AutoNum: a lot of changes

Schemas now get saved with a UUID and do not have to be looked up according to the form. They can be renamed and it gets reflected in existing elements. The GUI for
editing them is now much easier, e.g. forms can be reshuffled. A formula can be applied. Many options now also for conductors and sheets.

sources/qetgraphicsitem/element.cpp

@@ -20,6 +20,7 @@
 #include "../qetproject.h"
 #include "../PropertiesEditor/propertieseditordialog.h"
 #include "../autoNum/assignvariables.h"
+#include "../autoNum/elementautonumschemecommand.h"
 #include "../autoNum/numerotationcontextcommands.h"
 #include "../diagram.h"
 #include "../diagramcommands.h"
@@ -1495,8 +1496,41 @@ void Element::setGroupIndexForElement(Element *elmt, int index)
 	If new information is different of current infotmation emit elementInfoChange
 	@param dc
 */
+namespace {
+/**
+	An element follows a numbering scheme only through a formula: an
+	information context whose formula is emptied (paste with labels
+	erased, the formula deleted by hand...) no longer names one.
+*/
+void dropOrphanFormulaId(DiagramContext &dc)
+{
+	if (dc.contains(QETInformation::ELMT_FORMULA_ID)
+			&& dc.value(QETInformation::ELMT_FORMULA).toString().isEmpty()) {
+		dc.remove(QETInformation::ELMT_FORMULA_ID);
+	}
+}
+} // namespace
+
+/**
+	@brief Element::setFormulaSchemeId
+	Make this element follow the element numbering scheme with uuid @p id,
+	or none if @p id is null, without touching anything else: no label
+	update, no signal, no undo. For QETProject when it ties freshly loaded
+	elements to their schemes.
+*/
+void Element::setFormulaSchemeId(const QUuid &id)
+{
+	if (id.isNull()) {
+		m_data.m_informations.remove(QETInformation::ELMT_FORMULA_ID);
+	} else {
+		m_data.m_informations.addValue(QETInformation::ELMT_FORMULA_ID,
+									   id.toString(), false);
+	}
+}
+
 void Element::setElementInformations(DiagramContext dc)
 {
+	dropOrphanFormulaId(dc);
 	if (m_data.m_informations == dc) {
 		return;
 	}
@@ -1549,6 +1583,7 @@ ElementData Element::elementData() const
  */
 void Element::setElementData(ElementData data)
 {
+	dropOrphanFormulaId(data.m_informations);
 	auto old_info = m_data.m_informations;
 	auto old_plc = m_data.m_type == ElementData::Master && m_data.m_master_type == ElementData::PLC
 		? m_data.plcMasterData() : ElementData::PlcMasterData();
@@ -1776,15 +1811,48 @@ void Element::setUpFormula(bool code_letter, QUndoCommand *parent_undo)
 		QString element_currentAutoNum = diagram()
 				->project()
 				->elementCurrentAutoNum();
+		const QUuid scheme_id = diagram()->project()->elementAutoNumId(element_currentAutoNum);
+		setFormulaSchemeId(formula.isEmpty() ? QUuid() : scheme_id);
 		NumerotationContext nc = diagram()
 				->project()
 				->elementAutoNum(element_currentAutoNum);
-		NumerotationContextCommands ncc (nc);
+
+			//The number given is the first whose label no other element of
+			//the project carries: a counter set back, or an element which
+			//was given a number by hand, must not make a second element
+			//with the same label. The counter then goes on from there.
+		NumerotationContext given = nc;
+		if (!formula.isEmpty())
+		{
+			const QSet<QString> held = ElementAutoNumSchemeCommand::labelsHeldBesides(
+						diagram()->project(), this);
+			for (int attempt = 0 ; !held.isEmpty() && attempt < 100000 ; ++attempt)
+			{
+				autonum::sequentialNumbers probe;
+				autonum::setSequential(formula, probe, given, diagram(), element_currentAutoNum);
+				const QString candidate = autonum::AssignVariables::formulaToLabel(
+							formula, probe, diagram(), this, nullptr);
+				if (candidate.isEmpty() || !held.contains(candidate)) {
+					break;
+				}
+				NumerotationContextCommands step (given);
+				const NumerotationContext advanced = step.next();
+				bool moved = advanced.size() != given.size();
+				for (int i = 0 ; !moved && i < given.size() ; ++i) {
+					moved = advanced.itemAt(i) != given.itemAt(i);
+				}
+				if (!moved) {
+					break;   //a numbering which cannot go on: nothing to skip to
+				}
+				given = advanced;
+			}
+		}
+		NumerotationContextCommands ncc (given);
 
 		m_autoNum_seq.clear();
 		autonum::setSequential(formula,
 					   m_autoNum_seq,
-					   nc,
+					   given,
 					   diagram(),
 					   element_currentAutoNum);