>You and the GP say it's not.
But I did not say that. In the reply to the comment you've linked you
write that "this thread believes Tk is as good as QT". I am puzzled by
this conclusion because I do not see any comparison to Qt at all.
Certainly, I didn't want to suggest any with my comments.
If you want to know
my option on how Tk compares to Qt, I currently believe that, for the most part, they serve different use cases, with some overlap in the middle. Tk is better than Qt in one area (roughly: small-to-medium applications developed by a lone hacker ASAP) and Qt is better than Tk in another (roughly: medium-to-large applications developed by a team on some sort of a schedule).
Qt does a lot more than Tk. It comes with more features, e.g., networking abstractions.
Compared to it, Tk is limited. Qt looks better, too — much better on *nix.
I would not recommend Tk over Qt in the general, catch-all,
could-become-a-kitchen-sink-application case. (In
fact, working well in the general case seems to be a major selling
point for Qt.) If you develop one, chances are you will find yourself
wanting to do something that Tk can't. In other words, I would expect a
large application to outgrow Tk before it outgrows Qt.
I recommended Tk specifically for making a GUI quickly. It is good for
prototyping and rapid iteration and has neat widgets like canvas and the
text editor that help a lot with that. Tcl with Tk is expressive, so you can do a
lot in under 1000 lines of code (toy example: [1]). The
Tcl REPL helps more still, as does a great binary deployment story. After the prototype or MVP, once you understand what you want to do better,
you may stay with Tk if you decide it suits your needs or switch to
something else.
>Is there anything Tk can't do?
That is a very open-ended question. One thing that comes to mind is
integrating with the host platform's accessibility features. Most
cross-platform GUI toolkits suck at it. There is a wishlist wiki page
[2] that might offer some hints at what other things Tk
users find missing.
>Does Tk make it possible to use webfonts I see on websites?
Not easily. See [3].
[1] https://tcl.wiki/41294
[2] https://tcl.wiki/4055
[3] https://www.reddit.com/r/Tcl/comments/456ydh/is_there_a_way_...