Re: wadd_wch() operates on wrong coords for non-spacing chars

[Thomas Dickey]

On Wed, Jul 05, 2023 at 10:21:55PM -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

I read the example as
        addwstr( L"aa\u0301a");  

and did not recall whether add_wch called addch (checking the source, I see
that it updates the cells directly).  If it did that, then the move()
calls could interfere with the process (see man addch).

But the move() calls are probably relevant - something to see on Saturday.

> 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.)

Solaris' X/Open curses might - I can check that.
I seem to recall that NetBSD doesn't - but can check that.

-- 
Thomas E. Dickey <dickey@invisible-island.net>
https://invisible-island.net

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