Why is my application's window border grey in Windows 8, rather than being based off the desktop like other windows?

Question

I have a large legacy application which is showing up with a perpetually grey border on every Windows 8 machine we run it on, while the other windows for other apps accurately use a color derived from the desktop background. For the life of me I can't find out why.

I've tried my best google-fu to crawl MSDN for APIs to control this but came up empty. The app looks like all others in Windows XP, Vista, and 7...just Windows 8 is grey in color. We definitely haven't added Win8 specific code to treat this otherwise.

It's just an MFC window on the outside, but inside it embeds a .NET/WPF component and a Direct3D 9-enabled visual area.

My best guess is it could somehow be related to having a Direct3D surface in the window, but I couldn't validate that anywhere.

Any help would be greatly appreciated!

Thanks

Edit: The grey matches the effect of not having focus, and we definitely do play games with window focus...so that could be it.

Answer 1

The problem was a developer overloaded OnNcActivate() and returned TRUE at the end. They needed to call up to the baseclass's (CWnd) OnNcActivate instead.

This was visible on Windows 7 as well if you looked close enough.