Hey, I’m trying to get the size of a docked panel with GetWide() but it doesn’t work. Is there a specific way to do that?
Pic of my problem : http://prntscr.com/g9sy78
As you can see the button is not at the limit of my docked panel (in white)
try :InvalidateLayout(true) after docking 
If you want to stay consistent you can always dock the button to the right and set large top+right+bottom dock margins, or you can update its position in ActionContainer:PerformLayout().