Subgroup: Rule

Class: QgsRuleBasedRenderer

class qgis.core.QgsRuleBasedRenderer(root: QgsRuleBasedRenderer.Rule)

Bases: qgis._core.QgsFeatureRenderer

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)

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

Methods

capabilities
checkLegendSymbolItem
clone
convertFromRenderer creates a 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
copyRendererData
create Creates a new rule-based renderer instance from XML
createFromSld
dump
filter
filterNeedsGeometry
legendKeysForFeature
legendSymbolItemChecked
legendSymbolItems
legendSymbolItemsCheckable
originalSymbolsForFeature
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
renderFeatureWithSymbol
renderVertexMarker
renderVertexMarkerPolygon
renderVertexMarkerPolyline
rootRule
save
setLegendSymbolItem
startRender
stopRender
symbolForFeature return symbol for current feature.
symbols
symbolsForFeature
toSld
usedAttributes
willRenderFeature

Signals

Attributes

FeatDrawMarkers
FeatIsSelected
FeatDrawMarkers = 2
FeatIsSelected = 1
class FeatureFlags

Bases: int

class FeatureToRender(_f: QgsFeature, _flags: int)

Bases: sip.wrapper

QgsRuleBasedRenderer.FeatureToRender(QgsRuleBasedRenderer.FeatureToRender)

feat
flags
class RenderJob

Bases: sip.wrapper

Feature to render

ftr
symbol
class RenderLevel(z: int)

Bases: sip.wrapper

QgsRuleBasedRenderer.RenderLevel(other: QgsRuleBasedRenderer.RenderLevel)

jobs
zIndex
class Rule(symbol: QgsSymbol, maximumScale: int = 0, minimumScale: int = 0, filterExp: str = '', label: str = '', description: str = '', elseRule: bool = False)

Bases: sip.wrapper

Constructor takes ownership of the symbol

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.

Filtered = 0
Inactive = 1
class RenderResult

Bases: int

Rendered = 2
active(self) → bool

Returns if this rule is active

Returns:True if the rule is active
appendChild(self, rule: QgsRuleBasedRenderer.Rule)

add child rule, take ownership, sets this as parent

children(self) → object

Return all children rules of this rule

Returns:A list of rules
clone(self) → QgsRuleBasedRenderer.Rule

clone this rule, return new instance

collectZLevels(self) → object

get all used z-levels from this rule and children

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

Create a rule from an XML definition

Parameters:
  • ruleElem – The XML rule element
  • symbolMap – Symbol map
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.

dependsOnScale(self) → bool
descendants(self) → object

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

Returns:A list of descendant rules
description(self) → str

A human readable description for this rule

Returns:Description
dump(self, indent: int = 0) → str

Dump for debug purpose

Parameters:indent – How many characters to indent. Will increase by two with every of the recursive calls
Returns:A string representing this rule
filter(self) → QgsExpression

A filter that will check if this rule applies

Returns:An expression
filterExpression(self) → str

A filter that will check if this rule applies

Returns:An expression
findRuleByKey(self, key: str) → QgsRuleBasedRenderer.Rule

Try to find a rule given its unique key

New in version 2.6.

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

add child rule, take ownership, sets this as parent

isElse(self) → bool

Check if this rule is an ELSE rule

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:
  • f – The feature to test
  • context – The context in which the rendering happens
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.

Returns:If the rule will be evaluated at this scale
label(self) → str
legendKeysForFeature(self, feat: QgsFeature, context: QgsRenderContext = None) → Set[str]

Returns which legend keys match the feature

New in version 2.14.

legendSymbolItems(self, currentLevel: int = -1) → object

New in version 2.6.

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.

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.

needsGeometry(self) → bool

Returns true if this rule or one of its chilren needs the geometry to be applied.

parent(self) → QgsRuleBasedRenderer.Rule

The parent rule

Returns:Parent rule
removeChild(self, rule: QgsRuleBasedRenderer.Rule)

delete child rule

removeChildAt(self, i: int)

delete child rule

renderFeature(self, featToRender: QgsRuleBasedRenderer.FeatureToRender, context: QgsRenderContext, renderQueue: object) → QgsRuleBasedRenderer.Rule.RenderResult

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

Parameters:
  • featToRender – The feature to render
  • context – The rendering context
  • renderQueue – The rendering queue to which the feature should be added
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.

