weird tiny libreoffice writer embedded

[magowiz]

Hi,
I was trying some of the examples available in website, the one with Writer in a Swing JFrame, the code works but as soon as it starts I get the frame size normal (500x500) but the libreoffice writer "window" is tiny and misplaced and cannot resize/access all controls.
I'm using Java Oracle SDK 8, in Ubuntu Linux 15.10, Gnome-Shell Desktop

I provide you a screenshot and the code used by me (even if is almost the same of original from your wiki, despite changes).

LibrePanel.zip

[gitxpy]

for reference, problem is similar with issue #18 (gtk3),
and it's working ok with gtk2 (rh6).