[Common] allow access to the reference comparator plots in derived classes

The changes allow to use the ReferenceComparatorTask as a base class,
providing access to the reference comparison plots for the derived classes.

A typical use case would be a post-processing task that produces some
derived plots, which also need to compared with some reference.
With the current production code, this involves adding a dedicated
ReferenceComparatorTask in the workflow, that fetches the plots from the
post-processing task from the QCDB.

This commit allows to solve the above problem by deriving the post-processing
task from the ReferenceComparatorTask, such that the reference comparison
plots can be filled directly by the derived task, without going through
the QCDB.

This is achieved with the following two changes:
* addition of a function that exposes the reference comparison plots in the ReferenceComparatorTask interface
* storage of the pointer to the reference histogram in the ReferenceComparatorPlot object, such that it does not need to be passed to the `update()` method

Author: aferrero2707

Modules/Common/include/Common/ReferenceComparatorPlot.h

@@ -48,7 +48,7 @@ class ReferenceComparatorPlot
   virtual ~ReferenceComparatorPlot() = default;
 
   TObject* getMainCanvas();
-  void update(TH1* histogram, TH1* referenceHistogram);
+  void update(TH1* histogram);
 
  private:
   std::shared_ptr<ReferenceComparatorPlotImpl> mImplementation;

Modules/Common/include/Common/ReferenceComparatorTask.h

@@ -50,6 +50,9 @@ class ReferenceComparatorTask : public quality_control::postprocessing::PostProc
   void update(quality_control::postprocessing::Trigger, framework::ServiceRegistryRef) override;
   void finalize(quality_control::postprocessing::Trigger, framework::ServiceRegistryRef) override;
 
+  std::map<std::string, std::shared_ptr<ReferenceComparatorPlot>>& getComparatorPlots() { return mHistograms; }
+  std::shared_ptr<ReferenceComparatorPlot> getComparatorPlot(std::string plotName);
+
   struct HistoWithRef {
     std::shared_ptr<TH1> mPlot;
     std::shared_ptr<TH1> mRefPlot;

Modules/Common/src/ReferenceComparatorPlot.cxx

@@ -159,21 +159,21 @@ static std::shared_ptr<HIST> createHisto2D(const char* name, const char* title,
 class ReferenceComparatorPlotImpl
 {
  public:
-  ReferenceComparatorPlotImpl(bool scaleReference)
-    : mScaleReference(scaleReference)
+  ReferenceComparatorPlotImpl(TH1* referenceHistogram, bool scaleReference)
+    : mReferenceHistogram(referenceHistogram), mScaleReference(scaleReference)
   {
   }
 
   virtual ~ReferenceComparatorPlotImpl() = default;
 
-  virtual TObject* init(TH1* referenceHistogram, std::string outputPath, bool scaleReference, bool drawRatioOnly, std::string drawOption)
+  virtual TObject* getMainCanvas()
   {
     return nullptr;
   }
 
-  virtual TObject* getMainCanvas()
+  TH1* getReferenceHistogram()
   {
-    return nullptr;
+    return mReferenceHistogram;
   }
 
   void setScaleRef(bool scaleReference)
@@ -183,9 +183,10 @@ class ReferenceComparatorPlotImpl
 
   bool getScaleReference() { return mScaleReference; }
 
-  virtual void update(TH1* histogram, TH1* referenceHistogram) = 0;
+  virtual void update(TH1* histogram) = 0;
 
  private:
+  TH1* mReferenceHistogram{ nullptr };
   bool mScaleReference{ true };
 };
 
@@ -200,7 +201,7 @@ class ReferenceComparatorPlotImpl1D : public ReferenceComparatorPlotImpl
                                 bool drawRatioOnly,
                                 double legendHeight,
                                 const std::string& drawOption)
-    : ReferenceComparatorPlotImpl(scaleReference), mLegendHeight(legendHeight)
+    : ReferenceComparatorPlotImpl(referenceHistogram, scaleReference), mLegendHeight(legendHeight)
   {
     float labelSize = 0.04;
 
@@ -343,8 +344,9 @@ class ReferenceComparatorPlotImpl1D : public ReferenceComparatorPlotImpl
     return mCanvas.get();
   }
 
-  void update(TH1* hist, TH1* referenceHistogram)
+  void update(TH1* hist)
   {
+    TH1* referenceHistogram = getReferenceHistogram();
     if (!hist || !referenceHistogram) {
       return;
     }
@@ -389,7 +391,7 @@ class ReferenceComparatorPlotImpl2D : public ReferenceComparatorPlotImpl
                                 bool scaleReference,
                                 bool drawRatioOnly,
                                 const std::string& drawOption)
-    : ReferenceComparatorPlotImpl(scaleReference)
+    : ReferenceComparatorPlotImpl(referenceHistogram, scaleReference)
   {
     if (!referenceHistogram) {
       return;
@@ -498,8 +500,9 @@ class ReferenceComparatorPlotImpl2D : public ReferenceComparatorPlotImpl
     return mCanvas.get();
   }
 
-  void update(TH1* histogram, TH1* referenceHistogram)
+  void update(TH1* histogram)
   {
+    TH1* referenceHistogram = getReferenceHistogram();
     if (!histogram || !referenceHistogram) {
       return;
     }
@@ -559,10 +562,10 @@ TObject* ReferenceComparatorPlot::getMainCanvas()
   return (mImplementation.get() ? mImplementation->getMainCanvas() : nullptr);
 }
 
-void ReferenceComparatorPlot::update(TH1* histogram, TH1* referenceHistogram)
+void ReferenceComparatorPlot::update(TH1* histogram)
 {
   if (mImplementation) {
-    mImplementation->update(histogram, referenceHistogram);
+    mImplementation->update(histogram);
   }
 }
 

Modules/Common/src/ReferenceComparatorTask.cxx

@@ -167,6 +167,18 @@ void ReferenceComparatorTask::initialize(quality_control::postprocessing::Trigge
 
 //_________________________________________________________________________________________
 
+std::shared_ptr<ReferenceComparatorPlot> ReferenceComparatorTask::getComparatorPlot(std::string plotName)
+{
+  // check if a corresponding output plot was initialized
+  auto iter = mHistograms.find(plotName);
+  if (iter == mHistograms.end()) {
+    return {};
+  }
+  return iter->second;
+}
+
+//_________________________________________________________________________________________
+
 void ReferenceComparatorTask::update(quality_control::postprocessing::Trigger trigger, framework::ServiceRegistryRef services)
 {
   auto& qcdb = services.get<repository::DatabaseInterface>();
@@ -194,10 +206,7 @@ void ReferenceComparatorTask::update(quality_control::postprocessing::Trigger tr
       }
 
       // update the plot ratios and the histograms with superimposed reference
-      auto referenceMO = mReferencePlots[plotName];
-      TH1* referenceHistogram = dynamic_cast<TH1*>(referenceMO->getObject());
-
-      iter->second->update(histogram, referenceHistogram);
+      iter->second->update(histogram);
     }
   }
 }