TreeNode - (internal) class to manage the display state of tree nodes in TreeWidgets
TreeNode
instances manage the display
state of nodes in trees displayed by a
TreeWidget.
Their use is primarily internal.
However, they expose a small set of useful methods
to control the display of subtrees.
When a NodeData
instance is mapped (i.e. displayed), its
_treenode
attribute contains a reference
to the associated TreeNode
instance.
This allows e.g. (modifying) NodeData
actions
to call for an update of its subtree.
TreeNode
's parent
or None
, if it is the root.
expand=-1
expands the complete subtree.