.TH "QwtDateScaleEngine" 3 "Wed Jan 2 2019" "Version 6.1.4" "Qwt User's Guide" \" -*- nroff -*-
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.SH NAME
QwtDateScaleEngine \- A scale engine for date/time values\&.  

.SH SYNOPSIS
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.PP
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\fC#include <qwt_date_scale_engine\&.h>\fP
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Inherits \fBQwtLinearScaleEngine\fP\&.
.SS "Public Member Functions"

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.RI "\fBQwtDateScaleEngine\fP (Qt::TimeSpec=Qt::LocalTime)"
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.RI "Constructor\&. "
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.RI "virtual \fB~QwtDateScaleEngine\fP ()"
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.RI "Destructor\&. "
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.RI "void \fBsetTimeSpec\fP (Qt::TimeSpec)"
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.RI "Qt::TimeSpec \fBtimeSpec\fP () const"
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.RI "void \fBsetUtcOffset\fP (int seconds)"
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.RI "int \fButcOffset\fP () const"
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.RI "void \fBsetWeek0Type\fP (\fBQwtDate::Week0Type\fP)"
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.RI "\fBQwtDate::Week0Type\fP \fBweek0Type\fP () const"
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.RI "void \fBsetMaxWeeks\fP (int)"
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.RI "int \fBmaxWeeks\fP () const"
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.RI "virtual void \fBautoScale\fP (int maxNumSteps, double &x1, double &x2, double &stepSize) const"
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.RI "virtual \fBQwtScaleDiv\fP \fBdivideScale\fP (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize=0\&.0) const"
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.RI "Calculate a scale division for a date/time interval\&. "
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.RI "virtual \fBQwtDate::IntervalType\fP \fBintervalType\fP (const QDateTime &, const QDateTime &, int maxSteps) const"
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.RI "QDateTime \fBtoDateTime\fP (double) const"
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.SS "Protected Member Functions"

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.RI "virtual QDateTime \fBalignDate\fP (const QDateTime &, double stepSize, \fBQwtDate::IntervalType\fP, bool up) const"
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.SS "Additional Inherited Members"
.SH "Detailed Description"
.PP 
A scale engine for date/time values\&. 

\fBQwtDateScaleEngine\fP builds scales from a time intervals\&. Together with \fBQwtDateScaleDraw\fP it can be used for axes according to date/time values\&.
.PP
Years, months, weeks, days, hours and minutes are organized in steps with non constant intervals\&. \fBQwtDateScaleEngine\fP classifies intervals and aligns the boundaries and tick positions according to this classification\&.
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\fBQwtDateScaleEngine\fP 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\&.
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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 \fBQwtDate::toDateTime()\fP\&.
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\fBSee also:\fP
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\fBQwtDate\fP, \fBQwtPlot::setAxisScaleEngine()\fP, \fBQwtAbstractScale::setScaleEngine()\fP 
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.SH "Constructor & Destructor Documentation"
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.SS "QwtDateScaleEngine::QwtDateScaleEngine (Qt::TimeSpec timeSpec = \fCQt::LocalTime\fP)"

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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 \fBQwtDate::FirstThursday\fP\&.
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\fBParameters:\fP
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\fItimeSpec\fP Time specification
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\fBSee also:\fP
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\fBsetTimeSpec()\fP, \fBsetMaxWeeks()\fP, \fBsetWeek0Type()\fP 
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.SH "Member Function Documentation"
.PP 
.SS "QDateTime QwtDateScaleEngine::alignDate (const QDateTime & dateTime, double stepSize, \fBQwtDate::IntervalType\fP intervalType, bool up) const\fC [protected]\fP, \fC [virtual]\fP"
Align a date/time value for a step size
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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 ) \fBalignDate()\fP has to be overloaded\&.
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\fBParameters:\fP
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\fIdateTime\fP Date/time value 
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\fIstepSize\fP Step size 
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\fIintervalType\fP Interval type 
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\fIup\fP When true dateTime is ceiled - otherwise it is floored
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\fBReturns:\fP
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Aligned date/time value 
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.SS "void QwtDateScaleEngine::autoScale (int maxNumSteps, double & x1, double & x2, double & stepSize) const\fC [virtual]\fP"
Align and divide an interval
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The algorithm aligns and divides the interval into steps\&.
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Datetime interval divisions are usually not equidistant and the calculated stepSize can only be used as an approximation for the steps calculated by \fBdivideScale()\fP\&.
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\fBParameters:\fP
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\fImaxNumSteps\fP Max\&. number of steps 
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\fIx1\fP First limit of the interval (In/Out) 
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\fIx2\fP Second limit of the interval (In/Out) 
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\fIstepSize\fP Step size (Out)
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\fBSee also:\fP
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\fBQwtScaleEngine::setAttribute()\fP 
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Reimplemented from \fBQwtLinearScaleEngine\fP\&.
.SS "\fBQwtScaleDiv\fP QwtDateScaleEngine::divideScale (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize = \fC0\&.0\fP) const\fC [virtual]\fP"

