Abstract base class for processing algorithms. More...

#include <qgsprocessingalgorithm.h>

Inheritance diagram for QgsProcessingAlgorithm:

Public Types
enum	Flag { FlagHideFromToolbox = 1 << 1, FlagHideFromModeler = 1 << 2, FlagSupportsBatch = 1 << 3, FlagCanCancel = 1 << 4, FlagRequiresMatchingCrs = 1 << 5, FlagNoThreading = 1 << 6, FlagDisplayNameIsLiteral = 1 << 7, FlagSupportsInPlaceEdits = 1 << 8, FlagKnownIssues = 1 << 9, FlagDeprecated = FlagHideFromToolbox \| FlagHideFromModeler }
	Flags indicating how and when an algorithm operates and should be exposed to users. More...

Public Member Functions
	QgsProcessingAlgorithm ()=default
	Constructor for QgsProcessingAlgorithm. More...

	QgsProcessingAlgorithm (const QgsProcessingAlgorithm &other)=delete
	Algorithms cannot be copied - create() should be used instead. More...

virtual	~QgsProcessingAlgorithm ()

virtual QString	asPythonCommand (const QVariantMap &parameters, QgsProcessingContext &context) const
	Returns a Python command string which can be executed to run the algorithm using the specified parameters. More...

virtual bool	canExecute (QString *errorMessage=nullptr) const
	Returns `true` if the algorithm can execute. More...

virtual bool	checkParameterValues (const QVariantMap &parameters, QgsProcessingContext &context, QString *message=nullptr) const
	Checks the supplied parameter values to verify that they satisfy the requirements of this algorithm in the supplied context. More...

int	countVisibleParameters () const
	Returns the number of visible (non-hidden) parameters defined by this algorithm. More...

QgsProcessingAlgorithm *	create (const QVariantMap &configuration=QVariantMap()) const SIP_THROW(QgsProcessingException)
	Creates a copy of the algorithm, ready for execution. More...

virtual QWidget *	createCustomParametersWidget (QWidget *parent=nullptr) const
	If an algorithm subclass implements a custom parameters widget, a copy of this widget should be constructed and returned by this method. More...

virtual QgsExpressionContext	createExpressionContext (const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeatureSource *source=nullptr) const
	Creates an expression context relating to the algorithm. More...

QgsProcessingParameterDefinitions	destinationParameterDefinitions () const
	Returns a list of destination parameters definitions utilized by the algorithm. More...

virtual QString	displayName () const =0
	Returns the translated algorithm name, which should be used for any user-visible display of the algorithm name. More...

virtual Flags	flags () const
	Returns the flags indicating how and when the algorithm operates and should be exposed to users. More...

virtual QString	group () const
	Returns the name of the group this algorithm belongs to. More...

virtual QString	groupId () const
	Returns the unique ID of the group this algorithm belongs to. More...

bool	hasHtmlOutputs () const
	Returns `true` if this algorithm generates HTML outputs. More...

virtual Q_DECL_DEPRECATED QString	helpString () const
	Returns a localised help string for the algorithm. More...

virtual QString	helpUrl () const
	Returns a url pointing to the algorithm's help page. More...

virtual QIcon	icon () const
	Returns an icon for the algorithm. More...

QString	id () const
	Returns the unique ID for the algorithm, which is a combination of the algorithm provider's ID and the algorithms unique name (e.g. More...

virtual QString	name () const =0
	Returns the algorithm name, used for identifying the algorithm. More...

QgsProcessingAlgorithm &	operator= (const QgsProcessingAlgorithm &other)=delete
	Algorithms cannot be copied- create() should be used instead. More...

const QgsProcessingOutputDefinition *	outputDefinition (const QString &name) const
	Returns a matching output by name. More...

QgsProcessingOutputDefinitions	outputDefinitions () const
	Returns an ordered list of output definitions utilized by the algorithm. More...

const QgsProcessingParameterDefinition *	parameterDefinition (const QString &name) const
	Returns a matching parameter by name. More...

QgsProcessingParameterDefinitions	parameterDefinitions () const
	Returns an ordered list of parameter definitions utilized by the algorithm. More...

QVariantMap	postProcess (QgsProcessingContext &context, QgsProcessingFeedback *feedback)
	Should be called in the main thread following the completion of runPrepared(). More...

bool	prepare (const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback)
	Prepares the algorithm for execution. More...

virtual QVariantMap	preprocessParameters (const QVariantMap &parameters)
	Pre-processes a set of parameters, allowing the algorithm to clean their values. More...

QgsProcessingProvider *	provider () const
	Returns the provider to which this algorithm belongs. More...

QVariantMap	run (const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback feedback, bool ok=nullptr, const QVariantMap &configuration=QVariantMap()) const
	Executes the algorithm using the specified parameters. More...

QVariantMap	runPrepared (const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback) SIP_THROW(QgsProcessingException)
	Runs the algorithm, which has been prepared by an earlier call to prepare(). More...

void	setProvider (QgsProcessingProvider *provider)
	Associates this algorithm with its provider. More...

virtual QString	shortDescription () const
	Returns an optional translated short description of the algorithm. More...

virtual QString	shortHelpString () const
	Returns a localised short helper string for the algorithm. More...

virtual QString	svgIconPath () const
	Returns a path to an SVG version of the algorithm's icon. More...

virtual QStringList	tags () const
	Returns a list of tags which relate to the algorithm, and are used to assist users in searching for suitable algorithms. More...

virtual bool	validateInputCrs (const QVariantMap &parameters, QgsProcessingContext &context) const
	Checks whether the coordinate reference systems for the specified set of parameters are valid for the algorithm. More...

Protected Member Functions
bool	addOutput (QgsProcessingOutputDefinition *outputDefinition)
	Adds an output definition to the algorithm. More...

bool	addParameter (QgsProcessingParameterDefinition *parameterDefinition, bool createOutput=true)
	Adds a parameter definition to the algorithm. More...

virtual QgsProcessingAlgorithm *	createInstance () const =0
	Creates a new instance of the algorithm class. More...

virtual void	initAlgorithm (const QVariantMap &configuration=QVariantMap())=0
	Initializes the algorithm using the specified configuration. More...

bool	parameterAsBool (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a static boolean value. More...

bool	parameterAsBoolean (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a static boolean value. More...

QColor	parameterAsColor (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context)
	Evaluates the parameter with matching name to a color, or returns an invalid color if the parameter was not set. More...

QString	parameterAsCompatibleSourceLayerPath (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context, const QStringList &compatibleFormats, const QString &preferredFormat=QString("shp"), QgsProcessingFeedback *feedback=nullptr)
	Evaluates the parameter with matching name to a source vector layer file path of compatible format. More...

