When scrolling back up some of the bottom comes up as a sort of sleeve

[Wise Melon]

I have recently noticed that when viewing a manpage in gnome-terminal that if scrolling down, when I scroll back up again some of the bottom part of the page comes up too sort of like a sleeve. I have attached some example screenshots, so I ran 'man dpkg' and this is what it looked like initially dpkg_man_top1.png, but when I scrolled down to the bottom of the page and then back up again to the top, the top looked somewhat different as you can see: dpkg_man_top2.png. Now, it wouldn't matter where I had scrolled down to, nor where I had gone up to, the effect witnessed would have been the same.

---

OS Information:

    No LSB modules are available.
    Distributor ID: Ubuntu
    Description: Ubuntu 15.04
    Release: 15.04
    Codename: vivid
    Flavour: GNOME
    GNOME Version: 3.16

Package Information:

    manpages:
      Installed: 3.74-1ubuntu1
      Candidate: 3.74-1ubuntu1
      Version table:
     *** 3.74-1ubuntu1 0
            500 http://archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages
            100 /var/lib/dpkg/status

    less:
      Installed: 458-3
      Candidate: 458-3
      Version table:
     *** 458-3 0
            500 http://archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages
            100 /var/lib/dpkg/status

    gnome-terminal:
      Installed: 3.16.2-1ubuntu1~vivid1
      Candidate: 3.16.2-1ubuntu1~vivid1
      Version table:
     *** 3.16.2-1ubuntu1~vivid1 0
            500 http://ppa.launchpad.net/gnome3-team/gnome3-staging/ubuntu/ vivid/main amd64 Packages
            100 /var/lib/dpkg/status
         3.14.2-0ubuntu3 0
            500 http://archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages
         3.12.3-0ubuntu1~utopic2 0
            500 http://ppa.launchpad.net/gnome3-team/gnome3/ubuntu/ vivid/main amd64 Packages

[Colin Watson (cjwatson)]

This isn't the fault of the manual page documents themselves. I'm not sure exactly what *is* going wrong here; it's probably either a bug in the terminal emulator itself or a bug in the pager you're using. You should add information to this bug about what pager you're using (if you don't know, it's probably "less", but perhaps you changed it).

[Wise Melon (wise-melon-deactivatedaccount)]

@Colin Watson, ok, I have updated my report. And no, I have not changed the default pager so that should be less.

[Wise Melon (wise-melon-deactivatedaccount)]

Please let me know if I should add more information to my report.

[Egmont Koblinger (egmont-gmail)]

The half-painted line suggests that it's a bug in gnome-terminal/vte, or some component underneath (Gtk+, X, video driver)... No app running inside the terminal, no matter how buggy, should be able to produce such partial lines.

Nikita, how do you scroll exactly? Using the Up/Down or PageUp/PageDown keys, or mouse, touchpad...?

Is it only gnome-terminal that you upgraded from Gnome3 staging, or the entire Gnome stack? Any chance you could test whether mainstream Vivid or Wily beta suffers from this bug?

The extra black padding at the bottom of the screenshots suggests that the window is maximized or fullscreened. Can you reproduce the bug if you manually resize the terminal to almost as big as this one, but not maximized/fullscreen? Or any other smaller size? (In that case less's status line will be at the bottom of the window.)

What's the value of $LESS ? (What I'm interested in is whether 'X' is there, I assume not.)

What's the terminal size, as reported by "stty size"? Seems to me it's 150x37, correct?

[Egmont Koblinger (egmont-gmail)]

One more question: Do you have anything like tmux, screen, ssh, or similar additional layer of software running? Or you just open the terminal, type "man dpkg" and it's buggy?

[Egmont Koblinger (egmont-gmail)]

This one might stupid, but just in case: Are you absolutely sure that it's gnome-terminal, and some other similar app (xfce-terminal, mate-terminal...)? What's the output of echo $VTE_VERSION ?

[Wise Melon (wise-melon-deactivatedaccount)]

Ok, after I restarted the machine (although not Terminal) the strange behaviour seems to have disappeared although it does come and go. But I will give you the information you asked for as it may help you to figure it out.

I scroll with the Up/Down keys, I have not tried any other way but will do next time and report back.

I have been using Ubuntu and GNOME for a very long time now and I have never seen anything like this on any other version other than GNOME3 Staging. I will attempt to get a VM running Wily Beta up and running and see if I can reproduce the bug there.

Yes, I am able to reproduce this bug when not maximized, when maximized, and also when manually resizing the Terminal window.

$LESS has no value.

"stty size" reports "37 150".

No, I don't have any additional layer of software running when this issue occurs.

Yes, I am absolutely sure that it is gnome-terminal. The output of "echo $VTE_VERSION" is: "4002". I hope that this helps and I will run the same checks again when the issue returns and let you know if they are the same as I have reported here.

[Egmont Koblinger (egmont-gmail)]

Vte used to contain such drawing bugs, but we fixed all the known ones about 1.5 years ago and I haven't seen any display corruption like yours since then; nor have seen any other user complaining (I keep an eye on official gnome-terminal bugzilla, Ubuntu, Debian and Red Hat bugtracker).

I use Wily beta and cannot reproduce your issue.

This gives me a hunch that it's probably something wrong with Gnome3 staging, or perhaps your X driver or something like that.

But of course it can be a gnome-terminal/vte bug which only occurs on your computer.

Reproducing in a VM with Wily: if you can reproduce then that's definitely helpful; but if you can't then that means nothing: it still could be buggy with Wily directly on your computer.

Are you planning to update any time soon? My recommendation is to wait until you upgrade and use mainstream Wily (no Gnome3 staging) and still can reproduce it there. If it's still an issue I'd be happy to start debugging it with you, but I would first like to exclude the possibility that something in Gnome3 staging is the culprit.