Re: [bug-ncurses] wadd_wch() operates on wrong coords for non-spacing chars

[Bill Gray]

   Demo program of possible interest for investigating this :

https://github.com/Bill-Gray/PDCursesMod/blob/master/demos/widetest.c

   You'll see,  at line 30,  that the string

Ångstrom̧̂ Piñata Façade Æsop café Noël côte

   is stored with the combining characters following the characters 
they're supposed to modify :

L"A\x30angstrom\x327\x302 Pin\x303" L"ata Fac\x327ade"
L" \xc6sop cafe\x301 Noe\x308l co\x302te"

   So I'm convinced that ncurses is doing the right thing here. 
Whether it's following specifications,  I don't know.

-- Bill

On 7/6/23 04:14, Dr. Werner Fink wrote:
> On 2023/07/05 22:21:55 -0400, Bill Gray wrote:
> > On 7/5/23 19:41, Thomas Dickey wrote:
> > > On Wed, Jul 05, 2023 at 09:51:32PM +0200, Roman Zilka wrote:
> > > > Hello,
> > > >
> > > > according to curs_add_wch(3x) add_wch() adds non-spacing characters to
> > > > the base character on the current coordinates. Therefore, the
> > > > following program should print "aáa". It prints "áaa", however.
> > >
> > > thanks - I can reproduce this, will investigate
> >
> >     More simply,  addwstr( L"a\u0301aa");  will emit áaa,  not aáa.  So does
> > wprintf( "La\u0301aa").  I noticed this some years back and assumed it was
> > supposed to be that way:  the combining character modifies the preceding
> > character.  A bit of Web searching suggests that's the way it's supposed to
> > work;  to get á,  you emit a and then \u0301,  not \u0301 and then a.
> >
> >     Seen from that angle,  Roman's program is working correctly;
> >
> >      move(0, 1); add_wch(&ccmod);
> >
> >     says "add an accent to the character just to the left of (0, 1)."
> > However,  I have to admit that the man page description,  I think, supports
> > Roman's expected behavior.
> >
> >     I would find it annoying to use \u0301aaa for curses and a\u0301aa for
> > everything else.
> >
> >     Are there any implementations of curses other than ncurses and
> > PDCursesMod that handle combining characters?  (I copied the ncurses
> > behavior for PDCursesMod,  so that's not independent support for the ncurses
> > behavior.)
>
> Ack .. the /usr/bin/printf as well as the builtin printf of the bash do show
>
>    áaa
>
> that is a Combining Acute Accent which is a nonspacing mark and inherit its
> characteristics from the preceding character
>
> Werner