QwtScaleEngine(3)

📦

version 6.3.0 · 6 versions

🎀 QwtScaleEngine(3) — Library Functions Manual, Qwt User's Guide edition ✨

okay bestie, this is the manual page for QwtScaleEngine(3), and yes the base-class energy is real 💅 We're gonna get through every single member together, no skipping.

🌸 NAME

Base class for scale engines.

Short, sweet, iconic.

✨ SYNOPSIS

#include <qwt_scale_engine.h>

Inherited by QwtLinearScaleEngine, and QwtLogScaleEngine.

🫶 Public Types

enum Attribute { NoAttribute = 0x00, IncludeReference = 0x01, Symmetric = 0x02, Floating = 0x04, Inverted = 0x08 } — the layout-attribute enum, full lineup included.
typedef QFlags< Attribute > Attributes — an ORed combination of Attribute values.

🧚 Public Member Functions

QwtScaleEngine (uint base=10) — constructor, with base defaulting to 10.
virtual ~QwtScaleEngine () — destructor.
void setBase (uint base) — set the base of the scale engine.
uint base () const — get the base of the scale engine.
void setAttribute (Attribute, bool on=true) — change a scale attribute.
bool testAttribute (Attribute) const — test whether an attribute is enabled.
void setAttributes (Attributes) — set the scale attributes.
Attributes attributes () const — get the scale attributes.
void setReference (double) — specify a reference point.
double reference () const — get the reference value.
void setMargins (double lower, double upper) — specify margins at the scale's endpoints.
double lowerMargin () const — get the lower margin.
double upperMargin () const — get the upper margin.
virtual void autoScale (int maxNumSteps, double &x1, double &x2, double &stepSize) const =0 — pure virtual; align and divide an interval.
virtual QwtScaleDiv divideScale (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize=0.0) const =0 — pure virtual; calculate a scale division.
void setTransformation (QwtTransform *) — assign a transformation.
QwtTransform * transformation () const — get a clone of the transformation.

🦋 Protected Member Functions

bool contains (const QwtInterval &, double value) const — check if an interval contains a value.
QList< double > strip (const QList< double > &, const QwtInterval &) const — strip ticks that aren't inside an interval.
double divideInterval (double intervalSize, int numSteps) const — calculate a step size for an interval size.
QwtInterval buildInterval (double value) const — build an interval around a value.

💖 Detailed Description

Base class for scale engines.

A scale engine tries to find "reasonable" ranges and step sizes for scales.

The layout of the scale can be varied with setAttribute().

Qwt offers implementations for logarithmic and linear scales.

Definition at line 45 of file qwt_scale_engine.h.

🦋 Member Typedef Documentation

`typedef QFlags<Attribute > QwtScaleEngine::Attributes`

An ORed combination of Attribute values.

Definition at line 78 of file qwt_scale_engine.h.

🌈 Member Enumeration Documentation

`enum QwtScaleEngine::Attribute`

Layout attributes.

See also: setAttribute(), testAttribute(), reference(), lowerMargin(), upperMargin().

Enumerator:

NoAttribute — No attributes.
IncludeReference — Build a scale which includes the reference() value.
Symmetric — Build a scale which is symmetric to the reference() value.
Floating — The endpoints of the scale are supposed to be equal the outmost included values plus the specified margins (see setMargins()). If this attribute is not set, the endpoints of the scale will be integer multiples of the step size.
Inverted — Turn the scale upside down.

Definition at line 54 of file qwt_scale_engine.h.

🎀 Constructor & Destructor Documentation

`QwtScaleEngine::QwtScaleEngine (uint base = 10)` `[explicit]`

Constructor.

Parameters:

base — Base of the scale engine

`QwtScaleEngine::~QwtScaleEngine ()` `[virtual]`

Destructor.

Definition at line 230 of file qwt_scale_engine.cpp.

🧁 Member Function Documentation

`QwtScaleEngine::Attributes QwtScaleEngine::attributes () const`

Returns: Scale attributes.

See also: Attribute, setAttributes(), testAttribute().

Definition at line 451 of file qwt_scale_engine.cpp.

`virtual void QwtScaleEngine::autoScale (int maxNumSteps, double & x1, double & x2, double & stepSize) const` `[pure virtual]`

Align and divide an interval.

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 (Return value)

Implemented in QwtDateScaleEngine, QwtLinearScaleEngine, and QwtLogScaleEngine.

