Class: QgsRuleBasedRenderer

class qgis.core.QgsRuleBasedRenderer

Bases: QgsFeatureRenderer

Rule based renderer.

When drawing a vector layer with rule-based renderer, it goes through the rules and draws features with symbols from rules that match.

QgsRuleBasedRenderer(root: QgsRuleBasedRenderer.Rule) Constructs the renderer from given tree of rules (takes ownership)

QgsRuleBasedRenderer(defaultSymbol: QgsSymbol) Constructor for convenience. Creates a root rule and adds a default rule with symbol (takes ownership)

Methods

accept

param visitor

capabilities

rtype

QgsFeatureRenderer.Capabilities

checkLegendSymbolItem

param key

clone

rtype

QgsRuleBasedRenderer

convertFromRenderer

Creates a new QgsRuleBasedRenderer from an existing renderer.

convertSymbolRotation

convertSymbolSizeScale

convertToDataDefinedSymbology

helper function to convert the size scale and rotation fields present in some other renderers to data defined symbology

create

Creates a new rule-based renderer instance from XML

createFromSld

param element

dump

rtype

str

filter

param fields

filterNeedsGeometry

rtype

bool

legendKeysForFeature

param feature

legendSymbolItemChecked

param key

legendSymbolItems

rtype

List[QgsLegendSymbolItem]

legendSymbolItemsCheckable

rtype

bool

originalSymbolsForFeature

param feature

refineRuleCategories

take a rule and create a list of new rules based on the categories from categorized symbol renderer

refineRuleRanges

take a rule and create a list of new rules based on the ranges from graduated symbol renderer

refineRuleScales

take a rule and create a list of new rules with intervals of scales given by the passed scale denominators

renderFeature

param feature

renderFeatureWithSymbol

Render the feature with the symbol using context.

renderVertexMarker

render editing vertex marker at specified point

renderVertexMarkerPolygon

render editing vertex marker for a polygon

renderVertexMarkerPolyline

render editing vertex marker for a polyline

rootRule

rtype

QgsRuleBasedRenderer.Rule

save

param doc

saveRendererData

Saves generic renderer data into the specified element.

setLegendSymbolItem

param key

startRender

param context

stopRender

param context

symbolForFeature

Returns symbol for current feature.

symbols

param context

symbolsForFeature

param feature

toSld

param doc

usedAttributes

param context

willRenderFeature

param feature

Attributes

FeatDrawMarkers

FeatIsSelected

FeatDrawMarkers = 2
FeatIsSelected = 1
class FeatureFlags

Bases: int

class FeatureToRender(_f: QgsFeature, _flags: int)
class FeatureToRender(QgsRuleBasedRenderer.FeatureToRender)

Bases: sip.wrapper

feat
flags
class RenderJob

Bases: sip.wrapper

Feature to render

ftr
symbol
class RenderLevel(z: int)
class RenderLevel(other: QgsRuleBasedRenderer.RenderLevel)

Bases: sip.wrapper

jobs
zIndex
class Rule

Bases: sip.wrapper

This class keeps data about a rules for rule-based renderer.

A rule consists of a symbol, filter expression and range of scales. If filter is empty, it matches all features. If scale range has both values zero, it matches all scales. If one of the min/max scale denominators is zero, there is no lower/upper bound for scales. A rule matches if both filter and scale range match.

QgsRuleBasedRenderer.Rule(symbol: QgsSymbol, maximumScale: int = 0, minimumScale: int = 0, filterExp: str = ‘’, label: str = ‘’, description: str = ‘’, elseRule: bool = False) Constructor takes ownership of the symbol

Filtered = 0
Inactive = 1
class RenderResult

Bases: int

Rendered = 2
accept(self, visitor: QgsStyleEntityVisitorInterface) bool

Accepts the specified symbology visitor, causing it to visit all child rules associated with the rule.

Returns True if the visitor should continue visiting other objects, or False if visiting should be canceled.

New in version 3.10.

Parameters

visitor (QgsStyleEntityVisitorInterface) –

Return type

bool

active(self) bool

Returns if this rule is active

Return type

bool

Returns

True if the rule is active

appendChild(self, rule: QgsRuleBasedRenderer.Rule)

add child rule, take ownership, sets this as parent

Parameters

rule (QgsRuleBasedRenderer.Rule) –

children(self) List[QgsRuleBasedRenderer.Rule]

Returns all children rules of this rule

Return type

List[QgsRuleBasedRenderer.Rule]

Returns

A list of rules

clone(self) QgsRuleBasedRenderer.Rule

clone this rule, return new instance

Return type

QgsRuleBasedRenderer.Rule

collectZLevels(self) object

Gets all used z-levels from this rule and children

Return type

object

create(ruleElem: QDomElement, symbolMap: object) QgsRuleBasedRenderer.Rule

Create a rule from an XML definition

Parameters
  • ruleElem (QDomElement) – The XML rule element

  • symbolMap (object) – Symbol map

Return type

QgsRuleBasedRenderer.Rule

Returns

A new rule

createFromSld(element: QDomElement, geomType: QgsWkbTypes.GeometryType) QgsRuleBasedRenderer.Rule

Create a rule from the SLD provided in element and for the specified geometry type.

