How to install gimp-GAP for gimp snap

I have a fresh install of Ubuntu 20.04 and I've installed Gimp via Software Manager (so that it became a snap, located in /snap/gimp/252/). Now I want to install gimp-GAP. I see no other way than to use "gimp-gap-2.6.0.tar.bz2" from . However, after unpacking, when running ./configure it complains:

> No package 'gimp-2.0' found
> No package 'gimpui-2.0' found
> No package 'gimpthumb-2.0' found
>
> Consider adjusting the PKG_CONFIG_PATH environment variable if you
> installed software in a non-standard prefix.

Apparently, this gimp-GAP package assumes Gimp has been installed the classical way (not as a snap). What should I do?

Edit:
echo $PKG_CONFIG_PATH gives the empty result and PKG_CONFIG_PATH (as one string) does not occur anywhere in the top-level files of the gimp-GAP installation files.
Searching for gimp-2.0 and gimpui-2.0 and gimpthumb-2.0 gives these locations:

/snap/gimp/252/usr/lib/libgimp-2.0.so
/snap/gimp/252/usr/lib/libgimp-2.0.so.0
/snap/gimp/252/usr/lib/libgimp-2.0.so.0.1000.18
/snap/gimp/252/usr/share/aclocal/gimp-2.0.m4
/snap/gimp/252/usr/lib/libgimpui-2.0.so
/snap/gimp/252/usr/lib/libgimpui-2.0.so.0
/snap/gimp/252/usr/lib/libgimpui-2.0.so.0.1000.18
/snap/gimp/252/usr/lib/libgimpthumb-2.0.so
/snap/gimp/252/usr/lib/libgimpthumb-2.0.so.0
/snap/gimp/252/usr/lib/libgimpthumb-2.0.so.0.1000.18

Should I set PKG_CONFIG_PATH to /snap/gimp/252/usr/lib/ and then again invoke configure?

2 Answers

In the general case you can install plugins as user plugins in the Gimp user profile. Go to Edit>Preferences>Folders>Plugins, this lists two folders, the "system" one in the snap package (or /usr/lib), and the "user" one in /home (~/.config/GIMP/2.10 in recent versions,~/.gimp-2.8` in earlier versions). Just drop you executables in the "user" one.

If you need to recompile your plugin, you need Gimp header files and the best way to get them is to compile your own Gimp, which is not too complicated, since the Gimp development+install output put the necessary files in places coherent with plugin compilation if you use the same environment settings). However your GAP is for Gimp 2.6 and Gimp has moved quite a bit since so I don't know how far you can go with this antique thing, especially if you need Gimp header files.

This said, many functions in GAP have equivalent with Python or Scheme scripts.

My solution is:

1. Remove the gimp snap:
2. sudo apt install gimp
3. sudo apt install gimp-gap

This solution is presented in