Cross-platform UI with Qt4 and Ruby – Mac/Linux HOWTO

Today I’ve spent the day working on figuring out how to make UIs using Ruby and Qt4. If you haven’t heard of it, Qt4 is an awesome UI framework written in C++. Since C++ is way too much work, some great KDE devs wrote a bindings generator for Qt4 called qt4-qtruby. While this package is fairly “linuxy”, it’s pretty easy to build it on Mac OS X too, making it possible to write GUI programs for OS X without having to delve into RubyCocoa which has too much hackiness (in my opinion), or even worse, Objective C. Furthermore, your code that you write on OS X will look great on Windows and Linux too!

Starting from scratch

First, install Ruby. If you’re using Linux, you’ll probably use the package manager to install Ruby and the Ruby development libraries! (Ubuntu will run sudo apt-get install ruby irb ruby-dev) OS X Tiger ships with Ruby by default, but you’ll want to install an updated version, via the Ruby one-click installer, then disable the old Ruby by using the following command:

## Only do this on Mac! Linux doesn’t need this nonsense ##

touch ~/.bashrc && echo ‘export PATH="/usr/local/bin:$PATH"’ >> ~/.bashrc

sudo mv /usr/lib/libruby.1.dylib /usr/lib/_libruby.1.dylib

Installing Qt4 and QtRuby

First, install Qt4 by using your package manager on Linux (in Ubuntu, use the -kdecopy packages, they are more up to date), or by downloading the DMG from the Qt/Mac Open Source Edition Download page. You’ll also need MacPorts (and by proxy, the XCode tools). Also, download the Qt4 Ruby bindings source code from Rubyforge and save it to the Desktop.

Here’s the cool thing about QtRuby, and the advantage of building it from source: the build framework for QtRuby scans through whatever version of Qt you have installed, and dynamically builds the bindings. This means, there’s no waiting for new Qt features to be available in Ruby, it’s always up-to-date! Which is quite handy, because it seems like every minor version of Qt has new cool stuff.

Next, we have to do a bit of hackery – unfortunately, there’s no easy way to install QtRuby but it’s not so hard. Here’s what you’ll run:

cd ~/Desktop

sudo port install cmake   ## CMake is a cool build system

tar -xzvf qt4-qtruby-1.4.9.tgz && cd ./qt4-qtruby-1.4.9

cmake .

make && sudo make install

Try it out!

Once you’ve got it built, try this sample code to see some of the new features in Qt 4.3 – this code will run a natively-styled wizard in Windows, Mac, and Linux without any changes! Unfortunately, this code isn’t very elegant or Ruby-like, but it’s a base that someone could write a really elegant UI framework over like RoR.

require ‘Qt’

a = Qt::Application.new(ARGV)
def create_intro_page

        page = Qt::WizardPage.new do |p|

                p.title = "Introduction"

        end
        label = Qt::Label.new("This is a wizard!")

        label.word_wrap = true

        layout = Qt::VBoxLayout.new do |v|

                v.add_widget(label)

        end

        page.layout = layout

        page

end
wiz = Qt::Wizard.new do |x|

        x.add_page(create_intro_page())

        x.set_window_title("Test Wizard")

        x.show

end
a.exec