QwtDateScaleEngine(3) Qwt User's Guide QwtDateScaleEngine(3) NAME QwtDateScaleEngine - A scale engine for date/time values. SYNOPSIS #include Inherits QwtLinearScaleEngine. Public Member Functions QwtDateScaleEngine (Qt::TimeSpec=Qt::LocalTime) Constructor. virtual ~QwtDateScaleEngine () Destructor. void setTimeSpec (Qt::TimeSpec) Qt::TimeSpec timeSpec () const void setUtcOffset (int seconds) int utcOffset () const void setWeek0Type (QwtDate::Week0Type) QwtDate::Week0Type week0Type () const void setMaxWeeks (int) int maxWeeks () const virtual void autoScale (int maxNumSteps, double &x1, double &x2, double &stepSize) const override virtual QwtScaleDiv divideScale (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize=0.0) const override Calculate a scale division for a date/time interval. virtual QwtDate::IntervalType intervalType (const QDateTime &, const QDateTime &, int maxSteps) const QDateTime toDateTime (double) const Protected Member Functions virtual QDateTime alignDate (const QDateTime &, double stepSize, QwtDate::IntervalType, bool up) const Additional Inherited Members Detailed Description A scale engine for date/time values. QwtDateScaleEngine builds scales from a time intervals. Together with QwtDateScaleDraw it can be used for axes according to date/time values. Years, months, weeks, days, hours and minutes are organized in steps with non constant intervals. QwtDateScaleEngine classifies intervals and aligns the boundaries and tick positions according to this classification. QwtDateScaleEngine supports representations depending on Qt::TimeSpec specifications. The valid range for scales is limited by the range of QDateTime, that differs between Qt4 and Qt5. Datetime values are expected as the number of milliseconds since 1970-01-01T00:00:00 Universal Coordinated Time - also known as 'The Epoch', that can be converted to QDateTime using QwtDate::toDateTime(). See also QwtDate, QwtPlot::setAxisScaleEngine(), QwtAbstractScale::setScaleEngine() Definition at line 42 of file qwt_date_scale_engine.h. Constructor & Destructor Documentation QwtDateScaleEngine::QwtDateScaleEngine (Qt::TimeSpec timeSpec = Qt::LocalTime) [explicit] Constructor. The engine is initialized to build scales for the given time specification. It classifies intervals > 4 weeks as >= Qt::Month. The first week of a year is defined like for QwtDate::FirstThursday. Parameters timeSpec Time specification See also setTimeSpec(), setMaxWeeks(), setWeek0Type() Definition at line 747 of file qwt_date_scale_engine.cpp. Member Function Documentation QDateTime QwtDateScaleEngine::alignDate (const QDateTime & dateTime, double stepSize, QwtDate::IntervalType intervalType, bool up) const [protected], [virtual] Align a date/time value for a step size For Qt::Day alignments there is no 'natural day 0' - instead the first day of the year is used to avoid jumping major ticks positions when panning a scale. For other alignments ( f.e according to the first day of the month ) alignDate() has to be overloaded. Parameters dateTime Date/time value stepSize Step size intervalType Interval type up When true dateTime is ceiled - otherwise it is floored Returns Aligned date/time value Definition at line 1108 of file qwt_date_scale_engine.cpp. void QwtDateScaleEngine::autoScale (int maxNumSteps, double & x1, double & x2, double & stepSize) const [override], [virtual] Align and divide an interval The algorithm aligns and divides the interval into steps. Datetime interval divisions are usually not equidistant and the calculated stepSize can only be used as an approximation for the steps calculated by divideScale(). Parameters maxNumSteps Max. number of steps x1 First limit of the interval (In/Out) x2 Second limit of the interval (In/Out) stepSize Step size (Out) See also QwtScaleEngine::setAttribute() Reimplemented from