bug#51968: Missing dependency for Xournal++

[Alexander Asteroth]

Hi Daniel,

On Mon, Dec 20 2021, 14:47:24, Daniel Meißner 
<daniel.meissner-i4k@ruhr-uni-bochum.de> wrote:
>> I can reproduce the missing icons issue by running 
>>
>>> guix shell --pure -f xournalpp-fix.scm -- xournalpp
>>
>> as suggested below. Wondering why the icons are not missing when I run
>> xournalpp in my environment I discovered that
>>
>>> guix shell --pure gtk+ -f xournalpp-fix.scm -- xournalpp
>>
>> resolves this problem.
>
> This is weird since gtk+ already is an input to xournalpp (despite not a
> propagated one).  What desktop environment are you using?

That is *really* strange, is it? I'm using no desktop environment. Just
EXWM as window manager.

>
>> Looking at your xournalpp-fix.scm file I wondered what the function
>> modify-input exactly does (and how to add gtk+ to the append
>> clause). I don't find neither documentation in the manuals nor code
>> for it in a guix checkout (when I do a recursive grep in the source
>> for guix or gnu modules the result is empty).
>
> This ‘modify-input’ form is actually a macro and it is documented in the
> latest version of the manual [1].  This macro is part of a big surface
> level syntax change for packages which arrived with the
> core-updates-frozen merge. See [2] for a nice blog post.

In the meantime I found that as well. But the documentation (from my
perspective) is unfortunately incomplete. It neither specifies the full
semantics (without looking into the macro-code) nor does it tell me,
what kind of clauses I can put e.g. into (modify-input ...). How is
(append ...) translated? The web document links to the list append
function which it might somehow translate to but that is not documented
either (at least I dont find it).

This seems to be a general problem with the documentation to me (that
it doesn't fully document neither syntax nor semantics). Others have
problems using guile (which I don't have)...

Cheers,

Alex

> As I have
> mentioned, gtk+ is already an input for xournalpp.  If it were not, you
> could add it using:
>
> (modify-inputs (package-inputs xournalpp)
>   (append adwaita-icon-theme gtk+))
>
> Best,
> Daniel
>
> 1: 
> https://guix.gnu.org/manual/devel/en/html_node/Defining-Package-Variants.html#index-modify_002dinputs
> 2: https://guix.gnu.org/de/blog/2021/the-big-change/