bug#2343: Color highlighting leaves a trail of cursors on the screen

bug#2343: Color highlighting leaves a trail of cursors on the screen

[Kim Rose Carlsen]

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Hi

When using emacs in -nw mode, the cursor seems to hang quite often leaving back a cursor block. 
The block is redrawn correctly if the window is resized or refreshed. I have attached a few low-res screenshots of the behaviour.

How to reproduce:
In a terminal 
1) start emacs (emacs -nw)
2) switch to scratch buffer 
2) Change to c mode (M-x c-mode)
3) type 'if (aa == 1)'

You should now see (a green) cursor block between 'aa' and '==' like the screenshot.

Tested on:
Freebsd, Debian, Gentoo, Ubuntu

Tested with terminal:
Gnome-terminal (term=xterm || term=linux)
xfce-terminal  (term=xterm || term=linux)
rox-terminal   (term=xterm || term=linux)

Cannot reproduce with 
linux console (term=linux || term=xterm)
xterm (term=xterm || term=linux)

There are many places where this bug could be, and im not too sure if its the terminal, the major mode or emacs that causes it.


Best Regards
Kim Carlsen

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bug#2343: Color highlighting leaves a trail of cursors on the screen

[Chong Yidong]

Kim Rose Carlsen <KRC@fullrate.dk> wrote:

> How to reproduce:
> In a terminal 
> 1) start emacs (emacs -nw)
> 2) switch to scratch buffer 
> 2) Change to c mode (M-x c-mode)
> 3) type 'if (aa == 1)'
>
> You should now see (a green) cursor block between 'aa' and '==' like the
> screenshot.
>
> Tested with terminal:
> Gnome-terminal (term=xterm || term=linux)
> xfce-terminal  (term=xterm || term=linux)
> rox-terminal   (term=xterm || term=linux)
>
> Cannot reproduce with 
> linux console (term=linux || term=xterm)
> xterm (term=xterm || term=linux)

I'm pretty baffled by this one.  I can reproduce it using
gnome-terminal, and a slightly different version of the bug seems to
show up in Emacs 22 too.  Anyone have any idea?

bug#2343: Color highlighting leaves a trail of cursors on the screen

[David De La Harpe Golden]

Chong Yidong wrote:
> Kim Rose Carlsen <KRC@fullrate.dk> wrote:

>> Tested with terminal:
>> Gnome-terminal (term=xterm || term=linux)
>> xfce-terminal  (term=xterm || term=linux)
>> rox-terminal   (term=xterm || term=linux)
>>

All those use the libvte terminal emulator widget underneath.
It _may_ be some issue with that rather than emacs, there is an 
unconfirmed bug report of various redraw issues in recent vte
when cursor positioning is used:
http://bugzilla.gnome.org/show_bug.cgi?id=528077


>> Cannot reproduce with 
>> linux console (term=linux || term=xterm)
>> xterm (term=xterm || term=linux)
> 
> I'm pretty baffled by this one.  I can reproduce it using
> gnome-terminal, and a slightly different version of the bug seems to
> show up in Emacs 22 too.  Anyone have any idea?
> 

I can reproduce something like it with xfce4-terminal with

emacs -nw -Q

Without -Q, I have my usual non-default dark blue background set on my 
default face in emacs, and then the block artifact doesn't appear,
so maybe there's some place (whether in emacs or the vte widget I don't 
know) where a background redraw is being skipped when it shouldn't be,
probably as an optimisation for the terminal-default background case.

bug#2343: Color highlighting leaves a trail of cursors on the screen

[David De La Harpe Golden]

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David De La Harpe Golden wrote:

> (whether in emacs or the vte widget I don't  know) 

Try (interactively) typing the following on one of the problematic 
terminal emulators, after doing just doing a "cat" (hit ctrl-c to exit 
when you're done) , say:

a a SPC TAB BACKSPACE = =

(7 keypresses)

On my system with xfce4-terminal (=>libvte), that makes a bit of a 
(transient) mess that I doubt is intended behaviour in the terminal
emulator.

And emacs -nw -Q  does just such a tab backspace sequence (see script 
excerpt) for whatever reason at just the point the artifact shows up, 
though I think the cursor is supposed to be hidden at the time.




























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bug#2343: Color highlighting leaves a trail of cursors on the screen

[Sven Joachim]

On 2009-02-19 04:35 +0100, Chong Yidong wrote:

> Kim Rose Carlsen <KRC@fullrate.dk> wrote:
>
>> How to reproduce:
>> In a terminal 
>> 1) start emacs (emacs -nw)
>> 2) switch to scratch buffer 
>> 2) Change to c mode (M-x c-mode)
>> 3) type 'if (aa == 1)'
>>
>> You should now see (a green) cursor block between 'aa' and '==' like the
>> screenshot.
>>
>> Tested with terminal:
>> Gnome-terminal (term=xterm || term=linux)
>> xfce-terminal  (term=xterm || term=linux)
>> rox-terminal   (term=xterm || term=linux)
>>
>> Cannot reproduce with 
>> linux console (term=linux || term=xterm)
>> xterm (term=xterm || term=linux)
>
> I'm pretty baffled by this one.  I can reproduce it using
> gnome-terminal, and a slightly different version of the bug seems to
> show up in Emacs 22 too.  Anyone have any idea?

Probably that's http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=457483
aka http://bugzilla.gnome.org/show_bug.cgi?id=514632.

Sven

bug#2343: Color highlighting leaves a trail of cursors on the screen

[Kim Rose Carlsen]

I can confirm that upgrading to the latest version of vte fixes the problem.

Old vte version 0.17.4
new vte version 0.19.4 

Best regards
Kim Carlsen

-----Original Message-----
From: Sven Joachim [mailto:svenjoac@gmx.de] 
Sent: Thursday, February 19, 2009 11:13 AM
Subject: Re: bug#2343: Color highlighting leaves a trail of cursors on the screen

On 2009-02-19 04:35 +0100, Chong Yidong wrote:

> Kim Rose Carlsen wrote:
>
>> How to reproduce:
>> In a terminal 
>> 1) start emacs (emacs -nw)
>> 2) switch to scratch buffer 
>> 2) Change to c mode (M-x c-mode)
>> 3) type 'if (aa == 1)'
>>
>> You should now see (a green) cursor block between 'aa' and '==' like the
>> screenshot.
>>
>> Tested with terminal:
>> Gnome-terminal (term=xterm || term=linux)
>> xfce-terminal  (term=xterm || term=linux)
>> rox-terminal   (term=xterm || term=linux)
>>
>> Cannot reproduce with 
>> linux console (term=linux || term=xterm)
>> xterm (term=xterm || term=linux)
>
> I'm pretty baffled by this one.  I can reproduce it using
> gnome-terminal, and a slightly different version of the bug seems to
> show up in Emacs 22 too.  Anyone have any idea?

Probably that's http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=457483
aka http://bugzilla.gnome.org/show_bug.cgi?id=514632.

Sven