QGIS API Documentation 3.37.0-Master (08041ddf763)
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qgsalgorithmgeometrybyexpression.cpp
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1/***************************************************************************
2 qgsalgorithmgeometrybyexpression.cpp
3 ------------------------
4 begin : November 2019
5 copyright : (C) 2019 by Alexander Bruy
6 email : alexander dot bruy at gmail dot com
7 ***************************************************************************/
8
9/***************************************************************************
10 * *
11 * This program is free software; you can redistribute it and/or modify *
12 * it under the terms of the GNU General Public License as published by *
13 * the Free Software Foundation; either version 2 of the License, or *
14 * (at your option) any later version. *
15 * *
16 ***************************************************************************/
17
19#include "qgsvariantutils.h"
20
22
23QString QgsGeometryByExpressionAlgorithm::name() const
24{
25 return QStringLiteral( "geometrybyexpression" );
26}
27
28QString QgsGeometryByExpressionAlgorithm::displayName() const
29{
30 return QObject::tr( "Geometry by expression" );
31}
32
33QStringList QgsGeometryByExpressionAlgorithm::tags() const
34{
35 return QObject::tr( "geometry,expression,create,modify,update" ).split( ',' );
36}
37
38QString QgsGeometryByExpressionAlgorithm::group() const
39{
40 return QObject::tr( "Vector geometry" );
41}
42
43QString QgsGeometryByExpressionAlgorithm::groupId() const
44{
45 return QStringLiteral( "vectorgeometry" );
46}
47
48QString QgsGeometryByExpressionAlgorithm::outputName() const
49{
50 return QObject::tr( "Modified geometry" );
51}
52
53QString QgsGeometryByExpressionAlgorithm::shortHelpString() const
54{
55 return QObject::tr( "This algorithm updates existing geometries (or creates new geometries) for input "
56 "features by use of a QGIS expression. This allows complex geometry modifications "
57 "which can utilize all the flexibility of the QGIS expression engine to manipulate "
58 "and create geometries for output features.\n\n"
59 "For help with QGIS expression functions, see the inbuilt help for specific functions "
60 "which is available in the expression builder." );
61}
62
63QgsGeometryByExpressionAlgorithm *QgsGeometryByExpressionAlgorithm::createInstance() const
64{
65 return new QgsGeometryByExpressionAlgorithm();
66}
67
68QList<int> QgsGeometryByExpressionAlgorithm::inputLayerTypes() const
69{
70 return QList< int >() << static_cast< int >( Qgis::ProcessingSourceType::Vector );
71}
72
73Qgis::WkbType QgsGeometryByExpressionAlgorithm::outputWkbType( Qgis::WkbType ) const
74{
75 return mWkbType;
76}
77
78Qgis::ProcessingFeatureSourceFlags QgsGeometryByExpressionAlgorithm::sourceFlags() const
79{
81}
82
83void QgsGeometryByExpressionAlgorithm::initParameters( const QVariantMap & )
84{
85 addParameter( new QgsProcessingParameterEnum( QStringLiteral( "OUTPUT_GEOMETRY" ), QObject::tr( "Output geometry type" ),
86 QStringList() << QObject::tr( "Polygon" ) << QObject::tr( "Line" ) << QObject::tr( "Point" ), false, 0 ) );
87 addParameter( new QgsProcessingParameterBoolean( QStringLiteral( "WITH_Z" ), QObject::tr( "Output geometry has z dimension" ), false ) );
88 addParameter( new QgsProcessingParameterBoolean( QStringLiteral( "WITH_M" ), QObject::tr( "Output geometry has m values" ), false ) );
89 addParameter( new QgsProcessingParameterExpression( QStringLiteral( "EXPRESSION" ), QObject::tr( "Geometry expression" ),
90 QStringLiteral( "$geometry" ), QStringLiteral( "INPUT" ) ) );
91}
92
93bool QgsGeometryByExpressionAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
