Merge #1473: no position columns, a later format opened read-only

A symbol changed on a folio kept as it was needs the place its
information goes back to: its part is checked for the marker
(QetContainer::split()), where the position column said it before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sources/container/qetcontainer.cpp

@@ -169,16 +169,18 @@ bool QetContainer::isZip(const QByteArray &content)
 /**
 	@brief QetContainer::readDocument
 	The project document held in @p content: unzipped and joined for a
-	.qetz, parsed for a .qet.
+	.qetz, parsed for a .qet. @p format, if any: the .qetz's format, 0
+	for a .qet.
 */
 bool QetContainer::readDocument(const QByteArray &content, QDomDocument *document,
-								QString *error, Pictures *pictures)
+								QString *error, Pictures *pictures, int *format)
 {
+	if (format) *format = 0;
 	if (!isZip(content))
 		return parse(content, document, error);
 	QList<QetZip::Entry> entries;
 	return QetZip::fromBytes(content, &entries, error)
-			&& join(entries, document, error, nullptr, pictures);
+			&& join(entries, document, error, nullptr, pictures, format);
 }
 
 QString QetContainer::pictureFile(const QDomElement &image)
@@ -277,6 +279,29 @@ QList<QetZip::Entry> QetContainer::split(const QDomDocument &project, const QStr
 		//A folio written as it was read (<diagram qetz-kept-part="..."/>,
 		//stage D4) keeps its part and, through
 		//@p kept_from's project.sqlite, its rows
+		//A symbol changed on a folio kept as it was gets its information
+		//rows written anew: its part must have the place they go back to
+	for (const QDomElement &diagram : childElements(root, QStringLiteral("diagram")))
+	{
+		const QList<QDomElement> edited = childElements(diagram, QStringLiteral("qetz-edited-element"));
+		if (edited.isEmpty()) continue;
+		QDomDocument part;
+		if (!parse(kept_from.value(diagram.attribute(QStringLiteral("qetz-kept-part"))), &part, error))
+			return {};
+		QSet<QString> placed;
+		const QDomNodeList elements = part.elementsByTagName(QStringLiteral("element"));
+		for (int i = 0 ; i < elements.size() ; ++i) {
+			const QDomElement element = elements.at(i).toElement();
+			for (const QDomElement &marker : childElements(element, QStringLiteral("qetz-db")))
+				if (marker.attribute(QStringLiteral("block")) == QLatin1String("elementInformations"))
+					placed.insert(element.attribute(QStringLiteral("uuid")));
+		}
+		for (const QDomElement &symbol : edited)
+			if (!placed.contains(symbol.attribute(QStringLiteral("uuid")))) {
+				setError(error, QStringLiteral("a symbol changed on a folio kept as it was has no place for its information"));
+				return {};
+			}
+	}
 	const QByteArray database = QetContainerDb::extract(
 				root, error, kept_from.value(QStringLiteral("project.sqlite")));
 	if (database.isEmpty())
@@ -391,10 +416,11 @@ QList<QetZip::Entry> QetContainer::split(const QDomDocument &project, const QStr
 	nothing names are ignored, so a later format may add some.
 	With @p pictures, the pictures stay out of the document: see the
 	namespace. With @p folio_files, the part each folio was read from, in
-	order.
+	order. @p format, if any: the format the file says it is, above Format
+	for a later one this may read (its min-reader allows it).
 */
 bool QetContainer::join(const QList<QetZip::Entry> &entries, QDomDocument *project, QString *error,
-						QStringList *folio_files, Pictures *pictures)
+						QStringList *folio_files, Pictures *pictures, int *format)
 {
 	QHash<QString, QByteArray> files;
 	for (const QetZip::Entry &entry : entries)
@@ -415,6 +441,8 @@ bool QetContainer::join(const QList<QetZip::Entry> &entries, QDomDocument *proje
 				 .arg(Format));
 		return false;
 	}
+	if (format)
+		*format = manifest.documentElement().attribute(QStringLiteral("format")).toInt();
 
 	if (!parse(files.value(QStringLiteral("project.xml")), project, error))
 		return false;

