Most people use a mix of QT/KDE and GTK+/GNOME applications on their Linux system. Because both QT and GTK+ use their own widgets (which are all GUI elements, like buttons, toolbars, menus, checkboxes, etc…) and theme engine, QT and GTK+ applications look different from each other. This is especially bad if you use KDE in Debian: in that case by default no GTK+ theme is configured, making GTK+ applications, like Firefox, look like ugly Windows 95 applications. Mandriva on the contrary does use a common graphical theme for both GTK+ and KDE applications (called Ia Ora), but it’s not easy to change the GTK+ theme if you use KDE or the QT/KDE theme if you use GNOME.
Here’s a howto for Debian and Mandriva which explains how to make your desktop look nice if you’re using a mix of KDE and GTK+. Because Ubuntu is based on Debian, this howto might also apply to Ubuntu, but I have not verified this.
I assume that you are running either Debian Squeeze (testing) or Mandriva 2010.0 or a more recent version of these distributions. For Mandriva 2010.0, you also need to have activated the Backports repositories. You can activate them in the Mandriva Control Centre – Software Management – Configure media sources.
Using GTK+ applications in KDE
If you want to use a unified look for KDE and GTK+ applications, then I recommend using the QtCurve theme. Just like Mandriva’s Ia Ora, it consists of a theme engine for KDE and another one for GTK+ which looks exactly the same.
In Mandriva you install the kde4-style-qtcurve package. If you have urpmi’s “suggests” support enabled (it is by default), then this will automatically pull in both the KDE 4 and the GTK+ theme, and also systemsettings-qt-gtk, a tool which lets you choose the GTK+ theme to use in KDE.
In Debian you need the packages qtcurve and also system-config-gtk-kde to set up the GTK+ theme.
Once you have installed all packages, you can start KDE’s System Settings and go to Appearance. In the Style page, you can choose the theme to use in KDE applications, while in GTK+ Styles and Fonts, you select the theme used by GTK+ applications. If you choose QtCurve in both, KDE and GTK+ applications will look very similar and even use the same KDE icon set.
The QtCurve theme comes with different pre-defined styles. If you don’t like the default look of QtCurve, go to System Settings – Appearance – Style, and click on the Configure… button next to the QtCurve widget style box. Under the button Options there, you find the list of predefined styles.
Of course you can also further fine-tune the theme by going to the Colors and Windows pages in System Settings – Apperance, where you can choose a colour set and window manager theme to your liking (QtCurve has a matching colour set and window manager theme, but of course you can choose something else if you want).
Using QT/KDE applications in GNOME
If you are using GNOME and want to make QT and KDE applications look like all GNOME applications without using Ia Ora, you have to run the qtconfig application. In both Mandriva and Debian, you need to have the qt4-qtconfig package installed. Then in qtconfig you select GTK+ as the GUI style to use. If you run KDE applications, you will also need to set the KDE theme to GTK+. This can be done by running
$ kwriteconfig --file kdeglobals --group General --key widgetStyle gtk
in a terminal window. Before executing this command, you will need to have the kdebase4-runtime package installed in Mandriva or kdebase-runtime in Debian.