Class: QgsRenderContext

class qgis.core.QgsRenderContext

Bases: sip.wrapper

Contains information about the context of a rendering operation. The context of a rendering operation defines properties such as the conversion ratio between screen and map units, the extents to be rendered etc.

Enums

Methods

convertFromMapUnits Converts a size from map units to the specified units.
convertMetersToMapUnits Convert meter distances to active MapUnit values for QgsUnitTypes.RenderMetersInMapUnits note When the sourceCrs() is geographic, the center of the Extent will be used
convertToMapUnits Converts a size from the specified units to map units.
convertToPainterUnits Converts a size from the specified units to painter units (pixels).
coordinateTransform Returns the current coordinate transform for the context.
distanceArea A general purpose distance and area calculator, capable of performing ellipsoid based calculations.
drawEditingInformation
expressionContext Gets the expression context.
extent When rendering a map layer, calling this method returns the “clipping” extent for the layer (in the layer’s CRS).
featureFilterProvider Gets the filter feature provider used for additional filtering of rendered features.
flags Returns combination of flags used for rendering.
forceVectorOutput
fromMapSettings create initialized QgsRenderContext instance from given QgsMapSettings
fromQPainter Creates a default render context given a pixel based QPainter destination.
geometry Returns pointer to the unsegmentized geometry
mapToPixel
painter Returns the destination QPainter for the render operation.
pathResolver Returns the path resolver for conversion between relative and absolute paths during rendering operations, e.g.
rendererScale Returns the renderer map scale.
renderingStopped
scaleFactor Returns the scaling factor for the render to convert painter units to physical sizes.
segmentationTolerance Gets the segmentation tolerance applied when rendering curved geometries
segmentationToleranceType Gets segmentation tolerance type (maximum angle or maximum difference between curve and approximation)
selectionColor
setCoordinateTransform Sets the current coordinate transform for the context.
setDistanceArea A general purpose distance and area calculator, capable of performing ellipsoid based calculations.
setDrawEditingInformation
setExpressionContext Sets the expression context.
setExtent When rendering a map layer, calling this method sets the “clipping” extent for the layer (in the layer’s CRS).
setFeatureFilterProvider Set a filter feature provider used for additional filtering of rendered features.
setFlag Enable or disable a particular flag (other flags are not affected)
setFlags Set combination of flags that will be used for rendering.
setForceVectorOutput
setGeometry Sets pointer to original (unsegmentized) geometry
setMapToPixel
setPainter Sets the destination QPainter for the render operation.
setPathResolver Sets the path resolver for conversion between relative and absolute paths during rendering operations, e.g.
setRendererScale Sets the renderer map scale.
setRenderingStopped
setScaleFactor Sets the scaling factor for the render to convert painter units to physical sizes.
setSegmentationTolerance Sets the segmentation tolerance applied when rendering curved geometries
setSegmentationToleranceType Sets segmentation tolerance type (maximum angle or maximum difference between curve and approximation)
setSelectionColor
setShowSelection Sets whether vector selections should be shown in the rendered map
setTextRenderFormat Sets the text render format, which dictates how text is rendered (e.g.
setTransformContext Sets the context’s coordinate transform context, which stores various information regarding which datum transforms should be used when transforming points from a source to destination coordinate reference system.
setUseAdvancedEffects Used to enable or disable advanced effects such as blend modes
setUseRenderingOptimization
setVectorSimplifyMethod
showSelection Returns True if vector selections should be shown in the rendered map
testFlag Check whether a particular flag is enabled.
textRenderFormat Returns the text render format, which dictates how text is rendered (e.g.
transformContext Returns the context’s coordinate transform context, which stores various information regarding which datum transforms should be used when transforming points from a source to destination coordinate reference system.
useAdvancedEffects Returns True if advanced effects such as blend modes such be used
useRenderingOptimization Returns True if the rendering optimization (geometry simplification) can be executed
vectorSimplifyMethod Added in QGIS v2.4

Signals

Attributes

Antialiasing
DrawEditingInfo
DrawSelection
DrawSymbolBounds
ForceVectorOutput
RenderMapTile
RenderPartialOutput
RenderPreviewJob
TextFormatAlwaysOutlines
TextFormatAlwaysText
UseAdvancedEffects
UseRenderingOptimization
Antialiasing = 128
DrawEditingInfo = 1
DrawSelection = 16
DrawSymbolBounds = 32
class Flag

Bases: int

class Flags

Bases: sip.wrapper

QgsRenderContext.Flags(Union[QgsRenderContext.Flags, QgsRenderContext.Flag]) QgsRenderContext.Flags(QgsRenderContext.Flags)

ForceVectorOutput = 2
RenderMapTile = 64
RenderPartialOutput = 256
RenderPreviewJob = 512
TextFormatAlwaysOutlines = 0
TextFormatAlwaysText = 1
class TextRenderFormat

Bases: int

UseAdvancedEffects = 4
UseRenderingOptimization = 8
convertFromMapUnits(self, sizeInMapUnits: float, outputUnit: QgsUnitTypes.RenderUnit) → float

Converts a size from map units to the specified units.

