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Port GimpFu to Gimp 3?

This issue is for discussion of the future of GimpFu in Gimp 3, as was suggested on the dev irc.

PyGimp (GIMP Python) has two API's and many modules. GimpFu is the simple API. The full API of PyGimp could be obsoleted while keeping the GimpFu simple API. Some modules of PyGimp (e.g. gimpshelf and gimpui) could be obsoleted because their capabilities have been implemented in Gimp proper. GimpFu could be deprecated or obsoleted because GI lets authors write Gimp plugins in any language binding. But a ported GimpFu provides:

  1. backward compatibility for existing third party plugins
  2. a simpler API (continues to hide much complexity)

A prototype, proof-of-concept port of GimpFu to v3 is in a MR merge request referencing this issue. The code is in my GitLab fork of Gimp, at plug-ins/gimpfu (should eventually replace v2 plug-ins/pygimp. It should remain named gimpfu because existing plugins import that name.) The port's branch has a document "gimpfuPluginPortingGuide.txt" that tells plugin authors how to make the few changes to port a v2 GimpFu plugin to v3. The v2 document "GIMP Python Documentation" remains mostly accurate. Those documents tell what GimpFu does. To experience what the proposed GimpFu port does, you should try porting a Python plugin with and without the GimpFu port.

Status of the port. The prototype runs several existing v2 GimpFu plugins after minor edits to them. For example, the v2 clothify.py plugin will run in Gimp 2.99. However much work remains.

The port is pure Python (no compiled C.) The static binding of v2 is all dynamic in v3. The MR does not alter makefiles to install the port. The port can be installed as a third-party plugin simply by copying to ~/.config/GIMP/2.99/plug-ins. However it requires one hack of Gimp: comment out the preemptive return after the warning "Argument with name '%s' already exists" at line 1159 of libgimp/gimpprocedure.c. (I will open another issue about that.)

I do not necessarily suggest you accept the MR as is, since it is very rough. It is readable but contains notes, cruft, and TODO's. I think there are many Python programmers in the Gimp community who could understand, contribute to, rewrite, and maintain the code.

Its a case where I needed it, so I worked on it. The code is open sourced. I can continue to contribute. I hope the code can be put under the Gimp umbrella, I don't want to be solely responsible.