Patch for duplication of wide characters by chgat

[Aleksi Torhamo]

Hi,

I noticed that using chgat on a line with multicolumn characters duplicates
those characters on display. Chgat overwrites the bits in attr that tell if
a character takes up multiple columns, so ncurses thinks they are separate
characters. I'm unfamiliar with the ncurses internals, so I don't know where
the fix should go (should the fix be something like limiting the bits which
macros like SetAttr and SetPair overwrite, or should the fix be local to
chgat) but i made a temporary patch to chgat for preserving the multicolumn
bits.

Small test program (chgat-bug.c) and patch
(ncurses-5.6-chgat-multicolumn-duplication.patch) attached.

While researching the above bug, i also noticed an unrelated bug causing
program abort. Small test program (trace-bug.c) attached.

PS. Both test programs are utf8, and the used multicolumn character is the
"big A" from test/widechars-utf8.txt

Regards,
Aleksi Torhamo

chgat-bug.c
Description: Text Data

trace-bug.c
Description: Text Data

ncurses-5.6-chgat-multicolumn-duplication.patch
Description: Binary data