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qgraphicsitem_cast: replace runtime with compile-time check

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Specialize the cast template for QGraphicsItem, where we can skip the
runtime comparisons of the type.

In addition, replace the runtime check for QGraphicsItem::Type with a
compile time check in the main template.

We need to do both so that we correctly cast up to QGraphicsItem for
custom item types that don't provide their own Type alias.

Pick-to: 6.9 6.8
Change-Id: Ic1bff3404fe890747865ce1349cddbcfebb3b77b
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
This commit is contained in:
Volker Hilsheimer 2025-04-01 12:52:58 +02:00
parent b8de5ad1ed
commit 7af5912e61
1 changed files with 22 additions and 4 deletions
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26
src/widgets/graphicsview/qgraphicsitem.h
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@ -969,15 +969,33 @@ private:
template <class T> inline T qgraphicsitem_cast(QGraphicsItem *item)
{
typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type Item;
return int(Item::Type) == int(QGraphicsItem::Type)
|| (item && int(Item::Type) == item->type()) ? static_cast<T>(item) : nullptr;
constexpr int ItemType = int(Item::Type);
if constexpr (int(Item::Type) == int(QGraphicsItem::Type))
return static_cast<T>(item);
else
return (item && ItemType == item->type()) ? static_cast<T>(item) : nullptr;
}
template <class T> inline T qgraphicsitem_cast(const QGraphicsItem *item)
{
typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type Item;
return int(Item::Type) == int(QGraphicsItem::Type)
|| (item && int(Item::Type) == item->type()) ? static_cast<T>(item) : nullptr;
constexpr int ItemType = int(Item::Type);
if constexpr (ItemType == int(QGraphicsItem::Type))
return static_cast<T>(item);
else
return (item && ItemType == item->type()) ? static_cast<T>(item) : nullptr;
}
template <>
inline QGraphicsItem *qgraphicsitem_cast<QGraphicsItem *>(QGraphicsItem *item)
{
return item;
}
template <>
inline const QGraphicsItem *qgraphicsitem_cast<const QGraphicsItem *>(const QGraphicsItem *item)
{
return item;
}
#ifndef QT_NO_DEBUG_STREAM