QString	parameterAsCompatibleSourceLayerPathAndLayerName (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context, const QStringList &compatibleFormats, const QString &preferredFormat=QString("shp"), QgsProcessingFeedback feedback=nullptr, QString layerName=nullptr)
	Evaluates the parameter with matching name to a source vector layer file path and layer name of compatible format. More...

QgsCoordinateReferenceSystem	parameterAsCrs (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a coordinate reference system. More...

double	parameterAsDouble (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a static double value. More...

int	parameterAsEnum (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a enum value. More...

QList< int >	parameterAsEnums (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to list of enum values. More...

QString	parameterAsExpression (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to an expression. More...

QgsRectangle	parameterAsExtent (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context, const QgsCoordinateReferenceSystem &crs=QgsCoordinateReferenceSystem()) const
	Evaluates the parameter with matching name to a rectangular extent. More...

QgsCoordinateReferenceSystem	parameterAsExtentCrs (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context)
	Returns the coordinate reference system associated with an extent parameter value. More...

QgsGeometry	parameterAsExtentGeometry (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context, const QgsCoordinateReferenceSystem &crs=QgsCoordinateReferenceSystem())
	Evaluates the parameter with matching name to a rectangular extent, and returns a geometry covering this extent. More...

QStringList	parameterAsFields (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a list of fields. More...

QString	parameterAsFile (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a file/folder name. More...

QStringList	parameterAsFileList (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a list of files (for QgsProcessingParameterMultipleLayers in QgsProcessing:TypeFile mode). More...

QString	parameterAsFileOutput (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a file based output destination. More...

int	parameterAsInt (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a static integer value. More...

QList< int >	parameterAsInts (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a list of integer values. More...

QgsMapLayer *	parameterAsLayer (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a map layer. More...

QList< QgsMapLayer * >	parameterAsLayerList (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a list of map layers. More...

QgsPrintLayout *	parameterAsLayout (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context)
	Evaluates the parameter with matching name to a print layout. More...

QgsLayoutItem *	parameterAsLayoutItem (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context, QgsPrintLayout *layout)
	Evaluates the parameter with matching name to a print layout item, taken from the specified layout. More...

QVariantList	parameterAsMatrix (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a matrix/table of values. More...

QgsMeshLayer *	parameterAsMeshLayer (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a mesh layer. More...

QString	parameterAsOutputLayer (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a output layer destination. More...

QgsPointXY	parameterAsPoint (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context, const QgsCoordinateReferenceSystem &crs=QgsCoordinateReferenceSystem()) const
	Evaluates the parameter with matching name to a point. More...

QgsCoordinateReferenceSystem	parameterAsPointCrs (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context)
	Returns the coordinate reference system associated with an point parameter value. More...

QList< double >	parameterAsRange (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a range of values. More...

QgsRasterLayer *	parameterAsRasterLayer (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a raster layer. More...

QgsFeatureSink *	parameterAsSink (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context, QString &destinationIdentifier, const QgsFields &fields, QgsWkbTypes::Type geometryType=QgsWkbTypes::NoGeometry, const QgsCoordinateReferenceSystem &crs=QgsCoordinateReferenceSystem(), QgsFeatureSink::SinkFlags sinkFlags=nullptr) const
	Evaluates the parameter with matching name to a feature sink. More...

QgsProcessingFeatureSource *	parameterAsSource (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a feature source. More...

QString	parameterAsString (const QVariantMap &parameters, const QString &name, const QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a static string value. More...

QgsVectorLayer *	parameterAsVectorLayer (const QVariantMap &parameters, const QString &name, QgsProcessingContext &context) const
	Evaluates the parameter with matching name to a vector layer. More...

virtual QVariantMap	postProcessAlgorithm (QgsProcessingContext &context, QgsProcessingFeedback *feedback) SIP_THROW(QgsProcessingException)
	Allows the algorithm to perform any required cleanup tasks. More...

virtual bool	prepareAlgorithm (const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback) SIP_THROW(QgsProcessingException)
	Prepares the algorithm to run using the specified parameters. More...

virtual QVariantMap	processAlgorithm (const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback) SIP_THROW(QgsProcessingException)=0
	Runs the algorithm using the specified parameters. More...

void	removeParameter (const QString &name)
	Removes the parameter with matching name from the algorithm, and deletes any existing definition. More...

virtual bool	supportInPlaceEdit (const QgsMapLayer *layer) const
	Checks whether this algorithm supports in-place editing on the given layer Default implementation returns `false`. More...

Static Protected Member Functions
static QString	invalidRasterError (const QVariantMap &parameters, const QString &name)
	Returns a user-friendly string to use as an error when a raster layer input could not be loaded. More...

static QString	invalidSinkError (const QVariantMap &parameters, const QString &name)
	Returns a user-friendly string to use as an error when a sink parameter could not be created. More...

static QString	invalidSourceError (const QVariantMap &parameters, const QString &name)
	Returns a user-friendly string to use as an error when a source parameter could not be loaded. More...

Friends
class	QgsProcessingModelAlgorithm

class	QgsProcessingProvider

class	QgsProcessingToolboxProxyModel

class	TestQgsProcessing

Detailed Description

Abstract base class for processing algorithms.

Since: QGIS 3.0

Definition at line 51 of file qgsprocessingalgorithm.h.

Member Enumeration Documentation

◆ Flag

enum QgsProcessingAlgorithm::Flag

Flags indicating how and when an algorithm operates and should be exposed to users.

Enumerator
FlagHideFromToolbox	Algorithm should be hidden from the toolbox.
FlagHideFromModeler	Algorithm should be hidden from the modeler.
FlagSupportsBatch	Algorithm supports batch mode.
FlagCanCancel	Algorithm can be canceled.
FlagRequiresMatchingCrs	Algorithm requires that all input layers have matching coordinate reference systems.
FlagNoThreading	Algorithm is not thread safe and cannot be run in a background thread, e.g. for algorithms which manipulate the current project, layer selections, or with external dependencies which are not thread-safe.
FlagDisplayNameIsLiteral	Algorithm's display name is a static literal string, and should not be translated or automatically formatted. For use with algorithms named after commands, e.g. GRASS 'v.in.ogr'.
FlagSupportsInPlaceEdits	Algorithm supports in-place editing.
FlagKnownIssues	Algorithm has known issues.
FlagDeprecated	Algorithm is deprecated.

Definition at line 68 of file qgsprocessingalgorithm.h.

