Re: [PATCH v10 04/13] utf8: add function to align a string into given strbuf

[Karthik Nayak <karthik.188@gmail.com>]

On Wed, Aug 12, 2015 at 10:10 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Karthik Nayak <karthik.188@gmail.com> writes:
>
>> On Tue, Aug 11, 2015 at 11:52 PM, Junio C Hamano <gitster@pobox.com> wrote:
>>> Karthik Nayak <karthik.188@gmail.com> writes:
>>>
>>>> +void strbuf_utf8_align(struct strbuf *buf, align_type position, unsigned int width,
>>>> +                    const char *s)
>>>> +{
>>>> +     int display_len = utf8_strnwidth(s, strlen(s), 0);
>>>> +     int utf8_compenstation = strlen(s) - display_len;
>>>
>>> compensation, perhaps?  But notice you are running two strlen and
>>> then also a call to utf8-strnwidth here already, and then
>>>
>>
>> compensation it is.
>> probably have a single strlen() call and set the value to another variable.
>
> That is not what I meant.  If you want to keep the early return of
> "doing nothing for an empty string" (which you should *NOT*, by the
> way), declare these variables upfront, do the early return and then
> call utf8_strnwidth() to compute the value you are going to use,
> only when you know you are going to use them.  That is what I meant.
>

Oh okay, after reading your mail now that makes sense.

>>>> +     if (!strlen(s))
>>>> +             return;
>>>
>>> you return here without doing anything.
>>>
>>> Worse yet, this logic looks very strange.  If you give it a width of
>>> 8 because you want to align like-item on each record at that column,
>>> a record with 1-display-column item will be shown in 8-display-column
>>> with 7 SP padding (either at the beginning, or at the end, or on
>>> both ends to center).  If it happens to be an empty string, the entire
>>> 8-display-column disappears.
>>>
>>> Is that really what you meant to do?  The logic does not make much
>>> sense to me, even though the code may implement that logic correctly
>>> and clearly.
>>
>> Not sure what you meant.
>> But this does not act on empty strings and that was intentional.
>
> If it is truly intentional, then the design is wrong.  You are
> writing a public function that can be called by other people.
>
> Which one makes more sense?  Remember that you are going to have
> many callers over time in the course of project in the future.
>
>  (A) The caller is forced to always check the string that he is
>      merely passing on, i.e.
>
>         struct strbuf buf = STRBUF_INIT;
>         struct strbuf out = STRBUF_INIT;
>
>         fill_some_placeholder(&buf, fmt, args);
>         if (buf.len)
>                 strbuf_utf8_align(&out, ALIGN_LEFT, 8, buf.buf);
>         else
>                 strbuf_addchars(&out, ' ', 8);
>
>      only because the callee strbuf_utf8_align() refuses to do the
>      trivial work.
>
>  (B) The caller does not have to care, i.e.
>
>         struct strbuf buf = STRBUF_INIT;
>         struct strbuf out = STRBUF_INIT;
>
>         fill_some_placeholder(&buf, fmt, args);
>         strbuf_utf8_align(&out, ALIGN_LEFT, 8, buf.buf);
>

Yea, good point here, thanks for putting it out :)

>> It
>> does not make
>> sense to have an alignment on an empty string, where the caller could themselves
>> just do a `strbuf_addchars(&buf, " ", width)`.
>
> It simply does not make sense to force the caller to even care.
> What they want is a series of lines, whose columns are aligned.
>

My ignorance, sorry!

>>>> +     if (display_len >= width) {
>>>> +             strbuf_addstr(buf, s);
>>>> +             return;
>>>> +     }
>>>
>>> Mental note: this function values the information more than
>>> presentation; it refuses to truncate (to lose information) and
>>> instead accepts jaggy output.  OK.
>>
>> With regards to its usage in ref-filter, this is needed, don't you think?
>
> That is exactly why I said "OK".
>
> I was primarily trying to lead other reviewers by example,
> demonstrating that a review will become more credible if it shows
> that the reviewer actually read the patch by explaining the thinking
> behind what the code does in his own words.  I see too many "FWIW,
> reviewed by me" without indicating if it is "from just a cursory
> read it looks nice" or "I fully read and understood it and I agree
> with the design choices it makes", which does not help me very much
> when queuing a patch.
>
>

Ah! okay! was just wondering if you were looking for an explanation :)

-- 
Regards,
Karthik Nayak