[prev in list] [next in list] [prev in thread] [next in thread] 

List:       kde-core-devel
Subject:    Re: Review Request: Add more date formatting options
From:       "John Layt" <johnlayt () googlemail ! com>
Date:       2009-11-17 18:48:51
Message-ID: 20091117184851.28675.94166 () localhost
[Download RAW message or body]



> On 2009-11-15 15:14:38, Albert Astals Cid wrote:
> > In my opinion, this has a problem and it is that it encourages developers to do \
> > things like 
> > QString myDateString = KGlobal::locale()->calendar()->dateFormat( myDate, "%m %d" \
> > ); 
> > Which has internationalization problems since %m %d is obviously the wrong format \
> > for at least half of the world that uses "%d %m" so i'd like to ask if we really \
> > need that much flexibility and if we do i'd ask you to empathize in documentation \
> > that the code should be something like 
> > QString myDateString = KGlobal::locale()->calendar()->dateFormat( myDate, \
> > i18nc("This is a string that defines how date is shown when doing foo in bar \
> > program check with someurl what is the valid syntax", "%m %d") );
> 
> John Layt wrote:
> There is doco already in the apidox saying to i18nc() the format string and giving \
> example code, but I'll move it up to the top to make it more prominent. 
> There's already plenty of places where people do already do their own format \
> strings by copying the global KLocale and calling setDateFormat(), so it is \
> something that apps do need, and it's better we provide them with a way of doing it \
> that makes it easier for them to get it right, rather then leave it open for them \
> to make a mistake and possibly mess up the global format.  Also language is not \
> always a good heuristic for date formats, take for example someone living in the \
> USA but using Spanish language, which way round should it go then? (which I realise \
> is as good an argument against this change being public as for it). 
> Putting the method in KCalendarSystem rather than KLocale makes it harder to find \
> but still there for those who really need it. 
> If people feel it will be abused, then I can make it private so the only formats \
> available will be the predefined enum KLocale::DateFormat which currently are the \
> ShortDate and LongDate forms set in l10n/KCM.  I can then add to the enum some \
> other standard formats like IsoWeekDate and DayMonthOnly that can be passed into \
> formatDate() and readDate(), although this needs more thought and may require \
> separate input and output format enums (all this is already in the 4.4 feature plan \
> but may be more realistic for 4.5).  How user maintainable those would be is open \
> to debate, users would need to be able to set the month/day order on some of them \
> at least. 
> John Layt wrote:
> P.S. I think I would be more open to readDate() being private only, it's more open \
> to error. 
> Albert Astals Cid wrote:
> I agree the language is not the perfect heuristic to get the correct ordering but \
> better than always showing it wrong, right? 
> In my opinion enums would be the best solution, Chusslove had patch that did that \
> exactly but don't remember why he stopped pushing for it. 
> John Layt wrote:
> OK, I'll make them protected for 4.4 and see what I can do about some enums before \
> the freeze, but that's more likely to come in 4.5.  Hmm, that changes my patch for \
> the Plasma clock, I'll have to go back to the old way. 
> Actually, I can't make the readDate() protected, it's been public in both KLocale \
> and KCalendarSystem since 4.0, it's only formatDate() that I introduced as new in \
> 4.4.

More thoughts after looking at how more apps use date formatting.  I'm now inclined \
to make this public in 4.4, as I think we are making our app developers jump through \
hoops for no good reason, and they're making mistakes in the process.  Where apps do \
need one-off date formats they should be able to generate them as required in a \
controlled and standardised way rather than resorting to hacks, workarounds, or their \
own implementations that may not localise the calendar system or digit set properly.

In addition to people doing the copy locale trick described above, and a couple of \
places where apps temporarily change the global locale format (!), there are a lot of \
places using the string functions to do things like:

    *header = i18nc("Month String - Year String", "%1 %2",
                    KGlobal::locale()->calendar()->monthName(album->date(), \
                KCalendarSystem::LongName),
                    KGlobal::locale()->calendar()->yearString(album->date()));

And even more complex translation puzzles with 4 or 5 variables and literal \
characters.

So people are in effect doing their own date format strings just the long way around, \
and almost all are being translated already.  I don't see much wrong with giving them \
an easier way to do it that will also be easier and more consistent for the \
translators to follow and convert to their locally preferred format including \
literals, e.g. for the above (and the context is almost un-needed now):

    *header = KGlobal::locale()->calendar()->formatDate( album->date()
              i18nc("Month String - Year String", "%B %Y") );

The kdepim guys have even implemented a whole class in KMime::DateFormatter to do \
date formatting for them using a mixture of named formats in an enum and custom \
formatting using QDate and even calling strftime() directly (so not KDE localised \
which is correct for RFC formats, but not if used for any display formats where they \
could get the wrong calendar system or digit set).

A couple of plasmoids have also fully re-implemented the formatting standard as a \
wrapper around KCalendarSystem for their own purposes.

Thinking about using enums instead, I've been thinking what ones would be needed for \
the Plasma Clock, which is configurable to optionally display various date portions, \
so would need at least the following enums:

    DayShortNumber_MonthShortName
    DayShortNumber_MonthShortName_YearNumber
    WeekdayShortName_DayShortNumber_MonthShortName
    WeekdayShortName_DayShortNumber_MonthShortName_YearLongNumber
    WeekdayName

And that's just the short names, other apps will need long name versions, some might \
want literal chars included, and the list would just get longer and longer as each \
app adds what they want even if no-one else needs them.  Then there's problems around \
some of those formats not being valid for use with readDate(), so separate enums \
would be required for read and display, so the numbers double again...  Really, it \
would just end up as a long list of 'approved' date format strings, just with long \
and unwieldy names people won't want to use, even if they are consistently translated \
across all of KDE..

