Horizontal line at y=0 drawn also for negative "y" values

Dear experts,

I am preparing GUI application based on Qt 5.15.2, ROOT 6.28.04, using QtWebEngine and object from ROOT::Experimental (RCanvas, RH1D, etc.). I found that the horizontal line for y=0 is drawn if data has also negative y-values. Is it possible to remove/hide this line using new approach of “R” classes? (I know that using “TH1D” with draw options it is possible). Also I see the problem that the “line” object of the line y=0 is shared with histogram, thus if I change histogram line color, the y=0 line change color too.

I have prepared a simple example showing two frames. One is empty with axes drawn. In second frame the RH1D is drawn. How to draw RH1D object in the first frame without horizontal y=0 line? Thank you.

#include "ROOT/RHist.hxx"
#include "ROOT/RHistDrawable.hxx"
#include "ROOT/RFrameTitle.hxx"
#include "ROOT/RCanvas.hxx"
#include "ROOT/RPad.hxx"
#include "TRandom.h"
// macro must be here while cling is not capable to load
// library automatically for outlined function see ROOT-10336
using namespace ROOT::Experimental;
void rhist01()
    RAxisConfig xaxis(5, 0., 5.);
    auto pHist = std::make_shared<RH1D>(xaxis);
    pHist->GetImpl()->AddBinContent(1, -3);
    pHist->GetImpl()->AddBinContent(2, 2);
    pHist->GetImpl()->AddBinContent(3, 8);
    pHist->GetImpl()->AddBinContent(4, 5);
    pHist->GetImpl()->AddBinContent(5, -1);

    auto canvas = RCanvas::Create("zero");
    auto pads = canvas->Divide(2,1);
    auto pad1 = pads[0][0];
    auto pad2 = pads[1][0];

    auto frame1 = pad1->AddFrame();
    frame1->drawAxes = true;
    frame1->x.SetMinMax(0, 5);
    frame1->y.SetMinMax(-5, 10);
    pad1->Draw<RFrameTitle>("frame 1");

    auto frame2 = pad2->AddFrame();
    frame2->drawAxes = true;
    frame2->x.SetMinMax(0, 5);
    frame2->y.SetMinMax(-5, 10);
    pad2->Draw<RFrameTitle>("frame 2");
    auto draw = pad2->Draw(pHist);
    draw->line.color = RColor::kGreen;

    canvas->SetSize(800, 500);


ROOT Version: 6.28/04
Platform: x86_64 GNU/Linux Ubuntu 22.04
Compiler: gcc 11.3 (c++17)

That’s new web graphics. @linev will know.


Yes, I can reproduce the issue.

It should be fixed now in the 6.28 branch by this PR:

Fix in master branch will follow.
Thanks for reporting it!


Dear Sergey,

I can confirm that the patch fixed the problem. Thank you


p.s. I found (for stable ROOT 6.28.04 version) that if I draw RH1 as Line() or Marker(), the horizontal y=0 line will not draw …

auto draw = pad2->Draw(pHist);

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