This class is a base class for nodes in a layer tree. More...

#include <qgslayertreenode.h>

Inheritance diagram for QgsLayerTreeNode:

Public Types
enum	NodeType { NodeGroup, NodeLayer }
	Enumeration of possible tree node types. More...

Signals
void	willAddChildren (QgsLayerTreeNode *node, int indexFrom, int indexTo)
	Emitted when one or more nodes will be added to a node within the tree.
void	addedChildren (QgsLayerTreeNode *node, int indexFrom, int indexTo)
	Emitted when one or more nodes have been added to a node within the tree.
void	willRemoveChildren (QgsLayerTreeNode *node, int indexFrom, int indexTo)
	Emitted when one or more nodes will be removed from a node within the tree.
void	removedChildren (QgsLayerTreeNode *node, int indexFrom, int indexTo)
	Emitted when one or more nodes has been removed from a node within the tree.
void	visibilityChanged (QgsLayerTreeNode *node, Qt::CheckState state)
	Emitted when check state of a node within the tree has been changed.
void	customPropertyChanged (QgsLayerTreeNode *node, QString key)
	Emitted when a custom property of a node within the tree has been changed or removed.
void	expandedChanged (QgsLayerTreeNode *node, bool expanded)
	Emitted when the collapsed/expanded state of a node within the tree has been changed.

Public Member Functions
	~QgsLayerTreeNode ()
NodeType	nodeType ()
	Find out about type of the node. It is usually shorter to use convenience functions from QgsLayerTree namespace for that.
QgsLayerTreeNode *	parent ()
	Get pointer to the parent. If parent is a null pointer, the node is a root node.
QList< QgsLayerTreeNode * >	children ()
	Get list of children of the node. Children are owned by the parent.
virtual void	writeXML (QDomElement &parentElement)=0
	Write layer tree to XML.
virtual QString	dump () const =0
	Return string with layer tree structure. For debug purposes only.
virtual QgsLayerTreeNode *	clone () const =0
	Create a copy of the node. Returns new instance.
bool	isExpanded () const
	Return whether the node should be shown as expanded or collapsed in GUI.
void	setExpanded (bool expanded)
	Set whether the node should be shown as expanded or collapsed in GUI.
void	setCustomProperty (const QString &key, const QVariant &value)
	Set a custom property for the node.
QVariant	customProperty (const QString &key, const QVariant &defaultValue=QVariant()) const
	Read a custom property from layer.
void	removeCustomProperty (const QString &key)
	Remove a custom property from layer.
QStringList	customProperties () const
	Return list of keys stored in custom properties.

Static Public Member Functions
static QgsLayerTreeNode *	readXML (QDomElement &element)
	Read layer tree from XML. Returns new instance.

Protected Member Functions
	QgsLayerTreeNode (NodeType t)
	QgsLayerTreeNode (const QgsLayerTreeNode &other)
void	readCommonXML (QDomElement &element)
void	writeCommonXML (QDomElement &element)
void	insertChildrenPrivate (int index, QList< QgsLayerTreeNode * > nodes)
	Low-level insertion of children to the node. The children must not have any parent yet!
void	removeChildrenPrivate (int from, int count)
	Low-level removal of children from the node.

Protected Attributes
NodeType	mNodeType
	type of the node - determines which subclass is used
QgsLayerTreeNode *	mParent
	pointer to the parent node - null in case of root node
QList< QgsLayerTreeNode * >	mChildren
	list of children - node is responsible for their deletion
bool	mExpanded
	whether the node should be shown in GUI as expanded
QgsObjectCustomProperties	mProperties
	custom properties attached to the node

Detailed Description

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)

See Also: also QgsLayerTree, QgsLayerTreeLayer, QgsLayerTreeGroup

Note: added in 2.4

Member Enumeration Documentation

enum QgsLayerTreeNode::NodeType

Enumeration of possible tree node types.

Enumerator:

NodeGroup	container of other groups and layers
NodeLayer	leaf node pointing to a layer

Constructor & Destructor Documentation

QgsLayerTreeNode::~QgsLayerTreeNode ( )

QgsLayerTreeNode::QgsLayerTreeNode ( QgsLayerTreeNode::NodeType t )

protected

QgsLayerTreeNode::QgsLayerTreeNode ( const QgsLayerTreeNode & other )

protected

Member Function Documentation

void QgsLayerTreeNode::addedChildren	(	QgsLayerTreeNode *	node,
		int	indexFrom,
		int	indexTo
	)

signal

Emitted when one or more nodes have been added to a node within the tree.