Constructor & Destructor Documentation

◆ QgsProcessingAlgorithm() [1/2]

QgsProcessingAlgorithm::QgsProcessingAlgorithm ( )

default

Constructor for QgsProcessingAlgorithm.

initAlgorithm() should be called after creating an algorithm to ensure it can correctly configure its parameterDefinitions() and outputDefinitions(). Alternatively, calling create() will return a pre-initialized copy of the algorithm.

◆ ~QgsProcessingAlgorithm()

QgsProcessingAlgorithm::~QgsProcessingAlgorithm ( )

virtual

Definition at line 34 of file qgsprocessingalgorithm.cpp.

◆ QgsProcessingAlgorithm() [2/2]

QgsProcessingAlgorithm::QgsProcessingAlgorithm ( const QgsProcessingAlgorithm & other )

delete

Algorithms cannot be copied - create() should be used instead.

Member Function Documentation

◆ addOutput()

bool QgsProcessingAlgorithm::addOutput ( QgsProcessingOutputDefinition * outputDefinition )

protected

Adds an output definition to the algorithm.

Ownership of the definition is transferred to the algorithm. Returns true if the output could be successfully added, or false if the output could not be added (e.g. as a result of a duplicate name).

This should usually be called from a subclass' initAlgorithm() implementation.

Note that in some cases output creation can be automatically performed when calling addParameter(). See the notes in addParameter() for a description of when this occurs.

See also: addParameter(); initAlgorithm()

Definition at line 334 of file qgsprocessingalgorithm.cpp.

◆ addParameter()

bool QgsProcessingAlgorithm::addParameter	(	QgsProcessingParameterDefinition *	parameterDefinition,
		bool	createOutput = `true`
	)

protected

Adds a parameter definition to the algorithm.

Ownership of the definition is transferred to the algorithm. Returns true if parameter could be successfully added, or false if the parameter could not be added (e.g. as a result of a duplicate name).

This should usually be called from a subclass' initAlgorithm() implementation.

If the createOutput argument is true, then a corresponding output definition will also be created (and added to the algorithm) where appropriate. E.g. when adding a QgsProcessingParameterVectorDestination and createOutput is true, then a QgsProcessingOutputVectorLayer output will be created and added to the algorithm. There is no need to call addOutput() to manually add a corresponding output for this vector. If createOutput is false then this automatic output creation will not occur.

See also: initAlgorithm(); addOutput()

Definition at line 294 of file qgsprocessingalgorithm.cpp.

◆ asPythonCommand()

QString QgsProcessingAlgorithm::asPythonCommand	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context
	)		const

virtual

Returns a Python command string which can be executed to run the algorithm using the specified parameters.

Algorithms which cannot be run from a Python command should return an empty string.

Definition at line 274 of file qgsprocessingalgorithm.cpp.

◆ canExecute()

bool QgsProcessingAlgorithm::canExecute ( QString * errorMessage = nullptr ) const

virtual

Returns true if the algorithm can execute.

Algorithm subclasses can return false here to indicate that they are not able to execute, e.g. as a result of unmet external dependencies. If specified, the errorMessage argument will be filled with a localised error message describing why the algorithm cannot execute.

Definition at line 93 of file qgsprocessingalgorithm.cpp.

◆ checkParameterValues()

bool QgsProcessingAlgorithm::checkParameterValues	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context,
		QString *	message = `nullptr`
	)		const

virtual

Checks the supplied parameter values to verify that they satisfy the requirements of this algorithm in the supplied context.

The message parameter will be filled with explanatory text if validation fails. Overridden implementations should also check this base class implementation.

Returns: true if parameters are acceptable for the algorithm.

Definition at line 98 of file qgsprocessingalgorithm.cpp.

◆ countVisibleParameters()

int QgsProcessingAlgorithm::countVisibleParameters ( ) const

Returns the number of visible (non-hidden) parameters defined by this algorithm.

Definition at line 379 of file qgsprocessingalgorithm.cpp.

◆ create()

QgsProcessingAlgorithm * QgsProcessingAlgorithm::create ( const QVariantMap & configuration = QVariantMap() ) const

Creates a copy of the algorithm, ready for execution.

This method returns a new, preinitialized copy of the algorithm, ready for executing.

The configuration argument allows passing of a map of configuration settings to the algorithm, allowing it to dynamically adjust its initialized parameters and outputs according to this configuration. This is generally used only for algorithms in a model, allowing them to adjust their behavior at run time according to some user configuration.

Raises a QgsProcessingException if a new algorithm instance could not be created, e.g. if there is an issue with the subclass' createInstance() method.

See also: initAlgorithm()

Definition at line 40 of file qgsprocessingalgorithm.cpp.

◆ createCustomParametersWidget()

QWidget * QgsProcessingAlgorithm::createCustomParametersWidget ( QWidget * parent = nullptr ) const

virtual

If an algorithm subclass implements a custom parameters widget, a copy of this widget should be constructed and returned by this method.

The base class implementation returns nullptr, which indicates that an autogenerated parameters widget should be used.

Definition at line 151 of file qgsprocessingalgorithm.cpp.

◆ createExpressionContext()

QgsExpressionContext QgsProcessingAlgorithm::createExpressionContext	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context,
		QgsProcessingFeatureSource *	source = `nullptr`
	)		const

virtual

Creates an expression context relating to the algorithm.

This can be called by algorithms to create a new expression context ready for evaluating expressions within the algorithm. Optionally, a source can be specified which will be used to populate the context if it implements the QgsExpressionContextGenerator interface.

Definition at line 156 of file qgsprocessingalgorithm.cpp.

◆ createInstance()

virtual QgsProcessingAlgorithm* QgsProcessingAlgorithm::createInstance ( ) const

protectedpure virtual

Creates a new instance of the algorithm class.

This method should return a 'pristine' instance of the algorithm class.

◆ destinationParameterDefinitions()

QgsProcessingParameterDefinitions QgsProcessingAlgorithm::destinationParameterDefinitions ( ) const

Returns a list of destination parameters definitions utilized by the algorithm.

See also: QgsProcessingParameterDefinition::isDestination(); parameterDefinitions()

Definition at line 390 of file qgsprocessingalgorithm.cpp.

◆ displayName()

virtual QString QgsProcessingAlgorithm::displayName ( ) const

pure virtual

Returns the translated algorithm name, which should be used for any user-visible display of the algorithm name.

Algorithm display names should be short, e.g. ideally no more than 3 or 4 words. The name should use sentence case (e.g. "Raster layer statistics", not "Raster Layer Statistics").

See also: name(); shortDescription()

◆ flags()

QgsProcessingAlgorithm::Flags QgsProcessingAlgorithm::flags ( ) const

virtual

Returns the flags indicating how and when the algorithm operates and should be exposed to users.

Default flags are FlagSupportsBatch and FlagCanCancel.

