QC: add TCanvas into mergeable checks (#13897)

Co-authored-by: Michal Tichák <michal.tichak@cern.ch>

Author: justonedev1

Utilities/Mergers/include/Mergers/Mergeable.h

@@ -42,7 +42,7 @@ constexpr bool IsDerivedFrom = (std::derived_from<T, Ts> || ...);
 //
 // \parameter T type to be restricted
 template <typename T>
-concept Mergeable = IsDerivedFrom<std::remove_pointer_t<T>, mergers::MergeInterface, TCollection, TH1, TTree, TGraph, TEfficiency, THnBase>;
+concept Mergeable = IsDerivedFrom<std::remove_pointer_t<T>, mergers::MergeInterface, TCollection, TH1, TTree, TGraph, TEfficiency, THnBase, TCanvas>;
 
 // \brief runtime check whether TObject is mergeable
 bool isMergeable(TObject* obj);

Utilities/Mergers/src/Mergeable.cxx

@@ -9,6 +9,7 @@
 // granted to it by virtue of its status as an Intergovernmental Organization
 // or submit itself to any jurisdiction.
 
+#include <TCanvas.h>
 #include <TCollection.h>
 #include <TEfficiency.h>
 #include <TGraph.h>
@@ -30,7 +31,8 @@ bool isMergeable(TObject* obj)
          obj->InheritsFrom(THnBase::Class()) ||
          obj->InheritsFrom(TTree::Class()) ||
          obj->InheritsFrom(TGraph::Class()) ||
-         obj->InheritsFrom(TEfficiency::Class());
+         obj->InheritsFrom(TEfficiency::Class()) ||
+         obj->InheritsFrom(TCanvas::Class());
 }
 
 } // namespace o2::mergers