QList<QgsLayerTreeNode*> QgsLayerTreeNode::children ( )

inline

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

virtual QgsLayerTreeNode* QgsLayerTreeNode::clone ( ) const

pure virtual

Create a copy of the node. Returns new instance.

Implemented in QgsLayerTreeGroup, and QgsLayerTreeLayer.

QStringList QgsLayerTreeNode::customProperties ( ) const

Return list of keys stored in custom properties.

QVariant QgsLayerTreeNode::customProperty	(	const QString &	key,
		const QVariant &	defaultValue = `QVariant()`
	)		const

Read a custom property from layer.

Properties are stored in a map and saved in project file.

void QgsLayerTreeNode::customPropertyChanged	(	QgsLayerTreeNode *	node,
		QString	key
	)

signal

Emitted when a custom property of a node within the tree has been changed or removed.

virtual QString QgsLayerTreeNode::dump ( ) const

pure virtual

Return string with layer tree structure. For debug purposes only.

Implemented in QgsLayerTreeGroup, and QgsLayerTreeLayer.

void QgsLayerTreeNode::expandedChanged	(	QgsLayerTreeNode *	node,
		bool	expanded
	)

signal

Emitted when the collapsed/expanded state of a node within the tree has been changed.

void QgsLayerTreeNode::insertChildrenPrivate	(	int	index,
		QList< QgsLayerTreeNode * >	nodes
	)

protected

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

bool QgsLayerTreeNode::isExpanded ( ) const

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

NodeType QgsLayerTreeNode::nodeType ( )

inline

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

QgsLayerTreeNode* QgsLayerTreeNode::parent ( )

inline

Get pointer to the parent. If parent is a null pointer, the node is a root node.

void QgsLayerTreeNode::readCommonXML ( QDomElement & element )

protected

QgsLayerTreeNode * QgsLayerTreeNode::readXML ( QDomElement & element )

static

Read layer tree from XML. Returns new instance.

Reimplemented in QgsLayerTreeGroup, and QgsLayerTreeLayer.

void QgsLayerTreeNode::removeChildrenPrivate	(	int	from,
		int	count
	)

protected

Low-level removal of children from the node.

void QgsLayerTreeNode::removeCustomProperty ( const QString & key )

Remove a custom property from layer.

Properties are stored in a map and saved in project file.

void QgsLayerTreeNode::removedChildren	(	QgsLayerTreeNode *	node,
		int	indexFrom,
		int	indexTo
	)

signal

Emitted when one or more nodes has been removed from a node within the tree.

void QgsLayerTreeNode::setCustomProperty	(	const QString &	key,
		const QVariant &	value
	)

Set a custom property for the node.

Properties are stored in a map and saved in project file.

void QgsLayerTreeNode::setExpanded ( bool expanded )

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

void QgsLayerTreeNode::visibilityChanged	(	QgsLayerTreeNode *	node,
		Qt::CheckState	state
	)

signal

Emitted when check state of a node within the tree has been changed.

void QgsLayerTreeNode::willAddChildren	(	QgsLayerTreeNode *	node,
		int	indexFrom,
		int	indexTo
	)

signal

Emitted when one or more nodes will be added to a node within the tree.

void QgsLayerTreeNode::willRemoveChildren	(	QgsLayerTreeNode *	node,
		int	indexFrom,
		int	indexTo
	)

signal

Emitted when one or more nodes will be removed from a node within the tree.

void QgsLayerTreeNode::writeCommonXML ( QDomElement & element )

protected

virtual void QgsLayerTreeNode::writeXML ( QDomElement & parentElement )

pure virtual

Write layer tree to XML.

Implemented in QgsLayerTreeGroup, and QgsLayerTreeLayer.

Member Data Documentation

QList<QgsLayerTreeNode*> QgsLayerTreeNode::mChildren

protected

list of children - node is responsible for their deletion

bool QgsLayerTreeNode::mExpanded

protected

whether the node should be shown in GUI as expanded

NodeType QgsLayerTreeNode::mNodeType

protected

type of the node - determines which subclass is used

QgsLayerTreeNode* QgsLayerTreeNode::mParent

protected

pointer to the parent node - null in case of root node

QgsObjectCustomProperties QgsLayerTreeNode::mProperties

protected

custom properties attached to the node

The documentation for this class was generated from the following files:

/tmp/buildd/qgis-2.6.0+wheezy1/src/core/layertree/qgslayertreenode.h
/tmp/buildd/qgis-2.6.0+wheezy1/src/core/layertree/qgslayertreenode.cpp

Public Types

Signals

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation