Logo ROOT  
Reference Guide
draw_mt.cxx File Reference

Detailed Description

This macro demonstrate usage of ROOT7 graphics from many threads Three different canvases in three different threads are started and regularly updated.

Extra thread created in background and used to run http protocol, in/out websocket communications and process http requests Main application thread (CLING interactive session) remains fully functional

* Copyright (C) 1995-2015, 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/RCanvas.hxx"
#include "TRandom3.h"
#include "TEnv.h"
#include "TROOT.h"
#include <thread>
// macro must be here while cling is not capable to load
// library automatically for outlined function see ROOT-10336
using namespace ROOT::Experimental;
void draw_canvas(const std::string &title, RColor col)
// Create histograms
RAxisConfig xaxis(100, -10., 10.);
auto pHist = std::make_shared<RH1D>(xaxis);
auto pHist2 = std::make_shared<RH1D>(xaxis);
TRandom3 random;
Float_t px, py;
for (int n = 0; n < 10000; ++n) {
random.Rannor(px, py);
pHist->Fill(px - 2);
pHist2->Fill(py + 2);
// Create a canvas to be displayed.
auto canvas = RCanvas::Create(title + " canvas");
int maxloop = 50;
printf("%s started\n", title.c_str());
for (int loop = 0; loop < maxloop; ++loop) {
for (int n = 0; n < 10000; ++n) {
random.Rannor(px, py);
pHist->Fill(px - 2);
pHist2->Fill(py + 2);
canvas->Run(0.5); // let run canvas code for next 0.5 seconds
// if (loop == 0)
// canvas->SaveAs(title + "_first.png");
// if (loop == maxloop - 1)
// canvas->SaveAs(title + "_last.png");
printf("%s completed\n", title.c_str());
// remove from global list, will be destroyed with thread exit
void draw_mt()
gEnv->SetValue("WebGui.HttpThrd", "yes");
gEnv->SetValue("WebGui.SenderThrds", "yes");
// create instance in main thread, used to assign thread id as well
std::thread thrd1(draw_canvas, "First", RColor::kRed);
std::thread thrd2(draw_canvas, "Second", RColor::kBlue);
std::thread thrd3(draw_canvas, "Third", RColor::kGreen);
float Float_t
Definition: RtypesCore.h:57
Definition: Rtypes.h:472
@ kRed
Definition: Rtypes.h:66
@ kGreen
Definition: Rtypes.h:66
@ kBlue
Definition: Rtypes.h:66
R__EXTERN TEnv * gEnv
Definition: TEnv.h:171
Objects used to configure the different axis types.
Definition: RAxisConfig.hxx:35
The color class.
Definition: RColor.hxx:35
virtual void SetValue(const char *name, const char *value, EEnvLevel level=kEnvChange, const char *type=nullptr)
Set the value of a resource or create a new resource.
Definition: TEnv.cxx:736
Random number generator class based on M.
Definition: TRandom3.h:27
virtual void Rannor(Float_t &a, Float_t &b)
Return 2 numbers distributed following a gaussian with mean=0 and sigma=1.
Definition: TRandom.cxx:500
const Int_t n
Definition: legend1.C:16
void EnableThreadSafety()
Enables the global mutex to make ROOT thread safe/aware.
Definition: TROOT.cxx:494
This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback is welcome!
Sergey Linev

Definition in file draw_mt.cxx.