i have a fix work for me : change screen resolution open:dininput.ini and set your resolution (for example 1920 and 1080) if you wish to have the RO client at full screen.
I have 0 before i change my resolution
PHP:
; Override RO window position and size.
; Ignored if WindowWidth = 0 or WindowHeight = 0. ; Command line switch: -wX,Y,Width,Height
WindowPosX =0
WindowPosY =0
WindowWidth =1024
WindowHeight =768