I'm not familiar with this theme, or even GTK+2 theming in general, but from a quick search, it looks like this theme requires Nodoka theme engine, which presumably has to be installed separately.

Two suggestions: - Test with another GTK+2 application and see if it works. If it doesn't then it's probably unrelated to Geany and should be raised with GTK+ or the theme engine authors. I know the open source application [Hexchat](https://hexchat.github.io/) works on Windows and uses GTK+2, if you can't think of any other GTK+2 windows apps. - Try some other themes, particularly any which might be shipped by default, and see if they work. If so, it's probably something related to Nodoka like not having it installed.

Most likely there will be some debug messages printed if/when the theme fails to load, which you can see using `Help->Debug Messages`.

How can i find, which themes are installed

GTK+ has preset paths to look in, usually `$PREFIX/share/themes` and somewhere below your home directory (depends on the platform, on win32 it's a funny path like AppData or such, depending on Windows version). There is probably also an environment variable to control where GTK+ looks.

respectively where does Geany look for them?

Geany itself isn't involved, but the GTK+ bundled with Geany will look below Geany's installation directory as that's its `$PREFIX`, in addition to the themes directory below your home directory.

I thought that, if the GTK theme chooser is offering me a theme for selection, that the theme is there.

AFAIK there is no official GTK+ theme chooser, which if true means you may have installed some 3rd party utility (possibly bundled with a 3rd party release of GTK+?).

C:\p\GTK\2.0\share\themes\Nodoka-Squared

This `C:\p\GTK\2.0` directory doesn't come from Geany, it must be a separate GTK+ distribution that you installed separately, so the GTK+ bundled with Geany won't look there for themes. The GTK+ that comes with Geany would be found under it's directory in `C:\Program Files (x86)\Geany`, and most likely looks for themes in `C:\Program Files (x86)\Geany\share\themes` (can't say for sure as I don't have a win32 installation available).

Copying the themes worked, but it turned out to be more complicated than expected. Geany installs itself by default into "C:\Program Files (x86)", and it turned out that I did not have permissions to modify this directory. I finally started a new shell using "administrator privileges", and copied the theme files from this shell, and now my themes show up.

Closed #2429.