QwtLinearScaleEngine. Definition at line 925 of file qwt_date_scale_engine.cpp. QwtScaleDiv QwtDateScaleEngine::divideScale (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize = 0.0) const [override], [virtual] Calculate a scale division for a date/time interval. Parameters x1 First interval limit x2 Second interval limit maxMajorSteps Maximum for the number of major steps maxMinorSteps Maximum number of minor steps stepSize Step size. If stepSize == 0, the scaleEngine calculates one. Returns Calculated scale division Reimplemented from QwtLinearScaleEngine. Definition at line 992 of file qwt_date_scale_engine.cpp. QwtDate::IntervalType QwtDateScaleEngine::intervalType (const QDateTime & minDate, const QDateTime & maxDate, int maxSteps) const [virtual] Classification of a date/time interval division Parameters minDate Minimum ( = earlier ) of the interval maxDate Maximum ( = later ) of the interval maxSteps Maximum for the number of steps Returns Interval classification Definition at line 865 of file qwt_date_scale_engine.cpp. int QwtDateScaleEngine::maxWeeks () const Returns Upper limit for the number of weeks, when an interval can be classified as Qt::Week. See also setMaxWeeks(), week0Type() Definition at line 851 of file qwt_date_scale_engine.cpp. void QwtDateScaleEngine::setMaxWeeks (int weeks) Set a upper limit for the number of weeks, when an interval can be classified as Qt::Week. The default setting is 4 weeks. Parameters weeks Upper limit for the number of weeks Note In business charts a year is often divided into weeks [1-52] See also maxWeeks(), setWeek0Type() Definition at line 841 of file qwt_date_scale_engine.cpp. void QwtDateScaleEngine::setTimeSpec (Qt::TimeSpec timeSpec) Set the time specification used by the engine Parameters timeSpec Time specification See also timeSpec(), setUtcOffset(), toDateTime() Definition at line 765 of file qwt_date_scale_engine.cpp. void QwtDateScaleEngine::setUtcOffset (int seconds) Set the offset in seconds from Coordinated Universal Time Parameters seconds Offset in seconds Note The offset has no effect beside for the time specification Qt::OffsetFromUTC. See also QDate::utcOffset(), setTimeSpec(), toDateTime() Definition at line 789 of file qwt_date_scale_engine.cpp. void QwtDateScaleEngine::setWeek0Type (QwtDate::Week0Type week0Type) Sets how to identify the first week of a year. Parameters week0Type Mode how to identify the first week of a year See also week0Type(), setMaxWeeks() Note week0Type has no effect beside for intervals classified as QwtDate::Week. Definition at line 815 of file qwt_date_scale_engine.cpp. Qt::TimeSpec QwtDateScaleEngine::timeSpec () const Returns Time specification used by the engine See also setTimeSpec(), utcOffset(), toDateTime() Definition at line 774 of file qwt_date_scale_engine.cpp. QDateTime QwtDateScaleEngine::toDateTime (double value) const Translate a double value into a QDateTime object. For QDateTime result is bounded by QwtDate::minDate() and QwtDate::maxDate() Returns QDateTime object initialized with timeSpec() and utcOffset(). See also timeSpec(), utcOffset(), QwtDate::toDateTime() Definition at line 1298 of file qwt_date_scale_engine.cpp. int QwtDateScaleEngine::utcOffset () const Returns Offset in seconds from Coordinated Universal Time Note The offset has no effect beside for the time specification Qt::OffsetFromUTC. See also QDate::setUtcOffset(), setTimeSpec(), toDateTime() Definition at line 801 of file qwt_date_scale_engine.cpp. QwtDate::Week0Type QwtDateScaleEngine::week0Type () const Returns Setting how to identify the first week of a year. See also setWeek0Type(), maxWeeks() Definition at line 824 of file qwt_date_scale_engine.cpp. Author Generated automatically by Doxygen for Qwt User's Guide from the source code. Version 6.2.0 Sun Jul 18 2021 QwtDateScaleEngine(3)