GDI across process boundaries   

On Windows XP and Vista, is it legal for one process to draw to another 
process's window using GDI?

For example, if I have process #1 that spawns process #2 using 
CreateProcess and passes its hwnd as an argument, is it legal for 
process #2 to call GetDC and StretchDIBits to draw an image to process 
#1's window?

 From what testing I have done this appears to work on XP (I haven't 
tried on Vista), but is this legal code that I could ship in an application?

Thanks,
Steve.

date: Tue, 15 Apr 2008 17:43:05 +0100   author:   Steven Houston