I found a lot of tutorials how to build application with Ruby and Qt, but i have no idea how anybody else will be able to run it! I am using Ubuntu 11.10, ruby 1.9.2 with rvm and: rbqtapi -v output "QtRuby 2.0.5 using Qt-4.7.4"
P.S. I have no idea how to build *.deb, it will be my first desktop app, not web.
If you're sold on QT, then you will need your users to install all the support libraries for QT (and anything else), then you can upload a rubygem to rubygems.org for your users to download.
Once, they've installed the support libraries, you'd only need to update your rubygem, which is fairly quick and easy for updates.
You may also wan to look at visualruby. It uses GTK. Then you'd install the GTK libraries instead of the QT ones.
As far as .deb packages go, I tried to research the same thing with little success. The rubygems packaging system is designed to distribute ruby programs, so it is the best way to go. Also, you'll need to install different support libraries for different platforms. If you look at visualruby's install page, you can see how to install GTK for Linux and Windows.
Good Luck.
please have a look on http://shoesrb.com/ this is the best way I heard off for writing GUI apps.
Shoes has now not it's greatest time, but we put our best time to make it better, give it a try and someone will help you.
In case you are in need of assistance just ask as question on #shoes IRC channel on freenode servers.
