QwtDateScaleEngine - A scale engine for date/time values.

NAME

QwtDateScaleEngine − A scale engine for date/time values.

SYNOPSIS

#include <qwt_date_scale_engine.h>

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

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)
Specify a reference point.
double reference () const
void setMargins (double lower, double upper)
Specify margins at the scale’s endpoints.
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.
void buildTicks (const QwtInterval &, double stepSize, int maxMinorSteps, QList< double > ticks[QwtScaleDiv::NTickTypes]) const
Calculate ticks for an interval.
QList< double > buildMajorTicks (const QwtInterval &interval, double stepSize) const
Calculate major ticks for an interval.
void buildMinorTicks (const QList< double > &majorTicks, int maxMinorSteps, double stepSize, QList< double > &minorTicks, QList< double > &mediumTicks) const
Calculate minor/medium ticks for major ticks.

Protected Member Functions inherited from QwtScaleEngine

bool contains (const QwtInterval &, double value) const
QList< double > strip (const QList< double > &, const QwtInterval &) const
double divideInterval (double intervalSize, int numSteps) const
QwtInterval buildInterval (double value) const
Build an interval around a value.

Additional Inherited Members

Public Types inherited from QwtScaleEngine

enum Attribute { NoAttribute = 0x00, IncludeReference = 0x01, Symmetric = 0x02, Floating = 0x04, Inverted = 0x08 }
typedef QFlags< Attribute > 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()

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.

QwtDateScaleEngine::˜QwtDateScaleEngine () [virtual]

Destructor.

Definition at line 754 of file qwt_date_scale_engine.cpp.

Member Function Documentation

QDateTime QwtDateScaleEngine::alignDate (const QDateTime & dateTime, doublestepSize, 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, intmaxMajorSteps, 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.

Updated 2026-06-01 - jenkler.se | uex.se