tobject.cxx

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/// \file
/// \ingroup tutorial_rcanvas
///
/// This macro shows how ROOT objects like TH1, TH2, TGraph can be drawn in RCanvas.
///
/// \macro_image (rcanvas_js)
/// \macro_code
///
/// \date 2017-06-02
/// \warning This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback
/// is welcome!
/// \authors Axel Naumann <axel@cern.ch>, Sergey Linev <s.linev@gsi.de>
 
/*************************************************************************
 * Copyright (C) 1995-2021, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#include <ROOT/TObjectDrawable.hxx>
#include <ROOT/RPad.hxx>
#include <ROOT/RCanvas.hxx>
#include "TH1.h"
#include "TH2.h"
#include "TGraph.h"
#include "TMath.h"
#include "TStyle.h"
 
using namespace ROOT::Experimental;
 
// create RStyle here to keep reference alive after leaving tobject() function scope
auto tobject_style = RStyle::Parse("tgraph { line_width: 3; line_color: red; }");
 
void tobject()
{
   static constexpr int npoints = 10;
   static constexpr int nth1points = 100;
   static constexpr int nth2points = 40;
 
   double x[npoints] = {1., 2., 3., 4., 5., 6., 7., 8., 9., 10.};
   double y[npoints] = {.1, .2, .3, .4, .3, .2, .1, .2, .3, .4};
   auto gr = new TGraph(npoints, x, y);
 
   // create normal object to be able draw it once
   auto th1 = new TH1I("gaus", "Example of TH1", nth1points, -5, 5);
   // it is recommended to set directory to nullptr, but it is also automatically done in TObjectDrawable
   // th1->SetDirectory(nullptr);
   th1->FillRandom("gaus", 5000);
 
   // use std::shared_ptr<TH2I> to let draw same histogram twice with different draw options
   auto th2 = std::make_shared<TH2I>("gaus2", "Example of TH2", nth2points, -5, 5, nth2points, -5, 5);
   // is is highly recommended to set directory to nullptr to avoid ownership conflicts
   th2->SetDirectory(nullptr);
   for (int n = 0; n < nth2points; ++n) {
      for (int k = 0; k < nth2points; ++k) {
         double x = 10. * n / nth2points - 5.;
         double y = 10. * k / nth2points - 5.;
         th2->SetBinContent(th2->GetBin(n + 1, k + 1), (int)(1000 * TMath::Gaus(x) * TMath::Gaus(y)));
      }
   }
 
   gStyle->SetPalette(kRainBow);
 
   auto canvas = RCanvas::Create("RCanvas showing TObject-derived classes");
 
   // add gStyle object, will be applied on JSROOT side
   // set on the canvas before any other object is drawn
   canvas->Draw<TObjectDrawable>(TObjectDrawable::kStyle);
 
   // add ROOT colors, required when they are changed from default values
   canvas->Draw<TObjectDrawable>(TObjectDrawable::kColors);
 
   // copy custom palette to canvas, will be used for col drawings
   // style object does not include color settings
   canvas->Draw<TObjectDrawable>(TObjectDrawable::kPalette);
 
   // Divide canvas on 2x2 sub-pads to show different draw options
   auto subpads = canvas->Divide(2, 2);
 
   // draw graph with "AL" option, drawable take over object ownership
   subpads[0][0]->Draw<TObjectDrawable>(gr, "AL");
 
   // one can change basic attributes via v7 classes, value will be replaced on client side
   auto drawth1 = subpads[0][1]->Draw<TObjectDrawable>(th1);
   drawth1->line = RAttrLine(RColor::kBlue, 3., RAttrLine::kDashed);
 
   subpads[1][0]->Draw<TObjectDrawable>(th2, "colz");
 
   // show same object again, but with other draw options
   subpads[1][1]->Draw<TObjectDrawable>(th2, "lego2");
 
   // add style, here used to configure TGraph attributes, evaluated only on client side
   canvas->UseStyle(tobject_style);
 
   // new window in web browser should popup and async update will be triggered
   canvas->Show();
 
   // create SVG file
   // canvas->SaveAs("tobject.svg");
 
   // create PNG file
   // canvas->SaveAs("tobject.png");
}