Display issue while showing external process window

[maxmontgmx]

Hi all,
I need to embed external process main window into my WPF UI application.
For that, I use "user32" API (SetWindowLongPtr, SetParent, SetWindowPos) to make the external window child of a control of my app.
This mecanism works perfectly in a sample WPF projet, but in a WPF UI projet, I distinguish the window with all controls and controls are active. But the controls are like a filigram.
Do you know how I can display the window correctly?
Thanks for your help