Hello.
I know it is a recurring complaint about the small size of the preview image in some filters on GIMP 2.8 and earlier versions, but it seems that GIMP 2.9 has gone to the opposite extreme. Preview in GEGL filters is done over whole full image. If you work in a large image, the preview can be very slow and annoying (much more if you have a slow computer). I have seen that very few GEGL filters have an option to preview only the selected area, although it would be good also that you can move or change the selected area in real time.
But I think we should also have the option to choose that the preview filter is applied only in a smaller copy of the original image (similar to what happens in G'MIC).

So, do you know whether there are plans to improve the filters preview methods on GIMP 2.10? Or basically it will remain in the state that is in GIMP 2.9?

Well, in IRC GIMP channel was told that there are plans to improve the "preview" situation.
They have also made me realize that if you apply much zoom in the image, then the preview is applied faster to the visible area and you can pan at the same time. But this way I think it's difficult to have an overview of how the filter looks in the whole image. I still think that the kind of preview that has G'MIC is the best choice in most cases.

There was an article :
http://libregraphicsworld.org/blog/entr ... evelopment

About how performance and speed in Photoshop is simply better, with that had this interesting part :