GTK Theme is not being followed by all GTK Applications (on LXDE)

On my LXDE (Ubuntu Oneiric 11.10) setup, I have recently discovered that not all GTK applications are getting themed with the GTK theme (Adwaita) of my preference. 

My first obvious attempt was to reset theme with LXDE Menu > Preferences > Customize Look and Feel. I set Adwaita in the "Gadget" tab. That Didn't help. Many "sudo" applications along with some other normal GTK-3.0 applications (e.g. evince) stills stayed un-themed.


Ubuntu repository apparently has two tools to set GTK-2.0 themes:

1. gtk-chtheme
2. gtk-theme-switch

Gtk-chtheme is much better in my opinion. So, I gave it a shot and selected "Adwaita" from the list of installed GTK theme. Still no change.

Then as a last resort, I wanted check which GTK theme files are actually being accessed during the initialization of the applications. For that, I started Evince from the console with strace as below:

strace -e trace=access evince 2>&1 | less

After a quick checking through the output it was obvious that my GTK-3.0 themes are not being found by the applications and the theme files are being searched for both in:

1. /home/USER-NAME/gtk-3.0
2. /home/USER-NAME/.config/gtk-3.0

On Ubuntu, GTK themes are installed in /usr/share/themes. So, the quick, easy and clean solution to the problem was to create a sym-link to the GTK-3.0 theme of my preference as shown below:

ln -s /usr/share/themes/THEME-NAME/gtk-3.0 /home/USER-NAME/gtk-3.0

ln -s /usr/share/themes/THEME-NAME/gtk-3.0 /home/USER-NAME/.config/gtk-3.0

After creating the sym-links, I restarted Evince and voila! it's perfectly themed with Adwaita now.


P.S.
If you ware selecting another themes other than Adwaita, make sure /usr/share/themes/THEME-NAME/gtk-3.0 actually exists. Not all themes in /usr/share/themes/ are GTK-3.0 compatible and they will miss the gtk-3.0 directory inside the theme folder.