GUI looks ugly on xfce (xubuntu 16.04)

[Nafees]

On unity (ubuntu 14.04), my project's GUI looked good, but on xfce, it looks really ugly. I've attached screenshots.

on unity, it's running ambiance theme, and on xfce, Greybird.

Any ideas why it's happening?

[Thaddy]

That's simply the underlying engine. Nothing to do with Lazarus.

[Nafees]

so, there's no way to fix it? Is there a way to theme/skin it?

[dogriz]

Sure there is, Thaddy already answered it.
By the way, second image looks better to me. 

[Nafees]

Thanks Thaddy, I've fixed the problem (not 100% though). I changed the LCLWidgetSet (or whatever it is) from project options, to gtk2, it looks kinda better now.

[munair]

With XFCE 4.12 it is best to use themes and theme engines for gtk2. Some themes support both gtk2 and gtk3. I had the same problem and a few themes such as Greybird and Adwaita are ok. It is also important to copy/move any additional themes to /usr/share/themes so all applications can use them. If you use a theme from /.themes in your home folder some applications requiring root rights such as Synaptic default back to the unattractive standard theme.

[Nafees]

Thanks Artie, that solved another problem I had (with some other application).