Cache group view geometry -- speed up instance view by caching sizes of stuff

gui/groupview/GroupView.cpp

@@ -8,6 +8,7 @@
 #include <QPersistentModelIndex>
 #include <QDrag>
 #include <QMimeData>
+#include <QCache>
 #include <QScrollBar>
 
 #include "Group.h"
@@ -68,6 +69,7 @@ void GroupView::rowsAboutToBeRemoved(const QModelIndex &parent, int start, int e
 
 void GroupView::updateGeometries()
 {
+	geometryCache.clear();
 	int previousScroll = verticalScrollBar()->value();
 
 	QMap<QString, Group *> cats;
@@ -658,6 +660,13 @@ QRect GroupView::geometryRect(const QModelIndex &index) const
 		return QRect();
 	}
 
+	int row = index.row();
+	if(geometryCache.contains(row))
+	{
+		return *geometryCache[row];
+	}
+	else
+	{
 		const Group *cat = category(index);
 		QPair<int, int> pos = categoryInternalPosition(index);
 		int x = pos.first;
@@ -667,9 +676,10 @@ QRect GroupView::geometryRect(const QModelIndex &index) const
 		out.setTop(cat->verticalPosition() + cat->headerHeight() + 5 + categoryInternalRowTop(index));
 		out.setLeft(m_spacing + x * (itemWidth() + m_spacing));
 		out.setSize(itemDelegate()->sizeHint(viewOptions(), index));
-
+		const_cast<QCache<int, QRect>&>(geometryCache).insert(row, new QRect(out));
 		return out;
 	}
+}
 
 /*
 void CategorizedView::startCategoryEditor(Category *category)

gui/groupview/GroupView.h

@@ -3,6 +3,7 @@
 #include <QListView>
 #include <QLineEdit>
 #include <QScrollBar>
+#include <QCache>
 
 struct GroupViewRoles
 {
@@ -128,6 +129,7 @@ private: /* variables */
 	QItemSelectionModel::SelectionFlag m_ctrlDragSelectionFlag;
 	QPoint m_lastDragPosition;
 	int m_spacing = 5;
+	QCache<int, QRect> geometryCache;
 
 private: /* methods */
 	QPair<int, int> categoryInternalPosition(const QModelIndex &index) const;