Issue using Show Desktop with SetParent in WPF

Question

I am working on a simple active desktop replacement for a school that is migrating to Windows 7. The idea is to create a window with a few large buttons with pictures on so that young children who have trouble reading can use them.

I am using SetParent() to set my window's parent to 'Progman' so that it is always at the back and is not minimised when a user chooses to 'Show Desktop'. Everything works fine on Windows XP but on Windows 7 when users click 'Show Desktop' the window remains but the contents are replaced with the users Windows background. The buttons still work (you just can't see them) and if you resize or otherwise update the window they appear again. A picture of the problem:

Any ideas why this is happening? Does anyone know a way I could force a refresh of the window when 'Show Desktop' is pressed?

Answer 1

I suspect in your case your app is throwing an exception but not crashing. WPF apps have a tendency to do this if the exception is thrown during the ctor of some UI element. It can disrupt the rendering stack.

I tried to reproduce the problem but was unsuccessful. From my tests I was able to get the handle to 'Progman' and set the main window as the parent when using the Windows 7 basic theme (no Arrow glass).

When I used the Arrow theme, calling SetParent would cause the window to vanish. A little research turned up a possible fix. Instead of setting the parent as the 'Progman' window, you can try using the 'SysListView32' child (the child window used to hold the desktop icons).

The problem is obtaining 'SysListView32' isn't easy. It used to be a matter of traversing through 'Progman' to 'SHELLDLL_DefView' and then 'SysListView32', however, Windows 7 has changed that. 'SHELLDLL_DefView' is now a child of WorkerW.... some of the time.

Here is the best article I could find explaining this: http://fernandomachadopirizen.wordpress.com/2010/08/09/give-me-a-handle-and-i-will-move-the-earth/