Hey, On Sat, Sep 24, 2016 at 07:23:30PM +0200, Jon Nordby wrote: > On 10 September 2016 at 23:12, Philip R. Dutton > <fooledbyprimes@xxxxxxxxx> wrote: > > I ran across much talk and some implementation of GEGL. I can see how the > > Undo /History features would make great use of the DAG graph data structure > > used by GEGL. > > > > Q: How hard will it be to log the GEGL graph evolution to disk in real-time > > using perhaps a rolling log? What is the best approach for an idea like > > this? > > For the approach, pippin and I sketched together a basic spec a couple > of years back. > https://mail.gnome.org/archives/gegl-developer-list/2012-June/msg00004.html > https://git.gnome.org/browse/gegl/tree/docs/journal.txt > > [...] > > *However*, I believe the GEGL graphs used in GIMP are still "short > lived" - used for the duration of one operation and then applied > destructively. Meaning that there is no one graph which represents the > entire document and thus the evolution of your artwork. > It may be possible to try to stich together a sort of journal from all > these , but probably there would be need for a significant amount of > GIMP specific logic in addition... Not sure of the feasibility here. Other than what Jon already said, I wanted to point out that if you ran gnome-photos [*] with G_MESSAGES_DEBUG=all and GNOME_PHOTOS_DEBUG=gegl, then it logs an XML representation of the graph whenever something causes it to change. The final graph is stored persistently (as XML) in ~/.local/share/gnome-photos. Since the editing UI is relatively simple compared to GIMP, we use snapshots to undo a whole series of operations, instead of undoing every single change in the properties. I think this is similar to transactions in Jon's references. The snapshots are again just XML in memory. All this is pretty straightforward in gnome-photos, because, unlike current GIMP versions, it is structured for non-destructive editing. Cheers, Rishi [*] You'd need at least version 3.20.x.
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