Problem moving window

[Matias Szeinfeld <matinger gmail com>]

Environment: Ubuntu 12.04 with Unity and with Gnome3
Hi, i have a problem using gtk_window_move with gnome. There are two
windows, and a function to move one window (not decorated) respect to
the other window (decorated) using gtk_window_move. The problem is the
result. Because not always is the expected. Sometimes the window
(undecorated) position is wrong.

This situation appear first when i use gtkwebkit with the undecorated
parent. Then i try without gtkwebkit, and usually works but not
always. So try more times if you choose the option without gtkwebkit.
The problem is show better if you attach a gtkwebkit to the not
decorated window (uncomment code in the main.c).

This program works in Ubuntu 12.04 with XFCE and not in Ubuntu 12.04
with gnome or Unity.
Can someone help me please?
I send you the main.c.
Compile: gcc -o main main.c `pkg-config --cflags --libs gtk+-2.0 webkit-1.0`

RealPos: http://imageshack.us/a/img404/861/realpos.png
BadPos: http://imageshack.us/a/img840/5949/badpos.png
BadPos2: http://imageshack.us/a/img705/3136/badpos2.png
BadPosWithWebKit: http://imageshack.us/a/img441/4392/badposwithwebkit.png
RealPosWithWebKit: http://imageshack.us/a/img528/4655/realposwithwebkit.png