Abstract base class for objects which transform the calculated value of a property. More...

#include <qgspropertytransformer.h>

Inheritance diagram for QgsPropertyTransformer:

[legend]

Public Types
enum	Type { GenericNumericTransformer , SizeScaleTransformer , ColorRampTransformer }
	Transformer types. More...

Public Member Functions
	QgsPropertyTransformer (const QgsPropertyTransformer &other)
	Copy constructor.

	QgsPropertyTransformer (double minValue=0.0, double maxValue=1.0)
	Constructor for QgsPropertyTransformer.

virtual	~QgsPropertyTransformer ()

virtual QgsPropertyTransformer *	clone () const =0
	Returns a clone of the transformer.

QgsCurveTransform *	curveTransform () const
	Returns the curve transform applied to input values before they are transformed by the individual transform subclasses.

virtual bool	loadVariant (const QVariant &transformer)
	Loads this transformer from a QVariantMap, wrapped in a QVariant.

double	maxValue () const
	Returns the maximum value expected by the transformer.

double	minValue () const
	Returns the minimum value expected by the transformer.

QgsPropertyTransformer &	operator= (const QgsPropertyTransformer &other)

void	setCurveTransform (QgsCurveTransform *transform)
	Sets a curve transform to apply to input values before they are transformed by the individual transform subclasses.

void	setMaxValue (double max)
	Sets the maximum value expected by the transformer.

void	setMinValue (double min)
	Sets the minimum value expected by the transformer.

virtual QString	toExpression (const QString &baseExpression) const =0
	Converts the transformer to a QGIS expression string.

virtual QVariant	toVariant () const
	Saves this transformer to a QVariantMap, wrapped in a QVariant.

virtual QVariant	transform (const QgsExpressionContext &context, const QVariant &value) const =0
	Calculates the transform of a value.

virtual Type	transformerType () const =0
	Returns the transformer type.

Static Public Member Functions
static QgsPropertyTransformer *	create (Type type)
	Factory method for creating a new property transformer of the specified type.

static QgsPropertyTransformer *	fromExpression (const QString &expression, QString &baseExpression, QString &fieldName)
	Attempts to parse an expression into a corresponding property transformer.

Protected Member Functions
double	transformNumeric (double input) const
	Applies base class numeric transformations.

Protected Attributes
std::unique_ptr< QgsCurveTransform >	mCurveTransform
	Optional curve transform.

double	mMaxValue
	Maximum value expected by the transformer.

double	mMinValue
	Minimum value expected by the transformer.

Detailed Description

Abstract base class for objects which transform the calculated value of a property.

Possible uses include transformers which map a value into a scaled size or color from a gradient.

Definition at line 168 of file qgspropertytransformer.h.

Member Enumeration Documentation

◆ Type

enum QgsPropertyTransformer::Type

Transformer types.

Enumerator
GenericNumericTransformer	Generic transformer for numeric values (QgsGenericNumericTransformer)
SizeScaleTransformer	Size scaling transformer (QgsSizeScaleTransformer)
ColorRampTransformer	Color ramp transformer (QgsColorRampTransformer)

Definition at line 187 of file qgspropertytransformer.h.

Constructor & Destructor Documentation

◆ QgsPropertyTransformer() [1/2]

QgsPropertyTransformer::QgsPropertyTransformer	(	double	minValue = `0.0`,
		double	maxValue = `1.0`
	)

Constructor for QgsPropertyTransformer.

Parameters

minValue	minimum expected value from source property
maxValue	maximum expected value from source property

Definition at line 49 of file qgspropertytransformer.cpp.

◆ QgsPropertyTransformer() [2/2]

QgsPropertyTransformer::QgsPropertyTransformer ( const QgsPropertyTransformer & other )

Copy constructor.

Definition at line 54 of file qgspropertytransformer.cpp.

◆ ~QgsPropertyTransformer()

QgsPropertyTransformer::~QgsPropertyTransformer ( )

virtualdefault

Member Function Documentation

◆ clone()

virtual QgsPropertyTransformer * QgsPropertyTransformer::clone ( ) const

pure virtual

Returns a clone of the transformer.

Implemented in QgsGenericNumericTransformer, QgsSizeScaleTransformer, and QgsColorRampTransformer.

◆ create()

QgsPropertyTransformer * QgsPropertyTransformer::create ( QgsPropertyTransformer::Type type )

static

Factory method for creating a new property transformer of the specified type.

Parameters

type	transformer type to create

Definition at line 31 of file qgspropertytransformer.cpp.

◆ curveTransform()

QgsCurveTransform * QgsPropertyTransformer::curveTransform ( ) const

inline

Returns the curve transform applied to input values before they are transformed by the individual transform subclasses.

See also: setCurveTransform()

Definition at line 276 of file qgspropertytransformer.h.

◆ fromExpression()

QgsPropertyTransformer * QgsPropertyTransformer::fromExpression	(	const QString &	expression,
		QString &	baseExpression,
		QString &	fieldName
	)

static

Attempts to parse an expression into a corresponding property transformer.

Parameters

expression	expression to parse
baseExpression	will be set to the component of the source expression which is used to calculate the input to the property transformer. This will be set to an empty string if a field reference is the transformer input.
fieldName	will be set to a field name which is used to calculate the input to the property transformer. This will be set to an empty string if an expression is the transformer input.