Reimplemented in QgsProcessingFeatureBasedAlgorithm.

Definition at line 88 of file qgsprocessingalgorithm.cpp.

◆ group()

virtual QString QgsProcessingAlgorithm::group ( ) const

inlinevirtual

Returns the name of the group this algorithm belongs to.

This string should be localised.

See also: groupId(); tags()

Definition at line 219 of file qgsprocessingalgorithm.h.

◆ groupId()

virtual QString QgsProcessingAlgorithm::groupId ( ) const

inlinevirtual

Returns the unique ID of the group this algorithm belongs to.

This string should be fixed for the algorithm, and must not be localised. The group id should be unique within each provider. Group id should contain lowercase alphanumeric characters only and no spaces or other formatting characters.

See also: group()

Definition at line 228 of file qgsprocessingalgorithm.h.

◆ hasHtmlOutputs()

bool QgsProcessingAlgorithm::hasHtmlOutputs ( ) const

Returns true if this algorithm generates HTML outputs.

Definition at line 411 of file qgsprocessingalgorithm.cpp.

◆ helpString()

QString QgsProcessingAlgorithm::helpString ( ) const

virtual

Returns a localised help string for the algorithm.

Algorithm subclasses should implement either helpString() or helpUrl().

See also: helpUrl(); shortHelpString()

Deprecated:: Unused, will be removed in QGIS 4.0

Definition at line 68 of file qgsprocessingalgorithm.cpp.

◆ helpUrl()

QString QgsProcessingAlgorithm::helpUrl ( ) const

virtual

Returns a url pointing to the algorithm's help page.

See also: helpString(); shortHelpString()

Definition at line 73 of file qgsprocessingalgorithm.cpp.

◆ icon()

QIcon QgsProcessingAlgorithm::icon ( ) const

virtual

Returns an icon for the algorithm.

See also: svgIconPath()

Definition at line 78 of file qgsprocessingalgorithm.cpp.

◆ id()

QString QgsProcessingAlgorithm::id ( ) const

Returns the unique ID for the algorithm, which is a combination of the algorithm provider's ID and the algorithms unique name (e.g.

"qgis:mergelayers" ).

See also: name(); provider()

Definition at line 50 of file qgsprocessingalgorithm.cpp.

◆ initAlgorithm()

virtual void QgsProcessingAlgorithm::initAlgorithm ( const QVariantMap & configuration = QVariantMap() )

protectedpure virtual

Initializes the algorithm using the specified configuration.

This should be called directly after creating algorithms and before retrieving any parameterDefinitions() or outputDefinitions().

Subclasses should use their implementations to add all required input parameter and output definitions (which can be dynamically adjusted according to configuration).

Dynamic configuration can be used by algorithms which alter their behavior when used inside processing models. For instance, a "feature router" type algorithm which sends input features to one of any number of outputs sinks based on some preconfigured filter parameters can use the init method to create these outputs based on the specified configuration.

See also: addParameter(); addOutput()

Implemented in QgsProcessingFeatureBasedAlgorithm.

◆ invalidRasterError()

QString QgsProcessingAlgorithm::invalidRasterError	(	const QVariantMap &	parameters,
		const QString &	name
	)

staticprotected

Returns a user-friendly string to use as an error when a raster layer input could not be loaded.

The parameters argument should give the algorithms parameter map, and the name should correspond to the invalid source parameter name.

See also: invalidSourceError(); invalidSinkError()

Since: QGIS 3.2

Definition at line 757 of file qgsprocessingalgorithm.cpp.

◆ invalidSinkError()

QString QgsProcessingAlgorithm::invalidSinkError	(	const QVariantMap &	parameters,
		const QString &	name
	)

staticprotected

Returns a user-friendly string to use as an error when a sink parameter could not be created.

The parameters argument should give the algorithms parameter map, and the name should correspond to the invalid source parameter name.

See also: invalidSourceError(); invalidRasterError()

Since: QGIS 3.2

Definition at line 779 of file qgsprocessingalgorithm.cpp.

◆ invalidSourceError()

QString QgsProcessingAlgorithm::invalidSourceError	(	const QVariantMap &	parameters,
		const QString &	name
	)

staticprotected

Returns a user-friendly string to use as an error when a source parameter could not be loaded.

The parameters argument should give the algorithms parameter map, and the name should correspond to the invalid source parameter name.

See also: invalidRasterError(); invalidSinkError()

Since: QGIS 3.2

Definition at line 725 of file qgsprocessingalgorithm.cpp.

◆ name()

virtual QString QgsProcessingAlgorithm::name ( ) const

pure virtual

Returns the algorithm name, used for identifying the algorithm.

This string should be fixed for the algorithm, and must not be localised. The name should be unique within each provider. Names should contain lowercase alphanumeric characters only and no spaces or other formatting characters.

See also: displayName(); group(); tags()

◆ operator=()

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

delete

Algorithms cannot be copied- create() should be used instead.

◆ outputDefinition()

const QgsProcessingOutputDefinition * QgsProcessingAlgorithm::outputDefinition ( const QString & name ) const

Returns a matching output by name.

Matching is done in a case-insensitive manner.

See also: outputDefinitions()

Definition at line 401 of file qgsprocessingalgorithm.cpp.

◆ outputDefinitions()

QgsProcessingOutputDefinitions QgsProcessingAlgorithm::outputDefinitions ( ) const

inline

Returns an ordered list of output definitions utilized by the algorithm.

See also: addOutput(); outputDefinition()

Definition at line 301 of file qgsprocessingalgorithm.h.

◆ parameterAsBool()

bool QgsProcessingAlgorithm::parameterAsBool	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a static boolean value.

Definition at line 590 of file qgsprocessingalgorithm.cpp.

◆ parameterAsBoolean()

bool QgsProcessingAlgorithm::parameterAsBoolean	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a static boolean value.

Since: QGIS 3.8

Definition at line 595 of file qgsprocessingalgorithm.cpp.

◆ parameterAsColor()

QColor QgsProcessingAlgorithm::parameterAsColor	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)

protected

Evaluates the parameter with matching name to a color, or returns an invalid color if the parameter was not set.

Since: QGIS 3.10

Definition at line 720 of file qgsprocessingalgorithm.cpp.

◆ parameterAsCompatibleSourceLayerPath()

QString QgsProcessingAlgorithm::parameterAsCompatibleSourceLayerPath	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context,
		const QStringList &	compatibleFormats,
		const QString &	preferredFormat = `QString( "shp" )`,
		QgsProcessingFeedback *	feedback = `nullptr`
	)

protected

Evaluates the parameter with matching name to a source vector layer file path of compatible format.

