Class: QgsSymbolRenderContext¶

Encapsulates the context in which a symbol is being rendered.

Methods

`expressionContextScope`	This scope is always available when a symbol of this type is being rendered.
`feature`	Returns the current feature being rendered.
`fields`	Fields of the layer.
`forceVectorRendering`	Returns `True` if symbol must be rendered using vector methods, and optimisations like pre-rendered images must be disabled.
`geometryPartCount`	Part count of current geometry
`geometryPartNum`	Part number of current geometry
`mapUnitScale`
`opacity`	Returns the opacity for the symbol.
`originalGeometryType`	Returns the geometry type for the original feature geometry being rendered.
`outputLineWidth`
`outputPixelSize`
`outputUnit`	Returns the output unit for the context.
`patchShape`	Returns the symbol patch shape, to use if rendering symbol preview icons.
`renderContext`	Returns a reference to the context's render context.
`renderHints`	Returns the rendering hint flags for the symbol.
`selected`	Returns `True` if symbols should be rendered using the selected symbol coloring and style.
`setExpressionContextScope`	Set an expression scope for this symbol.
`setFeature`
`setGeometryPartCount`	Sets the part count of current geometry
`setGeometryPartNum`	Sets the part number of current geometry
`setMapUnitScale`
`setOpacity`	Sets the opacity for the symbol.
`setOriginalGeometryType`	Sets the geometry type for the original feature geometry being rendered.
`setOriginalValueVariable`	Sets the original value variable value for data defined symbology
`setOutputUnit`	Sets the output unit for the context.
`setPatchShape`	Sets the symbol patch shape, to use if rendering symbol preview icons.
`setRenderHint`	Sets a rendering hint flag for the symbol.
`setRenderHints`	Sets rendering hint flags for the symbol.
`setSelected`	Sets whether symbols should be rendered using the selected symbol coloring and style.

class qgis.core.QgsSymbolRenderContext[source]¶

Bases: object

__init__(c: QgsRenderContext, u: Qgis.RenderUnit, opacity: float = 1, selected: bool = False, renderHints: Qgis.SymbolRenderHints | Qgis.SymbolRenderHint = Qgis.SymbolRenderHints(), f: QgsFeature | None = None, fields: QgsFields = QgsFields(), mapUnitScale: QgsMapUnitScale = QgsMapUnitScale())

Constructor for QgsSymbolRenderContext

Parameters:

c (QgsRenderContext)
u (Qgis.RenderUnit)
opacity (float = 1) – value between 0 (fully transparent) and 1 (fully opaque)
selected (bool = False) – set to True if symbol should be drawn in a “selected” state
renderHints (Union[Qgis.SymbolRenderHints, Qgis.SymbolRenderHint] = Qgis.SymbolRenderHints()) – flags controlling rendering behavior
f (Optional[QgsFeature] = None)
fields (QgsFields = QgsFields())
mapUnitScale (QgsMapUnitScale = QgsMapUnitScale())

expressionContextScope(self) → QgsExpressionContextScope | None[source]¶

This scope is always available when a symbol of this type is being rendered.

Return type:: Optional[QgsExpressionContextScope]
Returns:: An expression scope for details about this symbol

feature(self) → QgsFeature | None[source]¶

Returns the current feature being rendered. This may be None.

Return type:: Optional[QgsFeature]

fields(self) → QgsFields[source]¶

Fields of the layer. Currently only available in startRender() calls to allow symbols with data-defined properties prepare the expressions (other times fields() returns an empty QgsFields object).

Return type:: QgsFields

forceVectorRendering(self) → bool[source]¶

Returns True if symbol must be rendered using vector methods, and optimisations like pre-rendered images must be disabled.

Added in version 3.40.

Return type:: bool

geometryPartCount(self) → int[source]¶

Part count of current geometry

Return type:: int

geometryPartNum(self) → int[source]¶

Part number of current geometry

Return type:: int

mapUnitScale(self) → QgsMapUnitScale[source]¶

Deprecated since version 3.40.

Will be removed in QGIS 4.0.

Return type:: QgsMapUnitScale

opacity(self) → float[source]¶

Returns the opacity for the symbol.

Return type:: float
Returns:: opacity value between 0 (fully transparent) and 1 (fully opaque)

See also

setOpacity()

originalGeometryType(self) → Qgis.GeometryType[source]¶

Returns the geometry type for the original feature geometry being rendered. This can be useful if symbol layers alter their appearance based on geometry type - eg offsetting a simple line style will look different if the simple line is rendering a polygon feature (a closed buffer) vs a line feature (an unclosed offset line).

See also

originalGeometryType()

Return type:: Qgis.GeometryType

outputLineWidth(self, width: float) → float[source]¶

Deprecated since version 3.40.

Use the size conversion methods in QgsRenderContext instead.

Parameters:: width (float)
Return type:: float

outputPixelSize(self, size: float) → float[source]¶

Deprecated since version 3.40.

Use the size conversion methods in QgsRenderContext instead.

Parameters:: size (float)
Return type:: float

outputUnit(self) → Qgis.RenderUnit[source]¶

Returns the output unit for the context.

Deprecated since version 3.40: No longer used and will be removed in QGIS 4.0.

Return type:: Qgis.RenderUnit

patchShape(self) → QgsLegendPatchShape | None[source]¶

Returns the symbol patch shape, to use if rendering symbol preview icons.

See also

setPatchShape()

Added in version 3.14.

Return type:: Optional[QgsLegendPatchShape]

renderContext(self) → QgsRenderContext¶

Returns a reference to the context’s render context.

Return type:: QgsRenderContext

renderHints(self) → Qgis.SymbolRenderHints[source]¶

Returns the rendering hint flags for the symbol.

See also

setRenderHints()

Return type:: Qgis.SymbolRenderHints

selected(self) → bool[source]¶

Returns True if symbols should be rendered using the selected symbol coloring and style.

See also

setSelected()

Return type:: bool

setExpressionContextScope(self, contextScope: QgsExpressionContextScope | None)[source]¶

Set an expression scope for this symbol.

Will take ownership.

Parameters:: contextScope (Optional[QgsExpressionContextScope]) – An expression scope for details about this symbol

setFeature(self, f: QgsFeature | None)[source]¶

Parameters:: f (Optional[QgsFeature])

setGeometryPartCount(self, count: int)[source]¶

Sets the part count of current geometry

Parameters:: count (int)

setGeometryPartNum(self, num: int)[source]¶

Sets the part number of current geometry

Parameters:: num (int)

setMapUnitScale(self, scale: QgsMapUnitScale)[source]¶

Deprecated since version 3.40.

Will be removed in QGIS 4.0.

Parameters:: scale (QgsMapUnitScale)

setOpacity(self, opacity: float)[source]¶

Sets the opacity for the symbol.

Parameters:: opacity (float) – opacity value between 0 (fully transparent) and 1 (fully opaque)

See also

opacity()

setOriginalGeometryType(self, type: Qgis.GeometryType)[source]¶

Sets the geometry type for the original feature geometry being rendered.

See also

originalGeometryType()

Parameters:: type (Qgis.GeometryType)

setOriginalValueVariable(self, value: Any)[source]¶

Sets the original value variable value for data defined symbology

Parameters:: value (Any) – value for original value variable. This usually represents the symbol property value before any data defined overrides have been applied.

setOutputUnit(self, u: Qgis.RenderUnit)[source]¶