KDE Core/QtMerge/QDateTime: Difference between revisions

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The following are proposed additions to Qt's Date/Time support which KDE would like to see to enable dropping of our own Date/Time support, or would help improve Qt's localization under Win/OSX/CLDR.
The initial proposal for merging KDE features in Qt5 as presented at QtCS is documented on the QtCS wiki at http://developer.qt.nokia.com/groups/qt_contributors_summit/wiki/QDateTime


== Code Quality ==
This page documents specific API proposals.


* important code is inline and no d-> means impossible to change implementation without breaking BC, this should be fixed
== Full CLDR Date Format and Calendar System support ==
* poor overflow checking in places returns incorrect results instead of an invalid date


== Date Range ==
The CLDR Date Format support and Calendar System support are closely connected and need to be designed together, although they will be separately implemented.  The following API design is based on the CLDR standard.


The date is stored as a Julian Day Number in a uint with jd == 0 erroneously considered to be invalid.  This restricts dates to a range of 2January 4713BC to about 11 million AD.  Changing the uint into an int32 or a int64 will make this date range more useful scientifically:
Backwards source compatibility is required to be maintained by the QDate class using the QT4_COMPAT directive.
* int32 =  5 x 10^6
* int64 = 25 x 10^15
* Geological time: Age of Earth =  5 x 10^9
* Astronomical time: Age of Universe = 13.75 x 10^9


Currently used formulas do not reliably support a date range outside of 8000BC to 8000AD so these should be the limits for now, but can be later extended.
The Qt4 API is inconsistent, incomplete, and requires modification to fully support CLDR, so the opportunity should be taken to fully overhaul the API.  Most apps will be unaffected as they should simply be using the default toString()/fromString() methods.


Invalidity (e.g. when adding and you go out-of-bounds) will probably need a bool, or just a very large number considered out-of-range.
=== Object Model ===


== Date/Time Format Codes ==
The physical object model is still uncertain.  The logical model is as follows:


The Qt to/from string format codes are mostly based on the Unicode CLDR formats but have a number of problems:
QLocale - The locale class, container for type of calendar system, date/time formats, and date/time name translations, and accessor methods to format/parse date/times in that locale.  Existing class to be modified.
* Only a small sub-set of CLDR codes are supported
* A few Qt format codes are not in the CLDR standard


These format codes also have equivalents in the standard Posix, Windows and OSX date/time formats which are used in localization, so by not supporting them Qt may not be correctly localizing dates to the users system date/time formats.  Many apps also need more flexibility in formatting dates.
QDate - A container class to hold a Julian Day number.  Shouldn't have any ymd or string methods, but to maintain full backwards compatibility will use QT4_COMPAT for all existing ymd and string methods.


Many of the missing format codes are just string forms of existing Qt api.
QDateCalculator.  A calculator class for converting a QDate to/from YMD values.  No virtuals to be used.


Reference:
QDateTimeParser - Takes an input string, date/time format, and locale and returns a QDateTime. Existing private class to be modified.
* http://www.unicode.org/reports/tr35/tr35-15.html#Date_Format_Patterns


Qt currently supports the following format codes:
QDateTimeFormatter - Takes a QDateTime, date/time format and locale and returns a QString.  New private class based on the QLocale formatter.  The QDateTime formatter is to be deleted.


d    Day as a number without a leading zero (1 to 31)
The QDateCalculator will be awkward to use directly so we will provide either a QLocalDate class combining all the above in a single convenience wrapper, or a method on QDate to access the calculator such as QDate::calendar(), or both.
dd  Day as a number with a leading zero (01 to 31)
ddd  Weekday abbreviated localized name (e.g. 'Mon' to 'Sun').
dddd Weekday long localized name (e.g. 'Monday' to 'Sunday').
M    Month as a number without a leading zero (1 to 12)
MM  Month as a number with a leading zero (01 to 12)
MMM  Month abbreviated localized name (e.g. 'Jan' to 'Dec').
MMMM Month long localized name (e.g. 'January' to 'December').
yy  Year as two digit number (00 to 99)
yyyy Year as four digit number. (-9999 to 9999)


h    Hour without a leading zero (0 to 23 or 1 to 12 if AM/PM)
=== API Changes ===
hh  Hour with a leading zero (00 to 23 or 01 to 12 if AM/PM)
H    24 Hour without a leading zero (0 to 23)
HH  24 Hour with a leading zero (00 to 23)
m    Minute without a leading zero (0 to 59)
mm  Minute with a leading zero (00 to 59)
s    Second without a leading zero (0 to 59)
ss  Second with a leading zero (00 to 59)
z    Milliseconds without leading zeroes (0 to 999)
zzz  Milliseconds with leading zeroes (000 to 999)
AP  AM/PM uppercase
ap  AM/PM lowercase
A    AM/PM uppercase
a    AM/PM lowercase
t    Timezone (for example "CEST")


