Suppress opening the GKSQT app when plotting inline

[piechologist]

When using KittyTerminalImages.jl and Plots.jl with its default GR backend, the GKSQT app is automatically launched in the background. This is a bit annoying and adds to the TTFP.

The Plots.jl package suggests to set ENV["GKSwstype"] = "nul" when you just want to plot inline.

I could make a PR that adds

• ENV["GKSwstype"] = "nul" to pushKittyDisplay!() and
• delete!(ENV, "GKSwstype") to popKittyDisplay!().

That makes it possible to switch back and forth between inline and GUI plotting during a REPL session. I tested it locally and it works well.

What do you think?

[simonschoelly]

Kind of makes sense - although I feel a bit conflicted as maybe the authors of GR explicitly wanted the users to be able to change the behavior themself by setting that environment variable? Do you know how it is handled when using Jupyter? But if there is no better solution, then lets go with the one you proposed here.

[piechologist]

We had a discussion on discourse last year and the author of GR himself (jheinen) suggested to set that ENV variable. I guess the variable is there as a workaround because GR is a framework written in C and Plots.jl just wraps it. Just a guess though.

I'm not familiar with Jupyter, sorry.

How about something like set_kitty_config!(:suppress_launching_gui_app, false) to allow opting out?