Status:
As I confirmed that GtkSourceView3 depends on Gtk3, I prepared the switch in small steps... but it failed:
Beside GtkSourceView UFORadiant depends on GtkGlExt for it's OpenGL rendering and gtkglext1 is not compatible with Gtk3.
I found a Gtkglext3 port on GitHub, but it is broken and abandoned - neither its automake scripts working..
Gtk 3.16+ supports GL rendering natively in a GlArea widget, so I tried to port our glwidget to it... GlArea widget however need OpenGL 3.2+ core profile at least.... so I failed for now.
What I'm gonna do is make gtksourceview2 an optional dependency, you you can compile UFORadiant with or without it. For Gtk3 I'm going to open a branch and will be a mid-term goal.
Yes, I would like to get 2.6 ready for Buster. The build system didn't change I believe. We have an experimental CMake setup, but it is unfinished. You can use our regular (custom) ./configure + make system. I'm not aware of any new dependencies.
Btw would it be possible to upgrade libpng in Buster? As I see testing still has 6.2 which is quite old. (8.0 we are compatible with for sure, 9.0 maybe not..)
hth,
-geever