rulesForFeature(self, feat: QgsFeature, context: QgsRenderContext = None, onlyActive: bool = True) → object

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

Parameters:
  • feat – The feature for which rules have to be find
  • context – The rendering context
  • onlyActive – True to search for active rules only, false otherwise
save(self, doc: QDomDocument, symbolMap: object) → QDomElement
setActive(self, state: bool)

Sets if this rule is active

Parameters:state – Determines if the rule should be activated or deactivated
setDescription(self, description: str)

Set a human readable description for this rule

Parameters:description – Description
setFilterExpression(self, filterExp: str)

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

Parameters:filterExp – An expression
setIsElse(self, iselse: bool)

Sets if this rule is an ELSE rule

Parameters:iselse – If true, this rule is an ELSE rule
setLabel(self, 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()

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()

setRuleKey(self, key: str)

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

New in version 2.6.

setSymbol(self, sym: QgsSymbol)

set a new symbol (or NULL). Deletes old symbol.

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

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

stopRender(self, context: QgsRenderContext)

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

Parameters:context – The rendering context
symbol(self) → QgsSymbol
symbols(self, context: QgsRenderContext = QgsRenderContext()) → object

Note

available in Python bindings as symbol2

symbolsForFeature(self, feat: QgsFeature, context: QgsRenderContext = None) → object

tell which symbols will be used to render the feature

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

take child rule out, set parent as null

takeChildAt(self, i: int) → QgsRuleBasedRenderer.Rule

take child rule out, set parent as null

toSld(self, doc: QDomDocument, element: QDomElement, props: Dict[str, str])
usedAttributes(self, context: QgsRenderContext) → Set[str]

Return the attributes used to evaluate the expression of this rule

Returns:A set of attribute names
willRenderFeature(self, feat: QgsFeature, context: QgsRenderContext = None) → bool

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

capabilities(self) → QgsFeatureRenderer.Capabilities
checkLegendSymbolItem(self, key: str, state: bool = True)
clone(self) → QgsRuleBasedRenderer
convertFromRenderer(renderer: QgsFeatureRenderer) → QgsRuleBasedRenderer

creates a QgsRuleBasedRenderer from an existing renderer.

Returns:a new renderer if the conversion was possible, otherwise 0.

New in version 2.5.

convertSymbolRotation()
convertSymbolSizeScale()
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

copyRendererData()
create(element: QDomElement, context: QgsReadWriteContext) → QgsFeatureRenderer

Creates a new rule-based renderer instance from XML

createFromSld(element: QDomElement, geomType: QgsWkbTypes.GeometryType) → QgsFeatureRenderer
dump(self) → str
filter(self, fields: QgsFields = QgsFields()) → str
filterNeedsGeometry(self) → bool
legendKeysForFeature(self, feature: QgsFeature, context: QgsRenderContext) → Set[str]
legendSymbolItemChecked(self, key: str) → bool
legendSymbolItems(self) → object
legendSymbolItemsCheckable(self) → bool
originalSymbolsForFeature(self, feat: QgsFeature, context: QgsRenderContext) → object
refineRuleCategories(initialRule: QgsRuleBasedRenderer.Rule, r: QgsCategorizedSymbolRenderer)

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

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

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

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

renderFeature(self, feature: QgsFeature, context: QgsRenderContext, layer: int = -1, selected: bool = False, drawVertexMarker: bool = False) → bool
renderFeatureWithSymbol()
renderVertexMarker()
renderVertexMarkerPolygon()
renderVertexMarkerPolyline()
rootRule(self) → QgsRuleBasedRenderer.Rule
save(self, doc: QDomDocument, context: QgsReadWriteContext) → QDomElement
setLegendSymbolItem(self, key: str, symbol: QgsSymbol)
startRender(self, context: QgsRenderContext, fields: QgsFields)
stopRender(self, context: QgsRenderContext)
symbolForFeature(self, feature: QgsFeature, context: QgsRenderContext) → QgsSymbol

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

symbols(self, context: QgsRenderContext) → object
symbolsForFeature(self, feat: QgsFeature, context: QgsRenderContext) → object
toSld(self, doc: QDomDocument, element: QDomElement, props: Dict[str, str] = {})
usedAttributes(self, context: QgsRenderContext) → Set[str]
willRenderFeature(self, feat: QgsFeature, context: QgsRenderContext) → bool