Stack cross-references snapped to the bottom of a folio instead of overlapping (#1178)

With "snap to bottom", each master's cross was centred under it at the
bottom of the folio on its own, so two coils in one column drew their
crosses on the same spot and the references printed over each other.

The crosses of a folio are now placed together: when two would overlap,
the one of the higher element goes above the other, so a column of
coils gets its crosses in the same order. Crosses that do not overlap
stay where they were. Moving an element sideways now re-places them
too, since it can move a cross into or out of another's column.

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

sources/qetgraphicsitem/crossrefitem.cpp

@@ -117,6 +117,7 @@ void CrossRefItem::setUpConnection()
 		set=true;
 	else if(m_properties.snapTo() == XRefProperties::Bottom && !m_text && !m_group) //Snap to bottom of element and parent is the element itself
 	{
+		m_update_connection << connect(m_element, &Element::xChanged, this, &CrossRefItem::autoPos);
 		m_update_connection << connect(m_element, &Element::yChanged, this, &CrossRefItem::autoPos);
 		m_update_connection << connect(m_element, &Element::rotationChanged, this, &CrossRefItem::autoPos);
 		set=true;
@@ -329,15 +330,74 @@ void CrossRefItem::autoPos()
 
 	//We calculate the position according to the snapTo of the xrefproperties
 	if (m_properties.snapTo() == XRefProperties::Bottom)
-		QGIUtility::centerToBottomDiagram(this,
-				      m_element,
-				      m_properties.offset() <= 40
-				      ? 5
-				      : m_properties.offset());
+		stackAtBottom();
 	else
 		QGIUtility::centerToParentBottom(this);
 }
 
+/**
+	@brief CrossRefItem::stackAtBottom
+	Places every cross reference of this folio that snaps to the bottom.
+	Each one is centred under its element at the bottom of the folio, and
+	when two would overlap, the one of the higher element goes above the
+	other: several coils in one column get their crosses stacked in the
+	same order as the coils, instead of all on the same spot.
+*/
+void CrossRefItem::stackAtBottom()
+{
+	Diagram *diagram = m_element->diagram();
+	if (!diagram) return;
+
+	QList<CrossRefItem *> xrefs;
+	for (QGraphicsItem *item : diagram->items()) {
+		if (item->type() != CrossRefItem::Type) continue;
+		auto xref = static_cast<CrossRefItem *>(item);
+		if (xref->m_properties.snapTo() == XRefProperties::Bottom
+			&& !xref->m_text && !xref->m_group
+			&& xref->m_element->elementData().m_master_type != ElementData::PLC)
+			xrefs << xref;
+	}
+	if (!xrefs.contains(this)) xrefs << this;
+
+	// The lowest element first, so it keeps the bottom of the folio.
+	// Position, then uuid, so the order is the same on every load.
+	std::sort(xrefs.begin(), xrefs.end(),
+			  [](const CrossRefItem *a, const CrossRefItem *b) {
+		const QPointF pa = a->m_element->sceneBoundingRect().center();
+		const QPointF pb = b->m_element->sceneBoundingRect().center();
+		if (pa.y() != pb.y()) return pa.y() > pb.y();
+		if (pa.x() != pb.x()) return pa.x() < pb.x();
+		return a->m_element->uuid() < b->m_element->uuid();
+	});
+
+	const qreal gap = 5;
+	QList<QRectF> placed;
+	for (CrossRefItem *xref : std::as_const(xrefs)) {
+		const qreal offset = xref->m_properties.offset();
+		QGIUtility::centerToBottomDiagram(xref, xref->m_element,
+										  offset <= 40 ? 5 : offset);
+		if (xref->boundingRect().isEmpty()) continue;
+
+		// Move up past every cross already placed that it would overlap.
+		QRectF rect = xref->sceneBoundingRect();
+		const qreal bottom = rect.bottom();
+		for (bool moved = true; moved; ) {
+			moved = false;
+			for (const QRectF &other : std::as_const(placed))
+				if (rect.left() < other.right() && other.left() < rect.right()
+					&& rect.top() < other.bottom() + gap
+					&& other.top() - gap < rect.bottom()) {
+					rect.moveBottom(other.top() - gap);
+					moved = true;
+				}
+		}
+		if (rect.bottom() != bottom)
+			xref->setPos(xref->parentItem()->mapFromScene(
+				xref->scenePos() + QPointF(0, rect.bottom() - bottom)));
+		placed << rect;
+	}
+}
+
 /**
 	@brief CrossRefItem::sceneEvent
 	@param event

sources/qetgraphicsitem/crossrefitem.h

@@ -58,6 +58,7 @@ class CrossRefItem : public QGraphicsObject
 	private:
 		void init();
 		void setUpConnection();
+		void stackAtBottom();
 	
 	public:
 		enum { Type = UserType + 1009 };