This is Kubuntu 14.04.5 LTS / x86_64 with gcc 4.8.4 (so, running KDE desktop, if that matters) here.
I tried the macro from my previous post here and I still get the same problem with the newest “v5-34-00-patches” and “6.10.04” (see the second line of every output -> it’s sometimes “800 600” and sometimes “798 573”):
[...] $ for i in {1..10}; do root -l -n -q TestSetWindowSize.cxx; done
root [0]
Processing TestSetWindowSize.cxx...
798 573
800 600
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
800 600
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
800 600
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
798 573
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
800 600
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
800 600
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
798 573
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
798 573
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
800 600
798 573
800 600
796 572
796 572
796 572
800 600
root [0]
Processing TestSetWindowSize.cxx...
798 573
800 600
798 573
800 600
796 572
796 572
796 572
800 600
BTW. Even the newest TCanvas class description does not clearly say what one should expect from the TCanvas::SetWindowSize in batch mode. See the “last line - 2” of every output above -> there’s always “796 572”, so it seems to be completely ignored. Is this a bug or a “feature”?