If the parameter is evaluated to an existing layer, and that layer is not of the format listed in the compatibleFormats argument, then the layer will first be exported to a compatible format in a temporary location. The function will then return the path to that temporary file.

compatibleFormats should consist entirely of lowercase file extensions, e.g. 'shp'.

The preferredFormat argument is used to specify to desired file extension to use when a temporary layer export is required.

When an algorithm is capable of handling multi-layer input files (such as Geopackage), it is preferable to use parameterAsCompatibleSourceLayerPathAndLayerName() which may avoid conversion in more situations.

Definition at line 610 of file qgsprocessingalgorithm.cpp.

◆ parameterAsCompatibleSourceLayerPathAndLayerName()

QString QgsProcessingAlgorithm::parameterAsCompatibleSourceLayerPathAndLayerName	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context,
		const QStringList &	compatibleFormats,
		const QString &	preferredFormat = `QString( "shp" )`,
		QgsProcessingFeedback *	feedback = `nullptr`,
		QString *	layerName = `nullptr`
	)

protected

Evaluates the parameter with matching name to a source vector layer file path and layer name of compatible format.

If the parameter is evaluated to an existing layer, and that layer is not of the format listed in the compatibleFormats argument, then the layer will first be exported to a compatible format in a temporary location. The function will then return the path to that temporary file.

compatibleFormats should consist entirely of lowercase file extensions, e.g. 'shp'.

The preferredFormat argument is used to specify to desired file extension to use when a temporary layer export is required. This defaults to shapefiles, because shapefiles are the future (don't believe the geopackage hype!).

This method should be preferred over parameterAsCompatibleSourceLayerPath() when an algorithm is able to correctly handle files with multiple layers. Unlike parameterAsCompatibleSourceLayerPath(), it will not force a conversion in this case and will return the target layer name in the layerName argument.

Parameters

parameters	input parameter value map
name	name of target parameter
context	processing context
compatibleFormats	a list of lowercase file extensions compatible with the algorithm
preferredFormat	preferred format extension to use if conversion if required
feedback	feedback object
layerName	will be set to the target layer name for multi-layer sources (e.g. Geopackage)

Returns: path to source layer, or nearly converted compatible layer

See also: parameterAsCompatibleSourceLayerPath()

Since: QGIS 3.10

Definition at line 615 of file qgsprocessingalgorithm.cpp.

◆ parameterAsCrs()

QgsCoordinateReferenceSystem QgsProcessingAlgorithm::parameterAsCrs	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a coordinate reference system.

Definition at line 650 of file qgsprocessingalgorithm.cpp.

◆ parameterAsDouble()

double QgsProcessingAlgorithm::parameterAsDouble	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a static double value.

Definition at line 565 of file qgsprocessingalgorithm.cpp.

◆ parameterAsEnum()

int QgsProcessingAlgorithm::parameterAsEnum	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a enum value.

Definition at line 580 of file qgsprocessingalgorithm.cpp.

◆ parameterAsEnums()

QList< int > QgsProcessingAlgorithm::parameterAsEnums	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to list of enum values.

Definition at line 585 of file qgsprocessingalgorithm.cpp.

◆ parameterAsExpression()

QString QgsProcessingAlgorithm::parameterAsExpression	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to an expression.

Definition at line 560 of file qgsprocessingalgorithm.cpp.

◆ parameterAsExtent()

QgsRectangle QgsProcessingAlgorithm::parameterAsExtent	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context,
		const QgsCoordinateReferenceSystem &	crs = `QgsCoordinateReferenceSystem()`
	)		const

protected

Evaluates the parameter with matching name to a rectangular extent.

If crs is set, and the original coordinate reference system of the parameter can be determined, then the extent will be automatically reprojected so that it is in the specified crs. In this case the extent of the reproject rectangle will be returned.

See also: parameterAsExtentGeometry()

Definition at line 660 of file qgsprocessingalgorithm.cpp.

◆ parameterAsExtentCrs()

QgsCoordinateReferenceSystem QgsProcessingAlgorithm::parameterAsExtentCrs	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)

protected

Returns the coordinate reference system associated with an extent parameter value.

See also: parameterAsExtent()

Definition at line 655 of file qgsprocessingalgorithm.cpp.

◆ parameterAsExtentGeometry()

QgsGeometry QgsProcessingAlgorithm::parameterAsExtentGeometry	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context,
		const QgsCoordinateReferenceSystem &	crs = `QgsCoordinateReferenceSystem()`
	)

protected

Evaluates the parameter with matching name to a rectangular extent, and returns a geometry covering this extent.

If crs is set, and the original coordinate reference system of the parameter can be determined, then the extent will be automatically reprojected so that it is in the specified crs. Unlike parameterAsExtent(), the reprojected rectangle returned by this function will no longer be a rectangle itself (i.e. this method returns the geometry of the actual reprojected rectangle, while parameterAsExtent() returns just the extent of the reprojected rectangle).

See also: parameterAsExtent()

Definition at line 665 of file qgsprocessingalgorithm.cpp.

◆ parameterAsFields()

QStringList QgsProcessingAlgorithm::parameterAsFields	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a list of fields.

Definition at line 705 of file qgsprocessingalgorithm.cpp.

◆ parameterAsFile()

QString QgsProcessingAlgorithm::parameterAsFile	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a file/folder name.

Definition at line 680 of file qgsprocessingalgorithm.cpp.

◆ parameterAsFileList()

QStringList QgsProcessingAlgorithm::parameterAsFileList	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a list of files (for QgsProcessingParameterMultipleLayers in QgsProcessing:TypeFile mode).

Since: QGIS 3.10

Definition at line 695 of file qgsprocessingalgorithm.cpp.

◆ parameterAsFileOutput()

QString QgsProcessingAlgorithm::parameterAsFileOutput	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a file based output destination.

Definition at line 640 of file qgsprocessingalgorithm.cpp.

◆ parameterAsInt()

int QgsProcessingAlgorithm::parameterAsInt	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a static integer value.

Definition at line 570 of file qgsprocessingalgorithm.cpp.

◆ parameterAsInts()

QList< int > QgsProcessingAlgorithm::parameterAsInts	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a list of integer values.

Since: QGIS 3.4

Definition at line 575 of file qgsprocessingalgorithm.cpp.

◆ parameterAsLayer()

QgsMapLayer * QgsProcessingAlgorithm::parameterAsLayer	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a map layer.

Layers will either be taken from context's active project, or loaded from external sources and stored temporarily in the context. In either case, callers do not need to handle deletion of the returned layer.

Definition at line 620 of file qgsprocessingalgorithm.cpp.

◆ parameterAsLayerList()

QList< QgsMapLayer * > QgsProcessingAlgorithm::parameterAsLayerList	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a list of map layers.

