On some windows such as Sumatra PDF, or Office 2010, by avoiding to get the ancestor window before the WM_NCHITTEST message.
SumatraPDF discussion: https://github.com/sumatrapdfreader/sumatrapdf/issues/1979
I had to add the HitTestTimeout() function that checks the response of the WM_NCHITTEST on the pointed NChwnd, if it returns HTTRANSPARENT, then I check the parent window until there is a parent or the HitTest returned something different than Transparent.
PS: I also added the HTHELP (small interrogation dot [?] button in the title bar) to the area that lower the window.
On some windows such as Sumatra PDF, or Office 2010, by avoiding to get the ancestor window before the WM_NCHITTEST message. SumatraPDF discussion: https://github.com/sumatrapdfreader/sumatrapdf/issues/1979 I had to add the HitTestTimeout() function that checks the response of the WM_NCHITTEST on the pointed NChwnd, if it returns HTTRANSPARENT, then I check the parent window until there is a parent or the HitTest returned something different than Transparent.
PS: I also added the HTHELP (small interrogation dot [?] button in the title bar) to the area that lower the window.