autoBreakConductors: share conductors_handled/used_terminals across batch

When multiple elements are pasted or moved in one batch, each call to
autoBreakConductors() now receives the shared state from the previous
call.  This prevents two elements in the same batch from independently
claiming the same conductor, which would result in a double-delete on
redo().

Requested by ispyisail in PR review.

sources/autobreakconductor.cpp

@@ -71,16 +71,15 @@ qreal distanceToSegment(const QPointF &point, const QLineF &segment)
 QSet<Terminal *> autoBreakConductors(
 	Diagram *diagram,
 	Element *element,
-	QUndoCommand *parent)
+	QUndoCommand *parent,
+	QList<Conductor *> &conductors_handled,
+	QSet<Terminal *> &used_terminals)
 {
 	QSet<Terminal *> broken_endpoints;
 
 	if (!diagram->project()->autoBreakConductor())
 		return broken_endpoints;
 
-	QList<Conductor *> conductors_handled;
-	QSet<Terminal *> used_terminals;
-
 	foreach (Terminal *t, element->terminals())
 	{
 		if (used_terminals.contains(t))

sources/autobreakconductor.h

@@ -19,10 +19,12 @@
 #define AUTOBREAKCONDUCTOR_H
 
 #include <QSet>
+#include <QList>
 
 class Diagram;
 class Element;
 class Terminal;
+class Conductor;
 class QUndoCommand;
 
 /**
@@ -34,15 +36,22 @@ class QUndoCommand;
 	conductors are left untouched.
 	@param diagram            the diagram containing the conductors
 	@param element            the element whose terminals trigger breaks
-	@param parent   undo command under which break/reconnect sub-commands
+	@param parent             undo command under which break/reconnect
-	                are created (may be nullptr, in which case no undo is
+	                          sub-commands are created
-	                recorded)
+	@param conductors_handled shared list of conductors already claimed by
+	                          a previous call in the same batch (prevents
+	                          double-processing when multiple elements are
+	                          broken in one pass)
+	@param used_terminals     shared set of terminals already used as
+	                          connect_to or other_terminal in the same batch
 	@return set of terminals that were connected to a broken conductor's
 	        far-end (useful for preventing duplicate auto-connect)
 */
 QSet<Terminal *> autoBreakConductors(
 	Diagram *diagram,
 	Element *element,
-	QUndoCommand *parent);
+	QUndoCommand *parent,
+	QList<Conductor *> &conductors_handled,
+	QSet<Terminal *> &used_terminals);
 
 #endif // AUTOBREAKCONDUCTOR_H

sources/diagramcommands.cpp

@@ -115,8 +115,11 @@ void PasteDiagramCommand::redo()
 		if (diagram->project()->autoBreakConductor())
 		{
 			m_break_cmd = new QUndoCommand();
+			QList<Conductor *> conductors_handled;
+			QSet<Terminal *> used_terminals;
 			for (Element *e : content.m_elements) {
-				autoBreakConductors(diagram, e, m_break_cmd);
+				autoBreakConductors(diagram, e, m_break_cmd,
+						    conductors_handled, used_terminals);
 			}
 			if (m_break_cmd->childCount() == 0) {
 				delete m_break_cmd;

sources/diagramevent/diagrameventaddelement.cpp

@@ -265,7 +265,10 @@ void DiagramEventAddElement::addElement()
 		//Auto break conductor: if a terminal of the new element lies on an existing
 		//conductor, break the conductor and reconnect through the new element's terminal.
 		//Track the endpoints of broken conductors so auto-connect doesn't create duplicates.
-	QSet<Terminal *> broken_endpoints = autoBreakConductors(m_diagram, element, undo_object);
+	QList<Conductor *> conductors_handled;
+	QSet<Terminal *> used_terminals;
+	QSet<Terminal *> broken_endpoints = autoBreakConductors(m_diagram, element, undo_object,
+							    conductors_handled, used_terminals);
 
 		//Auto-connect: collect all aligned pairs first, then filter and process.
 	QList<QPair<Terminal *, Terminal *>> aligned_pairs;

sources/elementsmover.cpp

@@ -184,8 +184,11 @@ void ElementsMover::endMovement()
 		//the element.  The element is already at its final position on screen.
 	if (m_diagram->project()->autoBreakConductor())
 	{
+		QList<Conductor *> conductors_handled;
+		QSet<Terminal *> used_terminals;
 		for (Element *e : m_moved_content.m_elements) {
-			autoBreakConductors(m_diagram, e, undo_object);
+			autoBreakConductors(m_diagram, e, undo_object,
+					    conductors_handled, used_terminals);
 		}
 	}