QwtDoubleRange(3)

💖 QwtDoubleRange 💖

okay so bestie, welcome to the Qwt User's Guide — that's the manual this page lives in — and today's main character is QwtDoubleRange. sit down, get comfy, we're doing inheritance and step rasters and it's gonna be adorable. 🎀

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📛 NAME 📛

QwtDoubleRange — and the description? literally nothing. the original page just has a lonely little dash hanging there with no words after it. iconic behavior honestly. the vibe is mysterious. 💀

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✨ SYNOPSIS ✨

#include <qwt_double_range.h>

Inherited by QwtAbstractSlider, and QwtCounter. (so if you're reading this because one of those two sent you here — hi, you're in the right place 🫶)

🌈 Public Member Functions 🌈

• QwtDoubleRange ()
• virtual ~QwtDoubleRange ()
• virtual void fitValue (double)
• virtual void incPages (int)
• virtual void incValue (int)
• bool isValid () const
• double maxValue () const
• double minValue () const
• int pageSize () const
• bool periodic () const
• void setPeriodic (bool tf)
• void setRange (double vmin, double vmax, double vstep=0.0, int pagesize=1)
• void setStep (double)
• void setValid (bool)
• virtual void setValue (double)
• double step () const
• double value () const

🦋 Protected Member Functions 🦋

• double exactPrevValue () const
• double exactValue () const
• double prevValue () const
• virtual void rangeChange ()
• virtual void stepChange ()
• virtual void valueChange ()

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🌸 Detailed Description 🌸

so what is this thing? it's a class which controls a value within an interval. periodt.

it's useful as a base class, or as a member, for sliders. it represents an interval of type double within which a value can be moved. and the value can be one of two flavors:

• an arbitrary point inside the interval — see QwtDoubleRange::setValue
• OR fitted into a step raster — see QwtDoubleRange::fitValue and QwtDoubleRange::incValue

and then there's the special case, the plot twist: a QwtDoubleRange can be periodic. what that means is a value outside the interval gets mapped to a value inside the interval whenever QwtDoubleRange::setValue(), QwtDoubleRange::fitValue(), QwtDoubleRange::incValue() or QwtDoubleRange::incPages() get called. it just cannot stay outside. it always comes home. 😭

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🎀 Constructor & Destructor Documentation 🎀

QwtDoubleRange::QwtDoubleRange ()

fresh out of the box, the range is initialized to [0.0, 100.0], the step size is 1.0, and the value is 0.0. baby's first defaults, she's perfect. ✨

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💅 Member Function Documentation 💅

double QwtDoubleRange::exactValue () const [protected]

returns the exact value. and what even is that? it's the value which QwtDoubleRange::value would have returned if the value hadn't been adjusted to the step raster. so it only differs from the current value if QwtDoubleRange::fitValue or QwtDoubleRange::incValue have been used before — otherwise they're the same girl.

this one is for internal use in derived classes, so it's not for everyone. iykyk. 🤫

void QwtDoubleRange::fitValue (double x) [virtual]

adjusts the value to the closest point in the step raster. snapping into place, no cap.

Parameters:

• x — value

⚠️ Warning: the value is clipped when it lies outside the range. but when the range is QwtDoubleRange::periodic, it will be mapped to a point in the interval such that

new value := x + n * (max. value - min. value)

with an integer number n.

Reimplemented in QwtAbstractSlider.

void QwtDoubleRange::incPages (int nPages) [virtual]

increments the value by a specified number of pages. like flipping pages in a book but the book is a slider. 📖

Parameters:

• nPages — Number of pages to increment. A negative number decrements the value.

⚠️ Warning: the page size is specified in the constructor. so if you're looking for it here… it's not here, bestie. it's over there. 👀

void QwtDoubleRange::incValue (int nSteps) [virtual]

increments the value by a specified number of steps. 🦶

Parameters:

• nSteps — Number of steps to increment

⚠️ Warning: as a result of this operation, the new value will always be adjusted to the step raster. no exceptions, she's committed.

Reimplemented in QwtAbstractSlider.

double QwtDoubleRange::maxValue () const

returns the value of the second border of the range. maxValue returns the value which has been specified as the second parameter in QwtDoubleRange::setRange.

See also: setRange()

double QwtDoubleRange::minValue () const

returns the value at the first border of the range. minValue returns the value which has been specified as the first parameter in setRange().

See also: setRange()

bool QwtDoubleRange::periodic () const

returns true if the range is periodic. that's it, that's the function. simple queen. 👑

See also: setPeriodic()

void QwtDoubleRange::rangeChange () [protected], [virtual]

notify a change of the range. this virtual function gets called whenever the range changes. and the default implementation? does absolutely nothing. silent. unbothered. 💅

Reimplemented in QwtDial, QwtCounter, and QwtSlider.

void QwtDoubleRange::setPeriodic (bool tf)

makes the range periodic. when the range is periodic, the value will be set to a point inside the interval such that

point = value + n * width .fi

if the user tries to set a new value which is outside the range. (yes the .fi is really in there, it's a whole Doxygen artifact, we don't question it, we respect it 🙈)

if the range is nonperiodic (which is the default), values outside the range will be clipped instead. no mapping, no math, just ✂️.

Parameters:

• tf — true for a periodic range

void QwtDoubleRange::setRange (double vmin, double vmax, double vstep = 0.0, int pageSize = 1)

specify range and step size. the glow-up setup call. ✨

Parameters:

• vmin — lower boundary of the interval
• vmax — higher boundary of the interval
• vstep — step width
• pageSize — page size in steps

⚠️ Warning: - A change of the range changes the value if it lies outside the new range. The current value will not be adjusted to the new step raster. - vmax < vmin is allowed. - If the step size is left out or set to zero, it will be set to 1/100 of the interval length. - If the step size has an absurd value, it will be corrected to a better one. (the class is doing a vibe check on your step size and fixing it for you 🫶)

void QwtDoubleRange::setStep (double vstep)

change the step raster.

Parameters:

• vstep — new step width

⚠️ Warning: the value will not be adjusted to the new step raster. she's staying exactly where she is, thank you.

Reimplemented in QwtCounter.

void QwtDoubleRange::setValue (double x) [virtual]

sets a new value without adjusting to the step raster. free-spirited. ungovernable. 🦋

Parameters:

• x — new value

⚠️ Warning: the value is clipped when it lies outside the range. when the range is QwtDoubleRange::periodic, it will be mapped to a point in the interval such that

new value := x + n * (max. value - min. value)

with an integer number n.

Reimplemented in QwtCounter, and QwtAbstractSlider.

double QwtDoubleRange::step () const

Returns:

• the step size

See also: setStep(), setRange()

Reimplemented in QwtCounter.

void QwtDoubleRange::stepChange () [protected], [virtual]

notify a change of the step size. this virtual function gets called whenever the step size changes. default implementation? nothing. nada. silence, but make it chic. 🤐

void QwtDoubleRange::valueChange () [protected], [virtual]

notify a change of value. this virtual function gets called whenever the value changes. default implementation does nothing, again. consistent icon.

Reimplemented in QwtDial, QwtAbstractSlider, QwtSlider, and QwtWheel.

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👑 Author 👑

Generated automatically by Doxygen for Qwt User's Guide from the source code. yes bestie, a robot wrote this about a robot-adjacent thing. we love a full circle moment. 🎀

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and that's the whole page!! mwah. 😘 this was Version 5.2.3, dated Tue Nov 20 2012 — so yes, she's a vintage queen and she still slays. go adjust some step rasters, you got this. 💖✨🌸🦋