Improve performance when searching for blocks w/o draw objects

... by returning when the first object in the lookup range has been found

Follow-up for 3a2a430a

Change-Id: I5cc9a268793eb8d156a39b0a2de557220da96748
Reviewed-on: https://gerrit.libreoffice.org/48395Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>

sc/inc/drwlayer.hxx

@@ -183,6 +183,7 @@ public:
     static void             UpdateCellAnchorFromPositionEnd( const SdrObject &rObj, ScDrawObjData &rAnchor, const ScDocument &rDoc, SCTAB nTab, bool bUseLogicRect = true );
     static ScAnchorType     GetAnchorType( const SdrObject& );
     std::vector<SdrObject*> GetObjectsAnchoredToCell(const ScAddress& rPos);
+    bool                    HasObjectsAnchoredInRange(ScRange& rRange);
     void MoveObject(SdrObject* pObj, ScAddress& rNewPosition);
 
     // positions for detektive lines

sc/source/core/data/column.cxx

@@ -1927,13 +1927,8 @@ bool ScColumn::IsDrawObjectsEmptyBlock(SCROW nStartRow, SCROW nEndRow) const
     if (!pDrawLayer)
         return true;
 
-    for (SCROW nCurrentRow = nStartRow; nCurrentRow <= nEndRow; nCurrentRow++)
-    {
-        ScAddress aCell(nCol, nCurrentRow, nTab);
-        if (!pDrawLayer->GetObjectsAnchoredToCell(aCell).empty())
-            return false;
-    }
-    return true;
+    ScRange aRange(nCol, nStartRow, nTab, nCol, nEndRow, nTab);
+    return !pDrawLayer->HasObjectsAnchoredInRange(aRange);
 }
 
 void ScColumn::SwapCol(ScColumn& rCol)

sc/source/core/data/drwlayer.cxx

@@ -2017,6 +2017,31 @@ std::vector<SdrObject*> ScDrawLayer::GetObjectsAnchoredToCell(const ScAddress& r
     return pObjects;
 }
 
+bool ScDrawLayer::HasObjectsAnchoredInRange(ScRange& rRange)
+{
+    // This only works for one table at a time
+    assert(rRange.aStart.Tab() == rRange.aEnd.Tab());
+
+    SdrPage* pPage = GetPage(static_cast<sal_uInt16>(rRange.aStart.Tab()));
+    if (!pPage || pPage->GetObjCount() < 1)
+        return false;
+
+    SdrObjListIter aIter( *pPage, SdrIterMode::Flat );
+    SdrObject* pObject = aIter.Next();
+    ScDrawObjData* pObjData;
+    while (pObject)
+    {
+        if (!dynamic_cast<SdrCaptionObj*>(pObject)) // Caption objects are handled differently
+        {
+            pObjData = GetObjData(pObject);
+            if (pObjData && rRange.In(pObjData->maStart)) // Object is in given range
+                return true;
+        }
+        pObject = aIter.Next();
+    }
+    return false;
+}
+
 void ScDrawLayer::MoveObject(SdrObject* pObject, ScAddress& rNewPosition)
 {
     // Get anchor data