QwtScaleEngine(3) Qwt User's Guide QwtScaleEngine(3)

QwtScaleEngine - Base class for scale engines.

#include <qwt_scale_engine.h>

Inherited by QwtLinearScaleEngine, and QwtLogScaleEngine.


enum Attribute { NoAttribute = 0x00, IncludeReference = 0x01, Symmetric = 0x02, Floating = 0x04, Inverted = 0x08 }
typedef QFlags< Attribute > Attributes
Layout attributes.


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)
Specify a reference point. double reference () const
void setMargins (double lower, double upper)
Specify margins at the scale's endpoints. double lowerMargin () const
double upperMargin () const
virtual void autoScale (int maxNumSteps, double &x1, double &x2, double &stepSize) const =0
virtual QwtScaleDiv divideScale (double x1, double x2, int maxMajorSteps, int maxMinorSteps, double stepSize=0.0) const =0
Calculate a scale division. void setTransformation (QwtTransform *)
QwtTransform * transformation () const


bool contains (const QwtInterval &, double value) const
QList< double > strip (const QList< double > &, const QwtInterval &) const
double divideInterval (double intervalSize, int numSteps) const
QwtInterval buildInterval (double value) const
Build an interval around a value.

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.

Layout attributes

See also:

setAttribute(), testAttribute(), reference(), lowerMargin(), upperMargin()

Enumerator

No attributes.
Build a scale which includes the reference() value.
Build a scale which is symmetric to the reference() value.
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.
Turn the scale upside down.

Constructor

Parameters:

base Base of the scale engine

See also:

setBase()

QwtScaleEngine::Attributes QwtScaleEngine::attributes () const

Returns:

Scale attributes

See also:

Attribute, setAttributes(), testAttribute()

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 QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.

Returns:

base Base of the scale engine

See also:

setBase()

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], otherwide it is [0.5 * v, 1.5 * v]

Parameters:

value Initial value

Returns:

Calculated interval

Check if an interval 'contains' a value

Parameters:

interval Interval
value Value

Returns:

True, when the value is inside the interval

Calculate a step size for an interval size

Parameters:

intervalSize Interval size
numSteps Number of steps

Returns:

Step size

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 QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.

Returns:

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

See also:

setMargins()

Returns:

the reference value

See also:

setReference(), setAttribute()

Change a scale attribute

Parameters:

attribute Attribute to change
on On/Off

See also:

Attribute, testAttribute()

Change the scale attribute

Parameters:

attributes Set scale attributes

See also:

Attribute, attributes()

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

See also:

base()

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()

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.

See also:

Attribute

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()

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

Parameters:

ticks Tick list
interval Interval

Returns:

Stripped tick list

Returns:

True, if attribute is enabled.

Parameters:

attribute Attribute to be tested

See also:

Attribute, setAttribute()

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 transfomation

See also:

setTransformation()

Returns:

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

See also:

setMargins()

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Wed Jan 2 2019 Version 6.1.4