Parameters
Return type

QgsRuleBasedRenderer.Rule

dependsOnScale(self) bool
Return type

bool

descendants(self) List[QgsRuleBasedRenderer.Rule]

Returns all children, grand-children, grand-grand-children, grand-gra… you get it

Return type

List[QgsRuleBasedRenderer.Rule]

Returns

A list of descendant rules

description(self) str

A human readable description for this rule

Return type

str

Returns

Description

dump(self, indent: int = 0) str

Dump for debug purpose

Parameters

indent (int = 0) – How many characters to indent. Will increase by two with every of the recursive calls

Return type

str

Returns

A string representing this rule

filter(self) QgsExpression

A filter that will check if this rule applies

Return type

QgsExpression

Returns

An expression

filterExpression(self) str

A filter that will check if this rule applies

Return type

str

Returns

An expression

findRuleByKey(self, key: str) QgsRuleBasedRenderer.Rule

Try to find a rule given its unique key

New in version 2.6.

Parameters

key (str) –

Return type

QgsRuleBasedRenderer.Rule

initFilter(self)
insertChild(self, i: int, rule: QgsRuleBasedRenderer.Rule)

add child rule, take ownership, sets this as parent

Parameters
isElse(self) bool

Check if this rule is an ELSE rule

Return type

bool

Returns

True if this rule is an else rule

isFilterOK(self, f: QgsFeature, context: QgsRenderContext = None) bool

Check if a given feature shall be rendered by this rule

Parameters
Return type

bool

Returns

True if the feature shall be rendered

isScaleOK(self, scale: float) bool

Check if this rule applies for a given scale. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. If set to 0, it will always return True.

Return type

bool

Returns

If the rule will be evaluated at this scale

Parameters

scale (float) –

label(self) str
Return type

str

legendKeysForFeature(self, feature: QgsFeature, context: QgsRenderContext = None) Set[str]

Returns which legend keys match the feature

New in version 2.14.

Parameters
Return type

Set[str]

legendSymbolItems(self, currentLevel: int = -1) List[QgsLegendSymbolItem]

New in version 2.6.

Parameters

currentLevel (int = -1) –

Return type

List[QgsLegendSymbolItem]

maximumScale(self) float

Returns the maximum map scale (i.e. most “zoomed in” scale) at which the rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no maximum scale visibility.

See also

minimumScale()

New in version 3.0.

Return type

float

minimumScale(self) float

Returns the minimum map scale (i.e. most “zoomed out” scale) at which the rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no minimum scale visibility.

See also

maximumScale()

New in version 3.0.

Return type

float

needsGeometry(self) bool

Returns True if this rule or one of its children needs the geometry to be applied.

Return type

bool

parent(self) QgsRuleBasedRenderer.Rule

The parent rule

Return type

QgsRuleBasedRenderer.Rule

Returns

Parent rule

removeChild(self, rule: QgsRuleBasedRenderer.Rule)

delete child rule

Parameters

rule (QgsRuleBasedRenderer.Rule) –

removeChildAt(self, i: int)

delete child rule

Parameters

i (int) –

renderFeature(self, featToRender: QgsRuleBasedRenderer.FeatureToRender, context: QgsRenderContext, renderQueue: Iterable[QgsRuleBasedRenderer.RenderLevel]) QgsRuleBasedRenderer.Rule.RenderResult

Render a given feature, will recursively call subclasses and only render if the constraints apply.

Parameters
Return type

QgsRuleBasedRenderer.Rule.RenderResult

Returns

The result of the rendering. In explicit if the feature is added to the queue or the reason for not rendering the feature.

ruleKey(self) str

Unique rule identifier (for identification of rule within renderer)

New in version 2.6.

Return type

str

rulesForFeature(self, feature: QgsFeature, context: QgsRenderContext = None, onlyActive: bool = True) List[QgsRuleBasedRenderer.Rule]

Returns the list of rules used to render the feature in a specific context.

