feature: add x_at, y_at, z_at and m_at expressions

qgis · Nov 29, 2022 · d8131a0 · d8131a0
1 parent ec689c5
commit d8131a0
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Showing 6 changed files with 350 additions and 36 deletions.
diff --git a/resources/function_help/json/m_at b/resources/function_help/json/m_at
@@ -0,0 +1,18 @@
+{
+  "name": "m_at",
+  "type": "function",
+  "groups": ["GeometryGroup"],
+  "description": "Retrieves a m coordinate of the geometry, or NULL if the geometry has no m value.",
+  "arguments": [{
+    "arg": "geometry",
+    "description": "geometry object"
+  }, {
+    "arg": "i",
+    "description": "index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)"
+  }],
+  "examples": [{
+    "expression": "m_at(geom_from_wkt('LineStringZM(0 0 0 0, 10 10 0 5, 10 10 0 0)'), 1)",
+    "returns": "5"
+  }],
+  "tags": ["retrieves", "coordinate", "measure"]
+}
diff --git a/resources/function_help/json/x_at b/resources/function_help/json/x_at
@@ -0,0 +1,18 @@
+{
+  "name": "x_at",
+  "type": "function",
+  "groups": ["GeometryGroup"],
+  "description": "Retrieves a x coordinate of the geometry.",
+  "arguments": [{
+    "arg": "geometry",
+    "description": "geometry object"
+  }, {
+    "arg": "i",
+    "description": "index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)"
+  }],
+  "examples": [{
+    "expression": "x_at( geom_from_wkt( 'POINT(4 5)' ), 0 )",
+    "returns": "4"
+  }],
+  "tags": ["retrieves", "coordinate"]
+}
diff --git a/resources/function_help/json/y_at b/resources/function_help/json/y_at
@@ -0,0 +1,18 @@
+{
+  "name": "y_at",
+  "type": "function",
+  "groups": ["GeometryGroup"],
+  "description": "Retrieves a y coordinate of the geometry.",
+  "arguments": [{
+    "arg": "geometry",
+    "description": "geometry object"
+  }, {
+    "arg": "i",
+    "description": "index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)"
+  }],
+  "examples": [{
+    "expression": "y_at( geom_from_wkt( 'POINT(4 5)' ), 0 )",
+    "returns": "5"
+  }],
+  "tags": ["retrieves", "coordinate"]
+}
diff --git a/resources/function_help/json/z_at b/resources/function_help/json/z_at
@@ -0,0 +1,18 @@
+{
+  "name": "z_at",
+  "type": "function",
+  "groups": ["GeometryGroup"],
+  "description": "Retrieves a z coordinate of the geometry, or NULL if the geometry has no z value.",
+  "arguments": [{
+    "arg": "geometry",
+    "description": "geometry object"
+  }, {
+    "arg": "i",
+    "description": "index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)"
+  }],
+  "examples": [{
+    "expression": "z_at(geom_from_wkt('LineStringZ(0 0 0, 10 10 5, 10 10 0)'), 1)",
+    "returns": "5"
+  }],
+  "tags": ["retrieves", "coordinate", "3D"]
+}
diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
@@ -3778,44 +3778,134 @@ static QVariant fcnMakeRectangleFrom3Points( const QVariantList &values, const Q
   return QVariant::fromValue( QgsGeometry( rect.toPolygon() ) );
 }
 
