I use a lot Eclipse IDE, and the main issue is the ugly theme of the IDE which use GTK3 theme of Ubuntu Mate, I filled many bugs to eclipse community about the theme issue and all their responses point to use adwaita theme because it's the only theme they support on Ubuntu, so how can I use adwaita theme, and if there is any compact variation it's better ?
The theme seems to be in the repo as
gnome-themes-standard. Install it and change the theme from Appearance.
The Adwaita theme doesn't work in Ubuntu Mate. It's a pure Gnome3 theme.
If it doesn't appear, then as @Newhere said, it won't work on MATE desktop, i.e. it's a pure GNOME Shell theme.
Since Eclipse IDE is a Java environment, there should be a way to choose a theme from the IDE itself, or import one, rather then depend on the system's GTK theme, I think.
There is one other possible way to 'force' a different GTK theme (from this topic) via the terminal - but no guarantees it'll work:
env GTK_THEME="Adwaita" eclipse
Eclipse IDE uses SWT as GUI library which use native components on each OS, unlike Android Studio, IntelliJIDEA or NetBeans which use Swing as GUI library that lets IDE customize GUI components and looks the same on every OS.
You're right that, but that theme is the ugliest and the worst one I even seen.