From fc5004a9e14cfd5c462abca0c8af3cab614aa48d Mon Sep 17 00:00:00 2001
From: Neil <nyamatongwe@gmail.com>
Date: Thu, 23 Apr 2026 10:42:27 +1000
Subject: Add error status SC_STATUS_OUTSIDE_DOCUMENT that is set when
 operations are attempted on a position outside the document. Positions are
 checked earlier to prevent actions partly succeeding. This is implemented
 with a new exception type Failure which should be caught by platform layer's
 API handling code to produce a more granular error status.

---
 src/CellBuffer.h | 5 +++++
 src/Document.cxx | 9 ++++++++-
 src/Document.h   | 1 +
 src/Editor.cxx   | 3 +++
 4 files changed, 17 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/CellBuffer.h b/src/CellBuffer.h
index d54d2be8d..11479f14a 100644
--- a/src/CellBuffer.h
+++ b/src/CellBuffer.h
@@ -10,6 +10,11 @@
 
 namespace Scintilla::Internal {
 
+struct Failure : public std::runtime_error {
+	Status status;
+	Failure(Status status_) : std::runtime_error("failure with status"), status(status_) {}
+};
+
 // Interface to per-line data that wants to see each line insertion and deletion
 class PerLine {
 public:
diff --git a/src/Document.cxx b/src/Document.cxx
index f3dac9aaa..289fb6731 100644
--- a/src/Document.cxx
+++ b/src/Document.cxx
@@ -530,6 +530,13 @@ void SCI_METHOD Document::SetErrorStatus(int status) {
 	}
 }
 
+void Document::CheckPosition(Sci::Position pos) const {
+	PLATFORM_ASSERT((pos >= 0) && (pos <= LengthNoExcept()));
+	if ((pos < 0) || (pos > LengthNoExcept())) {
+		throw Failure(Status::OutsideDocument);
+	}
+}
+
 Sci_Position SCI_METHOD Document::LineFromPosition(Sci_Position pos) const {
 	return cb.LineFromPosition(pos);
 }
@@ -1485,7 +1492,7 @@ Sci::Position Document::InsertString(Sci::Position position, const char *s, Sci:
 	if (insertLength <= 0) {
 		return 0;
 	}
-	PLATFORM_ASSERT((position >= 0) && (position <= Length()));
+	CheckPosition(position);
 	CheckReadOnly();	// Application may change read only state here
 	if (cb.IsReadOnly()) {
 		return 0;
diff --git a/src/Document.h b/src/Document.h
index 7fd150f37..dfb0a7ff5 100644
--- a/src/Document.h
+++ b/src/Document.h
@@ -369,6 +369,7 @@ public:
 	int SCI_METHOD DEVersion() const noexcept override;
 
 	void SCI_METHOD SetErrorStatus(int status) override;
+	void CheckPosition(Sci::Position pos) const;
 
 	Sci_Position SCI_METHOD LineFromPosition(Sci_Position pos) const override;
 	Sci::Line SciLineFromPosition(Sci::Position pos) const noexcept;	// Avoids casting LineFromPosition
diff --git a/src/Editor.cxx b/src/Editor.cxx
index d946c7bd2..1dfa8fd6b 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -5899,6 +5899,8 @@ Sci::Position Editor::GetTag(char *tagValue, int tagNumber) {
 }
 
 Sci::Position Editor::ReplaceTarget(ReplaceType replaceType, std::string_view text) {
+	pdoc->CheckPosition(targetRange.start.Position());
+
 	UndoGroup ug(pdoc);
 
 	std::string substituted;	// Copy in case of re-entrance
@@ -6697,6 +6699,7 @@ sptr_t Editor::WndProc(Message iMessage, uptr_t wParam, sptr_t lParam) {
 			Sci::Position insertPos = PositionFromUPtr(wParam);
 			if (insertPos == -1)
 				insertPos = CurrentPosition();
+			pdoc->CheckPosition(insertPos);
 			Sci::Position newCurrent = CurrentPosition();
 			const char *sz = ConstCharPtrFromSPtr(lParam);
 			const Sci::Position lengthInserted = pdoc->InsertString(insertPos, sz, strlen(sz));
-- 
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