Definition at line 690 of file qgsprocessingalgorithm.cpp.

◆ parameterAsLayout()

QgsPrintLayout * QgsProcessingAlgorithm::parameterAsLayout	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)

protected

Evaluates the parameter with matching name to a print layout.

Warning: This method is not safe to run in a background thread, so it must either be used within a prepareAlgorithm implementation (which runs in the main thread), or the algorithm must return the FlagNoThreading flag.

Since: QGIS 3.8

Definition at line 710 of file qgsprocessingalgorithm.cpp.

◆ parameterAsLayoutItem()

QgsLayoutItem * QgsProcessingAlgorithm::parameterAsLayoutItem	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context,
		QgsPrintLayout *	layout
	)

protected

Evaluates the parameter with matching name to a print layout item, taken from the specified layout.

Warning: This method is not safe to run in a background thread, so it must either be used within a prepareAlgorithm implementation (which runs in the main thread), or the algorithm must return the FlagNoThreading flag.

Since: QGIS 3.8

Definition at line 715 of file qgsprocessingalgorithm.cpp.

◆ parameterAsMatrix()

QVariantList QgsProcessingAlgorithm::parameterAsMatrix	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a matrix/table of values.

Tables are collapsed to a 1 dimensional list.

Definition at line 685 of file qgsprocessingalgorithm.cpp.

◆ parameterAsMeshLayer()

QgsMeshLayer * QgsProcessingAlgorithm::parameterAsMeshLayer	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a mesh layer.

Layers will either be taken from context's active project, or loaded from external sources and stored temporarily in the context. In either case, callers do not need to handle deletion of the returned layer.

Since: QGIS 3.6

Definition at line 630 of file qgsprocessingalgorithm.cpp.

◆ parameterAsOutputLayer()

QString QgsProcessingAlgorithm::parameterAsOutputLayer	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a output layer destination.

Definition at line 635 of file qgsprocessingalgorithm.cpp.

◆ parameterAsPoint()

QgsPointXY QgsProcessingAlgorithm::parameterAsPoint	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context,
		const QgsCoordinateReferenceSystem &	crs = `QgsCoordinateReferenceSystem()`
	)		const

protected

Evaluates the parameter with matching name to a point.

If crs is set then the point will be automatically reprojected so that it is in the specified crs.

See also: parameterAsPointCrs()

Definition at line 670 of file qgsprocessingalgorithm.cpp.

◆ parameterAsPointCrs()

QgsCoordinateReferenceSystem QgsProcessingAlgorithm::parameterAsPointCrs	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)

protected

Returns the coordinate reference system associated with an point parameter value.

See also: parameterAsPoint()

Definition at line 675 of file qgsprocessingalgorithm.cpp.

◆ parameterAsRange()

QList< double > QgsProcessingAlgorithm::parameterAsRange	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a range of values.

Definition at line 700 of file qgsprocessingalgorithm.cpp.

◆ parameterAsRasterLayer()

QgsRasterLayer * QgsProcessingAlgorithm::parameterAsRasterLayer	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a raster layer.

Layers will either be taken from context's active project, or loaded from external sources and stored temporarily in the context. In either case, callers do not need to handle deletion of the returned layer.

Definition at line 625 of file qgsprocessingalgorithm.cpp.

◆ parameterAsSink()

QgsFeatureSink * QgsProcessingAlgorithm::parameterAsSink	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context,
		QString &	destinationIdentifier,
		const QgsFields &	fields,
		QgsWkbTypes::Type	geometryType = `QgsWkbTypes::NoGeometry`,
		const QgsCoordinateReferenceSystem &	crs = `QgsCoordinateReferenceSystem()`,
		QgsFeatureSink::SinkFlags	sinkFlags = `nullptr`
	)		const

protected

Evaluates the parameter with matching name to a feature sink.

Sinks will either be taken from context's active project, or created from external providers and stored temporarily in the context.

The fields, geometryType and crs parameters dictate the properties of the resulting feature sink.

The destinationIdentifier argument will be set to a string which can be used to retrieve the layer corresponding to the sink, e.g. via calling QgsProcessingUtils::mapLayerFromString().

This function creates a new object and the caller takes responsibility for deleting the returned object.

Definition at line 600 of file qgsprocessingalgorithm.cpp.

◆ parameterAsSource()

QgsProcessingFeatureSource * QgsProcessingAlgorithm::parameterAsSource	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a feature source.

Sources will either be taken from context's active project, or loaded from external sources and stored temporarily in the context.

This function creates a new object and the caller takes responsibility for deleting the returned object.

Definition at line 605 of file qgsprocessingalgorithm.cpp.

◆ parameterAsString()

QString QgsProcessingAlgorithm::parameterAsString	(	const QVariantMap &	parameters,
		const QString &	name,
		const QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a static string value.

Definition at line 555 of file qgsprocessingalgorithm.cpp.

◆ parameterAsVectorLayer()

QgsVectorLayer * QgsProcessingAlgorithm::parameterAsVectorLayer	(	const QVariantMap &	parameters,
		const QString &	name,
		QgsProcessingContext &	context
	)		const

protected

Evaluates the parameter with matching name to a vector layer.

Layers will either be taken from context's active project, or loaded from external sources and stored temporarily in the context. In either case, callers do not need to handle deletion of the returned layer.

Definition at line 645 of file qgsprocessingalgorithm.cpp.

◆ parameterDefinition()

const QgsProcessingParameterDefinition * QgsProcessingAlgorithm::parameterDefinition ( const QString & name ) const

Returns a matching parameter by name.

Matching is done in a case-insensitive manner, but exact case matches will be preferred.

See also: parameterDefinitions()

Definition at line 361 of file qgsprocessingalgorithm.cpp.

◆ parameterDefinitions()

QgsProcessingParameterDefinitions QgsProcessingAlgorithm::parameterDefinitions ( ) const

inline

Returns an ordered list of parameter definitions utilized by the algorithm.

See also: addParameter(); parameterDefinition(); destinationParameterDefinitions()

Definition at line 274 of file qgsprocessingalgorithm.h.

◆ postProcess()

QVariantMap QgsProcessingAlgorithm::postProcess	(	QgsProcessingContext &	context,
		QgsProcessingFeedback *	feedback
	)

Should be called in the main thread following the completion of runPrepared().

This method allows the algorithm to perform any required cleanup tasks. The returned variant map includes the results evaluated by the algorithm.

Note: This method modifies the algorithm instance, so it is not safe to call on algorithms directly retrieved from QgsProcessingRegistry and QgsProcessingProvider. Instead, a copy of the algorithm should be created with clone() and prepare()/runPrepared() called on the copy.

