From 0.9.183 version, xt7-player will try to find qt3 configuration tool for you, so part of the following text is outdated.
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The problem:
Xt7-Player is written in gambas2, which only supports qt3 widget style.
(gtk is also supported but not well enough)
If you're using another desktop manager like gnome,xfce or kde4, probably xt7-player will look like this:

Very ugly, i admit.
This is because probably you never configured a decent qt3 style
The solution:
When you install xt7-player along with its dependancies, you also install qt3 libraries,
they comes with a tool named qt3config which allows you to choose your preferred style.
Some distributions uses the name "qtconfig" instead of "qt3config", this is a little ambigue, because qt4 libraries uses a tool named qtconfig too.
If this is the case, you'll probably have two tools named qtconfig, one for qt3, one for qt4.
You will need to use the one for qt3.
So, to summarize:
- Launch xt7-player, if it looks bad,
- Search your hd for a tool named qt3config and choose a style that you like, save and restart xt7-player.
- if you don't find qt3config,
search for qtconfig, choose a style that you like, save and restart xt7-player.
- if nothing changed in xt7-player look, search again and find another tool named qtconfig, in a different folder of course.
Here is qt3config:

Here is xt7-player with new domino style applied