-static QVariant pointAt( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent ) // helper function
+static QVariant pointAt( const QgsGeometry &geom, int idx, QgsExpression *parent ) // helper function
 {
-  FEAT_FROM_CONTEXT( context, f )
-  int idx = QgsExpressionUtils::getNativeIntValue( values.at( 0 ), parent );
-  QgsGeometry g = f.geometry();
-  if ( g.isNull() )
+  if ( geom.isNull() )
     return QVariant();
 
   if ( idx < 0 )
   {
-    idx += g.constGet()->nCoordinates();
+    idx += geom.constGet()->nCoordinates();
   }
-  if ( idx < 0 || idx >= g.constGet()->nCoordinates() )
+  if ( idx < 0 || idx >= geom.constGet()->nCoordinates() )
   {
     parent->setEvalErrorString( QObject::tr( "Index is out of range" ) );
     return QVariant();
   }
+  return QVariant::fromValue( geom.vertexAt( idx ) );
+}
+
+// function used for the old $ style
+static QVariant fcnOldXat( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  FEAT_FROM_CONTEXT( context, feature )
+  const QgsGeometry geom = feature.geometry();
+  int idx = QgsExpressionUtils::getNativeIntValue( values.at( 0 ), parent );
+
+  QVariant v = pointAt( geom, idx, parent );
+
+  if ( !v.isNull() )
+    return QVariant( v.value<QgsPoint>().x() );
+  else
+    return QVariant();
+}
+static QVariant fcnXat( const QVariantList &values, const QgsExpressionContext *f, QgsExpression *parent, const QgsExpressionNodeFunction *node )
+{
+  if ( values.at( 1 ).isNull() || values.at( 0 ).isNull() ) // the case where the alias x_at function is called like a $ function (x_at(i))
+  {
+    return fcnOldXat( values, f, parent, node );
+  }
+  else if ( values.at( 0 ).isNull() && !values.at( 1 ).isNull() ) // same as above with x_at(i:=0) (this values is at the second position)
+  {
+    return fcnOldXat( QVariantList() << values[1], f, parent, node );
+  }
+
+  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
+  int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent ); // Should be one or 0 ???
+  if ( geom.isNull() )
+  {
+    return QVariant();
+  }
+
+  QVariant v = pointAt( geom, vertexNumber, parent );
+  if ( !v.isNull() )
+    return QVariant( v.value<QgsPoint>().x() );
+  else
+    return QVariant();
+}
+
+// function used for the old $ style
+static QVariant fcnOldYat( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  FEAT_FROM_CONTEXT( context, feature )
+  const QgsGeometry geom = feature.geometry();
+  int idx = QgsExpressionUtils::getNativeIntValue( values.at( 0 ), parent );
+
+  QVariant v = pointAt( geom, idx, parent );
+
+  if ( !v.isNull() )
+    return QVariant( v.value<QgsPoint>().y() );
+  else
+    return QVariant();
+}
+static QVariant fcnYat( const QVariantList &values, const QgsExpressionContext *f, QgsExpression *parent, const QgsExpressionNodeFunction *node )
+{
+  if ( values.at( 1 ).isNull() ) // the case where the alias y_at function is called like a $ function (y_at(i))
+  {
+    return fcnOldYat( values, f, parent, node );
+  }
+  else if ( values.at( 0 ).isNull() && !values.at( 1 ).isNull() ) // same as above with x_at(i:=0) (this values is at the second position)
+  {
+    return fcnOldYat( QVariantList() << values[1], f, parent, node );
+  }
 
-  QgsPointXY p = g.vertexAt( idx );
-  return QVariant( QPointF( p.x(), p.y() ) );
+  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
+  int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
+  if ( geom.isNull() )
+  {
+    return QVariant();
+  }
+
+  QVariant v = pointAt( geom, vertexNumber, parent );
+  if ( !v.isNull() )
+    return QVariant( v.value<QgsPoint>().y() );
+  else
+    return QVariant();
 }
 