Parameters
  • feature (QgsFeature) – The feature for which rules have to be find

  • context (QgsRenderContext = None) – The rendering context

  • onlyActive (bool = True) – True to search for active rules only, False otherwise

Return type

List[QgsRuleBasedRenderer.Rule]

save(self, doc: QDomDocument, symbolMap: object) QDomElement
Parameters
  • doc (QDomDocument) –

  • symbolMap (object) –

Return type

QDomElement

setActive(self, state: bool)

Sets if this rule is active

Parameters

state (bool) – Determines if the rule should be activated or deactivated

setDescription(self, description: str)

Set a human readable description for this rule

Parameters

description (str) – Description

setFilterExpression(self, filterExp: str)

Set the expression used to check if a given feature shall be rendered with this rule

Parameters

filterExp (str) – An expression

setIsElse(self, iselse: bool)

Sets if this rule is an ELSE rule

Parameters

iselse (bool) – If True, this rule is an ELSE rule

setLabel(self, label: str)
Parameters

label (str) –

setMaximumScale(self, scale: float)

Sets the maximum map scale (i.e. most “zoomed in” scale) at which the rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no maximum scale visibility.

See also

maximumScale()

Parameters

scale (float) –

setMinimumScale(self, scale: float)

Sets the minimum map scale (i.e. most “zoomed out” scale) at which the rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no minimum scale visibility.

See also

minimumScale()

Parameters

scale (float) –

setRuleKey(self, key: str)

Override the assigned rule key (should be used just internally by rule-based renderer)

New in version 2.6.

Parameters

key (str) –

setSymbol(self, sym: QgsSymbol)

Sets a new symbol (or None). Deletes old symbol.

Parameters

sym (QgsSymbol) –

startRender(self, context: QgsRenderContext, fields: QgsFields, filter: str) bool

prepare the rule for rendering and its children (build active children array)

Parameters
Return type

bool

stopRender(self, context: QgsRenderContext)

Stop a rendering process. Used to clean up the internal state of this rule

Parameters

context (QgsRenderContext) – The rendering context

symbol(self) QgsSymbol
Return type

QgsSymbol

symbols(self, context: QgsRenderContext = QgsRenderContext()) List[QgsSymbol]

Note

available in Python bindings as symbol2

Parameters

context (QgsRenderContext = QgsRenderContext()) –

Return type

List[QgsSymbol]

symbolsForFeature(self, feature: QgsFeature, context: QgsRenderContext = None) List[QgsSymbol]

tell which symbols will be used to render the feature

Parameters
Return type

List[QgsSymbol]

takeChild(self, rule: QgsRuleBasedRenderer.Rule) QgsRuleBasedRenderer.Rule

take child rule out, set parent as None

Parameters

rule (QgsRuleBasedRenderer.Rule) –

Return type

QgsRuleBasedRenderer.Rule

takeChildAt(self, i: int) QgsRuleBasedRenderer.Rule

take child rule out, set parent as None

Parameters

i (int) –

Return type

QgsRuleBasedRenderer.Rule

toSld(self, doc: QDomDocument, element: QDomElement, props: Dict[str, Any])

Saves the symbol layer as SLD

Parameters
  • doc (QDomDocument) –

  • element (QDomElement) –

  • props (Dict[str) –

usedAttributes(self, context: QgsRenderContext) Set[str]

Returns the attributes used to evaluate the expression of this rule

Return type

Set[str]

Returns

A set of attribute names

Parameters

context (QgsRenderContext) –

willRenderFeature(self, feature: QgsFeature, context: QgsRenderContext = None) bool

only tell whether a feature will be rendered without actually rendering it

Parameters
Return type

bool

accept(self, visitor: QgsStyleEntityVisitorInterface) bool
Parameters

visitor (QgsStyleEntityVisitorInterface) –

Return type

bool

capabilities(self) QgsFeatureRenderer.Capabilities
Return type

QgsFeatureRenderer.Capabilities

checkLegendSymbolItem(self, key: str, state: bool = True)
Parameters
  • key (str) –

  • state (bool = True) –

clone(self) QgsRuleBasedRenderer
Return type

QgsRuleBasedRenderer

convertFromRenderer(renderer: QgsFeatureRenderer, layer: QgsVectorLayer = None) QgsRuleBasedRenderer

Creates a new QgsRuleBasedRenderer from an existing renderer.

Since QGIS 3.20, the optional layer parameter is required for conversions of some renderer types.

Return type

QgsRuleBasedRenderer

Returns

a new renderer if the conversion was possible, otherwise None.

New in version 2.5.

