KeyHandler {
         prevReading.0.charComponents.forEach { theComposer.receiveKey(fromPhonabet: $0) }
         // 發現要覆寫的聲調與覆寫對象的聲調雷同的情況的話，直接跳過處理。
         let oldIntonation: Tekkon.Phonabet = theComposer.intonation
-        theComposer.receiveKey(fromCharCode: input.charCode)
+        theComposer.receiveKey(fromString: input.text)
         if theComposer.intonation == oldIntonation, mgrPrefs.specifyIntonationKeyBehavior == 1 { break proc }
         theComposer.intonation.clear()
         // 檢查新的漢字字音是否在庫。
@@ -59,7 +59,7 @@ extension KeyHandler {
         }
       }
 
-      composer.receiveKey(fromCharCode: input.charCode)
+      composer.receiveKey(fromString: input.text)
       keyConsumedByReading = true
 
       // 沒有調號的話，只需要 updateClientComposingBuffer() 且終止處理（return true）即可。
diff --git a/Source/Modules/ControllerModules/KeyHandler_HandleInput.swift b/Source/Modules/ControllerModules/KeyHandler_HandleInput.swift
index 43fd7e40..ebcb3ff4 100644
--- a/Source/Modules/ControllerModules/KeyHandler_HandleInput.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_HandleInput.swift
@@ -24,16 +24,15 @@ extension KeyHandler {
   ///   - errorCallback: 錯誤回呼。
   /// - Returns: 告知 IMK「該按鍵是否已經被輸入法攔截處理」。
   func handle(
-    input: InputSignal,
+    input: InputSignalProtocol,
     state: InputStateProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool {
     // 如果按鍵訊號內的 inputTest 是空的話，則忽略該按鍵輸入，因為很可能是功能修飾鍵。
-    guard !input.inputText.isEmpty else { return false }
+    guard !input.text.isEmpty else { return false }
 
-    let charCode: UniChar = input.charCode
-    let inputText: String = input.inputText
+    let inputText: String = input.text
     var state = state  // 常數轉變數。
 
     // 提前過濾掉一些不合規的按鍵訊號輸入，免得相關按鍵訊號被送給 Megrez 引發輸入法崩潰。
@@ -78,7 +77,7 @@ extension KeyHandler {
 
       /// 如果是 ASCII 當中的不可列印的字元的話，不使用「insertText:replacementRange:」。
       /// 某些應用無法正常處理非 ASCII 字符的輸入。
-      if charCode < 0x80, !charCode.isPrintableASCII {
+      if input.isASCII, !input.charCode.isPrintableASCII {
         return false
       }
 
@@ -309,7 +308,7 @@ extension KeyHandler {
       if input.isMainAreaNumKey, input.isShiftHold, input.isOptionHold, !input.isControlHold, !input.isCommandHold {
         // NOTE: 將來棄用 macOS 10.11 El Capitan 支援的時候，把這裡由 CFStringTransform 改為 StringTransform:
         // https://developer.apple.com/documentation/foundation/stringtransform
-        guard let stringRAW = input.mapMainAreaNumKey[input.keyCode] else { return false }
+        guard let stringRAW = input.mainAreaNumKeyChar else { return false }
         let string = NSMutableString(string: stringRAW)
         CFStringTransform(string, nil, kCFStringTransformFullwidthHalfwidth, true)
         stateCallback(
@@ -328,9 +327,7 @@ extension KeyHandler {
 
     let punctuationNamePrefix: String = generatePunctuationNamePrefix(withKeyCondition: input)
     let parser = currentMandarinParser
-    let arrCustomPunctuations: [String] = [
-      punctuationNamePrefix, parser, String(format: "%c", charCode.isPrintableASCII ? CChar(charCode) : inputText),
-    ]
+    let arrCustomPunctuations: [String] = [punctuationNamePrefix, parser, input.text]
     let customPunctuation: String = arrCustomPunctuations.joined(separator: "")
     if handlePunctuation(
       customPunctuation,
@@ -344,9 +341,7 @@ extension KeyHandler {
 
     /// 如果仍無匹配結果的話，看看這個輸入是否是不需要修飾鍵的那種標點鍵輸入。
 
-    let arrPunctuations: [String] = [
-      punctuationNamePrefix, String(format: "%c", charCode.isPrintableASCII ? CChar(charCode) : inputText),
-    ]
+    let arrPunctuations: [String] = [punctuationNamePrefix, input.text]
     let punctuation: String = arrPunctuations.joined(separator: "")
 
     if handlePunctuation(
@@ -386,9 +381,7 @@ extension KeyHandler {
             stateCallback(InputState.Empty())
             return true
           default:  // 包括 case 0，直接塞給組字區。
-            let letter: String! = String(
-              format: "%@%c", "_letter_", charCode.isPrintableASCII ? CChar(charCode) : inputText
-            )
+            let letter = "_letter_\(inputText)"
             if handlePunctuation(
               letter,
               state: state,
@@ -410,7 +403,7 @@ extension KeyHandler {
     /// 暫時只能先恢復這段，且補上偵錯彙報機制，方便今後排查故障。
     if (state is InputState.NotEmpty) || !composer.isEmpty {
       IME.prtDebugIntel(
-        "Blocked data: charCode: \(charCode), keyCode: \(input.keyCode)")
+        "Blocked data: charCode: \(input.charCode), keyCode: \(input.keyCode)")
       IME.prtDebugIntel("A9BFF20E")
       errorCallback()
       stateCallback(state)
diff --git a/Source/Modules/ControllerModules/KeyHandler_States.swift b/Source/Modules/ControllerModules/KeyHandler_States.swift
index c8dbf982..a2763e77 100644
--- a/Source/Modules/ControllerModules/KeyHandler_States.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_States.swift
@@ -170,7 +170,7 @@ extension KeyHandler {
   /// - Returns: 將按鍵行為「是否有處理掉」藉由 ctlInputMethod 回報給 IMK。
   func handleMarkingState(
     _ state: InputState.Marking,
-    input: InputSignal,
+    input: InputSignalProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool {
@@ -416,7 +416,7 @@ extension KeyHandler {
   /// - Returns: 將按鍵行為「是否有處理掉」藉由 ctlInputMethod 回報給 IMK。
   func handleBackSpace(
     state: InputStateProtocol,
-    input: InputSignal,
+    input: InputSignalProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool {
@@ -482,7 +482,7 @@ extension KeyHandler {
   /// - Returns: 將按鍵行為「是否有處理掉」藉由 ctlInputMethod 回報給 IMK。
   func handleDelete(
     state: InputStateProtocol,
-    input: InputSignal,
+    input: InputSignalProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool {
@@ -652,7 +652,7 @@ extension KeyHandler {
   /// - Returns: 將按鍵行為「是否有處理掉」藉由 ctlInputMethod 回報給 IMK。
   func handleForward(
     state: InputStateProtocol,
-    input: InputSignal,
+    input: InputSignalProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool {
@@ -726,7 +726,7 @@ extension KeyHandler {
   /// - Returns: 將按鍵行為「是否有處理掉」藉由 ctlInputMethod 回報給 IMK。
   func handleBackward(
     state: InputStateProtocol,
-    input: InputSignal,
+    input: InputSignalProtocol,
     stateCallback: @escaping (InputStateProtocol) -> Void,
     errorCallback: @escaping () -> Void
   ) -> Bool {