Created attachment 67575 [details]
Changes for the API

starting to look at this...

XDialog3.idl is missing from the patch, I don't understand the need for this
interface at all, also I don't understand the changes either to toolkit or vcl (
except the mnCancelClose change which seems to be a bug fix ) Alot of these
changes seem completely uncessesary. The changes to vcl and toolkit look like
they affect normal Dialog operation so they make me nervous, they also would be
harder to upstream, Additionally essentially duplicating the Eventlistener that
is in sbxmod.cxx in vbauserform.cxx doesn't seem a good thing to do.
With that in mind I rewrote the patch, it seems to work ( but I don't know what
you have tested your implementation against ) it attach it here, but... I still
wonder were there some reasons why the patch made the invasive changes to
toolkit and vcl, perhaps I missed something ???

Created attachment 68280 [details]
alternative patch

1. One change in vcl:
if ( mpWindowImpl->mxWindowPeer.is() && IsCreatedWithToolkit() && !IsInExecute()
&& !IsInShow() ). Adding '!IsInShow()' in the 'if' statement, is used to fix the
issue: When userform is showing in modeless, click the Close icon of the dialog
can't close the dialog.

2. another change in vcl:
    else if ( IsInShow() )
    {
        Hide();
        mbInClose = FALSE;
        return TRUE;
    }
Adding this 'else if' statement is used to fix the issue:
When showing the userform in modeless, click the Close icon to close the dialog,
the "Terminate" event of UserForm will be fired two times.