From d853508df8c3d391ff841aa9ad65670b4e163422 Mon Sep 17 00:00:00 2001
From: Zufu Liu <unknown>
Date: Fri, 22 Mar 2024 15:28:29 +1100
Subject: Bug [#2433]. Fix IME crash in windowed mode.

---
 doc/ScintillaHistory.html |  6 +++++-
 win32/ScintillaWin.cxx    | 18 ++++++++++++++----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 9ec26d44c..331a76420 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -584,7 +584,7 @@
     </table>
     <h2>Releases</h2>
     <h3>
-       <a href="https://www.scintilla.org/scintilla544.zip">Release 5.4.4</a>
+       <a href="https://www.scintilla.org/scintilla550.zip">Release 5.5.0</a>
     </h3>
     <ul>
 	<li>
@@ -596,6 +596,10 @@
 	When not set these default to SC_ELEMENT_SELECTION_INACTIVE_TEXT and SC_ELEMENT_SELECTION_INACTIVE_BACK.
 	<a href="https://sourceforge.net/p/scintilla/bugs/2417/">Bug #2417</a>.
 	</li>
+	<li>
+	Fix Win32 IME crash in windowed mode.
+	<a href="https://sourceforge.net/p/scintilla/bugs/2433/">Bug #2433</a>.
+	</li>
     </ul>
     <h3>
        <a href="https://www.scintilla.org/scintilla543.zip">Release 5.4.3</a>
diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index 806d915b7..c6733469c 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -277,6 +277,11 @@ public:
 		return attr;
 	}
 
+	LONG GetCompositionStringLength(DWORD dwIndex) const noexcept {
+		const LONG byteLen = ::ImmGetCompositionStringW(hIMC, dwIndex, nullptr, 0);
+		return byteLen / sizeof(wchar_t);
+	}
+
 	std::wstring GetCompositionString(DWORD dwIndex) {
 		const LONG byteLen = ::ImmGetCompositionStringW(hIMC, dwIndex, nullptr, 0);
 		std::wstring wcs(byteLen / 2, 0);
@@ -3184,9 +3189,14 @@ LRESULT ScintillaWin::ImeOnDocumentFeed(LPARAM lParam) const {
 	if (!imc.hIMC)
 		return 0;
 
-	const size_t compStrLen = imc.GetCompositionString(GCS_COMPSTR).size();
-	const int imeCaretPos = imc.GetImeCaretPos();
-	const Sci::Position compStart = pdoc->GetRelativePositionUTF16(curPos, -imeCaretPos);
+	DWORD compStrLen = 0;
+	Sci::Position compStart = curPos;
+	if (pdoc->TentativeActive()) {
+		// rcFeed contains current composition string
+		compStrLen = imc.GetCompositionStringLength(GCS_COMPSTR);
+		const int imeCaretPos = imc.GetImeCaretPos();
+		compStart = pdoc->GetRelativePositionUTF16(curPos, -imeCaretPos);
+	}
 	const Sci::Position compStrOffset = pdoc->CountUTF16(lineStart, compStart);
 
 	// Fill in reconvert structure.
@@ -3194,7 +3204,7 @@ LRESULT ScintillaWin::ImeOnDocumentFeed(LPARAM lParam) const {
 	rc->dwVersion = 0; //constant
 	rc->dwStrLen = static_cast<DWORD>(rcFeed.length());
 	rc->dwStrOffset = sizeof(RECONVERTSTRING); //constant
-	rc->dwCompStrLen = static_cast<DWORD>(compStrLen);
+	rc->dwCompStrLen = compStrLen;
 	rc->dwCompStrOffset = static_cast<DWORD>(compStrOffset) * sizeof(wchar_t);
 	rc->dwTargetStrLen = rc->dwCompStrLen;
 	rc->dwTargetStrOffset = rc->dwCompStrOffset;
-- 
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