text rendering problems about roxterm

[realh]

I've noticed problems with long lines in bash's command history but didn't realise it might be a terminal problem. If it is, I think it might be a bug in vte rather than roxterm. Can you reproduce this in gnome-terminal?

The "Pattern not found" message from man/less works for me too. It could be a problem with your colour scheme so the background colour is the same as the foreground for this message. For me with the "GTK" colour scheme the message is in inverted colours. If you rule that out can you reproduce this in gnome-terminal too?

Original comment by: realh

[realh]

The "Pattern not found" message from man/less works for me too.

Meaning you don't see any rendering artifacts?

It could be a problem with your colour scheme...

I am using a custom background and foreground color scheme, but that wouldn't explain the intermittent nature of the problem. Sometimes that exact same message from 'less' renders normally. Generally, inverted text renders fine.

I've noticed problems with long lines in bash's command history but didn't
realise it might be a terminal problem.

So then what did you attribute it to? bash outputing improper terminal escape codes?

I think it might be a bug in vte rather than roxterm.
Can you reproduce this in gnome-terminal?

Quite possible. I haven't used gnome-terminal hardly at all on this particular machine (I used it extensively on an Ubuntu 8.04 box without problems) but I did briefly try Konsole on this machine before settling on ROXterm, and I seem to recall it had rendering issues as well, and possibly with greater frequency.

Just recently I started up Konsole and played around for a bit, but I couldn't reproduce the problem. Does it use the vte library? (I did see some oddities in how the scrollback buffer is rendered. Odd glitches with portions of the screen not painted correctly.)

I just tried gnome-terminal and couldn't reproduce the problem.

Then again, I can't reproduce the problem at will in ROXterm either. With all three I tried editing an identical command that spanned 4 lines and searching for text that can't be found in a man page.

I really need to find a reproducible test case before I can draw any conclusions.

Lets see...I found a vttest package for testing terminal emulators...installing it via a Konsole window I see some of the output from aptitude didn't render correctly, so it looks like Konsole is affected.

OK, running vttest in each of the three shows:

Both gnome-terminal and ROXterm fails to render screen 2, 3, and 4 of test #1 correctly. I think they handle all of the screens of test #2 correctly. And I see that some explanatory text in screen 4 of test #1 is initially invisible, but if the window loses focus and regains it, the text appears. (I'll have to see if that applies to the real-world situation I observe in ROXterm.) This happens identically with both programs.

Konsole, on the other hand, fails to correctly render even the menu in vttest, and fails a bunch of the screens in test #1.

I'd gather from this that Konsole doesn't use vte, and yes, vte is probably the responsible component for the problems I'm seeing in ROXterm. What's your recommendation for how to proceed? Shall I figure out the responsible package on Ubuntu for vte and file a ticket against it, or file something with the upstream vte project (URL?)?

Original comment by: nobody

[realh]

The "Pattern not found" message from man/less works for me
too.

Meaning you don't see any rendering artifacts?

No, it all looks fine.

It could be a problem with your colour scheme...

I am using a custom background and foreground color scheme, but
that wouldn't explain the intermittent nature of the problem.
Sometimes that exact same message from 'less' renders normally.
Generally, inverted text renders fine.

I've noticed problems with long lines in bash's command
history but didn't realise it might be a terminal problem.

So then what did you attribute it to? bash outputing improper
terminal escape codes?

I didn't think about it that much. Maybe something to do with line
wrapping or a buffer overflow. I wouldn't describe the problem
I've seen as "rendering artifacts" BTW; the characters that do get
rendered get rendered correctly, it just doesn't display the whole
line correctly and characters get overwritten when I move the
cursor over them.

I think it might be a bug in vte rather than roxterm. Can you
reproduce this in gnome-terminal?

Quite possible. I haven't used gnome-terminal hardly at all on
this particular machine (I used it extensively on an Ubuntu 8.04
box without problems) but I did briefly try Konsole on this
machine before settling on ROXterm, and I seem to recall it had
rendering issues as well, and possibly with greater frequency.

Just recently I started up Konsole and played around for a bit,
but I couldn't reproduce the problem. Does it use the vte
library? (I did see some oddities in how the scrollback buffer
is rendered. Odd glitches with portions of the screen not
painted correctly.)

I don't think Konsole uses vte, because Konsole is Qt/KDE and vte
is based heavily on GTK.

I just tried gnome-terminal and couldn't reproduce the problem.

Then again, I can't reproduce the problem at will in ROXterm
either. With all three I tried editing an identical command that
spanned 4 lines and searching for text that can't be found in a
man page.

I really need to find a reproducible test case before I can draw
any conclusions.

Lets see...I found a vttest package for testing terminal
emulators...installing it via a Konsole window I see some of the
output from aptitude didn't render correctly, so it looks like
Konsole is affected.

OK, running vttest in each of the three shows:

Both gnome-terminal and ROXterm fails to render screen 2, 3, and
4 of test #1 correctly. I think they handle all of the screens
of test #2 correctly. And I see that some explanatory text in
screen 4 of test #1 is initially invisible, but if the window
loses focus and regains it, the text appears. (I'll have to see
if that applies to the real-world situation I observe in
ROXterm.) This happens identically with both programs.

Konsole, on the other hand, fails to correctly render even the
menu in vttest, and fails a bunch of the screens in test #1.

I'd gather from this that Konsole doesn't use vte, and yes, vte
is probably the responsible component for the problems I'm
seeing in ROXterm. What's your recommendation for how to
proceed? Shall I figure out the responsible package on Ubuntu
for vte and file a ticket against it, or file something with the
upstream vte project (URL?)?

The Ubuntu package is probably libvte9, that's what it is in
Debian. It might be worth reporting as an Ubuntu bug because I'm
not seeing the same thing with Debian. If you want to report it
upstream the tracker is at http://bugzilla.gnome.org/ in component
Desktop -> vte.

Original comment by: realh

[realh]

At least some of the problems observed with vttest still persist on a current Ubuntu 9.04 machine, but it seems a safe bet that the problem is with the underlying vte library. I guess I didn't follow through with filing a bug against vte, but I see there is already a relevant bug there that's many years old:

Bug 4993 - gnome-terminal fails many vttest terminal emulation test
https://bugzilla.gnome.org/show_bug.cgi?id=4993

I've added a comment to it, and referenced this bug.

It seems most of the rendering issues I ran across in real-world situations with ROXterm have gone away in the last 6 months since filing this bug. I don't recall the last time I encountered a problem. I think the real underlying problem was not even vte, but the X graphics driver and/or GNOME graphics libraries, which have slowly gotten fixed through Ubuntu updates.

Original comment by: tmetro