Class: QgsExpressionPreviewWidget¶
QgsExpressionPreviewWidget
is a widget to preview an
expression result. If the layer is set, one can browse across features
to see the different outputs.
Added in version 3.14.
Class Hierarchy¶
Base classes¶
Methods
Returns the current expression result preview text. |
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Will be set to |
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Returns the expression context for the widget. |
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Will be set to |
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Returns the expression parser errors |
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Returns the root node of the expression |
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sets the current feature used |
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Sets the widget to run using a custom preview generator. |
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Sets the expression context for the widget. |
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Sets the expression |
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Sets geometry calculator used in distance/area calculations. |
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Sets the layer used in the preview |
Signals
Will be set to |
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Emitted when the user changes the expression in the widget. |
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Will be set to |
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Emitted whenever the tool tip changed |
- class qgis.gui.QgsExpressionPreviewWidget[source]¶
Bases:
QWidget
- __init__(parent: QWidget | None = None)
Constructor
- Parameters:
parent (Optional[QWidget] = None)
- currentPreviewText(self) str [source]¶
Returns the current expression result preview text.
Added in version 3.38.
- Return type:
str
- evalError(self) bool [source]¶
Will be set to
True
if the current expression text reported an eval error with the context.- Return type:
bool
- signal evalErrorChanged[source]¶
Will be set to
True
if the current expression text reported an eval error with the context.
- expressionContext(self) QgsExpressionContext [source]¶
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
- Return type:
- signal expressionParsed(isValid: bool)[source]¶
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 (bool) – Is
True
if the expression the user has typed is valid.
- parserError(self) bool [source]¶
Will be set to
True
if the current expression text reports a parser error with the context.- Return type:
bool
- signal parserErrorChanged[source]¶
Will be set to
True
if the current expression text reported a parser error with the context.
- parserErrors(self) List[QgsExpression.ParserError] ¶
Returns the expression parser errors
- Return type:
- rootNode(self) QgsExpressionNode | None [source]¶
Returns the root node of the expression
- Return type:
Optional[QgsExpressionNode]
- setCurrentFeature(self, feature: QgsFeature)[source]¶
sets the current feature used
- Parameters:
feature (QgsFeature)
- setCustomPreviewGenerator(self, label: str | None, choices: Iterable[Tuple[str | None, Any]], a2: Callable[..., None])[source]¶
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 (Optional[str]) – 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 (Iterable[Tuple[Optional[str], Any]]) – 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.
Added in version 3.38.
- Parameters:
a2 (Callable[..., None])
- setExpressionContext(self, context: QgsExpressionContext)[source]¶
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 (QgsExpressionContext) – expression context
- setExpressionText(self, expression: str | None)[source]¶
Sets the expression
- Parameters:
expression (Optional[str])
- setGeomCalculator(self, da: QgsDistanceArea)[source]¶
Sets geometry calculator used in distance/area calculations.
- Parameters:
da (QgsDistanceArea)
- setLayer(self, layer: QgsVectorLayer | None)[source]¶
Sets the layer used in the preview
- Parameters:
layer (Optional[QgsVectorLayer])