Cocoa/ListView: get accurate visibleItems

NSCollectionView.visibleItems() returns the items that have been displayed.

lcl/interfaces/cocoa/cocoacollectionview.pas

@@ -95,6 +95,7 @@ type
 
 function AllocCocoaCollectionView: TCocoaCollectionView;
 function indexPathsWithOneIndex( cv: NSCollectionView; AIndex: Integer ): NSSet;
+function realVisibleItems( cv: NSCollectionView ): NSArray;
 
 implementation
 
@@ -131,6 +132,22 @@ begin
   Result:= NSSet.setWithObject( indexPath );
 end;
 
+// get the Real Visible Items.
+// NSCollectionView returns the items that have been displayed.
+function realVisibleItems( cv: NSCollectionView ): NSArray;
+var
+  visibleRect: NSRect;
+  item: NSCollectionViewItem;
+  items: NSMutableArray Absolute Result;
+begin
+  Result:= NSMutableArray.new;
+  visibleRect:= cv.visibleRect;
+  for item in cv.visibleItems do begin
+    if NSIntersectsRect( item.view.frame, visibleRect ) then
+      items.addObject( item );
+  end;
+end;
+
 { TCocoaCollectionItem }
 
 procedure TCocoaCollectionItem.loadView;
@@ -247,7 +264,7 @@ procedure TCocoaCollectionView.redrawVisibleItems;
 var
   item: NSCollectionViewItem;
 begin
-  for item in self.visibleItems do begin
+  for item in realVisibleItems(self) do begin
     item.view.setNeedsDisplay_( True );
   end;
 end;

lcl/interfaces/cocoa/cocoawscomctrls.pas

@@ -1200,7 +1200,7 @@ var
   item: NSCollectionViewItem;
 begin
   Result:= -1;
-  items:= _collectionView.visibleItems;
+  items:= CocoaCollectionView.realVisibleItems( _collectionView );
   if items.count > 0 then begin
     item:= NSCollectionViewItem(items.firstObject);
     Result:= _collectionView.indexPathForItem(item).item;
@@ -1209,7 +1209,7 @@ end;
 
 function TCocoaWSListView_CollectionViewHandler.GetVisibleRowCount: Integer;
 begin
-  Result:= _collectionView.visibleItems.count;
+  Result:= CocoaCollectionView.realVisibleItems(_collectionView).count;
 end;
 
 procedure TCocoaWSListView_CollectionViewHandler.SelectAll(const AIsSet: Boolean