Perf-sc: tdf#100709 SfxPoolItem::IsVoidItem() instead of dynamic_cast

SfxItemSet::GetItemState()
before, Ir:  4 048 231 416
 after, Ir:  2 577 117 709

Change-Id: I26d8b91ad5d851011a670b38b7b98e5582c319cf

3 files changed, 20 insertions, 1 deletions

diff --git a/include/svl/poolitem.hxx b/include/svl/poolitem.hxx
index eae64a52388c..2eefbf1f66cf 100644
--- a/include/svl/poolitem.hxx
+++ b/include/svl/poolitem.hxx
@@ -177,6 +177,13 @@ public:
     SfxItemKind       GetKind() const { return m_nKind; }
     virtual void dumpAsXml(struct _xmlTextWriter* pWriter) const;
 
+    /** Only SfxVoidItem shall and must return true for this.
+
+        This avoids costly calls to dynamic_cast<const SfxVoidItem*>()
+        specifically in SfxItemSet::GetItemState()
+     */
+    virtual bool             IsVoidItem() const;
+
 private:
     SfxPoolItem&             operator=( const SfxPoolItem& ) = delete;
 };
@@ -253,6 +260,9 @@ public:
 
     // create a copy of itself
     virtual SfxPoolItem*    Clone( SfxItemPool *pPool = nullptr ) const override;
+
+    /** Always returns true as this is an SfxVoidItem. */
+    virtual bool            IsVoidItem() const override;
 };
 
 class SVL_DLLPUBLIC SfxSetItem: public SfxPoolItem
diff --git a/svl/source/items/itemset.cxx b/svl/source/items/itemset.cxx
index e69418456833..ddd821d85218 100644
--- a/svl/source/items/itemset.cxx
+++ b/svl/source/items/itemset.cxx
@@ -440,7 +440,7 @@ SfxItemState SfxItemSet::GetItemState( sal_uInt16 nWhich,
                         // Different ones are present
                         return SfxItemState::DONTCARE;
 
-                    if ( dynamic_cast<const SfxVoidItem *>(*ppFnd) != nullptr )
+                    if ( (*ppFnd)->IsVoidItem() )
                         return SfxItemState::DISABLED;
 
                     if (ppItem)
diff --git a/svl/source/items/poolitem.cxx b/svl/source/items/poolitem.cxx
index ba27df64fcf1..5c2c77cae919 100644
--- a/svl/source/items/poolitem.cxx
+++ b/svl/source/items/poolitem.cxx
@@ -136,6 +136,10 @@ SfxPoolItem* SfxPoolItem::CloneSetWhich( sal_uInt16 nNewWhich ) const
     return pItem;
 }
 
+bool SfxPoolItem::IsVoidItem() const
+{
+    return false;
+}
 
 SfxPoolItem* SfxVoidItem::CreateDefault()
 {
@@ -186,6 +190,11 @@ SfxPoolItem* SfxVoidItem::Clone(SfxItemPool *) const
     return new SfxVoidItem(*this);
 }
 
+bool SfxVoidItem::IsVoidItem() const
+{
+    return true;
+}
+
 void SfxPoolItem::ScaleMetrics( long /*lMult*/, long /*lDiv*/ )
 {
 }