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QgsLayerTreeNode Class Referenceabstract

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

#include <qgslayertreenode.h>

Inheritance diagram for QgsLayerTreeNode:
Inheritance graph
[legend]

Public Types

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

Signals

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

Public Member Functions

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

Static Public Member Functions

static QgsLayerTreeNodereadXML (QDomElement &element)
 Read layer tree from XML. Returns new instance. More...
 

Protected Member Functions

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

Protected Attributes

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

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:

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:

See also
also QgsLayerTree, QgsLayerTreeLayer, QgsLayerTreeGroup
Note
added in 2.4

Definition at line 63 of file qgslayertreenode.h.

Member Enumeration Documentation

Enumeration of possible tree node types.

Enumerator
NodeGroup 

container of other groups and layers

NodeLayer 

leaf node pointing to a layer

Definition at line 69 of file qgslayertreenode.h.

Constructor & Destructor Documentation

QgsLayerTreeNode::~QgsLayerTreeNode ( )

Definition at line 45 of file qgslayertreenode.cpp.

QgsLayerTreeNode::QgsLayerTreeNode ( QgsLayerTreeNode::NodeType  t)
protected

Definition at line 25 of file qgslayertreenode.cpp.

QgsLayerTreeNode::QgsLayerTreeNode ( const QgsLayerTreeNode other)
protected

Definition at line 32 of file qgslayertreenode.cpp.

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.

Definition at line 82 of file qgslayertreenode.h.

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.

Definition at line 95 of file qgslayertreenode.cpp.

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.

Definition at line 84 of file qgslayertreenode.cpp.

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!

Definition at line 111 of file qgslayertreenode.cpp.

bool QgsLayerTreeNode::isExpanded ( ) const

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

Definition at line 62 of file qgslayertreenode.cpp.

NodeType QgsLayerTreeNode::nodeType ( )
inline

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

Definition at line 78 of file qgslayertreenode.h.

QgsLayerTreeNode* QgsLayerTreeNode::parent ( )
inline

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

Definition at line 80 of file qgslayertreenode.h.

void QgsLayerTreeNode::readCommonXML ( QDomElement &  element)
protected

Definition at line 100 of file qgslayertreenode.cpp.

QgsLayerTreeNode * QgsLayerTreeNode::readXML ( QDomElement &  element)
static

Read layer tree from XML. Returns new instance.

Definition at line 50 of file qgslayertreenode.cpp.

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

Low-level removal of children from the node.

Definition at line 143 of file qgslayertreenode.cpp.

void QgsLayerTreeNode::removeCustomProperty ( const QString &  key)

Remove a custom property from layer.

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

Definition at line 89 of file qgslayertreenode.cpp.

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.

Definition at line 78 of file qgslayertreenode.cpp.

void QgsLayerTreeNode::setExpanded ( bool  expanded)

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

Definition at line 68 of file qgslayertreenode.cpp.

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

Definition at line 105 of file qgslayertreenode.cpp.

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

Definition at line 148 of file qgslayertreenode.h.

bool QgsLayerTreeNode::mExpanded
protected

whether the node should be shown in GUI as expanded

Definition at line 150 of file qgslayertreenode.h.

NodeType QgsLayerTreeNode::mNodeType
protected

type of the node - determines which subclass is used

Definition at line 144 of file qgslayertreenode.h.

QgsLayerTreeNode* QgsLayerTreeNode::mParent
protected

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

Definition at line 146 of file qgslayertreenode.h.

QgsObjectCustomProperties QgsLayerTreeNode::mProperties
protected

custom properties attached to the node

Definition at line 152 of file qgslayertreenode.h.


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