sources/container/qetcontainer.h

@@ -57,12 +57,15 @@ namespace QetContainer
 		/// unless their min-reader allows this one.
 	constexpr int Format = 4;
 		/// 3: the database's rows keyed by the items' uuids, true/false as
-		/// 1/0, its PRAGMA user_version the format.
+		/// 1/0, its PRAGMA user_version the format, the symbols' type left
+		/// in the folio files, no column for where a block sat.
 		/// 4: what QElectroTech computes left out of the folios
 		/// (dropComputed()), the tables written without keys or indexes.
 		/// project.sqlite holds the engineering data once: QElectroTech's
 		/// own project database is built from it when the project opens.
-		/// Formats 2 and 3 are still read.
+		/// Formats 2 and 3 are still read; a later format whose min-reader
+		/// allows this one is read too, and said so through join()'s
+		/// @p format.
 
 	QList<QetZip::Entry> split(const QDomDocument &project,
 							   const QString &writer = QString(),
@@ -70,7 +73,7 @@ namespace QetContainer
 							   const QHash<QString, QByteArray> &kept_from = QHash<QString, QByteArray>());
 	bool join(const QList<QetZip::Entry> &entries, QDomDocument *project,
 			  QString *error = nullptr, QStringList *folio_files = nullptr,
-			  Pictures *pictures = nullptr);
+			  Pictures *pictures = nullptr, int *format = nullptr);
 		/// The file join() left the picture of @p image in, or an empty string
 	QString pictureFile(const QDomElement &image);
 
@@ -84,7 +87,7 @@ namespace QetContainer
 	bool isZip(const QByteArray &content);
 		/// The project document in @p content, a .qet or a .qetz
 	bool readDocument(const QByteArray &content, QDomDocument *document,
-					  QString *error = nullptr, Pictures *pictures = nullptr);
+					  QString *error = nullptr, Pictures *pictures = nullptr, int *format = nullptr);
 }
 
 #endif // QETCONTAINER_H

sources/container/qetcontainerdb.cpp

@@ -60,6 +60,15 @@ bool replaceMarker(QDomElement parent, const QDomElement &block)
 	return false;
 }
 
+	//true if @p parent holds the marker of a block @p tag moved out: where
+	//the block goes back, and that it was there at all
+bool hasMarker(const QDomElement &parent, const QString &tag)
+{
+	for (QDomElement m = parent.firstChildElement(MarkerTag) ; !m.isNull() ; m = m.nextSiblingElement(MarkerTag))
+		if (m.attribute(MarkerBlock) == tag) return true;
+	return false;
+}
+
 const QStringList FolioData = {
 	QStringLiteral("title"), QStringLiteral("author"), QStringLiteral("date"),
 	QStringLiteral("folio"), QStringLiteral("indexrev"), QStringLiteral("filename"),
@@ -116,11 +125,11 @@ QString schema()
 		"CREATE TABLE meta (key TEXT PRIMARY KEY, value TEXT);"
 		"CREATE TABLE project_property (ord INTEGER PRIMARY KEY, name TEXT, value TEXT, attrs TEXT);"
 		"CREATE TABLE folio (uuid TEXT PRIMARY KEY, pos INTEGER NOT NULL UNIQUE, %1,"
-		" props_at INTEGER, props_attrs TEXT);"
+		" props_attrs TEXT);"
 		"CREATE TABLE folio_property (folio_uuid TEXT NOT NULL REFERENCES folio, ord INTEGER NOT NULL,"
 		" name TEXT, value TEXT, attrs TEXT, PRIMARY KEY (folio_uuid, ord));"
 		"CREATE TABLE element (uuid TEXT PRIMARY KEY, folio_uuid TEXT NOT NULL REFERENCES folio, %2,"
-		" info_at INTEGER, info_attrs TEXT, links_at INTEGER, links_attrs TEXT);"
+		" info_attrs TEXT, links_attrs TEXT);"
 		"CREATE TABLE element_info (element_uuid TEXT NOT NULL REFERENCES element, ord INTEGER NOT NULL,"
 		" name TEXT, value TEXT, show INTEGER, attrs TEXT, PRIMARY KEY (element_uuid, ord));"
 		"CREATE TABLE link (element_uuid TEXT NOT NULL REFERENCES element, ord INTEGER NOT NULL,"
@@ -320,15 +329,6 @@ bool listBlock(const QDomElement &block, const QString &entry)
 	return true;
 }
 
