…idden dialogs

The WinOS Desktop Window Manager taskbar thumbnail live preview has obviously a problem with modeless only hidden dlgs which have the WS_DLGFRAME style - the preview initially shows such dialogs, even if they were already hidden.

Temporarily using the WS_EX_TOOLWINDOW style on such a problematic dlg, right before its hiding and then after the hiding immediately removing that style, does the trick (floating toolbar-wnds are not allowed on the taskbar (or in the ALT-TAB), so DWM probably will not consider them at all for such a preview...).