Open with every folio built when the database must come from them

With QET_LAZY_FOLIOS=1, a project whose database cannot be filled from
the file (folios or symbols with no saved uuid, two symbols sharing one,
a folio number using %autonum, wires naming their ends the older way)
had its folios left unbuilt, then built all at once while the database
was filled from them. That is slower than building them as they are
read: a 17 MB project reported on the pull request took 24.8 s to open
instead of 19.2 s, and most files saved by an older version have no
folio uuids.

The file is now checked for those reasons before the folios are read;
when one applies the project opens as without QET_LAZY_FOLIOS. The rarer
reasons, which need the definitions or every folio's links, still fall
back as before.

tst_lazyfolios opens a copy of industrial.qet with one symbol's uuid
given to another, and checks no folio is built after reading.

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

tests/qttest/lazy_folios_probe.cpp

@@ -37,6 +37,8 @@
 #include "../../sources/undocommand/deleteqgraphicsitemcommand.h"
 #include "../../sources/factory/elementfactory.h"
 #include "../../sources/undocommand/addgraphicsobjectcommand.h"
+#include "../../sources/dataBase/projectdatabase.h"
+#include <QDomDocument>
 
 static void check(bool value, const char *message) { if (!value) throw std::runtime_error(message); }
 
@@ -567,6 +569,44 @@ int main(int argc, char **argv)
 			check(potential(wire) == potential(usual_wire), "a potential followed as when built");
 			std::printf("potential through reports: %d wires, %d folios not built\n",
 						int(potential(wire).size()), followed.unloadedFolioCount());
+		}
+			//Two symbols sharing a uuid: the database is filled from the
+			//folios, which builds every one of them, so the project opens
+			//with every folio built rather than building them all later
+		{
+			QFile file(path);
+			check(file.open(QIODevice::ReadOnly), "fixture read");
+			QDomDocument document;
+			check(bool(document.setContent(&file)), "fixture parsed");
+			file.close();
+			check(projectDataBase::documentRefusal(document).isEmpty(), "the fixture fills the database itself");
+			QDomNodeList elements = document.elementsByTagName(QStringLiteral("element"));
+			QList<QDomElement> placed;
+			for (int i = 0; i < elements.size(); ++i) {
+				QDomElement e = elements.at(i).toElement();
+				if (Element::valideXml(e)) placed << e;
+			}
+			check(placed.size() > 1, "two placed symbols");
+			placed.last().setAttribute(QStringLiteral("uuid"), placed.first().attribute(QStringLiteral("uuid")));
+			check(!projectDataBase::documentRefusal(document).isEmpty(), "a shared uuid is seen before the folios are read");
+			const QString shared = output + "/lazy_folios_shared_uuid.qet";
+			QFile out(shared);
+			check(out.open(QIODevice::WriteOnly), "copy written");
+			out.write(document.toByteArray(4));
+			out.close();
+			qputenv("QET_LAZY_FOLIOS", "1");
+			qputenv("QET_LAZY_FOLIOS_TRACE", "1");
+			static int built_late; built_late = 0;
+			const QtMessageHandler previous = qInstallMessageHandler(
+					[](QtMsgType, const QMessageLogContext &, const QString &message) {
+				if (message.contains(QStringLiteral("built for a caller of diagrams()"))) ++built_late;
+			});
+			QETProject opened(shared);
+			qInstallMessageHandler(previous);
+			qunsetenv("QET_LAZY_FOLIOS_TRACE");
+			check(opened.state() == QETProject::Ok, "a project with a shared uuid opens");
+			check(opened.unloadedFolioCount() == 0, "a project with a shared uuid opens with every folio built");
+			check(built_late == 0, "a project with a shared uuid builds its folios as it reads them, not later");
 		}
 		std::printf("PASS: %d folios\n", int(folios.size()));
 	} catch (const std::exception &error) {