Putting window inside the desktop

Question

Hi,

I am trying to make a kind of desktop widgets using C#. So far, I've managed to create a window that gets added to the WorkerW window containing SHELLDLL_DefView. This way, my main form is inserted inside the desktop window over the wallpaper. This is exactly what I want except that I have a little problem. It seems like there is an opacity of 50% and a black is rendered as transparent. I don't know where this comes from and I don't know if I can change it. Does anybody knows what might be causing this and how can I fix it?

The code I used to do this is pretty simple. I find the handle to the WorkerW window that contains the SHELLDLL_DefView window as a child and then I call those functions to insert my own form inside as a child :

SetParent(this.Handle, hWndParent);
SetWindowLong(this.Handle, -16, new IntPtr(GetWindowLong(this.Handle, -16) | 0x40000000));

Thank you

Here's how it looks :