Remove all code switches for Qt<6 with one exception: caching in titlebordertemplate. Function for caching not called since Qt4; might profit from complete removal.

Another exception: one non-converted code path in projectprintwindow.cpp to be followed-up.

One issue found in the Qt6 code path of diagramview.cpp which has been fixed.

sources/ElementsCollection/elementslocation.cpp

@@ -778,30 +778,6 @@ bool ElementsLocation::setXml(const QDomDocument &xml_document) const
 		//Element doesn't exist, we create the element
 		else
 		{
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)	// ### Qt 6: remove
-			QString path_ = collectionPath(false);
-			QRegExp rx ("^(.*)/(.*\\.elmt)$");
-
-			if (rx.exactMatch(path_)) {
-				return project()
-						->embeddedElementCollection()
-						->addElementDefinition(
-							rx.cap(1),
-							rx.cap(2),
-							xml_document
-							.documentElement());
-			}
-			else {
-				qDebug() << "ElementsLocation::setXml :"
-						" rx don't match";
-			}
-#else
-#if TODO_LIST
-#pragma message("@TODO remove code for QT 6 or later")
-#		pragma message("@TODO ad Core5Compat to Cmake")
-#endif
-			qDebug() << "Help code for QT 6 or later";
-
 			QString			   path_ = collectionPath(false);
 			QRegularExpression rx("^(.*)/(.*\\.elmt)$");
 			QRegularExpressionMatch match = rx.match(path_);
@@ -820,7 +796,6 @@ bool ElementsLocation::setXml(const QDomDocument &xml_document) const
 				qDebug() << "ElementsLocation::setXml :"
 							" rx don't match";
 			}
-#endif
 		}
 	}