From 339e3fa8805f7c9411bf6e6df8d295b91b5a72a5 Mon Sep 17 00:00:00 2001
From: zufuliu <zufuliu@gmail.com>
Date: Thu, 21 Mar 2024 18:10:45 +0800
Subject: [PATCH] Fix crash due to incorrect IME document feed, issue #775. See
 https://sourceforge.net/p/scintilla/bugs/2433/

---
 scintilla/win32/ScintillaWin.cxx | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/scintilla/win32/ScintillaWin.cxx b/scintilla/win32/ScintillaWin.cxx
index 2f7185b808..4490dca408 100644
--- a/scintilla/win32/ScintillaWin.cxx
+++ b/scintilla/win32/ScintillaWin.cxx
@@ -3438,9 +3438,14 @@ LRESULT ScintillaWin::ImeOnDocumentFeed(LPARAM lParam) const {
 		return 0;
 	}
 
-	const DWORD compStrLen = imc.GetCompositionStringLength(GCS_COMPSTR);
-	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.