`uint QwtScaleEngine::base () const`

Returns: base — base of the scale engine.

`QwtInterval QwtScaleEngine::buildInterval (double value) const` `[protected]`

Build an interval around a value. In case of v == 0.0 the interval is [-0.5, 0.5], otherwise it is [0.5 * v, 1.5 * v].

Parameters:

value — Initial value

Returns: Calculated interval.

Definition at line 395 of file qwt_scale_engine.cpp.

`bool QwtScaleEngine::contains (const QwtInterval & interval, double value) const` `[protected]`

Check if an interval "contains" a value.

Parameters:

interval — Interval
value — Value

Returns: True, when the value is inside the interval.

Definition at line 341 of file qwt_scale_engine.cpp.

`double QwtScaleEngine::divideInterval (double intervalSize, int numSteps) const` `[protected]`

Calculate a step size for an interval size.

Parameters:

intervalSize — Interval size
numSteps — Number of steps

Returns: Step size.

Definition at line 326 of file qwt_scale_engine.cpp.

`virtual QwtScaleDiv QwtScaleEngine::divideScale (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize = 0.0) const` `[pure virtual]`

Calculate a scale division.

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 == 0.0, the scaleEngine calculates one.

Returns: Calculated scale division.

Implemented in QwtDateScaleEngine, QwtLinearScaleEngine, and QwtLogScaleEngine.

`double QwtScaleEngine::lowerMargin () const`

Returns: the margin at the lower end of the scale. The default margin is 0.

`double QwtScaleEngine::reference () const`

Returns: the reference value.

See also: setReference(), setAttribute().

Definition at line 474 of file qwt_scale_engine.cpp.

`void QwtScaleEngine::setAttribute (Attribute attribute, bool on = true)`

Change a scale attribute.

Parameters:

attribute — Attribute to change
on — On/Off

See also: Attribute, testAttribute().

Definition at line 417 of file qwt_scale_engine.cpp.

`void QwtScaleEngine::setAttributes (Attributes attributes)`

Change the scale attribute.

Parameters:

attributes — Set scale attributes

`void QwtScaleEngine::setBase (uint base)`

Set the base of the scale engine.

While a base of 10 is what 99.9% of all applications need certain scales might need a different base: f.e 2.

The default setting is 10.

Parameters:

base — Base of the engine

`void QwtScaleEngine::setMargins (double lower, double upper)`

Specify margins at the scale's endpoints.

Parameters:

lower — minimum distance between the scale's lower boundary and the smallest enclosed value
upper — minimum distance between the scale's upper boundary and the greatest enclosed value

Margins can be used to leave a minimum amount of space between the enclosed intervals and the boundaries of the scale.

Warning: QwtLogScaleEngine measures the margins in decades.

See also: upperMargin(), lowerMargin().

Definition at line 312 of file qwt_scale_engine.cpp.

`void QwtScaleEngine::setReference (double reference)`

Specify a reference point.

Parameters:

reference — New reference value

The reference point is needed if options IncludeReference or Symmetric are active. Its default value is 0.0.

`void QwtScaleEngine::setTransformation (QwtTransform * transform)`

Assign a transformation.

Parameters:

transform — Transformation

The transformation object is used as factory for clones that are returned by transformation().

The scale engine takes ownership of the transformation.

See also: QwtTransform::copy(), transformation().

Definition at line 248 of file qwt_scale_engine.cpp.

`QList< double > QwtScaleEngine::strip (const QList< double > & ticks, const QwtInterval & interval) const` `[protected]`

Remove ticks from a list, that are not inside an interval.

Parameters:

ticks — Tick list
interval — Interval

Returns: Stripped tick list.

Definition at line 364 of file qwt_scale_engine.cpp.

`bool QwtScaleEngine::testAttribute (Attribute attribute) const`

Returns: True, if attribute is enabled.

Parameters:

attribute — Attribute to be tested

See also: Attribute, setAttribute().

Definition at line 431 of file qwt_scale_engine.cpp.

`QwtTransform * QwtScaleEngine::transformation () const`

Create and return a clone of the transformation of the engine. When the engine has no special transformation NULL is returned, indicating no transformation.

Returns: A clone of the transformation.

`double QwtScaleEngine::upperMargin () const`

Returns: the margin at the upper end of the scale. The default margin is 0.

👑 Author

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QwtScaleEngine(3)