Class: QgsLayerTreeNode

class qgis.core.QgsLayerTreeNode(t: QgsLayerTreeNode.NodeType, checked: bool = True)

Bases: PyQt5.QtCore.QObject

Constructor

QgsLayerTreeNode(other: QgsLayerTreeNode)

This class is a base class for nodes in a layer tree. Layer tree is a hierarchical structure consisting of group and layer nodes: - group nodes are containers and may contain children (layer and group nodes) - layer nodes point to map layers, they do not contain further children

Layer trees may be used for organization of layers, typically a layer tree is exposed to the user using QgsLayerTreeView widget which shows the tree and allows manipulation with the tree.

Ownership of nodes: every node is owned by its parent. Therefore once node is added to a layer tree, it is the responsibility of the parent to delete it when the node is not needed anymore. Deletion of root node of a tree will delete all nodes of the tree.

Signals: signals are propagated from children to parent. That means it is sufficient to connect to root node in order to get signals about updates in the whole layer tree. When adding or removing a node that contains further children (i.e. a whole subtree), the addition/removal signals are emitted only for the root node of the subtree that is being added or removed.

Custom properties: Every node may have some custom properties assigned to it. This mechanism allows third parties store additional data with the nodes. The properties are used within QGIS code (whether to show layer in overview, whether the node is embedded from another project etc), but may be also used by third party plugins. Custom properties are stored also in the project file. The storage is not efficient for large amount of data.

Custom properties that have already been used within QGIS: - “loading” - whether the project is being currently loaded (root node only) - “overview” - whether to show a layer in overview - “showFeatureCount” - whether to show feature counts in layer tree (vector only) - “embedded” - whether the node comes from an external project - “embedded_project” - path to the external project (embedded root node only) - “legend/…” - properties for legend appearance customization - “expandedLegendNodes” - list of layer’s legend nodes’ rules in expanded state

See also

also()

New in version 2.4: Enums

Methods

checkedLayers Returns a list of any checked layers which belong to this node or its children.
childEvent
children Gets list of children of the node.
clone Create a copy of the node.
connectNotify
customEvent
customProperties Returns list of keys stored in custom properties
customProperty Read a custom property from layer.
disconnectNotify
dump Returns string with layer tree structure.
insertChildrenPrivate Low-level insertion of children to the node.
isExpanded Returns whether the node should be shown as expanded or collapsed in GUI
isItemVisibilityCheckedRecursive Returns whether this node is checked and all its children.
isItemVisibilityUncheckedRecursive Returns whether this node is unchecked and all its children.
isSignalConnected
isVisible Returns whether a node is really visible (ie checked and all its ancestors checked as well)
itemVisibilityChecked Returns whether a node is checked (independently of its ancestors or children)
name Returns name of the node
nodeType Find out about type of the node.
parent Gets pointer to the parent.
readCommonXml Read common XML elements.
readXml Read layer tree from XML.
receivers
removeChildrenPrivate Low-level removal of children from the node.
removeCustomProperty Remove a custom property from layer.
resolveReferences Turn textual references to layers into map layer object from project.
sender
senderSignalIndex
setCustomProperty Sets a custom property for the node.
setExpanded Sets whether the node should be shown as expanded or collapsed in GUI
setItemVisibilityChecked Check or uncheck a node (independently of its ancestors or children)
setItemVisibilityCheckedParentRecursive Check or uncheck a node and all its parents
setItemVisibilityCheckedRecursive Check or uncheck a node and all its children (taking into account exclusion rules)
setName Set name of the node.
takeChild Remove a child from a node
timerEvent
writeCommonXml Write common XML elements.
writeXml Write layer tree to XML

Signals

addedChildren Emitted when one or more nodes have been added to a node within the tree [signal]
customPropertyChanged Emitted when a custom property of a node within the tree has been changed or removed [signal]
expandedChanged Emitted when the collapsed/expanded state of a node within the tree has been changed [signal]
nameChanged Emitted when the name of the node is changed
removedChildren Emitted when one or more nodes has been removed from a node within the tree [signal]
visibilityChanged Emitted when check state of a node within the tree has been changed [signal]
willAddChildren Emitted when one or more nodes will be added to a node within the tree [signal]
willRemoveChildren Emitted when one or more nodes will be removed from a node within the tree [signal]

Attributes

NodeGroup
NodeLayer
NodeGroup = 0
NodeLayer = 1
class NodeType

Bases: int

addedChildren

Emitted when one or more nodes have been added to a node within the tree [signal]

checkedLayers(self) → List[QgsMapLayer]

Returns a list of any checked layers which belong to this node or its children.

