Contains information about the context in which a coordinate transform is executed. More...

#include <qgscoordinatetransformcontext.h>

Public Member Functions
	QgsCoordinateTransformContext ()
	Constructor for QgsCoordinateTransformContext. More...

	QgsCoordinateTransformContext (const QgsCoordinateTransformContext &rhs)
	Copy constructor. More...

	~QgsCoordinateTransformContext ()

bool	addSourceDestinationDatumTransform (const QgsCoordinateReferenceSystem &sourceCrs, const QgsCoordinateReferenceSystem &destinationCrs, int sourceTransformId, int destinationTransformId)
	Adds a new sourceTransform and destinationTransform to use when projecting coordinates from the the specified sourceCrs to the specified destinationCrs. More...

QgsDatumTransform::TransformPair	calculateDatumTransforms (const QgsCoordinateReferenceSystem &source, const QgsCoordinateReferenceSystem &destination) const
	Returns the pair of source and destination datum transforms to use for a transform from the specified source CRS to destination CRS. More...

void	clear ()
	Clears all stored transform information from the context. More...

bool	hasTransform (const QgsCoordinateReferenceSystem &source, const QgsCoordinateReferenceSystem &destination) const
	Returns true if the context has a valid datum transform to use when transforming from the specified source CRS to destination CRS. More...

QgsCoordinateTransformContext &	operator= (const QgsCoordinateTransformContext &rhs)
	Assignment operator. More...

void	readSettings ()
	Reads the context's state from application settings. More...

bool	readXml (const QDomElement &element, const QgsReadWriteContext &context, QStringList &missingTransforms)
	Reads the context's state from a DOM element. More...

void	removeSourceDestinationDatumTransform (const QgsCoordinateReferenceSystem &sourceCrs, const QgsCoordinateReferenceSystem &destinationCrs)
	Removes the source to destination datum transform pair for the specified sourceCrs and destinationCrs. More...

QMap< QPair< QString, QString >, QgsDatumTransform::TransformPair >	sourceDestinationDatumTransforms () const
	Returns the stored mapping for source to destination CRS pairs to associated datum transforms to use. More...

void	writeSettings ()
	Write the context's state to application settings. More...

void	writeXml (QDomElement &element, const QgsReadWriteContext &context) const
	Writes the context's state to a DOM element. More...

Detailed Description

Contains information about the context in which a coordinate transform is executed.

The context stores various information regarding which coordinate transforms should be used when transforming points from a source to destination coordinate reference system.

The highest priority transforms are those set using addSourceDestinationDatumTransform() and which the transform has a matching source to destination CRS pair.

Failing this, if the source CRS has a matching transform specified by addSourceDatumTransform() then this datum transform will be used. The same logic applies for destination CRS transforms set using addDestinationDatumTransform().

Note: QgsCoordinateTransformContext objects are thread safe for read and write.; QgsCoordinateTransformContext objects are implicitly shared.

See also: QgsDatumTransform; QgsCoordinateTransform

Since: QGIS 3.0

Definition at line 62 of file qgscoordinatetransformcontext.h.

Constructor & Destructor Documentation

◆ QgsCoordinateTransformContext() [1/2]

QgsCoordinateTransformContext::QgsCoordinateTransformContext ( )

Constructor for QgsCoordinateTransformContext.

Definition at line 23 of file qgscoordinatetransformcontext.cpp.

◆ ~QgsCoordinateTransformContext()

QgsCoordinateTransformContext::~QgsCoordinateTransformContext ( )

default

◆ QgsCoordinateTransformContext() [2/2]

QgsCoordinateTransformContext::QgsCoordinateTransformContext ( const QgsCoordinateTransformContext & rhs )

Copy constructor.

Definition at line 29 of file qgscoordinatetransformcontext.cpp.

