Summary

Currently, the minimum version of Tcl/Tk supported by mpl is 8.4, which is also the lowest supported version for CPython 8.5-8.10. However, as highlighted in #8680, we don't fully support 8.4: show() uses the -topmost attribute, which was only added to Linux in 8.5, and full_screen_toggle() uses -fullscreen, which only worked on Mac OS X before 8.5.

However, I haven't seen a single other bug report using 8.4, and can't find any builds of Python 3.8+ that ship with it, so that may explain the lack of issues other than #8680.

Proposed fix

Two options:

• Fix support for 8.4, catching TclErrors in the two functions above
• Drop support for 8.4. This would allow, among other things, setting a default and retrieving the selected format in Tk "save figure" dialogs, and using native Ttk widgets in any future updates (such as if anyone ever decides to port figureoptions to Tk).