How submit a bug fix to Ubuntu?

I've submitted a 'papercut' bug to launchpad, that I think I can possibly have a go at fixing.

What is the process for obtaining the relevant source code (I'm not entirely sure where I'd find the code responsible) and then submitting the change back to Ubuntu?

Main tool on Ubuntu/Launchpad to manage SW version controls and SW changes is Bazaar. You can find a wiki here.

In summary, to submit a change you should:

• Install bazaar: sudo apt-get install bzr
• Generate a SSH key and register it to you launchpad user ID (see the wiki mentioned above);
• Look for the package you want to fix. As an example let's say the package is 'swtobefixed'.
• Download the branch: bzr pull lp:swtobefixed
• Update the local code and test it on your machine
• Commit changes: bzr commit -m "Revision 1 Comment"
• Push the change to launchpad: bzr push lp:swtobefixed

Please consider packages works with permissions. References:

• http://daniel.holba.ch/blog/2011/03/ubuntu-development-guide-fixing-a-bug-in-ubuntu/