Note that:
Deprecate the old Qt and QDate enums:
* ddd and dddd formats are not valid CLDR forms but derived from Windows, they should be EEE and EEEE instead.
* AP and ap are not valid CLDR forms
* h and hh do not exactly match the CLDR definition
* t is not a valid CLDR form


The following CLDR codes should be supported:
<syntaxhighlight lang="cpp-qt">
  // Merges both format and field type!
  enum QLocale::FormatType { LongFormat, ShortFormat, NarrowFormat };


ddddd Day narrow localized name (e.g. 'M' to 'S').
  // Used for both month and day names!
MMMMM Month narrow localized name (e.g. 'J' to 'D').
  enum QDate::MonthNameType { DateFormat = 0, StandaloneFormat };
y    Year without a leading zero (1 to 9999)


D (1..3)
  enum Qt::DateFormat { TextDate,                    // default Qt
Day of Year, numeric with or without leading zeros.
                        ISODate,                      // ISO 8601
Matches existing dayOfYear() api.
                        SystemLocaleDate,            // deprecated
                        LocalDate = SystemLocaleDate, // deprecated
                        LocaleDate,                  // deprecated
                        SystemLocaleShortDate,
                        SystemLocaleLongDate,
                        DefaultLocaleShortDate,
                        DefaultLocaleLongDate };
</syntaxhighlight>


w (1-2)
Delete or Deprecate the old QLocale enums:
Week of Year, numeric with or without leading zero.
Matches existing weekNumber() api.


Y (1..n)
<syntaxhighlight lang="cpp-qt">
Week year, e.g. for ISO Week Number year week falls in, forms to match y.
  // Merges both format type and field type!
Matches existing weekNumber() api.
  enum QLocale::FormatType { LongFormat, ShortFormat, NarrowFormat };
</syntaxhighlight>


L (1..5)
Add new QLocale enums:
Stand-alone Month


E (1..5)
<syntaxhighlight lang="cpp-qt">
Weekday, abbreviated (e.g. 'Mon'), long (e.g. 'Monday') and narrow (e.g. 'M')
  // CLDR format length attribute for date/time/number/currency
  enum QLocale::StringFormat { FullFormat,
                              LongFormat,
                              MediumFormat,
                              ShortFormat };


c (1..5)
  // CLDR field width attribute
Stand-alone Weekday
  enum QLocale::FieldFormat { LongName,      // e.g. January
                              ShortName,    // e.g. Jan
                              NarrowName,    // e.g. J
                              LongNumber,    // e.g. 01
                              ShortNumber }; // e.g. 1


G (1..5)
  // CLDR context attribute
  Era localized name, abbreviated (e.g. 'AD'), long (e.g. 'Anno Domini') and narrow (e.g. 'A')
  enum QLocale::FieldContext { FormatContext,        // Use in a format
                              StandaloneContext }; // Use standalone


  z/Z/v/V
  // CLDR calendar attribute
Timezones. TODO. Depends on QTime support.
  enum QLocale::CalendarSystem { DefaultCalendar = 0, // i.e. locale default
                                GregorianCalendar = 1,
                                JulianCalendar = 2,
                                ... };


The following CLDR codes may be implemented but are not considered as important:
  // CLDR year type attribute, in Qt or QDateTime namespace instead?
  enum QLocale::YearType { StandardYear, LeapYear }


Q (1..4)
  // CLDR date time fields, maybe in Qt or QLocale namespace?
Quarter in year, '2', '02', 'Q2' or '2nd Quarter'
  enum QDateTime::DateTimeField { Year, Month, Day, Hour, Minute, Second, ... }


q (1..4)
  // Common standard formats, maybe in Qt or QLocale namespace?
Stand-alone Quarter in year
  enum QDateTime::DateTimeFormat { IsoFormat,
                                  RfcFormat,
                                  Rfc3339Format,
                                  WeekFormat,
                                  OrdinalFormat };
</syntaxhighlight>


W (1)
Week of Month, numeric.


F (1)
Add new QLocale calendar sytem methods:
Day of Week In Month, e.g. if today is 2nd Monday in Month = 2


e (1..5)
<syntaxhighlight lang="cpp-qt">
Weekday, localized numeric (1 or 01), abbreviated (e.g. 'Mon'), long (e.g. 'Monday') and narrow (e.g. 'M').
  CalendarSystem QLocale::calendarSystem(); const            // current calendar, usually locale default
Would require QLocale support for localized week number, i.e. US week as well as ISO week.
  QList<CalendarSystem> QLocale::calendarSystems() const;    // locale preferred list
  QList<CalendarSystem> QLocale::allCalendarSystems() const; // all calendars list
  QDateCalculator QLocale::calendar();                      // current calendar calculator
</syntaxhighlight>