-int childIndex(const QDomNode &child)
-{
-	int i = 0;
-	for (QDomNode n = child.parentNode().firstChild() ; !n.isNull() ; n = n.nextSibling(), ++i)
-		if (n == child) return i;
-	return -1;
-}
-
-
 	//The attributes @p names of @p e, taken out of it; one that cannot be
 	//stored stays, its value null
 QVariantList take(QDomElement e, const QStringList &names)
@@ -587,9 +587,11 @@ bool openDatabase(Database &db, const QByteArray &database, QString *error)
 		Statement format(db, QStringLiteral("SELECT value FROM meta WHERE key = 'format'"));
 		const QString text = format.next() ? format.value(0).toString() : QString();
 		db.m_format = text.toInt();
-		if (db.m_format < 2 || db.m_format > QetContainer::Format) {
-			setError(error, QStringLiteral("the project database is of format %1, this reads 2 to %2")
-					 .arg(text).arg(QetContainer::Format));
+			//A later format is read when the manifest's min-reader allows it
+			//(QetContainer::join()): its writer kept what this reads
+		if (db.m_format < 2) {
+			setError(error, QStringLiteral("the project database is of format %1, this reads format 2 on")
+					 .arg(text));
 			return false;
 		}
 	}
@@ -666,23 +668,25 @@ bool restoreDiagram(Database &db, QDomElement d, UsedRows &used, QString *error)
 	const QString id = keyOf(db, d, FolioAttribute);
 	if (id.isEmpty()) return true;
 	if (!used.use(used.folios, id, QStringLiteral("folio"), error)) return false;
-	Statement f(db, QStringLiteral("SELECT %1, props_at, props_attrs FROM folio WHERE %2 = ?")
+	Statement f(db, QStringLiteral("SELECT %1, props_attrs FROM folio WHERE %2 = ?")
 				.arg(quoted(FolioData), db.folioKey()));
 	f.bind({id});
 	if (!f.next()) { setError(error, QStringLiteral("folio %1 is not in the database").arg(id)); return false; }
 	QVariantList values;
-	for (int i = 0 ; i < FolioData.size() + 2 ; ++i) values << f.value(i);
+	for (int i = 0 ; i < FolioData.size() + 1 ; ++i) values << f.value(i);
 	put(d, FolioData, values, 0);
-	if (!values.at(FolioData.size()).isNull()) {
+		//A moved block goes back where its marker is: the marker says it
+		//was there
+	if (hasMarker(d, QStringLiteral("properties"))) {
 		QDomElement props = document.createElement(QStringLiteral("properties"));
-		setAttributesJson(props, values.at(FolioData.size() + 1));
+		setAttributesJson(props, values.at(FolioData.size()));
 		Statement p(db, QStringLiteral("SELECT name, value, attrs FROM folio_property WHERE %1 = ? ORDER BY ord")
 					.arg(db.folioRef()));
 		p.bind({id});
 		while (p.next())
 			props.appendChild(entry(p.value(0), QStringLiteral("name"), p.value(1), p.value(2),
 									QStringLiteral("property")));
-		restoreWhitespace(props, values.at(FolioData.size() + 1));
+		restoreWhitespace(props, values.at(FolioData.size()));
 		if (!replaceMarker(d, props)) {
 			setError(error, QStringLiteral("folio %1's properties have no place").arg(id));
 			return false;
@@ -696,40 +700,40 @@ bool restoreDiagram(Database &db, QDomElement d, UsedRows &used, QString *error)
 			const QString key = keyOf(db, e, KeyAttribute);
 			if (key.isEmpty()) continue;
 			if (!used.use(used.elements, key, QStringLiteral("symbol"), error)) return false;
-			Statement s(db, QStringLiteral("SELECT %1, info_at, info_attrs, links_at, links_attrs, %2 FROM element WHERE %3 = ?")
+			Statement s(db, QStringLiteral("SELECT %1, info_attrs, links_attrs, %2 FROM element WHERE %3 = ?")
 						.arg(quoted(element_data), db.folioRef(), db.itemKey()));
 			s.bind({key});
 			if (!s.next()) { setError(error, QStringLiteral("symbol %1 is not in the database").arg(key)); return false; }
-			if (s.value(element_data.size() + 4).toString() != id) {
+			if (s.value(element_data.size() + 2).toString() != id) {
 				setError(error, QStringLiteral("symbol %1 is on folio %2, the database says another").arg(key, id));
 				return false;
 			}
 			QVariantList v;
-			for (int i = 0 ; i < element_data.size() + 4 ; ++i) v << s.value(i);
+			for (int i = 0 ; i < element_data.size() + 2 ; ++i) v << s.value(i);
 			put(e, element_data, v, 0);
 			const int n = element_data.size();
 			QDomElement info, links;
-			if (!v.at(n).isNull()) {
+			if (hasMarker(e, QStringLiteral("elementInformations"))) {
 				info = document.createElement(QStringLiteral("elementInformations"));
-				setAttributesJson(info, v.at(n + 1));
+				setAttributesJson(info, v.at(n));
 				Statement i(db, QStringLiteral("SELECT name, value, attrs, %1 FROM element_info WHERE %2 = ? ORDER BY ord")
 							.arg(db.showColumn(), db.elementRef()));
 				i.bind({key});
 				while (i.next())
 					info.appendChild(entry(i.value(0), QStringLiteral("name"), i.value(1), i.value(2),
 										   QStringLiteral("elementInformation"), i.value(3)));
-				restoreWhitespace(info, v.at(n + 1));
+				restoreWhitespace(info, v.at(n));
 			}
-			if (!v.at(n + 2).isNull()) {
+			if (hasMarker(e, QStringLiteral("links_uuids"))) {
 				links = document.createElement(QStringLiteral("links_uuids"));
-				setAttributesJson(links, v.at(n + 3));
+				setAttributesJson(links, v.at(n + 1));
 				Statement l(db, QStringLiteral("SELECT linked_uuid, attrs FROM link WHERE %1 = ? ORDER BY ord")
 							.arg(db.elementRef()));
 				l.bind({key});
 				while (l.next())
 					links.appendChild(entry(l.value(0), QStringLiteral("uuid"), QVariant(), l.value(1),
 											QStringLiteral("link_uuid")));
-				restoreWhitespace(links, v.at(n + 3));
+				restoreWhitespace(links, v.at(n + 1));
 			}
 			if ((!info.isNull() && !replaceMarker(e, info))
 				|| (!links.isNull() && !replaceMarker(e, links))) {
@@ -829,9 +833,9 @@ QByteArray QetContainerDb::extract(QDomElement project, QString *error, const QB
 
