ADVANCED COMPOSITING & RETOUCHING - Chapter 4, Exercise 2
Why GEGL Doesn't Fully Match Smart Objects
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QUESTION:
A GIMP user says "GEGL means GIMP has non-destructive filters now, so it's
fully caught up with Photoshop's Smart Objects." Using this chapter's own
warning box, explain what's incomplete about this claim.

SOLUTION / EXPLANATION:

This chapter's warning box names two specific, concrete gaps that this claim
overlooks - it isn't just a matter of different terminology for the same
underlying capability.

First, GEGL's non-destructive behavior applies to individual filter
settings - reopening a filter dialog and finding its parameters still
adjustable. That's real and genuinely useful, but it's narrower than what a
Smart Object provides. A Smart Object preserves a layer's original pixel
data through an entire arbitrary sequence of TRANSFORMS - scaling, rotating,
skewing - not just filters. GIMP has no equivalent container for this: scale
a normal GIMP layer down and back up, and it loses quality in exactly the
same way an un-converted Photoshop layer would, because GIMP has nothing
that preserves the original data the way a Smart Object does. GEGL simply
doesn't address transforms at all - only filters.

Second, non-destructive behavior in GIMP isn't universal even within
filters. Not every GIMP filter or tool is GEGL-based, and some operations
remain immediately, permanently destructive once applied - with no "reopen
and adjust" option at all. In Photoshop, virtually any filter applied to a
Smart Object automatically becomes non-destructive as a Smart Filter,
consistently, across the board.

So the accurate framing isn't "GIMP is fully caught up" - it's that GIMP has
made real, welcome progress on non-destructive FILTER settings specifically,
while still lacking any equivalent to a Smart Object's broader guarantee
across transforms and its consistency across all filters and tools.

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WHY THIS WORKS AS AN ANSWER:
It separates the claim into its two distinct components (filters vs.
transforms, and universal vs. partial coverage), and shows specifically
where GEGL succeeds and where it falls short of a Smart Object, rather than
either fully endorsing or fully dismissing the GIMP user's claim.