The following new api will be required in QDateTime to support the format codes.
Deprecate the old QDate name methods:


enum QLocale::NameFormat {LongName, ShortName, NarrowName}  //Replaces QLocale::FormatType
<syntaxhighlight lang="cpp-qt">
enum QLocale::NameContext {SentanceFormat, StandaloneFormat}  //Replaces QDate::MonthNameType
  static QString QDate::shortMonthName(int month, MonthNameType type = QDate::DateFormat);
int QDate::quarter()
  static QString QDate::shortDayName(int weekday, MonthNameType type = QDate::DateFormat);
int QDate::weekOfMonth()
  static QString QDate::longMonthName(int month, MonthNameType type = QDate::DateFormat);
int QDate::weekdayInMonth()
  static QString QDate::longDayName(int weekday, MonthNameType type = QDate::DateFormat);
QString QDate::monthName(QLocale::NameFormat format, QLocale::NameContext context = QLocale::SentanceFormat)
</syntaxhighlight>
QString QDate::weekdayName(QLocale::NameFormat format, QLocale::NameContext context = QLocale::SentanceFormat)
QString QDate::quarterName(QLocale::NameFormat format, QLocale::NameContext context = QLocale::SentanceFormat)
QString QDate::eraName(QLocale::NameFormat format)


Note the month and day name api are already marked for change in Qt5.  An alternative is to merge NameFormat and NameContext.
Delete or Deprecate the old QLocale name methods:


Dropping the non-CLDR compliant codes should be considered
<syntaxhighlight lang="cpp-qt">
  QString QLocale::monthName(int month, FormatType format = LongFormat) const;
  QString QLocale::standaloneMonthName(int month, FormatType format = LongFormat) const;
  QString QLocale::dayName(int weekday, FormatType format = LongFormat) const;
  QString QLocale::standaloneDayName(int weekday, FormatType format = LongFormat) const;
  QString QLocale::amText() const;
  QString QLocale::pmText() const;
</syntaxhighlight>


== Date/Time Named Formats ==
Add new QLocale name methods:


Goal: To add more date/time named formats
<syntaxhighlight lang="cpp-qt">
  QString QLocale::monthName(int month,
                            FieldFormat format = LongName,
                            FieldContext context = StandaloneContext,
                            YearType yearType = StandardYear,
                            CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::weekdayName(int weekday,
                              FieldFormat format = LongName,
                              FieldContext context = StandaloneContext,
                              CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::dayPeriodName(QTime time,
                                FieldFormat format = LongName,
                                FieldContext context = StandaloneContext,
                                CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::eraName(int year,
                          FieldFormat format = LongName,
                          FieldContext context = StandaloneContext,
                          CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::quarterName(int quarter,
                              FieldFormat format = LongName,
                              FieldContext context = StandaloneContext,
                              CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::calendarName(CalendarSystem calendar = DefaultCalendar,
                                FieldFormat format = LongName,
                                FieldContext context = Standaloneontext) const;
</syntaxhighlight>


Rationale: Convenience for coders
Modify the QLocale date/time format methods:


Qt currently provides the following named date formats via an enum:
<syntaxhighlight lang="cpp-qt">
    QString QLocale::dateFormat(FormatType format = LongFormat) const;
    QString QLocale::timeFormat(FormatType format = LongFormat) const;
    QString QLocale::dateTimeFormat(FormatType format = LongFormat) const;
</syntaxhighlight>


    enum DateFormat {
to replace FormatType with StringType:
        TextDate,      // default Qt
        ISODate,      // ISO 8601
        SystemLocaleShortDate,
        SystemLocaleLongDate,
        DefaultLocaleShortDate,
        DefaultLocaleLongDate
    };


The following named date/time formats would be useful:
<syntaxhighlight lang="cpp-qt">
  QString QLocale::dateFormat(StringFormat format = LongFormat) const;
  QString QLocale::timeFormat(StringFormat format = LongFormat) const;
  QString QLocale::dateTimeFormat(StringFormat format = LongFormat) const;
</syntaxhighlight>


ISOTime          ISO 8601 format time
Deprecate all the QDateTime toString() and fromString() methods:
                  "hh[:mm[:ss[.sss]]]TZ"
ISODateTime      ISO 8601 format date and time
                  "[±]YYYY-MM-DDThh[:mm[:ss[.sss]]]TZ"
RFCDateTime      RFC 822/850/1036/1123/2822 format
                  "[Wdy,] DD Mon YYYY hh:mm[:ss] ±hhmm"
                  "Wdy Mon DD HH:MM:SS YYYY"
RFCDateTimeDay  RFC format including day of the week
                  "Wdy, DD Mon YYYY hh:mm:ss ±hhmm"
RFC3339DateTime  RFC 3339 format
                  "YYYY-MM-DDThh:mm:ss[.sss](Z|±hh:mm)"
ISOWeekDate,    ISO 8601 Week Date format
                  "YYYY-Www-D", e.g. 2009-W01-1
ISOOrdinalDate  ISO 8601 Ordinal Date format
                  "YYYY-DDD", e.g. 2009-001