New in version 3.0.

convertMetersToMapUnits(self, meters: float) → float

Convert meter distances to active MapUnit values for QgsUnitTypes.RenderMetersInMapUnits note When the sourceCrs() is geographic, the center of the Extent will be used

New in version 3.0.

convertToMapUnits(self, size: float, unit: QgsUnitTypes.RenderUnit, scale: QgsMapUnitScale = QgsMapUnitScale()) → float

Converts a size from the specified units to map units. The conversion respects the limits specified by the optional scale parameter.

New in version 3.0.

convertToPainterUnits(self, size: float, unit: QgsUnitTypes.RenderUnit, scale: QgsMapUnitScale = QgsMapUnitScale()) → float

Converts a size from the specified units to painter units (pixels). The conversion respects the limits specified by the optional scale parameter.

New in version 3.0.

coordinateTransform(self) → QgsCoordinateTransform

Returns the current coordinate transform for the context.

This represents the coordinate transform required to transform a layer which is being rendered back to the CRS of the rendered map. If no coordinate transformation is required, or the render context is not associated with a map layer render, then an invalid coordinate transformation is returned.

distanceArea(self) → QgsDistanceArea

A general purpose distance and area calculator, capable of performing ellipsoid based calculations.

New in version 3.0.

drawEditingInformation(self) → bool
expressionContext(self) → QgsExpressionContext

Gets the expression context. This context should be used for all expression evaluation associated with this render context.

New in version 2.12.

extent(self) → QgsRectangle

When rendering a map layer, calling this method returns the “clipping” extent for the layer (in the layer’s CRS).

This extent is a “worst-case” scenario, which is guaranteed to cover the complete visible portion of the layer when it is rendered to a map. It is often larger than the actual visible portion of that layer.

Warning

For some layers, depending on the visible extent and the coordinate transforms involved, this extent will represent the entire globe. This method should never be used to determine the actual visible extent of a map render.

See also

setExtent()

featureFilterProvider(self) → QgsFeatureFilterProvider

Gets the filter feature provider used for additional filtering of rendered features.

Returns:the filter feature provider

New in version 2.14.

flags(self) → QgsRenderContext.Flags

Returns combination of flags used for rendering.

New in version 2.14.

forceVectorOutput(self) → bool
fromMapSettings(mapSettings: QgsMapSettings) → QgsRenderContext

create initialized QgsRenderContext instance from given QgsMapSettings

New in version 2.4.

fromQPainter(painter: QPainter) → QgsRenderContext

Creates a default render context given a pixel based QPainter destination. If no painter is specified or the painter has no device, then a default DPI of 88 will be assumed.

New in version 3.0.

geometry(self) → QgsAbstractGeometry

Returns pointer to the unsegmentized geometry

mapToPixel(self) → QgsMapToPixel
painter(self) → QPainter

Returns the destination QPainter for the render operation.

See also

setPainter()

pathResolver(self) → QgsPathResolver

Returns the path resolver for conversion between relative and absolute paths during rendering operations, e.g. for resolving relative symbol paths.

New in version 3.0.

rendererScale(self) → float

Returns the renderer map scale. This will match the desired scale denominator for the rendered map, eg 1000.0 for a 1:1000 map render.

renderingStopped(self) → bool
scaleFactor(self) → float

Returns the scaling factor for the render to convert painter units to physical sizes. This is usually equal to the number of pixels per millimeter.

See also

setScaleFactor()

segmentationTolerance(self) → float

Gets the segmentation tolerance applied when rendering curved geometries

segmentationToleranceType(self) → QgsAbstractGeometry.SegmentationToleranceType

Gets segmentation tolerance type (maximum angle or maximum difference between curve and approximation)

selectionColor(self) → QColor
setCoordinateTransform(self, t: QgsCoordinateTransform)

Sets the current coordinate transform for the context.

This represents the coordinate transform required to transform the layer which is being rendered back to the CRS of the rendered map.

