Faking an undo step for functions that aren't undoable in Gimp

[Ofnuts]

Gimp 2.6.12? If you want to publish your thing you have better check that it still works with 2.10, and perhaps that there isno equivalent in 2.10 already, because things have improved significantly over the last 12 years.

Otherwise I can confirm the non-undoability of the pixel regions operations, but doing a set_pixel(get_pixel()) could be a bit more efficient than calling a GEGL operation over the whole layer...).