No, I think the global enum should be restricted to recognised and unambiguous \
standard formats like IsoDate, IsoWeekDate, IsoOrdinalDate, and the various RFC \
formats.  

To encourage consistency, we could also point people in the apidox to a TechBase page \
of standard i18nc() calls with standardised contexts and format strings?


- John


-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
http://reviewboard.kde.org/r/2177/#review3100
-----------------------------------------------------------


On 2009-11-15 02:21:15, John Layt wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> http://reviewboard.kde.org/r/2177/
> -----------------------------------------------------------
> 
> (Updated 2009-11-15 02:21:15)
> 
> 
> Review request for kdelibs.
> 
> 
> Summary
> -------
> 
> This change adds a number of new options for date formatting.
> 
> 1) New versions of formatDate() and readDate() have already been added to \
> KCalendarSystem in 4.4 to accept a date format string of the coders choice rather \
> than the locale defaults.  This saves coders writing something like: 
> KLocale *myLocale = new KLocale( *KGlobal::locale() );
> myLocale->setDateFormatShort( "%m %d" );
> QString myDateString = myLocal->dateFormat( myDate, KLocale::ShortDate );
> 
> They can now write:
> 
> QString myDateString = KGlobal::locale()->calendar()->dateFormat( myDate, "%m %d" \
> ); 
> This change adds new format codes to these methods to bring them into line with the \
> C / POSIX / CU / GNU standards: 
> The following codes are added to formatDate():
> 
> %C the 'century' portion of the year
> %j the day of the year number to three digits (e.g. "001"  for 1 Jan)
> %V the ISO week of the year number to two digits
> %G the year number in long form of the ISO week of the year
> %g the year number in short form of the ISO week of the year
> %u the day of the week number (e.g. "1"  for Monday)
> %D the US short date format (e.g. "%m/%d/%y")
> %F the ISO short date format (e.g. "%Y-%m-%d")
> %x the KDE locale short date format
> %t a tab character
> 
> formatDate() also adds the ability to define the case modifier, padding character, \
> and padding width as defined in the GNU version of the standard, e.g. "%05Y" = \
> "02009".  See the comprehensive apidox documentation for details. 
> There are 2 significant differences between the long-standing KDE implementation \
> and the standard: 
> %e in GNU/POSIX is space padded to 2 digits, in KDE is not padded
> %n in GNU/POSIX is newline, in KDE is short month number
> 
> Should we fix these to match the standard, or just live with them?
> 
> The following codes are added to readDate():
> 
> 	%j the day of the year number
> 	%V the ISO week of the year number
> 	%u the day of the week number
> 
> Note that only the codes supported by readDate() will be allowed to be used in the \
> locale global date formats, and coders are encouraged to use the locale formats \
> unless really necessary. 
> 2) New isValid() and setDate() methods to validate and set the date using either \
> Year and Day of Year, or Year, ISO Week Number, and Day of Week number, as required \
> by the readDate() changes above and as defined in the ISO standard. 
> 3) KDE4.3 introduced the ability to use different numeric Digit Sets, e.g. \
> Arabic-Indic or Devenagari instead of Arabic.  While some numeric methods in \
> KCalendarSystem have versions to return a string form which returns the correct \
> digit set (e.g. day() and dayString()), many do not have a string version such as \
> weekNumber().  This means a coder needs to know and remember to do the digit set \
> conversion themselves: 
> KGlobal::locale()->convertDigits(KGlobal::locale()->calendar()->weekNumber(date), \
> locale()->dateTimeDigitSet()); 
> This change adds the following convenience methods to improve this:
> 
> monthsInYearString()
> weeksInYearString()
> daysInYearString()
> daysInMonthString()
> daysInWeekString()
> dayOfYearString()
> dayOfWeekString()
> weekNumberString()
> 
> The existing string methods have all been converted to use the formatDate() method.
> 
> 4) A change this big to something so core couldn't be done without significant \
> testing.  The first real comprehensive unit tests for formatDate() and readDate() \
> are included.  In fact, the test cases took longer to write than the code :-) 
> 5) A number of corner-case bugs were uncovered in the existing code by the new test \
> cases which have been fixed as well. 
> 
> Diffs
> -----
> 
> trunk/KDE/kdelibs/kdecore/date/kcalendarsystem.h 1046844 
> trunk/KDE/kdelibs/kdecore/date/kcalendarsystem.cpp 1046844 
> trunk/KDE/kdelibs/kdecore/date/kcalendarsystemgregorian.cpp 1046844 
> trunk/KDE/kdelibs/kdecore/tests/kcalendartest.h 1046844 
> trunk/KDE/kdelibs/kdecore/tests/kcalendartest.cpp 1046844 
> 
> Diff: http://reviewboard.kde.org/r/2177/diff
> 
> 
> Testing
> -------
> 
> Extensive new unit tests written, as attached, which showed up a number of bugs in \
> the existing code.  More tests to be added for rest of calendar systems in next few \
> weeks. 
> 
> Thanks,
> 
> John
> 
> 


[prev in list] [next in list] [prev in thread] [next in thread]