 	Statement meta(db, QStringLiteral("INSERT INTO meta VALUES (?,?)"));
 	Statement project_property(db, QStringLiteral("INSERT INTO project_property VALUES (?,?,?,?)"));
-	Statement folio(db, QStringLiteral("INSERT INTO folio VALUES (?,?,%1,?,?)").arg(placeholders(FolioData.size())));
+	Statement folio(db, QStringLiteral("INSERT INTO folio VALUES (?,?,%1,?)").arg(placeholders(FolioData.size())));
 	Statement folio_property(db, QStringLiteral("INSERT INTO folio_property VALUES (?,?,?,?,?)"));
-	Statement element(db, QStringLiteral("INSERT INTO element VALUES (?,?,%1,?,?,?,?)").arg(placeholders(ElementData.size())));
+	Statement element(db, QStringLiteral("INSERT INTO element VALUES (?,?,%1,?,?)").arg(placeholders(ElementData.size())));
 	Statement element_info(db, QStringLiteral("INSERT INTO element_info VALUES (?,?,?,?,?,?)"));
 	Statement link(db, QStringLiteral("INSERT INTO link VALUES (?,?,?,?)"));
 	Statement conductor(db, QStringLiteral("INSERT INTO conductor VALUES (?,?,%1)").arg(placeholders(ConductorData.size())));
@@ -873,7 +877,6 @@ QByteArray QetContainerDb::extract(QDomElement project, QString *error, const QB
 		//Project properties
 	const QDomElement project_props = project.firstChildElement(QStringLiteral("properties"));
 	if (!project_props.isNull() && listBlock(project_props, QStringLiteral("property"))) {
-		ok = ok && meta.run({QStringLiteral("props_at"), QString::number(childIndex(project_props))});
 		ok = ok && meta.run({QStringLiteral("props_attrs"), blockJson(project_props)});
 		int ord = 0;
 		for (QDomElement p : children(project_props, QStringLiteral("property"))) {
@@ -925,7 +928,7 @@ QByteArray QetContainerDb::extract(QDomElement project, QString *error, const QB
 				setError(error, QStringLiteral("a folio kept as it was, without its database"));
 				return {};
 			}
-			Statement copy(db, QStringLiteral("INSERT INTO folio SELECT uuid, ?, %1, props_at, props_attrs "
+			Statement copy(db, QStringLiteral("INSERT INTO folio SELECT uuid, ?, %1, props_attrs "
 											  "FROM old.folio WHERE uuid = ?").arg(quoted(FolioData)));
 			ok = ok && copy.run({pos, id}) && sqlite3_changes(db.m_db) == 1;
 			for (const QString &sql : {
@@ -942,7 +945,8 @@ QByteArray QetContainerDb::extract(QDomElement project, QString *error, const QB
 				//Its symbols whose information changed since (QETProject::toXml()):
 				//their information rows written as a symbol's block writes them
 			for (const QDomElement &edited : children(d, QStringLiteral("qetz-edited-element"))) {
-				Statement find(db, QStringLiteral("SELECT uuid FROM element WHERE folio_uuid = ? AND uuid = ? AND info_at IS NOT NULL"));
+					//Its part has the place they go back to (QetContainer::split())
+				Statement find(db, QStringLiteral("SELECT uuid FROM element WHERE folio_uuid = ? AND uuid = ?"));
 				find.bind({id, edited.attribute(QStringLiteral("uuid"))});
 				if (!find.next()) {
 					setError(error, QStringLiteral("a symbol changed on folio %1 kept as it was is not in its database").arg(id));
@@ -979,8 +983,7 @@ QByteArray QetContainerDb::extract(QDomElement project, QString *error, const QB
 		row += take(d, FolioData);
 		QDomElement props = d.firstChildElement(QStringLiteral("properties"));
