[squeek502]

Appreciate the added context!

> |-separated lists of numeric or NOT

Note that | is not the only operator that can be used in style parameters, & + and - are all allowed too.

> perhaps Windows versions that don't support DIALOGEX also don't support GROUPBOX

Seems possible for sure. From [1]:

> The 16-bit extended dialog template is purely historical. The only operating systems to support it were the Windows 95/98/Me series.

[1] https://devblogs.microsoft.com/oldnewthing/20040622-00/?p=38...

> The examples below this also seem to have reversed the order of the input byte and the FF.

Good catch, fixed