Re: screen vertical split speed vs dvtm

[Chris Jones]

On Thu, Dec 24, 2009 at 03:37:04PM EST, Sadrul Habib Chowdhury wrote:

[..]

> Yes! I could reproduce the problem as well!
> 
> I have checked in a fix (a6eea7b4d). Please try it and let me know how
> it works.  Thanks for the report.

Hello Sadrul,

It's been over a couple of weeks, and here's what I observe with the
version of GNU/screen that I downloaded from the git repository:

1. the mutt help/status lines at the top & bottom of the screen are not
   redrawn correctly when changing screens.

2. various issues with ELinks: random display of spurious characters,
   flickering, & tearing.

Context:
-------

1. xterm with 256 colors enabled and a black background

2. UTF-8 locale

3. GNU/unifont or terminus

4. bce set or unset - see below.

Scenarios:
---------

1. mutt displays a 'quick help' bar at the top of the screen and a
   status line at the bottom of the screen. Both have their background
   set to a color that differs from the remainder of the screen. 
   
   The problems with mutt were observed with 'bce' set to 'on' and
   'term' set to 'screen-256color-bce'.

   With the new version, either or both of these lines appear truncated
   in the sense that their rightmost part is set to the background color
   of the xterm. This affects a random number of cells that range from
   just a few to more than half the width of the display. The loss of
   background color does not appear to be directly related to the
   presence or absence of text in the foreground. This happens every
   time I navigate between mutt's different screens or when I switch
   back and forth between mutt and an application running in another
   screen window. 
   
   Both lines are redrawn correctly when I issue a CTRL-L and are again
   randomly truncated as soon as I repeat the above.

   This does not happen when 'bce' is set to 'off' and 'term' set to
   'screen-256color'. But, as I will describe shortly, these settings
   cause other problems with the ELinks web browser.

2. ELinks lets you specify the background & foreground colors at the
   application level, regardless of the color settings of the underlying
   terminal. I use something that resembles Netscape's default colors.

   The following was observed with 'bce' set to 'off' and 'term' set to
   'screen-256color'.

   - When following a link, the display flickers briefly, showing a few
     horizontal black lines (the background color of my xterm).

   - There are spurious characters in random locations of the display,
     pretty much anything printable, alpha, punctuation, line-drawing
     characters.. Sometimes, but no always, the spurious characters are
     repeats of the last character of a preceding line. These artifacts
     are visible on all web pages, regardless of the language, English,
     Western European, CJK.. and with either of the fonts that I use.

   - A CTRL-L temporarily removes the artifacts but causes a number of
     lines of the display to be randomly truncated, with the light
     background not quite making it to the end of the line. This results
     in a jagged effect where a few columns' worth of the black
     background of the xterm show through alongside the right edge of
     the display. Navigating to a new page removes the black marks, but
     causes the reappearance of the spurious characters.

   - If I set 'bce' back to 'on' and bounce screen, I do not see any
     random artifacts, only the flickering black lines when I navigate
     to a different web page.

Notes:
-----

1. I ran the same tests with the debian lenny version (4.0.3-11+lenny1)
   of screen with 'bce' set to 'on' and I was unable to recreate any of
   the above problems.  

2. I run four similar programs in the same screen instance: Vim, slrn,
   weechat-curses, and cgdb. All four have 'bars' of one form or another
   at the top & bottom of the screen. Apart from some occasional
   flickering in the areas were the background is set to a different
   color than the xterm's, I have not observed any redrawing issues with
   these applications.

Thanks,

CJ