Definition at line 526 of file qgsprocessingalgorithm.cpp.

◆ postProcessAlgorithm()

QVariantMap QgsProcessingAlgorithm::postProcessAlgorithm	(	QgsProcessingContext &	context,
		QgsProcessingFeedback *	feedback
	)

protectedvirtual

Allows the algorithm to perform any required cleanup tasks.

The returned variant map includes the results evaluated by the algorithm. These may be output layer references, or calculated values such as statistical calculations.

The context argument specifies the context in which the algorithm was run.

Postprocess progress should be reported using the supplied feedback object. Additionally, well-behaved algorithms should periodically check feedback to determine whether the post processing should be canceled and exited early.

postProcessAlgorithm should be used to handle any thread-sensitive cleanup which is required by the algorithm. It will always be called from the same thread that context has thread affinity with. While this will generally be the main thread, it is not guaranteed. For instance, algorithms which are run as a step in a larger model or as a subcomponent of a script-based algorithm will call postProcessAlgorithm from the same thread as that model/script it being executed in.

postProcessAlgorithm will not be called if the prepareAlgorithm() step failed (returned false), or if an exception was raised by the processAlgorithm() step.

Returns: A map of algorithm outputs. These may be output layer references, or calculated values such as statistical calculations. Implementations which return a non-empty map will override any results returned by processAlgorithm().

See also: prepareAlgorithm(); processAlgorithm()

Definition at line 356 of file qgsprocessingalgorithm.cpp.

◆ prepare()

bool QgsProcessingAlgorithm::prepare	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context,
		QgsProcessingFeedback *	feedback
	)

Prepares the algorithm for execution.

This must be run in the main thread, and allows the algorithm to pre-evaluate input parameters in a thread-safe manner. This must be called before calling runPrepared() (which is safe to do in any thread).

See also: runPrepared(); postProcess()

Note: This method modifies the algorithm instance, so it is not safe to call on algorithms directly retrieved from QgsProcessingRegistry and QgsProcessingProvider. Instead, a copy of the algorithm should be created with clone() and prepare()/runPrepared() called on the copy.

Definition at line 453 of file qgsprocessingalgorithm.cpp.

◆ prepareAlgorithm()

bool QgsProcessingAlgorithm::prepareAlgorithm	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context,
		QgsProcessingFeedback *	feedback
	)

protectedvirtual

Prepares the algorithm to run using the specified parameters.

Algorithms should implement their logic for evaluating parameter values here. The evaluated parameter results should be stored in member variables ready for a call to processAlgorithm().

The context argument specifies the context in which the algorithm is being run.

prepareAlgorithm should be used to handle any thread-sensitive preparation which is required by the algorithm. It will always be called from the same thread that context has thread affinity with. While this will generally be the main thread, it is not guaranteed. For instance, algorithms which are run as a step in a larger model or as a subcomponent of a script-based algorithm will call prepareAlgorithm from the same thread as that model/script it being executed in.

Note that the processAlgorithm step uses a temporary context with affinity for the thread in which the algorithm is executed, making it safe for processAlgorithm implementations to load sources and sinks without issue. Implementing prepareAlgorithm is only required if special thread safe handling is required by the algorithm.

Algorithm preparation progress should be reported using the supplied feedback object. Additionally, well-behaved algorithms should periodically check feedback to determine whether the algorithm should be canceled and exited early.

If the preparation was successful algorithms must return true. If a false value is returned this indicates that the preparation could not be completed, and the algorithm execution will be canceled.

Returns: true if preparation was successful.

See also: processAlgorithm(); postProcessAlgorithm()

Definition at line 351 of file qgsprocessingalgorithm.cpp.

◆ preprocessParameters()

QVariantMap QgsProcessingAlgorithm::preprocessParameters ( const QVariantMap & parameters )

virtual

Pre-processes a set of parameters, allowing the algorithm to clean their values.

This method is automatically called after users enter parameters, e.g. via the algorithm dialog. This method should NOT be called manually by algorithms.

Definition at line 123 of file qgsprocessingalgorithm.cpp.

◆ processAlgorithm()

virtual QVariantMap QgsProcessingAlgorithm::processAlgorithm	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context,
		QgsProcessingFeedback *	feedback
	)

protectedpure virtual

Runs the algorithm using the specified parameters.

Algorithms should implement their custom processing logic here.

The context argument gives a temporary context with thread affinity matching the thread in which the algorithm is being run. This is a cut-back copy of the context passed to the prepareAlgorithm() and postProcessAlgorithm() steps, but it is generally safe for most algorithms to utilize this context for loading layers and creating sinks. Any loaded layers or sinks created within this temporary context will be transferred back to the main execution context upon successful completion of the processAlgorithm() step.

Algorithm progress should be reported using the supplied feedback object. Additionally, well-behaved algorithms should periodically check feedback to determine whether the algorithm should be canceled and exited early.

This method will not be called if the prepareAlgorithm() step failed (returned false).

c++ implementations of processAlgorithm can throw the QgsProcessingException exception to indicate that a fatal error occurred within the execution. Python based subclasses should raise GeoAlgorithmExecutionException for the same purpose.

Returns: A map of algorithm outputs. These may be output layer references, or calculated values such as statistical calculations. Unless the algorithm subclass overrides the postProcessAlgorithm() step this returned map will be used as the output for the algorithm.

See also: prepareAlgorithm(); postProcessAlgorithm()

Implemented in QgsProcessingFeatureBasedAlgorithm.

◆ provider()

QgsProcessingProvider * QgsProcessingAlgorithm::provider ( ) const

Returns the provider to which this algorithm belongs.

Definition at line 128 of file qgsprocessingalgorithm.cpp.

◆ removeParameter()

void QgsProcessingAlgorithm::removeParameter ( const QString & name )

protected

Removes the parameter with matching name from the algorithm, and deletes any existing definition.

Definition at line 324 of file qgsprocessingalgorithm.cpp.

◆ run()

QVariantMap QgsProcessingAlgorithm::run	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context,
		QgsProcessingFeedback *	feedback,
		bool *	ok = `nullptr`,
		const QVariantMap &	configuration = `QVariantMap()`
	)		const

Executes the algorithm using the specified parameters.

This method internally creates a copy of the algorithm before running it, so it is safe to call on algorithms directly retrieved from QgsProcessingRegistry and QgsProcessingProvider.

The context argument specifies the context in which the algorithm is being run.

Algorithm progress should be reported using the supplied feedback object.

If specified, ok will be set to true if algorithm was successfully run.

Returns: A map of algorithm outputs. These may be output layer references, or calculated values such as statistical calculations.