New in version 3.0.

childEvent()
children(self) → List[QgsLayerTreeNode]

Gets list of children of the node. Children are owned by the parent

clone(self) → QgsLayerTreeNode

Create a copy of the node. Returns new instance

connectNotify()
customEvent()
customProperties(self) → List[str]

Returns list of keys stored in custom properties

customProperty(self, key: str, defaultValue: Any = None) → Any

Read a custom property from layer. Properties are stored in a map and saved in project file.

customPropertyChanged

Emitted when a custom property of a node within the tree has been changed or removed [signal]

disconnectNotify()
dump(self) → str

Returns string with layer tree structure. For debug purposes only

expandedChanged

Emitted when the collapsed/expanded state of a node within the tree has been changed [signal]

insertChildrenPrivate(self, index: int, nodes: Iterable[QgsLayerTreeNode])

Low-level insertion of children to the node. The children must not have any parent yet!

isExpanded(self) → bool

Returns whether the node should be shown as expanded or collapsed in GUI

isItemVisibilityCheckedRecursive(self) → bool

Returns whether this node is checked and all its children.

New in version 3.0.

isItemVisibilityUncheckedRecursive(self) → bool

Returns whether this node is unchecked and all its children.

New in version 3.0.

isSignalConnected()
isVisible(self) → bool

Returns whether a node is really visible (ie checked and all its ancestors checked as well)

New in version 3.0.

itemVisibilityChecked(self) → bool

Returns whether a node is checked (independently of its ancestors or children)

New in version 3.0.

name(self) → str

Returns name of the node

New in version 3.0.

nameChanged

Emitted when the name of the node is changed

New in version 3.0: [signal]

nodeType(self) → QgsLayerTreeNode.NodeType

Find out about type of the node. It is usually shorter to use convenience functions from QgsLayerTree namespace for that

parent(self) → QgsLayerTreeNode

Gets pointer to the parent. If parent is None, the node is a root node

readCommonXml(self, element: QDomElement)

Read common XML elements.

readXml(element: QDomElement, context: QgsReadWriteContext) → QgsLayerTreeNode

Read layer tree from XML. Returns new instance. Does not resolve textual references to layers. Call resolveReferences() afterwards to do it.

readXml(element: QDomElement, project: QgsProject) -> QgsLayerTreeNode Read layer tree from XML. Returns new instance. Also resolves textual references to layers from the project (calls resolveReferences() internally).

New in version 3.0.

receivers()
removeChildrenPrivate(self, from_: int, count: int, destroy: bool = True)

Low-level removal of children from the node.

removeCustomProperty(self, key: str)

Remove a custom property from layer. Properties are stored in a map and saved in project file.

removedChildren

Emitted when one or more nodes has been removed from a node within the tree [signal]

resolveReferences(self, project: QgsProject, looseMatching: bool = False)

Turn textual references to layers into map layer object from project. This method should be called after readXml() If looseMatching is True then a looser match will be used, where a layer will match if the name, public source, and data provider match. This can be used to match legend customization from different projects where layers will have different layer IDs.

New in version 3.0.

sender()
senderSignalIndex()
setCustomProperty(self, key: str, value: Any)

Sets a custom property for the node. Properties are stored in a map and saved in project file.

setExpanded(self, expanded: bool)

Sets whether the node should be shown as expanded or collapsed in GUI

setItemVisibilityChecked(self, checked: bool)

Check or uncheck a node (independently of its ancestors or children)

New in version 3.0.

setItemVisibilityCheckedParentRecursive(self, checked: bool)

Check or uncheck a node and all its parents

New in version 3.0.

setItemVisibilityCheckedRecursive(self, checked: bool)

Check or uncheck a node and all its children (taking into account exclusion rules)

New in version 3.0.

setName(self, name: str)

Set name of the node. Emits nameChanged signal.

New in version 3.0.

takeChild(self, node: QgsLayerTreeNode) → bool

Remove a child from a node

timerEvent()
visibilityChanged

Emitted when check state of a node within the tree has been changed [signal]

willAddChildren

Emitted when one or more nodes will be added to a node within the tree [signal]

willRemoveChildren

Emitted when one or more nodes will be removed from a node within the tree [signal]

writeCommonXml(self, element: QDomElement)

Write common XML elements.

writeXml(self, parentElement: QDomElement, context: QgsReadWriteContext)

Write layer tree to XML