rcanvas_update.cxx

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/// \file
/// \ingroup tutorial_rcanvas
///
/// This macro shows how ROOT RCanvas::Update method is working.
/// One can do sync and/or async depending how important is that graphics is updated before next action will be
/// performed
///
/// \macro_image (rcanvas_js)
/// \macro_code
///
/// \date 2021-07-05
/// \warning This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback
/// is welcome!
/// \author 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/RCanvas.hxx>
#include "TGraph.h"
 
#include <iostream>
 
using namespace ROOT::Experimental;
 
void rcanvas_update()
{
   static constexpr int npoints = 10;
   double x[npoints] = {1., 2., 3., 4., 5., 6., 7., 8., 9., 10.};
   double y[npoints] = {.1, .2, .3, .2, .1, .2, .3, .2, .1, .2};
   auto gr = new TGraph(npoints, x, y);
 
   auto canvas = RCanvas::Create("Demo of RCanvas update");
 
   canvas->Draw<TObjectDrawable>(gr, "AL");
 
   // new window in web browser should popup and async update will be triggered
   canvas->Show();
 
   // synchronous, wait until drawing is really finished
   canvas->Update(false,
                  [](bool res) { std::cout << "First sync update done = " << (res ? "true" : "false") << std::endl; });
 
   // modify TGraph making different form
   gr->SetPoint(1, 1., .3);
   gr->SetPoint(3, 3., .1);
   gr->SetPoint(5, 5., .3);
   gr->SetPoint(7, 7., .1);
   gr->SetPoint(9, 9., .3);
 
   // invalidate canvas and force repainting with next Update()
   canvas->Modified();
 
   // call Update again, return before actual drawing will be performed by the browser
   canvas->Update(
      true, [](bool res) { std::cout << "Second async update done = " << (res ? "true" : "false") << std::endl; });
 
   std::cout << "This message appear normally before second async update" << std::endl;
}