Qwt User's Guide
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A scale engine for date/time values. More...
#include <qwt_date_scale_engine.h>
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 |
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. | |
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 |
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().
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.
timeSpec | Time specification |
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.
dateTime | Date/time value |
stepSize | Step size |
intervalType | Interval type |
up | When true dateTime is ceiled - otherwise it is floored |
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().
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) |
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.
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. |
Reimplemented from QwtLinearScaleEngine.
QwtDate::IntervalType QwtDateScaleEngine::intervalType | ( | const QDateTime & | minDate, |
const QDateTime & | maxDate, | ||
int | maxSteps | ||
) | const [virtual] |
Classification of a date/time interval division
minDate | Minimum ( = earlier ) of the interval |
maxDate | Maximum ( = later ) of the interval |
maxSteps | Maximum for the number of steps |
int QwtDateScaleEngine::maxWeeks | ( | ) | const |
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.
weeks | Upper limit for the number of weeks |
void QwtDateScaleEngine::setTimeSpec | ( | Qt::TimeSpec | timeSpec | ) |
Set the time specification used by the engine
timeSpec | Time specification |
void QwtDateScaleEngine::setUtcOffset | ( | int | seconds | ) |
Set the offset in seconds from Coordinated Universal Time
seconds | Offset in seconds |
void QwtDateScaleEngine::setWeek0Type | ( | QwtDate::Week0Type | week0Type | ) |
Sets how to identify the first week of a year.
week0Type | Mode how to identify the first week of a year |
Qt::TimeSpec QwtDateScaleEngine::timeSpec | ( | ) | const |
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()
int QwtDateScaleEngine::utcOffset | ( | ) | const |