Changing Gtk theme

[StefanMathis]

Hello,

I'm currently developing a GUI with GTK.jl and I'd like to change the theme at runtime (e.g. to the win32 theme when the program is executed on Windows). Is there an easy way to do this? I searched quite a bit on the web and found for example this explanation on how to do it with Python:
https://stackoverflow.com/questions/42881112/pygtk3-how-to-change-application-theme

However, as far as I understand, the themes for Gtk.jl are provided by the .jll packages in the main Gtk.jl file. Does this mean that for any specific theme a .jll-Package needs to be built? Furthermore, how can one select a specific theme? For example, in Gtk.jl the following packages are imported:
adwaita_icon_theme_jll, hicolor_icon_theme_jll
From the look and feel, I'd say that the Adwaita theme is used by default, however I could not identify where in the code this is actually specified.

Any help would be appreciated very much :-)

[tknopp]

Could you try setting it using an environment variable? See https://unix.stackexchange.com/questions/14129/gtk-enable-set-dark-theme-on-a-per-application-basis

[tknopp]

Yes this works

GTK_THEME=Adwaita:dark julia

makes all widgets dark.

[StefanMathis]

Thank you very much for your answer. To clarify a little bit for anyone as uninformed as myself who stumbles upon this thread: You can set the environment variable directly in Julia by the following command:
ENV["GTK_THEME"] = "win32"
I use this command in the __init__ function of my module. Works like a charm!

[tknopp]

I think there is also some possibility to do this at runtime within Gtk but actually this solution with the environment variable and the __init__ function is also fine from my perspective.

[StefanMathis]

I didn't test it, but I think you can actually change the theme at runtime because __init__ is just a function :-)