What I did for change the Qt apps style is add this line:
In the environment file:
Then reboot the system.
This is how Focus Writer looks like in my system:
AFAIK the L&F would probably be achieved delegating the rendering to GTK from the Qt app. The problem is that all of the eOS APIs, IIRC, are written in Vala therefore you won't be able to interact with them.
If you only care about the theming of the app to be the same as the OS make the Qt use the current gtk theme but if you care about the os APIs ...
This situation with VLC appeared on my Elementary-Os too.
I found a solution in the Ubuntu forum and videolan forum
So, what you can do is, open a terminal and open the environment file:
sudo nano /etc/environment
and add a line to it:
Save it and reboot your computer.
This helped me getting VLC in the right scaling....
You should go through this bug report.
qtgtk style cannot detect elementary gtk style
There are fixes mentioned in this report.
The first being(for x86_64):
gconftool-2 --set --type string /desktop/gnome/interface/gtk_theme Elementary
And for 32bit applications on x86_64:
According to this post ia32-libs is no longer included in the ...