-static QVariant fcnXat( const QVariantList &values, const QgsExpressionContext *f, QgsExpression *parent, const QgsExpressionNodeFunction * )
+static QVariant fcnZat( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
-  QVariant v = pointAt( values, f, parent );
-  if ( v.type() == QVariant::PointF )
-    return QVariant( v.toPointF().x() );
+  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
+  int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
+  if ( geom.isNull() )
+  {
+    return QVariant();
+  }
+
+  QVariant v = pointAt( geom, vertexNumber, parent );
+  if ( !v.isNull() && v.value<QgsPoint>().is3D() )
+    return QVariant( v.value<QgsPoint>().z() );
   else
     return QVariant();
 }
-static QVariant fcnYat( const QVariantList &values, const QgsExpressionContext *f, QgsExpression *parent, const QgsExpressionNodeFunction * )
+
+static QVariant fcnMat( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
-  QVariant v = pointAt( values, f, parent );
-  if ( v.type() == QVariant::PointF )
-    return QVariant( v.toPointF().y() );
+  QgsGeometry geom = QgsExpressionUtils::getGeometry( values.at( 0 ), parent );
+  int vertexNumber = QgsExpressionUtils::getNativeIntValue( values.at( 1 ), parent );
+  if ( geom.isNull() )
+  {
+    return QVariant();
+  }
+
+  QVariant v = pointAt( geom, vertexNumber, parent );
+  if ( !v.isNull() && v.value<QgsPoint>().isMeasure() )
+    return QVariant( v.value<QgsPoint>().m() );
   else
     return QVariant();
 }
+
+
 static QVariant fcnGeometry( const QVariantList &, const QgsExpressionContext *context, QgsExpression *, const QgsExpressionNodeFunction * )
 {
   if ( !context )
@@ -8022,11 +8112,18 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
 #endif
       QgsExpressionFunction::Parameter( QStringLiteral( "keep_collapsed" ), true, false )
     }, fcnGeomMakeValid, QStringLiteral( "GeometryGroup" ) );
-    QgsStaticExpressionFunction *xAtFunc = new QgsStaticExpressionFunction( QStringLiteral( "$x_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "i" ) ), fcnXat, QStringLiteral( "GeometryGroup" ), QString(), true, QSet<QString>(), false, QStringList() << QStringLiteral( "xat" ) << QStringLiteral( "x_at" ) );
+
+    functions << new QgsStaticExpressionFunction( QStringLiteral( "x_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "geometry" ), true ) << QgsExpressionFunction::Parameter( QStringLiteral( "i" ), true ), fcnXat, QStringLiteral( "GeometryGroup" ) );
+    functions << new QgsStaticExpressionFunction( QStringLiteral( "y_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "geometry" ), true ) << QgsExpressionFunction::Parameter( QStringLiteral( "i" ), true ), fcnYat, QStringLiteral( "GeometryGroup" ) );
+    functions << new QgsStaticExpressionFunction( QStringLiteral( "z_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "geometry" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "i" ), true ), fcnZat, QStringLiteral( "GeometryGroup" ) );
+    functions << new QgsStaticExpressionFunction( QStringLiteral( "m_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "geometry" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "i" ), true ), fcnMat, QStringLiteral( "GeometryGroup" ) );
+
+    QgsStaticExpressionFunction *xAtFunc = new QgsStaticExpressionFunction( QStringLiteral( "$x_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "i" ) ), fcnOldXat, QStringLiteral( "GeometryGroup" ), QString(), true, QSet<QString>(), false, QStringList() << QStringLiteral( "xat" ) );
     xAtFunc->setIsStatic( false );
     functions << xAtFunc;
 
-    QgsStaticExpressionFunction *yAtFunc = new QgsStaticExpressionFunction( QStringLiteral( "$y_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "i" ) ), fcnYat, QStringLiteral( "GeometryGroup" ), QString(), true, QSet<QString>(), false, QStringList() << QStringLiteral( "yat" ) << QStringLiteral( "y_at" ) );
+
+    QgsStaticExpressionFunction *yAtFunc = new QgsStaticExpressionFunction( QStringLiteral( "$y_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "i" ) ), fcnOldYat, QStringLiteral( "GeometryGroup" ), QString(), true, QSet<QString>(), false, QStringList() << QStringLiteral( "yat" ) );
     yAtFunc->setIsStatic( false );
     functions << yAtFunc;