How to easily modify a program in Ubuntu (updated)?

Some time ago we talked about how to modify easily a program in Ubuntu. We gave as an example the modification of gucharmap; we got the deb source package, made the change, compiled, created new .deb files and installed them.

We go the same (well, similar) route here, by modifying the gtk+ library (!!!). The purpose of the modification is to allow us to type, by default, all sort of interesting Unicode characters, including ⓣⓗⓘⓢ , ᾅᾷ, ṩ, and many more.

The result of this exercise is to create replacement .deb packages for the gtk+ library that we are going to install in place of the system libraries. Because these new libraries will not be original Ubuntu packages, the update manager will be pestering us to rollback to the official gtk+ packages. This is actually good in case you want to switch back; you will have the enhanced functionality for as long as you postpone that update.

There is a chance we might screw up our system, so please make backups, or have a few drinks first and come back. I take no responsibility if something bad happens on your system. If you are having any second thoughts, do not follow the next steps; use the safer alternative procedure. You may try however this guide just for the kicks; up to the dpkg command below, no changes are being made to your system.

We use Ubuntu 7.10 here. This should work in other versions, though your mileage may vary.

The compilation procedure takes time (about 30 minutes) and space. Make sure you use a partition with >2GB of free space. We are not going to use up 2GB (a bit less than 1GB), but it’s nice not to fill up partitions.

We are going to use the generic instructions on how to recompile a debian package by ducea.

First of all, install the development packages,

sudo apt-get install devscripts build-essential

Next, we use the apt-get source command to get the source code of the GTK+ 2 library,

cd /home/ubuntu/bigpartition_over2GB/
apt-get source libgtk2.0-0

We then pull in any dependencies that GTK+ may require. They are normally about a dozen packages, but we do not have to worry for the details.

apt-get build-dep libgtk2.0-0

At this stage we need to touch up the source code of GTK+ before we go into the compilation phase. Visit the bug report #321896 – Synch gdkkeysyms.h/gtkimcontextsimple.c with X.org 6.9/7.0 and download the patch (look under the Attachment section). You should get a file named gtk-compose-update.patch. If you have a look at the patch, you will notice that it expects to find the source of gtk+ in a directory called gtk+. Making a link solves the problem,

ln -s libgtk2.0-0 gtk+

We then attempt to apply the patch (perform a dry run), just in case.

patch -p0 --dry-run < /tmp/gtk-compose-update.patch

If this does not show an error message, you can the command again without the –dry-run.

patch -p0 < /tmp/gtk-compose-update.patch

Finally, we are ready to build our fresh GTK+ library.

cd libgtk2.0-0
debuild -us -uc

This will take time to complete, so go and do some healthy cooking.

At the end of the compilation, if all went OK, you should have about a dozen .deb files created. These are one directory higher (do a “cd ..“). To install, use dpkg,

dpkg -i *.deb

If you have any other deb files in this directory, it’s good to move them away before running the command. If all went ok, the .deb files should install without a hitch.

The final step is to restart your system. To test the new support, see the last section at this post. Use Firefox and OpenOffice.org to type those Unicode characters.

If you managed to wade through all these steps, I would appreciate it if you could post a comment.

Good luck!

1 comment

  • Rob Fisher

    I needed to fix a bug in a different package and the commands here got me through it. Better to modify the .deb on my system than to download the upstream source. For one thing, the distros all seem to configure things slightly differently. Thanks for the help.

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