Place the last element and folio references from the folio's context menu

Right-clicking an empty folio now also offers:

- "Insérer le dernier élément": the same action as Édition and the A
  key, shown once something has been placed.
- "Renvoi de folio": the folio report elements the project already
  uses, read from its embedded collection, with dated copies of the same
  element listed once. A project that has none yet gets the coming and
  going arrows of the common collection. An entry places its element
  where the menu was opened.

The submenu is rebuilt each time the menu opens, from the embedded
collection's XML, not from the folios' scenes. It is left empty, and so
hidden, on a read-only folio.

Discussion #1033.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01G2d2Zi8BfrYRPX88zhaoFG
(cherry picked from commit 94e3f61bf93689066b3964f2316e3c8f1ee7b673)

sources/diagramview.cpp

@@ -44,6 +44,7 @@
 #include <QDropEvent>
 #include <QPainter>
 #include <QPointer>
+#include <QSet>
 #include <algorithm>
 
 /**
@@ -97,6 +98,9 @@ DiagramView::DiagramView(Diagram *diagram, QWidget *parent) :
 	m_create_template = new QAction(tr("Créer un template", "context menu action"), this);
 	connect(m_create_template, &QAction::triggered, this, &DiagramView::createTemplateFromSelection);
 
+		//Filled each time the context menu opens, see updateFolioReportMenu()
+	m_folio_report_menu = new QMenu(tr("Renvoi de folio"), this);
+
 		//setup three separators, to be use in context menu
 	for(int i=0 ; i<3 ; ++i)
 	{
@@ -1471,6 +1475,8 @@ QList<QAction *> DiagramView::contextMenuActions() const
 				//level down where a stray click cannot reach them.
 			list << m_paste_here;
 			list << m_separators.at(0);
+			list << qde->m_insert_last_element;
+			list << m_folio_report_menu->menuAction();
 			list << qde->m_add_item_menu->menuAction();
 			list << m_separators.at(1);
 			list << qde->m_edit_diagram_properties;
@@ -1582,6 +1588,7 @@ void DiagramView::contextMenuEvent(QContextMenuEvent *e)
 	{
 		m_paste_here_pos = menu_pos;
 		m_paste_here->setEnabled(Diagram::clipboardMayContainDiagram());
+		updateFolioReportMenu();
 	}
 
 	QList <QAction *> list = contextMenuActions();
@@ -1594,6 +1601,78 @@ void DiagramView::contextMenuEvent(QContextMenuEvent *e)
 	}
 }
 
+/**
+	@brief DiagramView::updateFolioReportMenu
+	Fill the "Renvoi de folio" submenu of the context menu with the folio
+	report elements this project already uses -- the ones in its embedded
+	collection -- or, when it has none yet, the coming and going arrows of
+	the common collection. An entry places its element where the context
+	menu was opened. Left empty, and so hidden, on a read-only diagram.
+*/
+void DiagramView::updateFolioReportMenu()
+{
+	m_folio_report_menu->clear();
+	if (m_diagram->isReadOnly()) {
+		return;
+	}
+
+	QList<ElementsLocation> locations;
+	QETProject *project = m_diagram->project();
+	XmlElementCollection *collection =
+		project ? project->embeddedElementCollection() : nullptr;
+	if (collection)
+	{
+		QSet<QString> names;
+		const QDomNodeList definitions =
+			collection->root().elementsByTagName(QStringLiteral("definition"));
+		for (int i = 0 ; i < definitions.count() ; ++i)
+		{
+			const QDomElement definition = definitions.at(i).toElement();
+			const QString link_type = definition.attribute(QStringLiteral("link_type"));
+			if (link_type != QLatin1String("next_report")
+			    && link_type != QLatin1String("previous_report")) {
+				continue;
+			}
+			const ElementsLocation location =
+				collection->domToLocation(definition.parentNode().toElement());
+				//A project keeps dated copies of the same element
+				//(01previous_folio-20140521204742.elmt), so list each name once.
+			if (!location.exist() || names.contains(location.name())) {
+				continue;
+			}
+			names.insert(location.name());
+			locations << location;
+		}
+	}
+
+	if (locations.isEmpty())
+	{
+		for (const auto path : {
+			 "common://10_electric/10_allpole/100_folio_referencing/01coming_arrow.elmt",
+			 "common://10_electric/10_allpole/100_folio_referencing/02going_arrow.elmt"})
+		{
+			const ElementsLocation location(QString::fromLatin1(path));
+			if (location.exist()) {
+				locations << location;
+			}
+		}
+	}
+
+	std::sort(locations.begin(), locations.end(),
+		  [](const ElementsLocation &a, const ElementsLocation &b) {
+		return a.name().localeAwareCompare(b.name()) < 0;
+	});
+
+	for (const ElementsLocation &location : std::as_const(locations))
+	{
+		QAction *action = m_folio_report_menu->addAction(location.icon(),
+								 location.name());
+		connect(action, &QAction::triggered, this, [this, location]() {
+			startElementPlacement(location, mapToScene(m_paste_here_pos));
+		});
+	}
+}
+
 /**
  * @brief DiagramView::createTemplateFromSelection
  * Triggered from the context menu to create a new template (macro) from the current selection.