Absolute coordinates using "wl_shell_surface_set_transient"

[Tarnyko]

Hi folks, 

Wayland/Weston 1.2 here ; I recently needed to display a surface using 
absolute coordinates. Let's say, 100x100 starting from the upper left corner 
of the compositor. 

So here is the (working) approach I used : 

window->surface = wl_compositor_create_surface (display->compositor);
window->shell_surface = wl_shell_get_shell_surface (display->shell, 
window->surface);
wl_shell_surface_set_transient (window->shell_surface, window->surface, 100, 
100, 0); 


It works this way, surface always displays at 100x100.
But my question is : is it supposed to work in the first place ? And will it 
still be working in future releases ? 

Regards,
Tarnyko