Note the ISO dates should accept both basic and expanded formats.
<syntaxhighlight lang="cpp-qt">
  QString QDate::toString(Qt::DateFormat f = Qt::TextDate) const;
  QString QDate::toString(const QString &format) const;


Note: KDateTime uses regex's for these in an inefficient way, don't just copy.
  static QDate QDate::fromString(const QString &s, Qt::DateFormat f = Qt::TextDate);
  static QDate QDate::fromString(const QString &s, const QString &format);


== Date Eras ==
  QString QTime::toString(Qt::DateFormat f = Qt::TextDate) const;
  QString QTime::toString(const QString &format) const;


Many locales have an optional Era system for dates, others such as Japan use an era system in its official date formats.
  static QTime QTime::fromString(const QString &s, Qt::DateFormat f = Qt::TextDate);
  static QTime QTime::fromString(const QString &s, const QString &format);


== ISO Ordinal Date ==
  QString QDateTime::toString(Qt::DateFormat f = Qt::TextDate) const;
  QString QDateTime::toString(const QString &format) const;


== ISO Week Date ==
  static QDateTime QDateTime::fromString(const QString &s, Qt::DateFormat f = Qt::TextDate);
  static QDateTime QDateTime::fromString(const QString &s, const QString &format);
</syntaxhighlight>


== Date Maths ==
Mondify the QLocale toString() and fromString() methods:


Qt currently only provides standard date math functions for adding years, months or days.  Some more convenience functions could be added.
<syntaxhighlight lang="cpp-qt">
  QString QLocale::toString(const QDate &date, FormatType format = LongFormat) const;
  QString QLocale::toString(const QTime &time, FormatType format = LongFormat) const;
  QString QLocale::toString(const QDateTime &dateTime, FormatType format = LongFormat) const;


== Date Locale Functions ==
  QDate QLocale::toDate(const QString &string, FormatType = LongFormat) const;
  QTime QLocale::toTime(const QString &string, FormatType = LongFormat) const;
  QDateTime QLocale::toDateTime(const QString &string, FormatType format = LongFormat) const;
</syntaxhighlight>


Some additional localization options could be added to QLocale to support date formatting:
to replace FormatType with StringType:


* Week Start Day
<syntaxhighlight lang="cpp-qt">
* Working Week Start/End Days (or Weekend Start/End)
  QString QLocale::toString(const QDate &date, StringType format = LongFormat) const;
* Short Year Window
  QString QLocale::toString(const QTime &time, StringType format = LongFormat) const;
* Digit Sets
  QString QLocale::toString(const QDateTime &dateTime, StringType format = LongFormat) const;
* Calendar System
* Week Number System


These are also detailed on the QtMerge/QLocale page.
  QDate QLocale::toDate(const QString &string, StringType = LongFormat) const;
  QTime QLocale::toTime(const QString &string, StringType = LongFormat) const;
  QDateTime QLocale::toDateTime(const QString &string, StringType format = LongFormat) const;
</syntaxhighlight>


== Calendar Systems ==
Add the following new toString/fromSting methods to QLocale


<syntaxhighlight lang="cpp-qt">
  QString QLocale::toString(const QDate &date, QDateTime::DateTimeFormat format) const;
  QString QLocale::toString(const QTime &time, QDateTime::DateTimeFormat format) const;
  QString QLocale::toString(const QDateTime &dateTime, QDateTime::DateTimeFormat format) const;


  QString QLocale::toString(const QDate &date, QDateTime::DateTimeField field,
                            FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QString QLocale::toString(const QTime &time, QDateTime::DateTimeField field,
                            FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QString QLocale::toString(const QDateTime &dateTime, QDateTime::DateTimeField field,
                            FieldFormat format = LongName, FieldContext context = StandaloneContext) const;


The following api changes will be required
  QDate QLocale::toDate(const QString &string, QDateTime::DateTimeFormat format) const;
isNull() - Will now indicate an invalid date in any calendar system, e.g. addition resulting in out-of-bounds
  QTime QLocale::toTime(const QString &string, QDateTime::DateTimeFormat format) const;
isValid() - Will now indicate if date is valid within current calendar system, but date may still be valid in another calendar system.
  QDateTime QLocale::toDateTime(const QString &string, QDateTime::DateTimeFormat format) const;


== Time Zones ==
  QDate QLocale::toDate(const QString &string, QDateTime::DateTimeField field,
                        FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QTime QLocale::toTime(const QString &string, QDateTime::DateTimeField field,
                        FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QDateTime QLocale::toDateTime(const QString &string, QDateTime::DateTimeField field,
                                FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
</syntaxhighlight>