94{
95 const int geometryType = parameterAsInt( parameters, QStringLiteral( "OUTPUT_GEOMETRY" ), context );
96 switch ( geometryType )
97 {
98 case 0:
99 mWkbType = Qgis::WkbType::Polygon;
100 break;
101 case 1:
102 mWkbType = Qgis::WkbType::LineString;
103 break;
104 case 2:
105 mWkbType = Qgis::WkbType::Point;
106 break;
107 }
108
109 if ( parameterAsBoolean( parameters, QStringLiteral( "WITH_Z" ), context ) )
110 {
111 mWkbType = QgsWkbTypes::addZ( mWkbType );
112 }
113 if ( parameterAsBoolean( parameters, QStringLiteral( "WITH_M" ), context ) )
114 {
115 mWkbType = QgsWkbTypes::addM( mWkbType );
116 }
117
118 mExpression = QgsExpression( parameterAsString( parameters, QStringLiteral( "EXPRESSION" ), context ) );
119 if ( mExpression.hasParserError() )
120 {
121 feedback->reportError( mExpression.parserErrorString() );
122 return false;
123 }
124
125 mExpressionContext = createExpressionContext( parameters, context );
126 mExpression.prepare( &mExpressionContext );
127
128 return true;
129}
130
131QgsFeatureList QgsGeometryByExpressionAlgorithm::processFeature( const QgsFeature &f, QgsProcessingContext &, QgsProcessingFeedback * )
132{
133 QgsFeature feature = f;
134 mExpressionContext.setFeature( feature );
135 const QVariant value = mExpression.evaluate( &mExpressionContext );
136
137 if ( mExpression.hasEvalError() )
138 {
139 throw QgsProcessingException( QObject::tr( "Evaluation error: %1" ).arg( mExpression.evalErrorString() ) );
140 }
141
142 if ( QgsVariantUtils::isNull( value ) )
143 {
144 feature.setGeometry( QgsGeometry() );
145 }
146 else
147 {
148 if ( value.userType() == QMetaType::type( "QgsGeometry" ) )
149 {
150 const QgsGeometry geom = value.value<QgsGeometry>();
151 feature.setGeometry( geom );
152 }
153 else
154 {
155 throw QgsProcessingException( QObject::tr( "%1 is not a geometry" ).arg( value.toString() ) );
156 }
157 }
158
159 return QgsFeatureList() << feature;
160}
161
@ Vector
Tables (i.e. vector layers with or without geometry). When used for a sink this indicates the sink ha...
@ SkipGeometryValidityChecks
Invalid geometry checks should always be skipped. This flag can be useful for algorithms which always...
WkbType
The WKB type describes the number of dimensions a geometry has.
Definition qgis.h:201
@ LineString
LineString.
@ Polygon
Polygon.
QFlags< ProcessingFeatureSourceFlag > ProcessingFeatureSourceFlags
Flags which control how QgsProcessingFeatureSource fetches features.
Definition qgis.h:3148
Class for parsing and evaluation of expressions (formerly called "search strings").
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition qgsfeature.h:58
void setGeometry(const QgsGeometry &geometry)
Set the feature's geometry.
A geometry is the spatial representation of a feature.
Contains information about the context in which a processing algorithm is executed.
Custom exception class for processing related exceptions.
Base class for providing feedback from a processing algorithm.
virtual void reportError(const QString &error, bool fatalError=false)
Reports that the algorithm encountered an error while executing.
A boolean parameter for processing algorithms.
An enum based parameter for processing algorithms, allowing for selection from predefined values.
An expression parameter for processing algorithms.
static bool isNull(const QVariant &variant, bool silenceNullWarnings=false)
Returns true if the specified variant should be considered a NULL value.
static Qgis::WkbType addM(Qgis::WkbType type)
Adds the m dimension to a WKB type and returns the new type.
static Qgis::WkbType addZ(Qgis::WkbType type)
Adds the z dimension to a WKB type and returns the new type.
QList< QgsFeature > QgsFeatureList