Yes, but the big problem is that you are looking at *shared* code, not Inkscape-only code.
Shouldn't this be documented somewhere such as the wiki? Intending code to be shared vs other projects actually using it is also a different thing.
There are actually many other ways to get things in there, with the design such that an ege action can be set to create widgets of other types... so the ege code does not need to be changed, just told which class to use.
This also uses GTK+ directly, which is our main toolkit.
Wasn't one of the goals to change to gtkmm for everything? I seem to recall bryce and derek (jizzbug) working on the gtkmmification years ago. I don't recall their goal being partial gtkmmification and I don't recall any opposition to their work.
Also keep in mind that we have several different things going on here:
* C code
* GTK+ C code
* C++ code
* GtkMM code
And all are different.
This really needs to have documentation somewhere. This is the first mention I've seen about that we *want* C and GTK+ C in the codebase. We need to know what's used where and why (even if it's "we haven't gotten around to changing that yet") as well as what should be used where and why.