== Durations ==
Modify the existing string date field format codes to be CLDR compliant as follows:


== Widgets ==
<syntaxhighlight lang="cpp-qt">
  ddd - Weekday - Change to EEE
  dddd - Weekday - Change to EEEE
    AP - AM/PM - Remove, already have A
    ap - am/pm - Remove, already have a
    h - Hour - Modify behaviour to match CLDR
    hh - Hour - Modify behaviour to match CLDR
    t - Timezone - Change to z
</syntaxhighlight>


The various widgets will need modification to match the new features and api.
Add new CLDR date field format codes for existing or new api:


<syntaxhighlight lang="cpp-qt">
  ddddd - Weekday narrow name
  MMMMM - Month narrow name
      y - Year without leading zeros
      d - Day of Year
      w - Week of Year
      Y - Week Year
      L - Stand-alone Month
      e - Weekday
      E - Weekday
      c - Stand-alone Weekday
      G - Era name
      z - Timezone
      Z - Timezone
      v - Timezone
      V - Timezone
      Q - Quarter of Year
      q - Stand-alone Quarter of Year
      W - Week of Month
      F - Day of Week In Month
</syntaxhighlight>


From qt-interest list: QCalendarWidget to use Start of Week from Qlocale, but be able to override if needed.
== QDate API changes ==


== Summary all api proposals ==
The following QDate YMD methods will be deprecated using QT4_COMPAT:


enum QLocale::NameFormat {LongName, ShortName, NarrowName}  //Replaces QLocale::FormatType
<syntaxhighlight lang="cpp-qt">
enum QLocale::NameContext {SentanceFormat, StandaloneFormat}  //Replaces QDate::MonthNameType
    QDate(int y, int m, int d);
enum QLocale::CalendarSystem {...}


bool QDate::isValidOrdinalDate(int year, int dayOfYear)
    int year() const;
bool QDate::setOrdinalDate(int year, int dayOfYear)
    int month() const;
    int day() const;
    int dayOfWeek() const;
    int dayOfYear() const;
    int daysInMonth() const;
    int daysInYear() const;
    int weekNumber(int *yearNum = 0) const;


bool QDate::isValidEraDate(QString eraName, int yearInEra, int month, int day)
    bool setDate(int year, int month, int day);
bool QDate::setEraDate(QString eraName, int yearInEra, int month, int day)
    void getDate(int *year, int *month, int *day);


bool QDate::isValidWeekDate(int year, int weekOfYear, int dayOfWeek)
    QDate addDays(int days) const;
bool QDate::setWeekDate(int year, int weekOfYear, int dayOfWeek)
    QDate addMonths(int months) const;
    QDate addYears(int years) const;
    int daysTo(const QDate &) const;


QString QDate::eraName()
    static bool isValid(int y, int m, int d);
int     QDate::yearInEra()
     static bool isLeapYear(int year);
QString QDate::eraName(QLocale::NameFormat format)
</syntaxhighlight>


int QDate::monthsInYear()
The following new methods or variations will be added:
int QDate::weeksInYear()
int QDate::quarter()
int QDate::weekOfMonth()
int QDate::weekdayInMonth()


QString QDate::monthName(QLocale::NameFormat format, QLocale::NameContext context = QLocale::SentenceFormat)
<syntaxhighlight lang="cpp-qt">
QString QDate::weekdayName(QLocale::NameFormat format, QLocale::NameContext context = QLocale::SentenceFormat)
    static QDate gregorianDate(int year, int month, int day);
QString QDate::quarterName(QLocale::NameFormat format, QLocale::NameContext context = QLocale::SentenceFormat)
    static QDate localDate(int year, int month, int day, QLocale::CalendarSystem calSys = QLocale::DefaultCalendar);
</syntaxhighlight>


void QDate::setCalendarSystem(KLocale::CalendarSystem)
=== Implementation Plan ===
KLocale::CalendarSystem QDate::calendarSystem()


void QDate::dateDifference(const QDate &toDate, int *years, int *months, int *days, int *dir)
The following phased implementation is planned:
int  QDate::yearsDifference(const QDate &toDate)
int  QDate::monthsDifference(const QDate &toDate)
int  QDate::daysDifference(const QDate &toDate)


  QDate QDate::firstDayOfYear()
* Clean-up current code where required. All existing tests should still pass.
  QDate QDate::lastDayOfYear()
* Separate private QDateTimeParser into own file.  All existing tests should still pass.
  QDate QDate::firstDayOfMonth()
* Create new private QDateTimeFormatter class, move current formatting code from QLocale into QDateTimeFormatter, change QDateTime to make calls to it.  Delete QDateTime formatter code.  All existing tests should still pass.
  QDate QDate::lastDayOfMonth()
* Create new QDateCalculator class implementing most calendars.  Write new unit tests.
 
