Re: Surrogate pairs for addwstr?

[Bill Gray]

On 10/11/21 12:05 AM, Tim Allen wrote:
> On Sun, Oct 10, 2021 at 11:38:22AM -0400, Bill Gray wrote:
> >     The other way to put this would be to ask : if you're on a
> > system with 32-bit wchar_ts,  what should happen for this line?
> >
> >    mvaddwstr( 0, 2, L"\xd83d\xdd1e Treble clef with a surrogate pair");
>
> Honestly, what I'd *expect* to happen is a compile-time or run-time
> error.

   As you thought,  it can't be a compile-time error in C,
because the string is not necessarily a Unicode one;  other
locales are supported.

   The run-time error is an interesting thought.  At least in
PDCurses,  addch() only fails if it can't scroll.  I could
imagine a "couldn't render that character" error condition
as well.  In PDCurses,  that would occur within waddch() and
then cause waddstr() to return ERR.

   I would still be arguing in favor of handling surrogates in
all cases,  but your point about them still not being handled
elsewhere changed my mind.  That's a tougher hurdle to get around.

   And thanks for the WCHAR_MAX == 65535 pointer.  I can't see
why that wouldn't work.

   In re "just use UTF8" : agreed,  yet another good reason to
do so.

Thanks!        -- Bill

> Printing gibberish is never particularly helpful, but encouraging people
> to assume wide-string literals (or wide-strings in general) use UTF-16
> encoding seems like a bad idea. Sure, you can make it work transparently
> for curses, but there's other libraries (like libc) that are likely to
> get tripped up, and that seems like a foot-gun waiting to happen. Even
> if you provide a utf16towcs() helper, people are going to forget to call
> it since the input and output types are both wchar_t*.
>
> The absolute simplest and safest thing a portable program could do is to
> restrict itself to the Basic Multilingual Plane. The second simplest and
> safest thing would probably be to store strings as UTF-8 (narrow) string
> literals, and provide some kind of utf8stowcs() that decodes to UTF-16
> or to UTF-32 depending on the value of WCHAR_MAX.
>
>
> Tim.