Zoom TH1 with mouse wheel - speed is slow

ROOT
1

Hello,
when using TCanvas with a TH1 plotted, the speed of zoom/unzoom by mouse wheel is very very slow, like 0.5% of the range on one scroll. I realized, how useful it can be when using THTTPServer, where the speed in the browser is just optimal.

Is there a way to increase the zoom/unzoom speed? Thank you
Jaromir

2

On my Mac the zoom with the mouse wheel is as fast as the zoom with a range. It is real time. Unless you have a huge number of bins (like several 1000) I do not see any reason why it could be slow.

3

Hi Jaromir,

You mention THttpServer. Do you mean zooming speed in the web browser or zooming speed with normal ROOT graphics?

Regards,
Sergey

4

Dear Sergey,
THttpserver is fine. Fast and exactly matches typical needs.
Dear couet,
yes, I have 16000 bins th1 spectrum. Is there any chance to speed up the zoom/unzoom with the wheel?

Thank you

5

16000 … that must be the problem. Can you send the histogram so I can try ?
The only way to speed it would be to change the code doing the zoom.

6

Dear couet,
I am sending an example code with a peak few times wided than usual gamma peak.

TH1F *h=new TH1F("h","h",16000,0,16000)
for (int i=0;i<1000;i++){ h->Fill(  gRandom->Gaus(8000,10) );}
h->Draw()

Now I point to x-axis and roll…

I have some small hope that I do something not correctly and a bigger worry about the ‘change the code’.

Thank you for your responses,
Jaromir

7

As I said a code change is required. It is here:

Thanks for having reported this issue.

2 Likes
8

Thank you, one small and naive question - I guess that it will work now, if I compile root from current git repo. Since I am happy to have the opportunity of precompiled binary ( https://root.cern/download/root_v6.28.04.Linux-ubuntu22-x86_64-gcc11.3.tar.gz )- when could it be available precompiled for ubuntu ?
Thank you, bye
Jaromir

9

I guess you will need to download it from GitHub and install yourself.

1 Like
10

@jaromrax I think you can try this nightly build: root_v6.28.99.Linux-ubuntu22-x86_64-gcc11.3.tar.gz

1 Like
11

Well, I am not sure, if this nightly build Jun 20 2023, 23:44:00; From remotes/origin/v6-28-00-patches@v6-28-04-115-ge1c68d0647 really contains the change. When I check with 10000 bin histogram, it still goes 1 bin at a time. But I dont know the procedures for these builds.
Jaro

12

I just merged the fix recently. It is in master now.

1 Like
13

Thank you,
it works, two small comments
1- it could be a bit faster than 2% of the range
2- if it was sensitive on the position of the cursor, it would become a fantastic tool. I understand that it is not probably easy at all.
Thank you
Jaromir

14

If you need to zoom-wheel a specific part of the plot, first do a positionnal zoom in order to center the part you need and them use the zoom-wheel.

15

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