Parameters
convertSymbolRotation(symbol: QgsSymbol, field: str)

Note

this function is used to convert old rotations expressions to symbol level DataDefined angle

convertSymbolSizeScale(symbol: QgsSymbol, method: Qgis.ScaleMethod, field: str)

Note

this function is used to convert old sizeScale expressions to symbol level DataDefined size

convertToDataDefinedSymbology(symbol: QgsSymbol, sizeScaleField: str, rotationField: str = '')

helper function to convert the size scale and rotation fields present in some other renderers to data defined symbology

Parameters
  • symbol (QgsSymbol) –

  • sizeScaleField (str) –

  • rotationField (str = '') –

create(element: QDomElement, context: QgsReadWriteContext) QgsFeatureRenderer

Creates a new rule-based renderer instance from XML

Parameters
Return type

QgsFeatureRenderer

createFromSld(element: QDomElement, geomType: QgsWkbTypes.GeometryType) QgsFeatureRenderer
Parameters
Return type

QgsFeatureRenderer

dump(self) str
Return type

str

filter(self, fields: QgsFields = QgsFields()) str
Parameters

fields (QgsFields = QgsFields()) –

Return type

str

filterNeedsGeometry(self) bool
Return type

bool

legendKeysForFeature(self, feature: QgsFeature, context: QgsRenderContext) Set[str]
Parameters
Return type

Set[str]

legendSymbolItemChecked(self, key: str) bool
Parameters

key (str) –

Return type

bool

legendSymbolItems(self) List[QgsLegendSymbolItem]
Return type

List[QgsLegendSymbolItem]

legendSymbolItemsCheckable(self) bool
Return type

bool

originalSymbolsForFeature(self, feature: QgsFeature, context: QgsRenderContext) List[QgsSymbol]
Parameters
Return type

List[QgsSymbol]

refineRuleCategories(initialRule: QgsRuleBasedRenderer.Rule, r: QgsCategorizedSymbolRenderer)

take a rule and create a list of new rules based on the categories from categorized symbol renderer

Parameters
refineRuleRanges(initialRule: QgsRuleBasedRenderer.Rule, r: QgsGraduatedSymbolRenderer)

take a rule and create a list of new rules based on the ranges from graduated symbol renderer

Parameters
refineRuleScales(initialRule: QgsRuleBasedRenderer.Rule, scales: Iterable[int])

take a rule and create a list of new rules with intervals of scales given by the passed scale denominators

Parameters
renderFeature(self, feature: QgsFeature, context: QgsRenderContext, layer: int = -1, selected: bool = False, drawVertexMarker: bool = False) bool
Parameters
  • feature (QgsFeature) –

  • context (QgsRenderContext) –

  • layer (int = -1) –

  • selected (bool = False) –

  • drawVertexMarker (bool = False) –

Return type

bool

renderFeatureWithSymbol(self, feature: QgsFeature, symbol: QgsSymbol, context: QgsRenderContext, layer: int, selected: bool, drawVertexMarker: bool)

Render the feature with the symbol using context. Use layer to specify the symbol layer, selected to specify if it should be rendered as selected and drawVertexMarker to specify if vertex markers should be rendered.

renderVertexMarker(self, pt: Union[QPointF, QPoint], context: QgsRenderContext)

render editing vertex marker at specified point

renderVertexMarkerPolygon(self, pts: QPolygonF, rings: Iterable[QPolygonF], context: QgsRenderContext)

render editing vertex marker for a polygon

renderVertexMarkerPolyline(self, pts: QPolygonF, context: QgsRenderContext)

render editing vertex marker for a polyline

rootRule(self) QgsRuleBasedRenderer.Rule
Return type

QgsRuleBasedRenderer.Rule

save(self, doc: QDomDocument, context: QgsReadWriteContext) QDomElement
Parameters
Return type

QDomElement

saveRendererData(self, doc: QDomDocument, element: QDomElement, context: QgsReadWriteContext)

Saves generic renderer data into the specified element.

This method should be called in a subclass’ save() implementation in order to store all common base class properties in the DOM element.

New in version 3.22.

setLegendSymbolItem(self, key: str, symbol: QgsSymbol)
Parameters
startRender(self, context: QgsRenderContext, fields: QgsFields)
Parameters
stopRender(self, context: QgsRenderContext)
Parameters

context (QgsRenderContext) –

symbolForFeature(self, feature: QgsFeature, context: QgsRenderContext) QgsSymbol

Returns symbol for current feature. Should not be used individually: there could be more symbols for a feature

Parameters
Return type

QgsSymbol

symbols(self, context: QgsRenderContext) List[QgsSymbol]
Parameters

context (QgsRenderContext) –

Return type

List[QgsSymbol]

symbolsForFeature(self, feature: QgsFeature, context: QgsRenderContext) List[QgsSymbol]
Parameters
Return type

List[QgsSymbol]

toSld(self, doc: QDomDocument, element: QDomElement, props: Dict[str, Any] = {})
Parameters
  • doc (QDomDocument) –

  • element (QDomElement) –

  • props (Dict[str) –

usedAttributes(self, context: QgsRenderContext) Set[str]
Parameters

context (QgsRenderContext) –

Return type

Set[str]

willRenderFeature(self, feature: QgsFeature, context: QgsRenderContext) bool
Parameters
Return type

bool