 		const bool move_props = !props.isNull() && listBlock(props, QStringLiteral("property"));
-		row << (move_props ? QVariant(childIndex(props)) : QVariant())
-			<< (move_props ? blockJson(props) : QVariant());
+		row << (move_props ? blockJson(props) : QVariant());
 		ok = ok && folio.run(row);
 		if (move_props) {
 			moveProperties(props, folio_property, {id});
@@ -998,24 +1001,20 @@ QByteArray QetContainerDb::extract(QDomElement project, QString *error, const QB
 				QDomElement links = e.firstChildElement(QStringLiteral("links_uuids"));
 				if (!info.isNull() && !listBlock(info, QStringLiteral("elementInformation"))) info = QDomElement();
 				if (!links.isNull() && !listBlock(links, QStringLiteral("link_uuid"))) links = QDomElement();
-				const int info_at = info.isNull() ? -1 : childIndex(info);
-				const int links_at = links.isNull() ? -1 : childIndex(links);
-				erow << (info_at < 0 ? QVariant() : QVariant(info_at))
-					 << (info_at < 0 ? QVariant() : blockJson(info))
-					 << (links_at < 0 ? QVariant() : QVariant(links_at))
-					 << (links_at < 0 ? QVariant() : blockJson(links));
+				erow << (info.isNull() ? QVariant() : blockJson(info))
+					 << (links.isNull() ? QVariant() : blockJson(links));
 				ok = ok && element.run(erow);
-				if (info_at >= 0)
+				if (!info.isNull())
 					moveInformation(info, key);
-				if (links_at >= 0) {
+				if (!links.isNull()) {
 					int ord = 0;
 					for (QDomElement l : children(links, QStringLiteral("link_uuid")))
 						ok = ok && link.run({key, ord++, l.hasAttribute(QStringLiteral("uuid"))
 												? QVariant(l.attribute(QStringLiteral("uuid"))) : QVariant(),
 											 attributesJson(l, {QStringLiteral("uuid")}, QStringLiteral("link_uuid"))});
 				}
-				if (info_at >= 0) leaveMarker(info);
-				if (links_at >= 0) leaveMarker(links);
+				if (!info.isNull()) leaveMarker(info);
+				if (!links.isNull()) leaveMarker(links);
 				if (!own_key) e.setAttribute(KeyAttribute, key);
 			}
 		}
@@ -1088,7 +1087,7 @@ bool QetContainerDb::restore(QDomElement project, const QByteArray &database, QS
 		Statement s(db, QStringLiteral("SELECT key, value FROM meta"));
 		while (s.next()) meta.insert(s.value(0).toString(), s.value(1));
 	}
-	if (meta.contains(QStringLiteral("props_at"))) {
+	if (hasMarker(project, QStringLiteral("properties"))) {
 		QDomElement props = document.createElement(QStringLiteral("properties"));
 		setAttributesJson(props, meta.value(QStringLiteral("props_attrs")));
 		Statement s(db, QStringLiteral("SELECT name, value, attrs FROM project_property ORDER BY ord"));
@@ -1142,8 +1141,8 @@ bool QetContainerDb::currentFormat(const QByteArray &database)
 		return false;
 		//Its rows are copied as they are: the same columns as this writes
 	const QList<std::pair<QString, int>> columns = {
-		{QStringLiteral("folio"), int(FolioData.size()) + 4},
-		{QStringLiteral("element"), int(ElementData.size()) + 6},
+		{QStringLiteral("folio"), int(FolioData.size()) + 3},
+		{QStringLiteral("element"), int(ElementData.size()) + 4},
 		{QStringLiteral("conductor"), int(ConductorData.size()) + 2}};
 	for (const auto &table : columns) {
 		Statement s(db, QStringLiteral("SELECT count(*) FROM pragma_table_info('%1')").arg(table.first));

