Qt is not required (AND NOT RECOMMENDED) to draw histograms or any other ROOT object.
It is likely that somewhere in $ROOTSYS/etc/system.rootrc or in $HOME/.rootrc you have modified or activated lines like
Gui.Backend: qt
Gui.Factory: qt
if you have these lines, replace them by
Dear Rene,
many thanks for your quick reply. I managed to plot my histograms.
Now I have another question: I had set qt as gui.backend and gui.factory because I’m using qtroot for a c++/root/qt/qtroot application.
Should I run ‘one’ root for the application and ‘a different one’ for opening histos or there is a (simple) way to use the same root?
In principle you should be able to run one single version (say qtroot).
However the experience shows that the qt interfaces are quite weak and unstable
and source of several problems difficult to debug and follow for us.
[quote=“bomben”]…
Now I have another question: I had set qt as gui.backend and gui.factory because I’m using qtroot for a c++/root/qt/qtroot application.
Should I run ‘one’ root for the application and ‘a different one’ for opening histos or there is a (simple) way to use the same root?
[/quote]Yes, you can use it.
Can you clarify your installation?
If you use qtroot then libGQT.so does exist. If it does exist you should not see any problem. I do not understand why your root session can not find it.
[quote=“bomben”]… [quote]root [0] TFile *f = new TFile(“data/histo/calibration-100118-161040.root”,“READ”)
root [1] TH1F Cell_58_3_19 = (TH1F)f->Get(“Cell_58_3_19”)
root [2] Cell_58_3_19->Draw()
Error in TUnixSystem::DynamicPathName: GQt[.so | .sl | .dl | .a | .dll] does not exist in .:/home/bomben/root-520/root/lib::/home/bomben/root-[/quote]…
By the way, I do not understand why it is complaining about libGQt in reading back a file.
[/quote] I does not complain “reading back a file”. It complains as soon as you invoke the method Draw. root [2] Cell_58_3_19->Draw()
[quote=“brun”]…
However the experience shows that the qt interfaces are quite weak and unstable. . .
[/quote]I would like to take this opportunity to encourage all QtRoot users to send me all problems they encounter.
Do not hesitate to file a bug report. Please, do not keep it as a big secret.
I encourage all QtRoot users to keep their QtRoot version up-to-date. The fresh version can be always installed.
[quote=“brun”]… source of several problems difficult to debug and follow for us.[/quote]Rene , let me repeat, Please do not bother yourself with QtRoot issues. Please, do not waste your valuable time, Please forward all QtRoot related issues coming from QtRoot users to Brookhaven National Laboratory. Please advise them to use lists.bnl.gov/mailman/listinfo/qt-root-l list directly too.