only use tkagg or agg backends?

[stevengj]

Nowadays the Tk backend works pretty well and is available everywhere. Maybe we should just use it (or the Agg backend for non-interactive code) and drop support for all of the other backends (which complicate the code a lot for not much benefit).

@PaulSoderlind, you mentioned wanting the Qt5 backend; could you elaborate?

[PaulSoderlind]

wanting the Qt5 backend

I don't have a strong preference and I might well use Tk from now on.

I previously used Qt5 since it had two advantages compared to Tk: crashed less often and did not require me to click the figure window in order to get back to the REPL/editor (Windows 10). On the other hand, Tk seems to scale better with the screen dpi.