A scale engine for date/time values. More...

#include <qwt_date_scale_engine.h>

Inheritance diagram for QwtDateScaleEngine:

Public Member Functions
	QwtDateScaleEngine (Qt::TimeSpec=Qt::LocalTime)
	Constructor. More...

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

virtual QwtScaleDiv	divideScale (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize=0.0) const
	Calculate a scale division for a date/time interval. More...

virtual QwtDate::IntervalType	intervalType (const QDateTime &, const QDateTime &, int maxSteps) const

QDateTime	toDateTime (double) const

Public Member Functions inherited from QwtLinearScaleEngine
	QwtLinearScaleEngine (uint base=10)

virtual	~QwtLinearScaleEngine ()
	Destructor.

Public Member Functions inherited from QwtScaleEngine
	QwtScaleEngine (uint base=10)

virtual	~QwtScaleEngine ()
	Destructor.

void	setBase (uint base)

uint	base () const

void	setAttribute (Attribute, bool on=true)

bool	testAttribute (Attribute) const

void	setAttributes (Attributes)

Attributes	attributes () const

void	setReference (double reference)
	Specify a reference point. More...

double	reference () const

void	setMargins (double lower, double upper)
	Specify margins at the scale's endpoints. More...

double	lowerMargin () const

double	upperMargin () const

void	setTransformation (QwtTransform *)

QwtTransform *	transformation () const

Protected Member Functions
virtual QDateTime	alignDate (const QDateTime &, double stepSize, QwtDate::IntervalType, bool up) const

Protected Member Functions inherited from QwtLinearScaleEngine
QwtInterval	align (const QwtInterval &, double stepSize) const
	Align an interval to a step size. More...

void	buildTicks (const QwtInterval &, double stepSize, int maxMinSteps, QList< double > ticks[QwtScaleDiv::NTickTypes]) const
	Calculate ticks for an interval. More...

QList< double >	buildMajorTicks (const QwtInterval &interval, double stepSize) const
	Calculate major ticks for an interval. More...

void	buildMinorTicks (const QList< double > &majorTicks, int maxMinorSteps, double stepSize, QList< double > &minorTicks, QList< double > &mediumTicks) const
	Calculate minor/medium ticks for major ticks. More...

Protected Member Functions inherited from QwtScaleEngine
bool	contains (const QwtInterval &, double val) const

QList< double >	strip (const QList< double > &, const QwtInterval &) const

double	divideInterval (double interval, int numSteps) const

QwtInterval	buildInterval (double v) const
	Build an interval around a value. More...

Additional Inherited Members
Public Types inherited from QwtScaleEngine
enum	Attribute { NoAttribute = 0x00, IncludeReference = 0x01, Symmetric = 0x02, Floating = 0x04, Inverted = 0x08 }

typedef QFlags< Attribute >	Attributes
	Layout attributes.

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()

Constructor & Destructor Documentation

QwtDateScaleEngine::QwtDateScaleEngine ( Qt::TimeSpec timeSpec = Qt::LocalTime )

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()

Member Function Documentation

QDateTime QwtDateScaleEngine::alignDate	(	const QDateTime &	dateTime,
		double	stepSize,
		QwtDate::IntervalType	intervalType,
		bool	up
	)		const

protectedvirtual

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

void QwtDateScaleEngine::autoScale	(	int	maxNumSteps,
		double &	x1,
		double &	x2,
		double &	stepSize
	)		const

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.

QwtScaleDiv QwtDateScaleEngine::divideScale	(	double	x1,
		double	x2,
		int	maxMajorSteps,
		int	maxMinorSteps,
		double	stepSize = `0.0`
	)		const

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.