How to reduce size of file chooser dialog?

["Felix E. Klee" <felix klee inka de>]

What I tried already, on Arch:

    $ gsettings set org.gtk.Settings.FileChooser window-size '(800,600)'
    $ gsettings get org.gtk.Settings.FileChooser window-size
    (800, 600)
    $ evince
    $ gsettings get org.gtk.Settings.FileChooser window-size
    (1203, 902)
    $ pkg-config --modversion gtk+-3.0
    3.22.8

It seems that the size is reset every time a GTK+ 3 application is
started.

The file chooser dialog is unusable with only part of it visible. The
thing here is that the screen is a high res screen, and so I've enabled
`GDK_SCALE=2`. This unfortunately also doubles the size of the file
dialog.

What to do?