Bug#865738: apt: progress bar broken by full-screen maintainer script actions

[Christoph Berg <myon@debian.org>]

Package: apt
Version: 1.4.6
Severity: normal

Hi,

during the unpack phase, any full-screen terminal output (ucf, dialog,
less) from maintainer scripts seems to reset the term layout such that
the progress bar isn't properly displayed anymore. dpkg's messages use
the last terminal line as well, and the progress bar is only
flickering. Resizing the window fixes it.

-- System Information:
Debian Release: 9.0
  APT prefers stable
  APT policy: (800, 'stable'), (600, 'unstable'), (150, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.utf8, LC_CTYPE=de_DE.utf8 (charmap=UTF-8), LANGUAGE=de:en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages apt depends on:
ii  adduser                 3.115
ii  debian-archive-keyring  2017.5
ii  gpgv                    2.1.18-6
ii  init-system-helpers     1.48
ii  libapt-pkg5.0           1.4.6
ii  libc6                   2.24-11+deb9u1
ii  libgcc1                 1:6.3.0-18
ii  libstdc++6              6.3.0-18

Versions of packages apt recommends:
ii  gnupg   2.1.18-6
ii  gnupg1  1.4.21-4
ii  gnupg2  2.1.18-6

Versions of packages apt suggests:
pn  apt-doc                      <none>
pn  aptitude | synaptic | wajig  <none>
ii  dpkg-dev                     1.18.24
ii  powermgmt-base               1.31+nmu1
ii  python-apt                   1.4.0~beta3

-- no debconf information

Christoph