#------------------------------------------------------------------------------
# Copyright (c) 2012, Enthought, Inc.
# All rights reserved.
#------------------------------------------------------------------------------
from traits.api import Dict, Int, Property, cached_property
from .constraints_widget import ConstraintsWidget
from .stack_item import StackItem
[docs]class Stack(ConstraintsWidget):
""" A component which displays its children as a stack of widgets,
only one of which is visible at a time.
"""
#: The index of the visible widget in the stack. The widget itself
#: does not provide a means to changing this index. That control
#: must be supplied externally. If the given index falls outside of
#: the range of stack items, no widget will be visible.
index = Int(0)
#: The transition to use when change between stack items.
#: XXX Document the supported transitions.
transition = Dict
#: A read only property which returns the stack's StackItems
stack_items = Property(depends_on='children')
#--------------------------------------------------------------------------
# Initialization
#--------------------------------------------------------------------------
[docs] def snapshot(self):
""" Returns the snapshot for the control.
"""
snap = super(Stack, self).snapshot()
snap['index'] = self.index
snap['transition'] = self.transition
return snap
[docs] def bind(self):
""" Bind the change handlers for the control.
"""
super(Stack, self).bind()
self.publish_attributes('index', 'transition')
#--------------------------------------------------------------------------
# Message Handling
#--------------------------------------------------------------------------
[docs] def on_action_index_changed(self, content):
""" Handle the `index_changed` action from the client widget.
"""
with self.loopback_guard('index'):
self.index = content['index']
#--------------------------------------------------------------------------
# Private API
#--------------------------------------------------------------------------
@cached_property
def _get_stack_items(self):
""" The getter for the 'stack_items' property.
Returns
-------
result : tuple
The tuple of StackItem instances defined as children of
this Stack.
"""
isinst = isinstance
items = (child for child in self.children if isinst(child, StackItem))
return tuple(items)