sources/qetdiagrameditor.cpp

@@ -1984,6 +1984,16 @@ bool QETDiagramEditor::openAndAddProject(
 	addProject(project);
 	DialogWaiting::dropInstance();
 
+	if (interactive && project->isFromLaterVersion()) {
+		QET::QetMessageBox::warning(
+			this,
+			tr("Opening the file read-only", "message box title"),
+			tr("This project was saved by a later version of QElectroTech. "
+			   "It is opened read-only, so that saving it cannot lose what "
+			   "this version does not know. Use Save As to keep a copy "
+			   "in this version's format."));
+	}
+
 		//Report font descriptions which could not be read as-is (written by
 		//an incompatible Qt version or corrupted), so the user learns about
 		//it from somewhere else than the console. See issue #553.

sources/qetproject.cpp

@@ -484,11 +484,12 @@ QETProject::ProjectState QETProject::openFile(QFile *file)
 	m_container_files.clear();
 	m_folio_parts.clear();
 	bool read = false;
+	int container_format = 0;
 	if (QetContainer::isZip(content)) {
 		QList<QetZip::Entry> entries;
 		read = QetZip::fromBytes(content, &entries, &read_error)
 				&& QetContainer::join(entries, &xml_project, &read_error, &m_folio_parts,
-									  &m_container_pictures);
+									  &m_container_pictures, &container_format);
 		if (read)
 			for (const QetZip::Entry &entry : std::as_const(entries))
 				m_container_files.insert(entry.name, entry.data);
@@ -530,9 +531,16 @@ QETProject::ProjectState QETProject::openFile(QFile *file)
 			<< xml_parse_ms / 1000.0 << ", content "
 			<< (total_ms - xml_parse_ms) / 1000.0 << ")";
 
