Service Returns NULL Windowstation and Desktop Handles

ID: Q161337

3.51 4.00 WINDOWS NT kbprg

The information in this article applies to:

• Microsoft Win32 Application Programming Interface (API) for Windows NT, versions 3.51, 4.0

SUMMARY

On Windows NT 3.51, GetProcessWindowStation() and GetThreadDesktop() will return NULL handles from a service that has not called any USER or GDI APIs.

MORE INFORMATION

Initially, a service will not have a windowstation and desktop associated with it. In order to associate a windowstation and desktop to the service, the service must call a USER or GDI API that interacts with the service's desktop such as GetDesktopWindow() or CreateDC(). Once one of these APIs has been called, GetProcessWindowStation() and GetThreadDesktop() will return valid handles.

On Windows NT 4.0, a service will have a windowstation and desktop associated with it initially so there is no need to call a USER or GDI API to connect the service to the windowstation and desktop.

REFERENCES

For more information on windowstations and desktops, please refer to the Win32 SDK documentation.

KBCategory: kbprg KBSubcategory: BseService Additional reference words: 3.51 4.00 kbdss

Keywords          : kbKernBase kbService kbGrpKernBase 
Version           : 3.51 4.00
Platform          : NT WINDOWS

Last Reviewed: December 25, 1996