3 files changed, 23 insertions, 9 deletions

diff --git a/src/Document.cxx b/src/Document.cxx
index dcb087930..d67cac25e 100644
--- a/src/Document.cxx
+++ b/src/Document.cxx
@@ -184,7 +184,7 @@ Document::~Document() {
 }
 
 // Increase reference count and return its previous value.
-int Document::AddRef() {
+int SCI_METHOD Document::AddRef() noexcept {
 	return refCount++;
 }
 
@@ -461,6 +461,10 @@ Sci_Position SCI_METHOD Document::LineEnd(Sci_Position line) const {
 	return cb.LineEnd(line);
 }
 
+int SCI_METHOD Document::DEVersion() const noexcept {
+	return deRelease0;
+}
+
 void SCI_METHOD Document::SetErrorStatus(int status) {
 	// Tell the watchers an error has occurred.
 	for (const WatcherWithUserData &watcher : watchers) {
@@ -1341,8 +1345,12 @@ int SCI_METHOD Document::AddData(const char *data, Sci_Position length) {
 	return static_cast<int>(Status::Ok);
 }
 
+IDocumentEditable *Document::AsDocumentEditable() noexcept {
+	return static_cast<IDocumentEditable *>(this);
+}
+
 void * SCI_METHOD Document::ConvertToDocument() {
-	return this;
+	return AsDocumentEditable();
 }
 
 Sci::Position Document::Undo() {
diff --git a/src/Document.h b/src/Document.h
index f7f4eeedd..9f51fc719 100644
--- a/src/Document.h
+++ b/src/Document.h
@@ -259,7 +259,7 @@ struct CharacterExtracted {
 
 /**
  */
-class Document : PerLine, public Scintilla::IDocument, public Scintilla::ILoader {
+class Document : PerLine, public Scintilla::IDocument, public Scintilla::ILoader, public Scintilla::IDocumentEditable {
 
 public:
 	/** Used to pair watcher pointer with user data. */
@@ -329,7 +329,7 @@ public:
 	Document &operator=(Document &&) = delete;
 	~Document() override;
 
-	int AddRef();
+	int SCI_METHOD AddRef() noexcept override;
 	int SCI_METHOD Release() override;
 
 	// From PerLine
@@ -347,6 +347,7 @@ public:
 	int SCI_METHOD Version() const override {
 		return Scintilla::dvRelease4;
 	}
+	int SCI_METHOD DEVersion() const noexcept override;
 
 	void SCI_METHOD SetErrorStatus(int status) override;
 
@@ -383,6 +384,7 @@ public:
 	Sci::Position InsertString(Sci::Position position, std::string_view sv);
 	void ChangeInsertion(const char *s, Sci::Position length);
 	int SCI_METHOD AddData(const char *data, Sci_Position length) override;
+	IDocumentEditable *AsDocumentEditable() noexcept;
 	void * SCI_METHOD ConvertToDocument() override;
 	Sci::Position Undo();
 	Sci::Position Redo();
diff --git a/src/Editor.cxx b/src/Editor.cxx
index 28d680d7a..8f29d3a8f 100644
--- a/src/Editor.cxx
+++ b/src/Editor.cxx
@@ -6079,6 +6079,10 @@ constexpr Selection::SelTypes SelTypeFromMode(SelectionMode mode) {
 	}
 }
 
+sptr_t SPtrFromPtr(void *ptr) noexcept {
+	return reinterpret_cast<sptr_t>(ptr);
+}
+
 }
 
 void Editor::SetSelectionMode(uptr_t wParam, bool setMoveExtends) {
@@ -8216,11 +8220,11 @@ sptr_t Editor::WndProc(Message iMessage, uptr_t wParam, sptr_t lParam) {
 		break;
 
 	case Message::GetDocPointer:
-		return reinterpret_cast<sptr_t>(pdoc);
+		return SPtrFromPtr(pdoc->AsDocumentEditable());
 
 	case Message::SetDocPointer:
 		CancelModes();
-		SetDocPointer(static_cast<Document *>(PtrFromSPtr(lParam)));
+		SetDocPointer(static_cast<Document *>(static_cast<IDocumentEditable *>(PtrFromSPtr(lParam))));
 		return 0;
 
 	case Message::CreateDocument: {
@@ -8228,15 +8232,15 @@ sptr_t Editor::WndProc(Message iMessage, uptr_t wParam, sptr_t lParam) {
 			doc->AddRef();
 			doc->Allocate(PositionFromUPtr(wParam));
 			pcs = ContractionStateCreate(pdoc->IsLarge());
-			return reinterpret_cast<sptr_t>(doc);
+			return SPtrFromPtr(doc->AsDocumentEditable());
 		}
 
 	case Message::AddRefDocument:
-		(static_cast<Document *>(PtrFromSPtr(lParam)))->AddRef();
+		(static_cast<IDocumentEditable *>(PtrFromSPtr(lParam)))->AddRef();
 		break;
 
 	case Message::ReleaseDocument:
-		(static_cast<Document *>(PtrFromSPtr(lParam)))->Release();
+		(static_cast<IDocumentEditable *>(PtrFromSPtr(lParam)))->Release();
 		break;
 
 	case Message::GetDocumentOptions: