# UNDF: UNDF-2026-000000804
# UNDF: (leave blank)
# scribus-0003: Selection::addItems m_SelList.contains O(N×M)
#
# In scribus/selection.cpp, addItems() iterates over the items to add (N) and
# for each calls m_SelList.contains(item), which is O(M) on the existing
# QList<QPointer<PageItem>> selection list. Total: O(N×M). For a "Select All"
# on a 5000-item document adding to an existing selection of 2000, this is
# ~10M pointer comparisons.
#
# The single-item addItem() also calls m_SelList.contains(item) — O(M) per
# call — but is less severe since it adds one item at a time.
#
# Fix: build a QSet<PageItem*> from m_SelList before the loop for O(1) lookup,
# or maintain a companion QSet as a class member.
#
# Severity: MEDIUM — triggered on every multi-select operation (rubber-band,
# Select All, group selection); scales with document item count.
--- a/scribus/selection.cpp
+++ b/scribus/selection.cpp
@@ -194,6 +194,12 @@
 bool Selection::addItems(const QList<PageItem *>& items)
 {
 	if (items.isEmpty())
 		return false;

+	// Build hash set for O(1) membership check instead of O(M) QList::contains
+	QSet<PageItem*> existing;
+	existing.reserve(m_SelList.count());
+	for (int i = 0; i < m_SelList.count(); ++i)
+		existing.insert(m_SelList.at(i).data());
+
 	QList< QPointer<PageItem> > toAdd;
 	toAdd.reserve(items.count());
 	for (int i = 0; i < items.count(); ++i)
 	{
 		PageItem* item = items.at(i);
-		if (m_SelList.contains(item))
+		if (existing.contains(item))
 			continue;
 		toAdd.append(item);
+		existing.insert(item);
 		item->setSelected(true);
 	}