QgsExpressionPreviewWidget is a widget to preview an expression result. More...

#include <qgsexpressionpreviewwidget.h>

Inheritance diagram for QgsExpressionPreviewWidget:

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Public Slots
void	setCurrentFeature (const QgsFeature &feature)
	sets the current feature used

Signals
void	evalErrorChanged ()
	Will be set to `true` if the current expression text reported an eval error with the context.

void	expressionParsed (bool isValid)
	Emitted when the user changes the expression in the widget.

void	parserErrorChanged ()
	Will be set to `true` if the current expression text reported a parser error with the context.

void	toolTipChanged (const QString &toolTip)
	Emitted whenever the tool tip changed.

Public Member Functions
	QgsExpressionPreviewWidget (QWidget *parent=nullptr)
	Constructor.

QString	currentPreviewText () const
	Returns the current expression result preview text.

bool	evalError () const
	Will be set to `true` if the current expression text reported an eval error with the context.

QgsExpressionContext	expressionContext () const
	Returns the expression context for the widget.

bool	parserError () const
	Will be set to `true` if the current expression text reports a parser error with the context.

QList< QgsExpression::ParserError >	parserErrors () const
	Returns the expression parser errors.

const QgsExpressionNode *	rootNode () const
	Returns the root node of the expression.

void	setCustomPreviewGenerator (const QString &label, const QList< QPair< QString, QVariant > > &choices, const std::function< QgsExpressionContext(const QVariant &)> &previewContextGenerator)
	Sets the widget to run using a custom preview generator.

void	setExpressionContext (const QgsExpressionContext &context)
	Sets the expression context for the widget.

void	setExpressionText (const QString &expression)
	Sets the expression.

void	setGeomCalculator (const QgsDistanceArea &da)
	Sets geometry calculator used in distance/area calculations.

void	setLayer (QgsVectorLayer *layer)
	Sets the layer used in the preview.

Detailed Description

QgsExpressionPreviewWidget is a widget to preview an expression result.

If the layer is set, one can browse across features to see the different outputs.

Since: QGIS 3.14

Definition at line 39 of file qgsexpressionpreviewwidget.h.

Constructor & Destructor Documentation

◆ QgsExpressionPreviewWidget()

QgsExpressionPreviewWidget::QgsExpressionPreviewWidget ( QWidget * parent = nullptr )

explicit

Constructor.

Definition at line 27 of file qgsexpressionpreviewwidget.cpp.

Member Function Documentation

◆ currentPreviewText()

QString QgsExpressionPreviewWidget::currentPreviewText ( ) const

Returns the current expression result preview text.

Since: QGIS 3.38

Definition at line 230 of file qgsexpressionpreviewwidget.cpp.

◆ evalError()

bool QgsExpressionPreviewWidget::evalError ( ) const

Will be set to true if the current expression text reported an eval error with the context.

Definition at line 244 of file qgsexpressionpreviewwidget.cpp.

◆ evalErrorChanged

void QgsExpressionPreviewWidget::evalErrorChanged ( )

signal

Will be set to true if the current expression text reported an eval error with the context.

◆ expressionContext()

QgsExpressionContext QgsExpressionPreviewWidget::expressionContext ( ) const

inline

Returns the expression context for the widget.

The context is used for the expression preview result and for populating the list of available functions and variables.

See also: setExpressionContext

Definition at line 112 of file qgsexpressionpreviewwidget.h.

◆ expressionParsed

void QgsExpressionPreviewWidget::expressionParsed ( bool isValid )

signal

Emitted when the user changes the expression in the widget.

Users of this widget should connect to this signal to decide if to let the user continue.

Parameters

isValid Is true if the expression the user has typed is valid.

◆ parserError()

bool QgsExpressionPreviewWidget::parserError ( ) const

Will be set to true if the current expression text reports a parser error with the context.

Definition at line 225 of file qgsexpressionpreviewwidget.cpp.

◆ parserErrorChanged

void QgsExpressionPreviewWidget::parserErrorChanged ( )

signal

Will be set to true if the current expression text reported a parser error with the context.

◆ parserErrors()

QList< QgsExpression::ParserError > QgsExpressionPreviewWidget::parserErrors ( ) const

inline

Returns the expression parser errors.

Definition at line 140 of file qgsexpressionpreviewwidget.h.

◆ rootNode()

const QgsExpressionNode * QgsExpressionPreviewWidget::rootNode ( ) const

inline

Returns the root node of the expression.

Definition at line 137 of file qgsexpressionpreviewwidget.h.

◆ setCurrentFeature

void QgsExpressionPreviewWidget::setCurrentFeature ( const QgsFeature & feature )

slot

sets the current feature used

Definition at line 86 of file qgsexpressionpreviewwidget.cpp.

◆ setCustomPreviewGenerator()

void QgsExpressionPreviewWidget::setCustomPreviewGenerator	(	const QString &	label,
		const QList< QPair< QString, QVariant > > &	choices,
		const std::function< QgsExpressionContext(const QVariant &)> &	previewContextGenerator
	)

Sets the widget to run using a custom preview generator.

In this mode, the widget will call a callback function to generate a new QgsExpressionContext as the previewed object changes. This can be used to provide custom preview values for different objects (i.e. for objects which aren't vector layer features).

Parameters

label	The label to display for the combo box presenting choices of objects. This should be a representative name, eg "Band" if the widget is showing choices of raster layer bands
choices	A list of choices to present to the user. Each choice is a pair of a human-readable label and a QVariant representing the object to preview.
previewContextGenerator	A function which takes a QVariant representing the object to preview, and returns a QgsExpressionContext to use for previewing the object.

Since: QGIS 3.38

Definition at line 62 of file qgsexpressionpreviewwidget.cpp.

◆ setExpressionContext()

void QgsExpressionPreviewWidget::setExpressionContext ( const QgsExpressionContext & context )

Sets the expression context for the widget.

The context is used for the expression preview result and to populate the list of available functions and variables.

Parameters

context expression context

Definition at line 102 of file qgsexpressionpreviewwidget.cpp.

◆ setExpressionText()

void QgsExpressionPreviewWidget::setExpressionText ( const QString & expression )

Sets the expression.

Definition at line 77 of file qgsexpressionpreviewwidget.cpp.

◆ setGeomCalculator()

void QgsExpressionPreviewWidget::setGeomCalculator ( const QgsDistanceArea & da )

Sets geometry calculator used in distance/area calculations.

Definition at line 96 of file qgsexpressionpreviewwidget.cpp.

◆ setLayer()

void QgsExpressionPreviewWidget::setLayer ( QgsVectorLayer * layer )

Sets the layer used in the preview.

Definition at line 53 of file qgsexpressionpreviewwidget.cpp.

◆ toolTipChanged

void QgsExpressionPreviewWidget::toolTipChanged ( const QString & toolTip )

signal

Emitted whenever the tool tip changed.

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

/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/gui/qgsexpressionpreviewwidget.h
/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/gui/qgsexpressionpreviewwidget.cpp

Public Slots

Signals

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ QgsExpressionPreviewWidget()

Member Function Documentation

◆ currentPreviewText()

◆ evalError()

◆ evalErrorChanged

◆ expressionContext()

◆ expressionParsed

◆ parserError()

◆ parserErrorChanged

◆ parserErrors()

◆ rootNode()

◆ setCurrentFeature

◆ setCustomPreviewGenerator()

◆ setExpressionContext()

◆ setExpressionText()

◆ setGeomCalculator()

◆ setLayer()

◆ toolTipChanged