Re: Uninstalling a package removes other essential packages: What is the best course of action?

[<tomas@tuxteam.de>]

On Thu, Feb 17, 2022 at 07:05:33AM +0100, Stella Ashburne wrote:
> Dearie
> 
> > Sent: Wednesday, February 16, 2022 at 10:05 PM
> > From: tomas@tuxteam.de
> > To: debian-user@lists.debian.org
> > Subject: Re: Uninstalling a package removes other essential packages: What is the best course of action?
> >
> >
> > So why not do your research yourself?
> >
> Honestly I don't know where to start.

There are, of course, many ways to go about it. And, of course, it
has the potential to eat all the time resources available, and then
some. So everyone has to choose where to cut :)

I'll present one way here, which always reminds me of the incredible
gift we have: access to most of the source code for the things we
use. For our case (libthai), start with apt. The library package is
called libthai0, so (I'm on buster; YMMV):

  tomas@trotzki:~$ apt rdepends libthai0
  libthai0
  Reverse Depends:
    Depends: libthai-dev (= 0.1.28-3)
    Depends: php-wikidiff2 (>= 0.1.25)
    Depends: libsombok3 (>= 0.1.12)
    Depends: scim-thai (>= 0.1.12)
    Suggests: libqt5core5a
    Depends: libpango-1.0-0 (>= 0.1.25)
    Depends: libm17n-0 (>= 0.1.12)
    Depends: ibus-libthai (>= 0.1.19)
    Breaks: libthai-data (<< 0.1.10)
    Depends: gtk-im-libthai (>= 0.1.12)
    Depends: gtk3-im-libthai (>= 0.1.12)

That gives you the "reverse dependencies", i.e. which packages do
depend on libthai? Many of those (roughly: those having "im" in
their name) are "input methods". Also that ibus- thing. The two
dependencies with potential to "spread" are libpango (nearly
everything rendering text these days uses that) and libqt5core5a
(if you are using Qt applications).

Let's have a look at this libpango-1.0-0:

  tomas@trotzki:~$ apt show libpango-1.0-0
  Package: libpango-1.0-0
  Version: 1.46.2-3
  Priority: optional
  Section: libs
  Source: pango1.0
  Maintainer: Debian GNOME Maintainers <pkg-gnome-maintainers@lists.alioth.debian.org>
  Installed-Size: 441 kB
  Depends: fontconfig (>= 2.1.91), libc6 (>= 2.14), libfribidi0 (>= 1.0.0), libglib2.0-0 (>= 2.61.2), libharfbuzz0b (>= 2.1.1), libthai0 (>= 0.1.25)
  [...]

So the source package is pango1.0. You could install the source
package and have a look into it, but Debian offers you:

  https://sources.debian.org/

Enter "pango1.0" into that little box ("by package name"). If
you're bold, you can just stick that into the URL

  https://sources.debian.org/search/pango1.0/

You click on that one URL and there you have the sources, nicely
sorted by Debian version. Click on yours (mine is buster). You'll
notice that little box on the right labelled "search" (there's
also a dropdown: we'll ignore that). It is pre-set with
"package:pango1.0". We add to it (separated by a space) "libthai"
and click on "search".

Now it searches all of pango's sources for occurrences of libthai.

I'll leave that here. Explore. Come back with questions. And mind
those rabbit holes. Only pick the enjoyable ones :)

Cheers
-- 
t

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