From dd70417aab20b8b82db6d2d62fb01389cc9a6dfe Mon Sep 17 00:00:00 2001
From: ShikiSuen <shikisuen@outlook.com>
Date: Tue, 31 May 2022 12:43:52 +0800
Subject: [PATCH] KeyHandler // Implementing MS-New-Phonetic style rear-cursor
 mode.

---
 .../ControllerModules/KeyHandler_Core.swift   |  9 +++--
 .../ControllerModules/KeyHandler_Misc.swift   | 34 ++++++++++++-------
 .../ControllerModules/KeyHandler_States.swift |  5 ++-
 3 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/Source/Modules/ControllerModules/KeyHandler_Core.swift b/Source/Modules/ControllerModules/KeyHandler_Core.swift
index 4b4dfeb1..62332f68 100644
--- a/Source/Modules/ControllerModules/KeyHandler_Core.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_Core.swift
@@ -161,7 +161,7 @@ class KeyHandler {
   }
 
   func fixNode(value: String, respectCursorPushing: Bool = true) {
-    let cursorIndex: Int = actualCandidateCursorIndex
+    let cursorIndex = min(actualCandidateCursorIndex + (mgrPrefs.setRearCursorMode ? 1 : 0), builderLength)
     let selectedNode: Megrez.NodeAnchor = _builder.grid.fixNodeSelectedCandidate(
       location: cursorIndex, value: value
     )
@@ -244,7 +244,7 @@ class KeyHandler {
       IME.prtDebugIntel(
         "UOM: Suggestion retrieved, overriding the node score of the selected candidate.")
       _builder.grid.overrideNodeScoreForSelectedCandidate(
-        location: actualCandidateCursorIndex,
+        location: min(actualCandidateCursorIndex + (mgrPrefs.setRearCursorMode ? 1 : 0), builderLength),
         value: overrideValue,
         overridingScore: findHighestScore(nodes: rawNodes, epsilon: kEpsilon)
       )
@@ -309,10 +309,9 @@ class KeyHandler {
 
   var rawNodes: [Megrez.NodeAnchor] {
     /// 警告：不要對游標前置風格使用 nodesCrossing，否則會導致游標行為與 macOS 內建注音輸入法不一致。
-    /// 微軟新注音輸入法的游標後置風格也是不允許 nodeCrossing 的，但目前 Megrez 暫時缺乏對該特性的支援。
-    /// 所以暫時只能將威注音的游標後置風格描述成「跟 Windows 版雅虎奇摩注音一致」。
+    /// 微軟新注音輸入法的游標後置風格也是不允許 nodeCrossing 的。
     mgrPrefs.setRearCursorMode
-      ? _builder.grid.nodesCrossingOrEndingAt(location: actualCandidateCursorIndex)
+      ? _builder.grid.nodesBeginningAt(location: actualCandidateCursorIndex)
       : _builder.grid.nodesEndingAt(location: actualCandidateCursorIndex)
   }
 
diff --git a/Source/Modules/ControllerModules/KeyHandler_Misc.swift b/Source/Modules/ControllerModules/KeyHandler_Misc.swift
index e0b7594d..70996a4a 100644
--- a/Source/Modules/ControllerModules/KeyHandler_Misc.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_Misc.swift
@@ -35,19 +35,27 @@ extension KeyHandler {
 
   var actualCandidateCursorIndex: Int {
     var cursorIndex = builderCursorIndex
-    // Windows Yahoo Kimo IME style, phrase is *at the rear of* the cursor.
-    // (i.e. the cursor is always *before* the phrase.)
-    // This is different from MS Phonetics IME style ...
-    // ... since Windows Yahoo Kimo allows "node crossing".
-    if (mgrPrefs.setRearCursorMode
-      && (cursorIndex < builderLength))
-      || cursorIndex == 0
-    {
-      if cursorIndex == 0, !mgrPrefs.setRearCursorMode {
-        cursorIndex += keyLengthAtIndexZero
-      } else {
-        cursorIndex += 1
-      }
+    switch mgrPrefs.setRearCursorMode {
+      case false:
+        do {
+          // macOS built-in Zhuyin style.
+          // (i.e. the cursor is always in front of the phrase.)
+          // No crossing.
+          switch cursorIndex {
+            case 0: cursorIndex = 1
+            default: break
+          }
+        }
+      case true:
+        do {
+          // Microsoft new phonetics style.
+          // (i.e. the cursor is always at the rear of the phrase.)
+          // No crossing.
+          switch cursorIndex {
+            case builderLength: cursorIndex -= 1
+            default: break
+          }
+        }
     }
     return cursorIndex
   }
diff --git a/Source/Modules/ControllerModules/KeyHandler_States.swift b/Source/Modules/ControllerModules/KeyHandler_States.swift
index e0f7de2a..752faad0 100644
--- a/Source/Modules/ControllerModules/KeyHandler_States.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_States.swift
@@ -625,9 +625,12 @@ extension KeyHandler {
 
     var length = 0
     var currentAnchor = Megrez.NodeAnchor()
+    let cursorIndex = min(
+      actualCandidateCursorIndex + (mgrPrefs.useRearCursorMode ? 1 : 0), builderLength
+    )
     for anchor in _walkedNodes {
       length += anchor.spanningLength
-      if length >= actualCandidateCursorIndex {
+      if length >= cursorIndex {
         currentAnchor = anchor
         break
       }