Still fuzzy:
* Change QDateTimeFormatter and QDateTimeParser to fix the currently supported field codes to be CLDR compliant.  Modify existing tests to ensure they still pass.
* Implement new formatting api but making calls to existing backend code, for options that don't yet have the backend coded just translate to a sensible replacement, i.e. for FullDate return LongDate. Only supported CalendarSystem is DefaultCalendar.  All existing tests should still pass.
* Add to QDateTimeFormatter and QDateTimeParser the CLDR field codes that are already supported by existing QDate api.  Write new tests.
* Convert unit tests from old api to new api.  All existing tests should still pass.
* Convert widgets and other Qt code to new api.  All existing tests should still pass.
* Remove old api.  All existing tests should still pass.
* Modify QLocale CLDR backend to return full set of values for new api.  Write new tests.
* Modify QLocale Mac backend to return full set of values for new api. Write new tests.
* Modify QLocale Windows backend to return full set of values for new api. Write new tests.
* Add Era support
* Add Week Date support

Latest revision as of 17:51, 14 September 2011

The initial proposal for merging KDE features in Qt5 as presented at QtCS is documented on the QtCS wiki at http://developer.qt.nokia.com/groups/qt_contributors_summit/wiki/QDateTime

This page documents specific API proposals.

Full CLDR Date Format and Calendar System support

The CLDR Date Format support and Calendar System support are closely connected and need to be designed together, although they will be separately implemented. The following API design is based on the CLDR standard.

Backwards source compatibility is required to be maintained by the QDate class using the QT4_COMPAT directive.

The Qt4 API is inconsistent, incomplete, and requires modification to fully support CLDR, so the opportunity should be taken to fully overhaul the API. Most apps will be unaffected as they should simply be using the default toString()/fromString() methods.

Object Model

The physical object model is still uncertain. The logical model is as follows:

QLocale - The locale class, container for type of calendar system, date/time formats, and date/time name translations, and accessor methods to format/parse date/times in that locale. Existing class to be modified.

QDate - A container class to hold a Julian Day number. Shouldn't have any ymd or string methods, but to maintain full backwards compatibility will use QT4_COMPAT for all existing ymd and string methods.

QDateCalculator. A calculator class for converting a QDate to/from YMD values. No virtuals to be used.

QDateTimeParser - Takes an input string, date/time format, and locale and returns a QDateTime. Existing private class to be modified.

QDateTimeFormatter - Takes a QDateTime, date/time format and locale and returns a QString. New private class based on the QLocale formatter. The QDateTime formatter is to be deleted.

The QDateCalculator will be awkward to use directly so we will provide either a QLocalDate class combining all the above in a single convenience wrapper, or a method on QDate to access the calculator such as QDate::calendar(), or both.

API Changes

Deprecate the old Qt and QDate enums: 

  // Merges both format and field type!
  enum QLocale::FormatType { LongFormat, ShortFormat, NarrowFormat };

  // Used for both month and day names!
  enum QDate::MonthNameType { DateFormat = 0, StandaloneFormat };

  enum Qt::DateFormat { TextDate,                     // default Qt
                        ISODate,                      // ISO 8601
                        SystemLocaleDate,             // deprecated
                        LocalDate = SystemLocaleDate, // deprecated
                        LocaleDate,                   // deprecated
                        SystemLocaleShortDate,
                        SystemLocaleLongDate,
                        DefaultLocaleShortDate,
                        DefaultLocaleLongDate };

Delete or Deprecate the old QLocale enums: 

  // Merges both format type and field type!
  enum QLocale::FormatType { LongFormat, ShortFormat, NarrowFormat };

Add new QLocale enums: 

  // CLDR format length attribute for date/time/number/currency
  enum QLocale::StringFormat { FullFormat,
                               LongFormat,
                               MediumFormat,
                               ShortFormat };

  // CLDR field width attribute
  enum QLocale::FieldFormat { LongName,      // e.g. January
                              ShortName,     // e.g. Jan
                              NarrowName,    // e.g. J
                              LongNumber,    // e.g. 01
                              ShortNumber }; // e.g. 1

  // CLDR context attribute
  enum QLocale::FieldContext { FormatContext,        // Use in a format
                               StandaloneContext };  // Use standalone

  // CLDR calendar attribute
  enum QLocale::CalendarSystem { DefaultCalendar = 0,  // i.e. locale default
                                 GregorianCalendar = 1,
                                 JulianCalendar = 2,
                                 ... };

  // CLDR year type attribute, in Qt or QDateTime namespace instead?
  enum QLocale::YearType { StandardYear, LeapYear }

  // CLDR date time fields, maybe in Qt or QLocale namespace?
  enum QDateTime::DateTimeField { Year, Month, Day, Hour, Minute, Second, ... }

  // Common standard formats, maybe in Qt or QLocale namespace?
  enum QDateTime::DateTimeFormat { IsoFormat,
                                   RfcFormat,
                                   Rfc3339Format,	
                                   WeekFormat,
                                   OrdinalFormat };


