Re: Colors and progress indicators on buildprocesses

[Troy Sankey]

Quoting John Darrington (2016-09-28 10:05:52)
> On Wed, Sep 28, 2016 at 09:57:16AM +0000, ng0 wrote:
>      
>      The problem with colors is that the use of colors in build logs creates
>      very difficult to read logs if you don't filter them. 
> 
> This is true. But the build logs already dump some VT100 escape sequences,
> (for vertical  cursor movement).  And they also have to be filtered, so 
> if we say that colours are not permitted then we are not applying these
> rules consistently.

This is our chance make things right!  Determine if the terminal is
interactive [0] and filter escape codes if yes.

I've used Arch, and the coloring was pleasant, but primarily I enjoyed
the clear (and less buggy) progress bars.  For example:

    $ guix pull
    
    Starting download of /tmp/guix-file.O3WsYp
    From http://git.savannah.gnu.org/cgit/guix.git/snapshot/master.tar.gz...
     ….tar.gz                                   1.7MiB/s 00:06 | 10.5MiB 
transferred


The "From" line shows what is about to be downloaded, but the progress
par suggests that "….tar.gz" is being downloaded.  There is a lot of
whitespace after that, which is weird.

Also, here's a bug:

    copying and compiling to 
'/gnu/store/himp5ds1b9m0932dfzxp3gg3vvs7lxd4-guix-latest'...
    loading...       23.1% of 528 filesrandom seed for tests: 1475073161
    loading...       99.8% of 528 files

Something happens during the loading phase, and the string "random seed
for tests: 1475073161" gets printed (also inserting a newline).  The
progress indicator cannot cope, so it starts on a new line.  Also, it
stops at 99.8% which is confusing.

These non-color issues are more important to resolve, IMO.

Troy

[0] http://www.tldp.org/LDP/abs/html/intandnonint.html

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