Note: this method can only be called from the main thread. Use prepare(), runPrepared() and postProcess() if you need to run algorithms from a background thread, or use the QgsProcessingAlgRunnerTask class.

Definition at line 421 of file qgsprocessingalgorithm.cpp.

◆ runPrepared()

QVariantMap QgsProcessingAlgorithm::runPrepared	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context,
		QgsProcessingFeedback *	feedback
	)

Runs the algorithm, which has been prepared by an earlier call to prepare().

This method is safe to call from any thread. Returns true if the algorithm was successfully executed. After runPrepared() has finished, the postProcess() method should be called from the main thread to allow the algorithm to perform any required cleanup tasks and return its final result.

See also: prepare(); postProcess()

Note: This method modifies the algorithm instance, so it is not safe to call on algorithms directly retrieved from QgsProcessingRegistry and QgsProcessingProvider. Instead, a copy of the algorithm should be created with clone() and prepare()/runPrepared() called on the copy.

Definition at line 470 of file qgsprocessingalgorithm.cpp.

◆ setProvider()

void QgsProcessingAlgorithm::setProvider ( QgsProcessingProvider * provider )

Associates this algorithm with its provider.

No transfer of ownership is involved.

Definition at line 133 of file qgsprocessingalgorithm.cpp.

◆ shortDescription()

QString QgsProcessingAlgorithm::shortDescription ( ) const

virtual

Returns an optional translated short description of the algorithm.

This should be at most a single sentence, e.g. "Converts 2D features to 3D by sampling a DEM raster."

Since: QGIS 3.2

Definition at line 58 of file qgsprocessingalgorithm.cpp.

◆ shortHelpString()

QString QgsProcessingAlgorithm::shortHelpString ( ) const

virtual

Returns a localised short helper string for the algorithm.

This string should provide a basic description about what the algorithm does and the parameters and outputs associated with it.

See also: helpString(); helpUrl()

Definition at line 63 of file qgsprocessingalgorithm.cpp.

◆ supportInPlaceEdit()

bool QgsProcessingAlgorithm::supportInPlaceEdit ( const QgsMapLayer * layer ) const

protectedvirtual

Checks whether this algorithm supports in-place editing on the given layer Default implementation returns false.

Returns: true if the algorithm supports in-place editing

Since: QGIS 3.4

Reimplemented in QgsProcessingFeatureBasedAlgorithm.

Definition at line 806 of file qgsprocessingalgorithm.cpp.

◆ svgIconPath()

QString QgsProcessingAlgorithm::svgIconPath ( ) const

virtual

Returns a path to an SVG version of the algorithm's icon.

See also: icon()

Definition at line 83 of file qgsprocessingalgorithm.cpp.

◆ tags()

virtual QStringList QgsProcessingAlgorithm::tags ( ) const

inlinevirtual

Returns a list of tags which relate to the algorithm, and are used to assist users in searching for suitable algorithms.

These tags should be localised.

Definition at line 175 of file qgsprocessingalgorithm.h.

◆ validateInputCrs()

bool QgsProcessingAlgorithm::validateInputCrs	(	const QVariantMap &	parameters,
		QgsProcessingContext &	context
	)		const

virtual

Checks whether the coordinate reference systems for the specified set of parameters are valid for the algorithm.

For instance, the base implementation performs checks to ensure that all input CRS are equal Returns true if parameters have passed the CRS check.

Definition at line 180 of file qgsprocessingalgorithm.cpp.

Friends And Related Function Documentation

◆ QgsProcessingModelAlgorithm

friend class QgsProcessingModelAlgorithm

friend

Definition at line 924 of file qgsprocessingalgorithm.h.

◆ QgsProcessingProvider

friend class QgsProcessingProvider

friend

Definition at line 922 of file qgsprocessingalgorithm.h.

◆ QgsProcessingToolboxProxyModel

friend class QgsProcessingToolboxProxyModel

friend

Definition at line 925 of file qgsprocessingalgorithm.h.

◆ TestQgsProcessing

friend class TestQgsProcessing

friend

Definition at line 923 of file qgsprocessingalgorithm.h.

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

/build/qgis-3.10.0+15buster/src/core/processing/qgsprocessingalgorithm.h
/build/qgis-3.10.0+15buster/src/core/processing/qgsprocessingalgorithm.cpp

Public Types

Public Member Functions

Protected Member Functions

Static Protected Member Functions

Friends

Detailed Description

Member Enumeration Documentation

◆ Flag

Constructor & Destructor Documentation

◆ QgsProcessingAlgorithm() [1/2]

◆ ~QgsProcessingAlgorithm()

◆ QgsProcessingAlgorithm() [2/2]

Member Function Documentation

◆ addOutput()

◆ addParameter()

◆ asPythonCommand()

◆ canExecute()

◆ checkParameterValues()

◆ countVisibleParameters()

◆ create()

◆ createCustomParametersWidget()

◆ createExpressionContext()

◆ createInstance()

◆ destinationParameterDefinitions()

◆ displayName()

◆ flags()

◆ group()

◆ groupId()

◆ hasHtmlOutputs()

◆ helpString()

◆ helpUrl()

◆ icon()

◆ id()

◆ initAlgorithm()

◆ invalidRasterError()

◆ invalidSinkError()

◆ invalidSourceError()

◆ name()

◆ operator=()

◆ outputDefinition()

◆ outputDefinitions()

◆ parameterAsBool()

◆ parameterAsBoolean()

◆ parameterAsColor()

◆ parameterAsCompatibleSourceLayerPath()

◆ parameterAsCompatibleSourceLayerPathAndLayerName()

◆ parameterAsCrs()

◆ parameterAsDouble()

◆ parameterAsEnum()

◆ parameterAsEnums()

◆ parameterAsExpression()

◆ parameterAsExtent()

◆ parameterAsExtentCrs()

◆ parameterAsExtentGeometry()

◆ parameterAsFields()

◆ parameterAsFile()

◆ parameterAsFileList()

◆ parameterAsFileOutput()

◆ parameterAsInt()

◆ parameterAsInts()

◆ parameterAsLayer()

◆ parameterAsLayerList()

◆ parameterAsLayout()

◆ parameterAsLayoutItem()

◆ parameterAsMatrix()

◆ parameterAsMeshLayer()

◆ parameterAsOutputLayer()

◆ parameterAsPoint()

◆ parameterAsPointCrs()

◆ parameterAsRange()

◆ parameterAsRasterLayer()

◆ parameterAsSink()

◆ parameterAsSource()

◆ parameterAsString()

◆ parameterAsVectorLayer()

◆ parameterDefinition()

◆ parameterDefinitions()

◆ postProcess()

◆ postProcessAlgorithm()

◆ prepare()