Aw: Re: Starange behavior of bkgd when called after bkgdset

[Anton Vidovic]

Hello Thomas,

> > Interestingly enough, Solaris (SVr4) curses does this.
> > The colors may differ (no bce), but the +'s and -'s match up.
> >
> > > sure - if I conclude that it's correct.
> >
> > yes... more documentation is needed, to explain this.
>
> Actually it's there, in the second bullet:
>
>        Wherever  the former background character appears, it is changed to
>        the new background character.
>
> > In the logic which I adapted from Solaris, that comparison against
> > old_bkgd is checking each cell to determine if the cell used the
> > same background-character as the old value for the background-character.
> > If it did not, it leaves that untouched.
> >
> > Setting the background character to "+" without filling the screen with +'s
> > produces this special case.

thank you for the clarification. So the new (since 6.2) side effect of
bkgdset on the behavior of bkgd is indeed the intended behavior.

I do not know how big the impact of the change is on existing code,
but I think that it is a bit unfortunate that the two functions can
not be used independently any more.

Specifically, the new behavior excludes the possibility to independently
set the background/rendition of newly added text and the background
of the window.

I also think that it is unfortunate that the concept of a single
"background character" is now split into the character part and the
rendition part and that the character is handled differently than the
rendition.

The new behavior may be more compatible to SVR4 behavior, but it seems
to be less intuitive and less internally consistent. The question that
arises is whether SVR4 compatibility is still sufficiently important
today to revert several decades of ncurses behavior.

Thanks and kind regards,
Anton Vidovic