Some ideas and tools to develop Python 3.8 plugins for GIMP 2.99.4. GIMP 2.99.4 is a unstable pre-release of GIMP 3. It suppots Python 3, however it's documentation is rather poor, this is why I have been playing around to configure a setup to develope GIMP plugins based on Python. This aims to bring pip and related tools into the GIMP environment.

Also, a GIMP plugin must run inside GIMP... So, let's hack to have a proper developing environment!

GIMP 2.99.4 comes with pre-compiled binaries in a flatpak distribution. So, first of all if you don't have flatpak, assuming you are on a Debian-based Linux distro:

$ sudo apt install flatpak

Flatpak is a distribution system, like Apt, but focused on end-user applications and isolation. Like Docker, it isolates the compiled application in its own Sandbox, however it is not actually virtualized. Let's install GIMP 2.99.4:

⚠️ Note: There is a problem with the 2.99.6 release involving matplotlib and cairo install in the flatpak distribution. It will be addressed on the future. Thus, the commit of the flatpak GIMP where version 2.99.4 was released will be pinned.

flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
flatpak remote-add --if-not-exists flathub https://dl.flathub.org/beta-repo/flathub.flatpakrepo
flatpak install --user https://flathub.org/beta-repo/appstream/org.gimp.GIMP.flatpakref
flatpak update --commit=9878eaae0e90ac9395cfc7e62d85f8c4299769ddc7f19f3f20cd380ed72a9582 org.gimp.GIMP

Say yes to permissions, etc. Then you will be able to run GIMP from flatpak:

flatpak run org.gimp.GIMP//beta

GIMP is using a sandboxed Python distribution inside its flatpak distribution. This is a tricky way to finally achieve a separate Python distribution for GIMP. If you start GIMP and go to the menu entry
Filters > Development > Python-Fu > Python Console a window will be prompt with a Python console that will say:

GIMP 2.99.4 Python Console
Python 3.8.6 (default, Nov 10 2011, 15:00:00) 
[GCC 10.2.0]
>>> 

If you want to access the Python Console directly from your terminal emulator, you can run:

flatpak run --command=python org.gimp.GIMP//beta

Although this is possible, you have to remember that GIMP plugins have to run inside GIMP. This is because are based upon libraries importer using the gi.repository API that are only present when we are running inside GIMP.

If you want to set up a development environment for Python plugins you will need to install some tools, for example pip package manager and a debugger. To do so, a GIMP Python plugin has been developed which prepares the environment.

1. Add to GIMP the path to this repo plug-ins folder Preferences > Folders > Plug-ins.
2. Reboot GIMP.
3. Go to a new entry on the menu Python > Tools > Python Setup, click and wait. A prompt should appear with the output of the steps executed to install the environment.
4. Remember to add your site-packages plug-in folder to Preferences > Folders > Plug-ins.

• Create a minimal Python plug-in to create a PyDev client. → First version available.
• Fork Python Console plug-in to be able to run IPython. Only forked, for the moment states the same functionality. Update: now 4 consoles are working, some of them are more responsive, but no IPython for the moment.
• Create a minimal Python package which depends on IPython and pydev, and other dev stuff, to install it to be able to use the new plugins.
• Create a pip wrapper to show useful info like pip list and also install PyPI packages from GIMP to GIMP Python environment.
• Define proper licence in the repo. → GNU GPL v3 added.