Save a new title, author or revision without building the folio (stage D5)

A folio not built whose own data changed was built to save, with the
folios its links reach. When what changed is only title block fields
nothing on a folio is computed from -- its title, author, date,
revision index, version, file name, template; a formula reads the
folio's label, plant, location, extra fields and grid -- its items as
read are what building it would write: it is saved from them with its
own data as it is now (Diagram::deferredXmlWithHeader()), .qet and
.qetz alike, with the information of its symbols changed through the
project database (or built, when one of those needs it). Any other
change still builds it.

136-folio .qetz, revision index and author set on every folio by a
script: 0.8 s, saved in 6.8 s, no folio built; with every folio built,
the same file. tst_lazyfolios: a new revision on every folio of a .qet
and of a .qetz saved as when built, building only the folios holding a
table (fails, 47 built, when every change counts); a folio whose label
changed is built (fails when none counts). ctest 96/96 eager and lazy;
342 corpus projects save the same in all four arms and export the same.

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

sources/diagram.cpp

@@ -830,6 +830,57 @@ QList<Element *> Diagram::buildSymbols(const QSet<QUuid> &uuids)
 	return built;
 }
 
+namespace {
+	//The title block fields nothing on a folio is computed from: a formula
+	//reads the folio's label, plant, location, extra fields and grid
+	//(autonum::FormulaContext), none of these
+const QStringList ShownOnlyFields = {
+	QStringLiteral("title"), QStringLiteral("author"), QStringLiteral("date"),
+	QStringLiteral("indexrev"), QStringLiteral("version"), QStringLiteral("filename"),
+	QStringLiteral("titleblocktemplate"), QStringLiteral("titleblocktemplateCollection")};
+
+QString headerWithoutShownOnly(const QString &header)
+{
+	QDomDocument document;
+	document.setContent(header);
+	QDomElement root = document.documentElement();
+	for (const QString &field : ShownOnlyFields) root.removeAttribute(field);
+	return document.toString();
+}
+}
+
+/**
+	@brief Diagram::headerChangeShowsOnly
+	@return true if what changed in this folio's own data since it was read
+	(headerChanged()) is only title block fields nothing on the folio is
+	computed from (its title, author, date, revision, file name, template):
+	its items, as read, are what building it would write
+*/
+bool Diagram::headerChangeShowsOnly()
+{
+	return headerWithoutShownOnly(headerXml()) == headerWithoutShownOnly(m_opened_header);
+}
+
+/**
+	@brief Diagram::deferredXmlWithHeader
+	@return this folio, not built, as it saves: its own data as it is now
+	(writeHeader()) and its items as read (deferredXml()), in @p document --
+	when its items are what building it would write (headerChangeShowsOnly())
+*/
+QDomElement Diagram::deferredXmlWithHeader(QDomDocument &document)
+{
+	QDomElement folio = document.createElement(QStringLiteral("diagram"));
+	writeHeader(document, folio);
+	QSet<QString> header_children;
+	for (QDomElement child = folio.firstChildElement() ; !child.isNull() ; child = child.nextSiblingElement())
+		header_children.insert(child.tagName());
+	const QDomElement items = deferredXml();
+	for (QDomElement child = items.firstChildElement() ; !child.isNull() ; child = child.nextSiblingElement())
+		if (!header_children.contains(child.tagName()))
+			folio.appendChild(document.importNode(child, true));
+	return folio;
+}
+
 /**
 	@brief Diagram::deferredXml
 	@return the XML of this folio's items while they are not built: kept

sources/diagram.h

@@ -240,6 +240,8 @@ class Diagram : public QGraphicsScene
 			/// headerChanged() (QETProject::toXml())
 		void rememberHeader() {m_opened_header = headerXml();}
 		bool headerChanged() {return headerXml() != m_opened_header;}
+		bool headerChangeShowsOnly();
+		QDomElement deferredXmlWithHeader(QDomDocument &document);
 		void ensureLoaded();
 		bool buildDeferred();
 			//The last argument is only for a copy fragment: when it is

sources/qetproject.cpp

@@ -2374,9 +2374,17 @@ QDomDocument QETProject::toXml(QHash<int, QByteArray> *kept_folios, QStringList
 				changed << diagram;
 		}
 		buildFolios(changed);
-		for (Diagram *diagram : std::as_const(m_diagrams_list))
-			if (diagram->headerChanged())
+			//-- unless it changed only in what nothing is computed from (its
+			//title, date, revision...): written from its items as read
+			//(Diagram::deferredXmlWithHeader())
+		for (Diagram *diagram : std::as_const(m_diagrams_list)) {
+			if (!diagram->headerChanged()) continue;
+			bool edits_need_build = false;
+			if (!diagram->isLoaded())
+				m_data_base.unbuiltEditsOnFolio(diagram->uuid(), &edits_need_build);
+			if (diagram->isLoaded() || !diagram->headerChangeShowsOnly() || edits_need_build)
 				buildFolioToShow(diagram);
+		}
 			//A table filled from the database saves the size its rows
 			//give it, which any edit can change
 		if (m_edited_since_open)
@@ -2490,6 +2498,24 @@ QDomDocument QETProject::toXml(QHash<int, QByteArray> *kept_folios, QStringList
 			 << "["
 			 << diagram
 			 << "]";
+		if (keep && !diagram->isLoaded() && diagram->headerChanged()) {
+			QDomElement xml_diagram = diagram->deferredXmlWithHeader(xml_doc);
+				//Its symbols whose information changed while it was not built
+			const QHash<QUuid, DiagramContext> edits = m_data_base.unbuiltEditsOnFolio(diagram->uuid());
+			for (const QDomElement &list : QET::findInDomElement(xml_diagram, QStringLiteral("elements")))
+				for (QDomElement element = list.firstChildElement(QStringLiteral("element")) ; !element.isNull() ;
+					 element = element.nextSiblingElement(QStringLiteral("element"))) {
+					const auto edit = edits.constFind(QUuid(element.attribute(QStringLiteral("uuid"))));
+					if (edit == edits.constEnd()) continue;
+					QDomElement information = xml_doc.createElement(QStringLiteral("elementInformations"));
+					edit->toXml(information, QStringLiteral("elementInformation"));
+					const QDomElement old_information = element.firstChildElement(QStringLiteral("elementInformations"));
+					element.replaceChild(information, old_information);   //it has one (unbuiltEditsOnFolio())
+				}
+			xml_diagram.setAttribute("order", order_num ++);
+			project_root.appendChild(xml_diagram);
+			continue;
+		}
 		if (keep && !diagram->isLoaded() && kept_parts) {
 			auto placeholder = xml_doc.createElement(QStringLiteral("diagram"));
 			placeholder.setAttribute(QStringLiteral("qetz-kept-part"), diagram->deferredPart());