Add new QLocale calendar sytem methods: 

  CalendarSystem QLocale::calendarSystem(); const            // current calendar, usually locale default
  QList<CalendarSystem> QLocale::calendarSystems() const;    // locale preferred list
  QList<CalendarSystem> QLocale::allCalendarSystems() const; // all calendars list
  QDateCalculator QLocale::calendar();                       // current calendar calculator

Deprecate the old QDate name methods: 

  static QString QDate::shortMonthName(int month, MonthNameType type = QDate::DateFormat);
  static QString QDate::shortDayName(int weekday, MonthNameType type = QDate::DateFormat);
  static QString QDate::longMonthName(int month, MonthNameType type = QDate::DateFormat);
  static QString QDate::longDayName(int weekday, MonthNameType type = QDate::DateFormat);

Delete or Deprecate the old QLocale name methods: 

  QString QLocale::monthName(int month, FormatType format = LongFormat) const;
  QString QLocale::standaloneMonthName(int month, FormatType format = LongFormat) const;
  QString QLocale::dayName(int weekday, FormatType format = LongFormat) const;
  QString QLocale::standaloneDayName(int weekday, FormatType format = LongFormat) const;
  QString QLocale::amText() const;
  QString QLocale::pmText() const;

Add new QLocale name methods: 

  QString QLocale::monthName(int month,
                             FieldFormat format = LongName,
                             FieldContext context = StandaloneContext,
                             YearType yearType = StandardYear,
                             CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::weekdayName(int weekday,
                               FieldFormat format = LongName,
                               FieldContext context = StandaloneContext,
                               CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::dayPeriodName(QTime time,
                                 FieldFormat format = LongName,
                                 FieldContext context = StandaloneContext,
                                 CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::eraName(int year,
                           FieldFormat format = LongName,
                           FieldContext context = StandaloneContext,
                           CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::quarterName(int quarter,
                               FieldFormat format = LongName,
                               FieldContext context = StandaloneContext,
                               CalendarSystem calendar = DefaultCalendar) const;
  QString QLocale::calendarName(CalendarSystem calendar = DefaultCalendar,
                                FieldFormat format = LongName,
                                FieldContext context = Standaloneontext) const;

Modify the QLocale date/time format methods: 

    QString QLocale::dateFormat(FormatType format = LongFormat) const;
    QString QLocale::timeFormat(FormatType format = LongFormat) const;
    QString QLocale::dateTimeFormat(FormatType format = LongFormat) const;

to replace FormatType with StringType: 

  QString QLocale::dateFormat(StringFormat format = LongFormat) const;
  QString QLocale::timeFormat(StringFormat format = LongFormat) const;
  QString QLocale::dateTimeFormat(StringFormat format = LongFormat) const;

Deprecate all the QDateTime toString() and fromString() methods: 

  QString QDate::toString(Qt::DateFormat f = Qt::TextDate) const;
  QString QDate::toString(const QString &format) const;

  static QDate QDate::fromString(const QString &s, Qt::DateFormat f = Qt::TextDate);
  static QDate QDate::fromString(const QString &s, const QString &format);

  QString QTime::toString(Qt::DateFormat f = Qt::TextDate) const;
  QString QTime::toString(const QString &format) const;

  static QTime QTime::fromString(const QString &s, Qt::DateFormat f = Qt::TextDate);
  static QTime QTime::fromString(const QString &s, const QString &format);

  QString QDateTime::toString(Qt::DateFormat f = Qt::TextDate) const;
  QString QDateTime::toString(const QString &format) const;

  static QDateTime QDateTime::fromString(const QString &s, Qt::DateFormat f = Qt::TextDate);
  static QDateTime QDateTime::fromString(const QString &s, const QString &format);

Mondify the QLocale toString() and fromString() methods: 

  QString QLocale::toString(const QDate &date, FormatType format = LongFormat) const;
  QString QLocale::toString(const QTime &time, FormatType format = LongFormat) const;
  QString QLocale::toString(const QDateTime &dateTime, FormatType format = LongFormat) const;

  QDate QLocale::toDate(const QString &string, FormatType = LongFormat) const;
  QTime QLocale::toTime(const QString &string, FormatType = LongFormat) const;
  QDateTime QLocale::toDateTime(const QString &string, FormatType format = LongFormat) const;

to replace FormatType with StringType: 

  QString QLocale::toString(const QDate &date, StringType format = LongFormat) const;
  QString QLocale::toString(const QTime &time, StringType format = LongFormat) const;
  QString QLocale::toString(const QDateTime &dateTime, StringType format = LongFormat) const;

  QDate QLocale::toDate(const QString &string, StringType = LongFormat) const;
  QTime QLocale::toTime(const QString &string, StringType = LongFormat) const;
  QDateTime QLocale::toDateTime(const QString &string, StringType format = LongFormat) const;