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Calculate a scale division for a date/time interval\&. 
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\fBParameters:\fP
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\fIx1\fP First interval limit 
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\fIx2\fP Second interval limit 
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\fImaxMajorSteps\fP Maximum for the number of major steps 
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\fImaxMinorSteps\fP Maximum number of minor steps 
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\fIstepSize\fP Step size\&. If stepSize == 0, the scaleEngine calculates one\&. 
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\fBReturns:\fP
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Calculated scale division 
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Reimplemented from \fBQwtLinearScaleEngine\fP\&.
.SS "\fBQwtDate::IntervalType\fP QwtDateScaleEngine::intervalType (const QDateTime & minDate, const QDateTime & maxDate, int maxSteps) const\fC [virtual]\fP"
Classification of a date/time interval division
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\fBParameters:\fP
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\fIminDate\fP Minimum ( = earlier ) of the interval 
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\fImaxDate\fP Maximum ( = later ) of the interval 
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\fImaxSteps\fP Maximum for the number of steps
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\fBReturns:\fP
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Interval classification 
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.SS "int QwtDateScaleEngine::maxWeeks () const"

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\fBReturns:\fP
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Upper limit for the number of weeks, when an interval can be classified as Qt::Week\&. 
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\fBSee also:\fP
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\fBsetMaxWeeks()\fP, \fBweek0Type()\fP 
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.SS "void QwtDateScaleEngine::setMaxWeeks (int weeks)"
Set a upper limit for the number of weeks, when an interval can be classified as Qt::Week\&.
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The default setting is 4 weeks\&.
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\fBParameters:\fP
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\fIweeks\fP Upper limit for the number of weeks
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\fBNote:\fP
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In business charts a year is often divided into weeks [1-52] 
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\fBSee also:\fP
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\fBmaxWeeks()\fP, \fBsetWeek0Type()\fP 
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.SS "void QwtDateScaleEngine::setTimeSpec (Qt::TimeSpec timeSpec)"
Set the time specification used by the engine
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\fBParameters:\fP
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\fItimeSpec\fP Time specification 
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\fBSee also:\fP
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\fBtimeSpec()\fP, \fBsetUtcOffset()\fP, \fBtoDateTime()\fP 
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.SS "void QwtDateScaleEngine::setUtcOffset (int seconds)"
Set the offset in seconds from Coordinated Universal Time
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\fBParameters:\fP
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\fIseconds\fP Offset in seconds
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\fBNote:\fP
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The offset has no effect beside for the time specification Qt::OffsetFromUTC\&.
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\fBSee also:\fP
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QDate::utcOffset(), \fBsetTimeSpec()\fP, \fBtoDateTime()\fP 
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.SS "void QwtDateScaleEngine::setWeek0Type (\fBQwtDate::Week0Type\fP week0Type)"
Sets how to identify the first week of a year\&.
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\fBParameters:\fP
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\fIweek0Type\fP Mode how to identify the first week of a year
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\fBSee also:\fP
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\fBweek0Type()\fP, \fBsetMaxWeeks()\fP 
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\fBNote:\fP
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week0Type has no effect beside for intervals classified as \fBQwtDate::Week\fP\&. 
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.SS "Qt::TimeSpec QwtDateScaleEngine::timeSpec () const"

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\fBReturns:\fP
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Time specification used by the engine 
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\fBSee also:\fP
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\fBsetTimeSpec()\fP, \fButcOffset()\fP, \fBtoDateTime()\fP 
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.SS "QDateTime QwtDateScaleEngine::toDateTime (double value) const"
Translate a double value into a QDateTime object\&.
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For QDateTime result is bounded by \fBQwtDate::minDate()\fP and \fBQwtDate::maxDate()\fP
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\fBReturns:\fP
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QDateTime object initialized with \fBtimeSpec()\fP and \fButcOffset()\fP\&. 
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\fBSee also:\fP
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\fBtimeSpec()\fP, \fButcOffset()\fP, \fBQwtDate::toDateTime()\fP 
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.SS "int QwtDateScaleEngine::utcOffset () const"

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\fBReturns:\fP
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Offset in seconds from Coordinated Universal Time 
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\fBNote:\fP
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The offset has no effect beside for the time specification Qt::OffsetFromUTC\&.
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\fBSee also:\fP
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QDate::setUtcOffset(), \fBsetTimeSpec()\fP, \fBtoDateTime()\fP 
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.SS "\fBQwtDate::Week0Type\fP QwtDateScaleEngine::week0Type () const"

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\fBReturns:\fP
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Setting how to identify the first week of a year\&. 
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\fBSee also:\fP
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\fBsetWeek0Type()\fP, \fBmaxWeeks()\fP 
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.SH "Author"
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Generated automatically by Doxygen for Qwt User's Guide from the source code\&.