From 6658e397e2d0447bef4c5dd1db1c38d5d7917ac9 Mon Sep 17 00:00:00 2001
From: Zufu Liu <unknown>
Date: Sun, 15 Oct 2023 08:46:43 +1100
Subject: Bug [#2405]. Fix incorrect substitution when searching for a regular
 expression backwards.

---
 doc/ScintillaHistory.html  |  4 ++++
 src/Document.cxx           |  8 ++++++++
 test/unit/testDocument.cxx | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+)

diff --git a/doc/ScintillaHistory.html b/doc/ScintillaHistory.html
index 5a54725a2..7d1d9f48f 100644
--- a/doc/ScintillaHistory.html
+++ b/doc/ScintillaHistory.html
@@ -595,6 +595,10 @@
 	<a href="https://github.com/notepad-plus-plus/notepad-plus-plus/issues/13442">Notepad++ Issue #13442</a>.
 	</li>
 	<li>
+	Fix incorrect substitution when searching for a regular expression backwards.
+	<a href="https://sourceforge.net/p/scintilla/bugs/2405/">Bug #2405</a>.
+	</li>
+	<li>
 	For Cocoa, fix invisible text on macOS 14 Sonoma.
 	<a href="https://sourceforge.net/p/scintilla/bugs/2402/">Bug #2402</a>.
 	</li>
diff --git a/src/Document.cxx b/src/Document.cxx
index 0365b24db..a45479e4b 100644
--- a/src/Document.cxx
+++ b/src/Document.cxx
@@ -3294,7 +3294,11 @@ Sci::Position BuiltinRegex::FindText(Document *doc, Sci::Position minPos, Sci::P
 			if ((resr.increment == -1) && !searchforLineStart) {
 				// Check for the last match on this line.
 				int repetitions = 1000;	// Break out of infinite loop
+				RESearch::MatchPositions bopat{};
+				RESearch::MatchPositions eopat{};
 				while (success && (search.eopat[0] <= endOfLine) && (repetitions--)) {
+					bopat = search.bopat;
+					eopat = search.eopat;
 					success = search.Execute(di, pos+1, endOfLine);
 					if (success) {
 						if (search.eopat[0] <= minPos) {
@@ -3305,6 +3309,10 @@ Sci::Position BuiltinRegex::FindText(Document *doc, Sci::Position minPos, Sci::P
 						}
 					}
 				}
+				if (!success) {
+					search.bopat = bopat;
+					search.eopat = eopat;
+				}
 			}
 			break;
 		}
diff --git a/test/unit/testDocument.cxx b/test/unit/testDocument.cxx
index 3cfb54db4..4ed1dbbbd 100644
--- a/test/unit/testDocument.cxx
+++ b/test/unit/testDocument.cxx
@@ -453,6 +453,52 @@ TEST_CASE("Document") {
 		REQUIRE(doc.NextPosition(15, -1) == 14);
 	}
 
+	SECTION("RegexSearchAndSubstitution") {
+		DocPlus doc("\n\r\r\n 1a\xCE\x93z \n\r\r\n 2b\xCE\x93y \n\r\r\n", CpUtf8);// 1a gamma z 2b gamma y
+		const std::string finding = R"(\d+(\w+))";
+		Sci::Position lengthFinding = finding.length();
+		Sci::Position location = doc.FindNeedle(finding, FindOption::RegExp | FindOption::Posix, &lengthFinding);
+		REQUIRE(location == 5);
+		REQUIRE(lengthFinding == 5);
+
+		const std::string_view substituteText = R"(\t\1\n)";
+		Sci::Position lengthsubstitute = substituteText.length();
+		std::string substituted = doc.document.SubstituteByPosition(substituteText.data(), &lengthsubstitute);
+		REQUIRE(lengthsubstitute == 6);
+		REQUIRE(substituted == "\ta\xCE\x93z\n");
+
+		lengthFinding = finding.length();
+		location = doc.FindNeedleReverse(finding, FindOption::RegExp | FindOption::Posix, &lengthFinding);
+		REQUIRE(location == 16);
+		REQUIRE(lengthFinding == 5);
+
+		lengthsubstitute = substituteText.length();
+		substituted = doc.document.SubstituteByPosition(substituteText.data(), &lengthsubstitute);
+		REQUIRE(lengthsubstitute == 6);
+		REQUIRE(substituted == "\tb\xCE\x93y\n");
+
+		#ifndef NO_CXX11_REGEX
+		lengthFinding = finding.length();
+		location = doc.FindNeedle(finding, FindOption::RegExp | FindOption::Cxx11RegEx, &lengthFinding);
+		REQUIRE(location == 5);
+		REQUIRE(lengthFinding == 5);
+
+		lengthsubstitute = substituteText.length();
+		substituted = doc.document.SubstituteByPosition(substituteText.data(), &lengthsubstitute);
+		REQUIRE(lengthsubstitute == 6);
+		REQUIRE(substituted == "\ta\xCE\x93z\n");
+
+		lengthFinding = finding.length();
+		location = doc.FindNeedleReverse(finding, FindOption::RegExp | FindOption::Cxx11RegEx, &lengthFinding);
+		REQUIRE(location == 16);
+		REQUIRE(lengthFinding == 5);
+
+		lengthsubstitute = substituteText.length();
+		substituted = doc.document.SubstituteByPosition(substituteText.data(), &lengthsubstitute);
+		REQUIRE(lengthsubstitute == 6);
+		REQUIRE(substituted == "\tb\xCE\x93y\n");
+		#endif
+	}
 }
 
 TEST_CASE("Words") {
-- 
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