-	if (!fi.isWritable()) {
+		//Written by a later QElectroTech that lets this one read it: saving
+		//here would drop what this version does not know
+	m_from_later_version = container_format > QetContainer::Format;
+	if (!fi.isWritable() || m_from_later_version) {
 		setReadOnly(true);
 	}
+	if (m_from_later_version) {
+		qInfo().noquote() << QStringLiteral("Project %1 is of .qetz format %2 (this version writes %3): opened read-only")
+							 .arg(fi.fileName()).arg(container_format).arg(QetContainer::Format);
+	}
 	if(opened_here) {
 		file->close();
 	}

sources/qetproject.h

@@ -334,6 +334,8 @@ class QETProject : public QObject
 		bool close();
 		QETResult write();
 		bool isReadOnly() const;
+			/// Opened from a .qetz of a later format (opened read-only)
+		bool isFromLaterVersion() const {return m_from_later_version;}
 		void setReadOnly(bool);
 		bool isEmpty() const;
 		ElementsLocation importElement(ElementsLocation &location);
@@ -490,6 +492,7 @@ class QETProject : public QObject
 		bool m_modified = false;
 			/// Whether the project is read only
 		bool m_read_only = false;
+		bool m_from_later_version = false;
 			/// Filepath for which this project is considered read only
 		QString read_only_file_path_;
 			/// Default dimensions and properties for new diagrams created within the project

tests/qttest/tst_qetcontainer.cpp

@@ -379,6 +379,43 @@ private slots:
 	}
 
 	// A file whose manifest needs a later reader is refused, not half read
+	// A later format whose min-reader allows this one opens, and join() says
+	// it is later: QElectroTech opens it read-only
+	void laterFormatAllowedRead()
+	{
+		QDomDocument original;
+		QList<QetZip::Entry> entries = splitFile(QStringLiteral(QET_EXAMPLES_DIR "/industrial.qet"), &original);
+		QVERIFY(!entries.isEmpty());
+		const int later = QetContainer::Format + 1;
+		for (QetZip::Entry &e : entries)
+			if (e.name == QLatin1String("manifest.xml"))
+				e.data = QString::fromUtf8(e.data).replace(QRegularExpression(QStringLiteral(" format=\"\\d+\"")),
+														   QStringLiteral(" format=\"%1\"").arg(later)).toUtf8();
+		alterDatabase(entries, QStringLiteral("UPDATE meta SET value = '%1' WHERE key = 'format'")
+					  .arg(later).toUtf8().constData());
+		QDomDocument back;
+		QString error;
+		int format = 0;
+		QVERIFY2(QetContainer::join(entries, &back, &error, nullptr, nullptr, &format), qPrintable(error));
+		QCOMPARE(format, later);
+		const QString d = difference(withoutComputed(original).documentElement(), back.documentElement(), QString());
+		QVERIFY2(d.isEmpty(), qPrintable(d));
+	}
+
+	// The database holds data, not where a block sat in the XML: the folio
+	// file's marker says where it goes back
+	void noPositionColumns()
+	{
+		QDomDocument original;
+		const QList<QetZip::Entry> entries = splitFile(QStringLiteral(QET_EXAMPLES_DIR "/industrial.qet"), &original);
+		const QByteArray database = entry(entries, QStringLiteral("project.sqlite"));
+		QCOMPARE(query(database, "SELECT group_concat(name) FROM pragma_table_info('element')"),
+				 QStringLiteral("uuid,folio_uuid,prefix,freezeLabel,info_attrs,links_attrs"));
+		QCOMPARE(query(database, "SELECT count(*) FROM pragma_table_info('folio') WHERE name LIKE '%_at'"),
+				 QStringLiteral("0"));
+		QCOMPARE(query(database, "SELECT count(*) FROM meta WHERE key = 'props_at'"), QStringLiteral("0"));
+	}
+
 	void laterFormatRefused()
 	{
 		QDomDocument original;
@@ -455,8 +492,8 @@ private slots:
 		QTest::addColumn<QByteArray>("sql");
 		QTest::addColumn<QString>("said");
 		QTest::newRow("symbol row of no symbol")
-				<< QByteArray("INSERT INTO element SELECT 'x', folio_uuid, prefix, freezeLabel, info_at, info_attrs,"
-							  " links_at, links_attrs FROM element LIMIT 1")
+				<< QByteArray("INSERT INTO element SELECT 'x', folio_uuid, prefix, freezeLabel, info_attrs,"
+							  " links_attrs FROM element LIMIT 1")
 				<< QStringLiteral("symbol rows");
 		QTest::newRow("symbol row twice")
 				<< QByteArray("INSERT INTO element SELECT * FROM element LIMIT 1")