Member Function Documentation

◆ addSourceDestinationDatumTransform()

bool QgsCoordinateTransformContext::addSourceDestinationDatumTransform	(	const QgsCoordinateReferenceSystem &	sourceCrs,
		const QgsCoordinateReferenceSystem &	destinationCrs,
		int	sourceTransformId,
		int	destinationTransformId
	)

Adds a new sourceTransform and destinationTransform to use when projecting coordinates from the the specified sourceCrs to the specified destinationCrs.

If either sourceTransformId or destinationTransformId is -1, then no datum transform is required for transformations for that source or destination.

Returns true if the new transform pair was added successfully.

Note: Transforms set using this method will override any specific source or destination transforms set by addSourceDatumTransform() or addDestinationDatumTransform().

See also: sourceDestinationDatumTransforms(); removeSourceDestinationDatumTransform()

Definition at line 117 of file qgscoordinatetransformcontext.cpp.

◆ calculateDatumTransforms()

QgsDatumTransform::TransformPair QgsCoordinateTransformContext::calculateDatumTransforms	(	const QgsCoordinateReferenceSystem &	source,
		const QgsCoordinateReferenceSystem &	destination
	)		const

Returns the pair of source and destination datum transforms to use for a transform from the specified source CRS to destination CRS.

Returns an ID of -1 if a datum transform should not be used for the source or destination.

Note: source and destination are reversible.

Definition at line 141 of file qgscoordinatetransformcontext.cpp.

◆ clear()

void QgsCoordinateTransformContext::clear ( )

Clears all stored transform information from the context.

Definition at line 39 of file qgscoordinatetransformcontext.cpp.

◆ hasTransform()

bool QgsCoordinateTransformContext::hasTransform	(	const QgsCoordinateReferenceSystem &	source,
		const QgsCoordinateReferenceSystem &	destination
	)		const

Returns true if the context has a valid datum transform to use when transforming from the specified source CRS to destination CRS.

Note: source and destination are reversible.

Definition at line 134 of file qgscoordinatetransformcontext.cpp.

◆ operator=()

QgsCoordinateTransformContext & QgsCoordinateTransformContext::operator= ( const QgsCoordinateTransformContext & rhs )

Assignment operator.

Definition at line 33 of file qgscoordinatetransformcontext.cpp.

◆ readSettings()

void QgsCoordinateTransformContext::readSettings ( )

Reads the context's state from application settings.

See also: readSettings()

Definition at line 303 of file qgscoordinatetransformcontext.cpp.

◆ readXml()

bool QgsCoordinateTransformContext::readXml	(	const QDomElement &	element,
		const QgsReadWriteContext &	context,
		QStringList &	missingTransforms
	)

Reads the context's state from a DOM element.

Returns false if transforms stored in the XML are not available. In this case missingTransforms will be filled with missing datum transform strings.

See also: writeXml()

Definition at line 167 of file qgscoordinatetransformcontext.cpp.

◆ removeSourceDestinationDatumTransform()

void QgsCoordinateTransformContext::removeSourceDestinationDatumTransform	(	const QgsCoordinateReferenceSystem &	sourceCrs,
		const QgsCoordinateReferenceSystem &	destinationCrs
	)

Removes the source to destination datum transform pair for the specified sourceCrs and destinationCrs.

See also: addSourceDestinationDatumTransform()

Definition at line 129 of file qgscoordinatetransformcontext.cpp.

◆ sourceDestinationDatumTransforms()

QMap< QPair< QString, QString >, QgsDatumTransform::TransformPair > QgsCoordinateTransformContext::sourceDestinationDatumTransforms ( ) const

Returns the stored mapping for source to destination CRS pairs to associated datum transforms to use.

The map keys will be QgsCoordinateReferenceSystems::authid()s.

If either the source transform ID or destination transform ID is -1, then no datum transform is required for transformations for that source or destination.

Warning: This method should not be used to calculate the corresponding datum transforms to use for a coordinate transform. Instead, always use calculateDatumTransforms() to determine this.