Set to an invalid QgsCoordinateTransform to indicate that no transformation is required.

setDistanceArea(self, distanceArea: QgsDistanceArea)

A general purpose distance and area calculator, capable of performing ellipsoid based calculations. Will be used to convert meter distances to active MapUnit values for QgsUnitTypes.RenderMetersInMapUnits

New in version 3.0.

setDrawEditingInformation(self, b: bool)
setExpressionContext(self, context: QgsExpressionContext)

Sets the expression context. This context is used for all expression evaluation associated with this render context.

New in version 2.12.

setExtent(self, extent: QgsRectangle)

When rendering a map layer, calling this method sets the “clipping” extent for the layer (in the layer’s CRS).

This extent should be a “worst-case” scenario, which is guaranteed to completely cover the entire visible portion of the layer when it is rendered to the map. It may be larger than the actual visible area, but MUST contain at least the entire visible area.

See also

setExtent()

setFeatureFilterProvider(self, ffp: QgsFeatureFilterProvider)

Set a filter feature provider used for additional filtering of rendered features.

Parameters:ffp – the filter feature provider

New in version 2.14.

setFlag(self, flag: QgsRenderContext.Flag, on: bool = True)

Enable or disable a particular flag (other flags are not affected)

New in version 2.14.

setFlags(self, flags: Union[QgsRenderContext.Flags, QgsRenderContext.Flag])

Set combination of flags that will be used for rendering.

New in version 2.14.

setForceVectorOutput(self, force: bool)
setGeometry(self, geometry: QgsAbstractGeometry)

Sets pointer to original (unsegmentized) geometry

setMapToPixel(self, mtp: QgsMapToPixel)
setPainter(self, p: QPainter)

Sets the destination QPainter for the render operation. Ownership of the painter is not transferred and the QPainter destination must stay alive for the duration of any rendering operations.

See also

painter()

setPathResolver(self, resolver: QgsPathResolver)

Sets the path resolver for conversion between relative and absolute paths during rendering operations, e.g. for resolving relative symbol paths.

See also

pathResolver()

New in version 3.0.

setRendererScale(self, scale: float)

Sets the renderer map scale. This should match the desired scale denominator for the rendered map, eg 1000.0 for a 1:1000 map render.

See also

rendererScale()

setRenderingStopped(self, stopped: bool)
setScaleFactor(self, factor: float)

Sets the scaling factor for the render to convert painter units to physical sizes. This should usually be equal to the number of pixels per millimeter.

See also

scaleFactor()

setSegmentationTolerance(self, tolerance: float)

Sets the segmentation tolerance applied when rendering curved geometries

Parameters:tolerance – the segmentation tolerance*
setSegmentationToleranceType(self, type: QgsAbstractGeometry.SegmentationToleranceType)

Sets segmentation tolerance type (maximum angle or maximum difference between curve and approximation)

Parameters:type – the segmentation tolerance typename*
setSelectionColor(self, color: Union[QColor, Qt.GlobalColor, QGradient])
setShowSelection(self, showSelection: bool)

Sets whether vector selections should be shown in the rendered map

Parameters:showSelection – set to True if selections should be shown

See also

showSelection()

New in version 2.4.

setTextRenderFormat(self, format: QgsRenderContext.TextRenderFormat)

Sets the text render format, which dictates how text is rendered (e.g. as paths or real text objects).

New in version 3.4.3.

setTransformContext(self, context: QgsCoordinateTransformContext)

Sets the context’s coordinate transform context, which stores various information regarding which datum transforms should be used when transforming points from a source to destination coordinate reference system.

New in version 3.0.

setUseAdvancedEffects(self, enabled: bool)

Used to enable or disable advanced effects such as blend modes

setUseRenderingOptimization(self, enabled: bool)
setVectorSimplifyMethod(self, simplifyMethod: QgsVectorSimplifyMethod)
showSelection(self) → bool

Returns True if vector selections should be shown in the rendered map

Returns:True if selections should be shown

See also

selectionColor()

New in version 2.4.

testFlag(self, flag: QgsRenderContext.Flag) → bool

Check whether a particular flag is enabled.

New in version 2.14.

textRenderFormat(self) → QgsRenderContext.TextRenderFormat

Returns the text render format, which dictates how text is rendered (e.g. as paths or real text objects).

New in version 3.4.3.

transformContext(self) → QgsCoordinateTransformContext

Returns the context’s coordinate transform context, which stores various information regarding which datum transforms should be used when transforming points from a source to destination coordinate reference system.

New in version 3.0.

useAdvancedEffects(self) → bool

Returns True if advanced effects such as blend modes such be used

useRenderingOptimization(self) → bool

Returns True if the rendering optimization (geometry simplification) can be executed

vectorSimplifyMethod(self) → QgsVectorSimplifyMethod

Added in QGIS v2.4