Hum, the [docs on `g_win32_get_command_line()`](https://developer.gnome.org/glib/unstable/glib-Windows-Compatibility-Functio...) mention that [`g_option_context_parse()`](https://developer.gnome.org/glib/unstable/glib-Commandline-option-parser.htm...) (that we use) expects locale-encoded strings, not UTF-8 ones. GLib 2.40+ has [`g_option_context_parse_strv()`](https://developer.gnome.org/glib/unstable/glib-Commandline-option-parser.htm...) which expects *GLib filename encoding* (that is, UTF-8 on Windows), but it's fairly recent.
(Or we could please @codebrainz and rewrite using GApplication which does this for us… but that would be a lot of changes :))