Add the following new toString/fromSting methods to QLocale 

  QString QLocale::toString(const QDate &date, QDateTime::DateTimeFormat format) const;
  QString QLocale::toString(const QTime &time, QDateTime::DateTimeFormat format) const;
  QString QLocale::toString(const QDateTime &dateTime, QDateTime::DateTimeFormat format) const;

  QString QLocale::toString(const QDate &date, QDateTime::DateTimeField field,
                            FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QString QLocale::toString(const QTime &time, QDateTime::DateTimeField field,
                            FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QString QLocale::toString(const QDateTime &dateTime, QDateTime::DateTimeField field,
                            FieldFormat format = LongName, FieldContext context = StandaloneContext) const;

  QDate QLocale::toDate(const QString &string, QDateTime::DateTimeFormat format) const;
  QTime QLocale::toTime(const QString &string, QDateTime::DateTimeFormat format) const;
  QDateTime QLocale::toDateTime(const QString &string, QDateTime::DateTimeFormat format) const;

  QDate QLocale::toDate(const QString &string, QDateTime::DateTimeField field,
                        FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QTime QLocale::toTime(const QString &string, QDateTime::DateTimeField field,
                        FieldFormat format = LongName, FieldContext context = StandaloneContext) const;
  QDateTime QLocale::toDateTime(const QString &string, QDateTime::DateTimeField field,
                                FieldFormat format = LongName, FieldContext context = StandaloneContext) const;

Modify the existing string date field format codes to be CLDR compliant as follows: 

   ddd - Weekday - Change to EEE
  dddd - Weekday - Change to EEEE
    AP - AM/PM - Remove, already have A
    ap - am/pm - Remove, already have a
     h - Hour - Modify behaviour to match CLDR
    hh - Hour - Modify behaviour to match CLDR
     t - Timezone - Change to z

Add new CLDR date field format codes for existing or new api: 

  ddddd - Weekday narrow name
  MMMMM - Month narrow name
      y - Year without leading zeros
      d - Day of Year
      w - Week of Year
      Y - Week Year
      L - Stand-alone Month
      e - Weekday
      E - Weekday 
      c - Stand-alone Weekday
      G - Era name
      z - Timezone
      Z - Timezone
      v - Timezone
      V - Timezone
      Q - Quarter of Year
      q - Stand-alone Quarter of Year
      W - Week of Month
      F - Day of Week In Month

QDate API changes

The following QDate YMD methods will be deprecated using QT4_COMPAT: 

    QDate(int y, int m, int d);

    int year() const;
    int month() const;
    int day() const;
    int dayOfWeek() const;
    int dayOfYear() const;
    int daysInMonth() const;
    int daysInYear() const;
    int weekNumber(int *yearNum = 0) const;

    bool setDate(int year, int month, int day);
    void getDate(int *year, int *month, int *day);

    QDate addDays(int days) const;
    QDate addMonths(int months) const;
    QDate addYears(int years) const;
    int daysTo(const QDate &) const;

    static bool isValid(int y, int m, int d);
    static bool isLeapYear(int year);

The following new methods or variations will be added: 

    static QDate gregorianDate(int year, int month, int day);
    static QDate localDate(int year, int month, int day, QLocale::CalendarSystem calSys = QLocale::DefaultCalendar);

Implementation Plan

The following phased implementation is planned:

  • Clean-up current code where required. All existing tests should still pass.
  • Separate private QDateTimeParser into own file. All existing tests should still pass.
  • Create new private QDateTimeFormatter class, move current formatting code from QLocale into QDateTimeFormatter, change QDateTime to make calls to it. Delete QDateTime formatter code. All existing tests should still pass.
  • Create new QDateCalculator class implementing most calendars. Write new unit tests.

Still fuzzy:

  • Change QDateTimeFormatter and QDateTimeParser to fix the currently supported field codes to be CLDR compliant. Modify existing tests to ensure they still pass.
  • Implement new formatting api but making calls to existing backend code, for options that don't yet have the backend coded just translate to a sensible replacement, i.e. for FullDate return LongDate. Only supported CalendarSystem is DefaultCalendar. All existing tests should still pass.
  • Add to QDateTimeFormatter and QDateTimeParser the CLDR field codes that are already supported by existing QDate api. Write new tests.
  • Convert unit tests from old api to new api. All existing tests should still pass.
  • Convert widgets and other Qt code to new api. All existing tests should still pass.
  • Remove old api. All existing tests should still pass.
  • Modify QLocale CLDR backend to return full set of values for new api. Write new tests.
  • Modify QLocale Mac backend to return full set of values for new api. Write new tests.
  • Modify QLocale Windows backend to return full set of values for new api. Write new tests.
  • Add Era support
  • Add Week Date support
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