Qwt User's Guide  6.1.3
QwtDateScaleEngine Class Reference

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 *)
 
QwtTransformtransformation () 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< AttributeAttributes
 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
timeSpecTime 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
dateTimeDate/time value
stepSizeStep size
intervalTypeInterval type
upWhen 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
maxNumStepsMax. number of steps
x1First limit of the interval (In/Out)
x2Second limit of the interval (In/Out)
stepSizeStep 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
x1First interval limit
x2Second interval limit
maxMajorStepsMaximum for the number of major steps
maxMinorStepsMaximum number of minor steps
stepSizeStep size. If stepSize == 0, the scaleEngine calculates one.
Returns
Calculated scale division

Reimplemented from QwtLinearScaleEngine.

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

Classification of a date/time interval division

Parameters
minDateMinimum ( = earlier ) of the interval
maxDateMaximum ( = later ) of the interval
maxStepsMaximum for the number of steps
Returns
Interval classification
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()
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
weeksUpper limit for the number of weeks
Note
In business charts a year is often devided into weeks [1-52]
See also
maxWeeks(), setWeek0Type()
void QwtDateScaleEngine::setTimeSpec ( Qt::TimeSpec  timeSpec)

Set the time specification used by the engine

Parameters
timeSpecTime specification
See also
timeSpec(), setUtcOffset(), toDateTime()
void QwtDateScaleEngine::setUtcOffset ( int  seconds)

Set the offset in seconds from Coordinated Universal Time

Parameters
secondsOffset in seconds
Note
The offset has no effect beside for the time specification Qt::OffsetFromUTC.
See also
QDate::utcOffset(), setTimeSpec(), toDateTime()
void QwtDateScaleEngine::setWeek0Type ( QwtDate::Week0Type  week0Type)

Sets how to identify the first week of a year.

Parameters
week0TypeMode 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.
Qt::TimeSpec QwtDateScaleEngine::timeSpec ( ) const
Returns
Time specification used by the engine
See also
setTimeSpec(), utcOffset(), toDateTime()
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()
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()
QwtDate::Week0Type QwtDateScaleEngine::week0Type ( ) const
Returns
Setting how to identify the first week of a year.
See also
setWeek0Type(), maxWeeks()