On Fri, 15 Dec 2023 at 14:49, Tim Song <t.canens....@gmail.com> wrote:
>
>
>
> On Fri, Dec 15, 2023 at 4:43 AM Jonathan Wakely <jwak...@redhat.com> wrote:
>>
>> On Fri, 15 Dec 2023 at 01:17, Tim Song wrote:
>> >
>> > On Thu, Dec 14, 2023 at 6:05 PM Jonathan Wakely <jwak...@redhat.com> wrote:
>> >> + inline void
>> >> + vprint_unicode(ostream& __os, string_view __fmt, format_args __args)
>> >> + {
>> >> + ostream::sentry __cerb(__os);
>> >> + if (__cerb)
>> >> + {
>> >> +
>> >> + const streamsize __w = __os.width();
>> >> + const bool __left
>> >> + = (__os.flags() & ios_base::adjustfield) == ios_base::left;
>> >
>> >
>> > I'm pretty sure - when I wrote this wording anyway - that the intent was
>> > that it was just an unformatted write at the end. The wording in
>> > [ostream.formatted.print] doesn't use the "determines padding" words of
>> > power that would invoke [ostream.formatted.reqmts]/3.
>>
>> Ah, OK. I misunderstood "formatted output function" as implying
>> padding, failing to notice that we need those words of power to be
>> present. My thinking was that if the stream has padding set in its
>> format flags, it could be surprising if they're ignored by a formatted
>> output function. And padding in the format string applies to
>> individual replacement fields, not the whole string, and it's hard to
>> use the stream's fill character and alignment.
>
>
> But we would get none of the Unicode-aware padding logic we
> do in format, which puts it in a very weird place.
>
> And for cases where Unicode is not a problem, it's easy to get padding
> with just os << std::format(...);
Yes, good point.
>>
>> You can do this to use the ostream's width:
>>
>> std::print("{0:{1}}", std::format(...), os.width());
>>
>> But to reuse its fill char and adjustfield you need to do something
>> awful like I did in the committed code:
>>
>> std::string_view align;
>> if (os.flags() & ios::adjustfield) == ios::right)
>> align = ">"
>> auto fs = std::format("{{:{}{}{}}}", os.fill(), align, os.width());
>> std::vprint_nonunicode(os, fs, std::make_args(std::format(...)));
>>
>>
>> And now you have to hardcode a choice between vprint_unicode and
>> vprint_nonunicode, instead of letting std::print decide it. Let's hope
>> nobody ever needs to do any of that ;-)
>
>
> At least the upcoming runtime_format alleviates that :)
Right, that's on my list to implement "soon"!
>>
>>
>> I'll remove the code for padding the padding, thanks for checking the patch.
>>
