[Debconf-devel] Bug#989770: debconf: dialog frontend overwrites previous lines in terminal when spawning

[Matteo Settenvini]

Package: debconf
Version: 1.5.77
Severity: normal

Dear Maintainer,

whenever debconf spawns a dialog frontend, it overwrites previous lines in the
terminal output. This is an issue for instance when apt is logging useful 
information about package installation (such as actions to take manually), 
since Shift+PgUp will not show the full install output anymore.

It is still possible to check installation logs, but it is cumbersome and
not very friendly. Some things might be missed. I am used to have a quite
long buffer exactly for these use cases.

Ideally, before spawning the dialog frontend, enough blank lines should
be inserted matching the height of the terminal window, to avoid overwriting
previous outputted lines by other processes.

Bests,
Matteo

-- System Information:
Debian Release: 11.0
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.10.0-7-amd64 (SMP w/24 CPU threads)
Kernel taint flags: TAINT_OOT_MODULE
Locale: LANG=it_IT.utf8, LC_CTYPE=it_IT.utf8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages debconf depends on:
ii  perl-base  5.32.1-4

Versions of packages debconf recommends:
ii  apt-utils     2.2.4
ii  debconf-i18n  1.5.77

Versions of packages debconf suggests:
pn  debconf-doc                <none>
pn  debconf-kde-helper         <none>
pn  debconf-utils              <none>
ii  libgtk3-perl               0.038-1
pn  libnet-ldap-perl           <none>
pn  libterm-readline-gnu-perl  <none>
ii  perl                       5.32.1-4
ii  whiptail                   0.52.21-4+b3

-- debconf information:
  debconf-apt-progress/info:
* debconf/priority: medium
* debconf/frontend: Dialog
  debconf-apt-progress/preparing:
  debconf-apt-progress/media-change:
  debconf-apt-progress/title: