I had lockups where adding that style fixed the lockup. But I now get a lockup if I remove the last group in the task panel. The problem seems to be the style is on the panel at the time CJ calls GetNextDlgTabItem when OnSetFocus is called on the task panel.

 

OnSetFocus is called when the task panel group item destructor runs and it calls ShowWindow(h, SW_HIDE). I assume since I had to make the dialog a child of the panel the OS is setting focus to the panel when the window is hidden (well that and the stack trace.)

 

Microsoft has sent me a rather lengthy explanation of the rules that have to be followed to avoid the lockup and one of them is to never set focus on "a control that has WS_EX_CONTROLPARENT" style on it. I asked if any window counts as a control and the answer is yes.

 

I have currently subclassed the panel to intercept OnSetFocus and route the call directly to the CWnd class.

 

It depends on layout. Our Toolbox sample set WS_EX_CONTROLPARENT for MainFrame and Splitter for correct tab order.