Returns: corresponding property transformer, or nullptr if expression could not be parsed to a transformer.

Definition at line 103 of file qgspropertytransformer.cpp.

◆ loadVariant()

bool QgsPropertyTransformer::loadVariant ( const QVariant & transformer )

virtual

Loads this transformer from a QVariantMap, wrapped in a QVariant.

You can use QgsXmlUtils::readVariant to read it from an XML document.

See also: toVariant()

Reimplemented in QgsGenericNumericTransformer, QgsSizeScaleTransformer, and QgsColorRampTransformer.

Definition at line 70 of file qgspropertytransformer.cpp.

◆ maxValue()

double QgsPropertyTransformer::maxValue ( ) const

inline

Returns the maximum value expected by the transformer.

See also: minValue(); setMaxValue()

Definition at line 261 of file qgspropertytransformer.h.

◆ minValue()

double QgsPropertyTransformer::minValue ( ) const

inline

Returns the minimum value expected by the transformer.

See also: maxValue(); setMinValue()

Definition at line 246 of file qgspropertytransformer.h.

◆ operator=()

QgsPropertyTransformer & QgsPropertyTransformer::operator= ( const QgsPropertyTransformer & other )

Definition at line 60 of file qgspropertytransformer.cpp.

◆ setCurveTransform()

void QgsPropertyTransformer::setCurveTransform ( QgsCurveTransform * transform )

inline

Sets a curve transform to apply to input values before they are transformed by the individual transform subclasses.

Ownership of transform is transferred to the property transformer.

See also: curveTransform()

Definition at line 284 of file qgspropertytransformer.h.

◆ setMaxValue()

void QgsPropertyTransformer::setMaxValue ( double max )

inline

Sets the maximum value expected by the transformer.

Parameters

max	maximum value

See also: setMinValue(); maxValue()

Definition at line 269 of file qgspropertytransformer.h.

◆ setMinValue()

void QgsPropertyTransformer::setMinValue ( double min )

inline

Sets the minimum value expected by the transformer.

Parameters

min	minimum value

See also: setMaxValue(); minValue()

Definition at line 254 of file qgspropertytransformer.h.

◆ toExpression()

virtual QString QgsPropertyTransformer::toExpression ( const QString & baseExpression ) const

pure virtual

Converts the transformer to a QGIS expression string.

The baseExpression string consists of a sub-expression reflecting the parent property's state.

Implemented in QgsGenericNumericTransformer, QgsSizeScaleTransformer, and QgsColorRampTransformer.

◆ toVariant()

QVariant QgsPropertyTransformer::toVariant ( ) const

virtual

Saves this transformer to a QVariantMap, wrapped in a QVariant.

You can use QgsXmlUtils::writeVariant to save it to an XML document.

See also: loadVariant()

Reimplemented in QgsGenericNumericTransformer, QgsSizeScaleTransformer, and QgsColorRampTransformer.

Definition at line 89 of file qgspropertytransformer.cpp.

◆ transform()

virtual QVariant QgsPropertyTransformer::transform	(	const QgsExpressionContext &	context,
		const QVariant &	value
	)		const

pure virtual

Calculates the transform of a value.

Derived classes must implement this to perform their transformations on input values

Parameters

context	expression context
value	input value to transform

Implemented in QgsGenericNumericTransformer, QgsSizeScaleTransformer, and QgsColorRampTransformer.

◆ transformerType()

virtual Type QgsPropertyTransformer::transformerType ( ) const

pure virtual

Returns the transformer type.

Implemented in QgsGenericNumericTransformer, QgsSizeScaleTransformer, and QgsColorRampTransformer.

◆ transformNumeric()

double QgsPropertyTransformer::transformNumeric ( double input ) const

protected

Applies base class numeric transformations.

Derived classes should call this to transform an input numeric value before they apply any transform to the result. This applies any curve transforms which may exist on the transformer.

Definition at line 114 of file qgspropertytransformer.cpp.

Member Data Documentation

◆ mCurveTransform

std::unique_ptr< QgsCurveTransform > QgsPropertyTransformer::mCurveTransform

protected

Optional curve transform.

Definition at line 330 of file qgspropertytransformer.h.

◆ mMaxValue

double QgsPropertyTransformer::mMaxValue

protected

Maximum value expected by the transformer.

Definition at line 327 of file qgspropertytransformer.h.

◆ mMinValue

double QgsPropertyTransformer::mMinValue

protected

Minimum value expected by the transformer.

Definition at line 324 of file qgspropertytransformer.h.

The documentation for this class was generated from the following files:

/home/fischer/src/qgis-3.38/src/core/qgspropertytransformer.h
/home/fischer/src/qgis-3.38/src/core/qgspropertytransformer.cpp

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ Type

Constructor & Destructor Documentation

◆ QgsPropertyTransformer() [1/2]

◆ QgsPropertyTransformer() [2/2]

◆ ~QgsPropertyTransformer()

Member Function Documentation

◆ clone()

◆ create()

◆ curveTransform()

◆ fromExpression()

◆ loadVariant()

◆ maxValue()

◆ minValue()

◆ operator=()

◆ setCurveTransform()

◆ setMaxValue()

◆ setMinValue()

◆ toExpression()

◆ toVariant()

◆ transform()

◆ transformerType()

◆ transformNumeric()

Member Data Documentation

◆ mCurveTransform

◆ mMaxValue

◆ mMinValue