QHistoryState

The QHistoryState class provides a means of returning to a previously active substate. More…

New in version 4.6.

Synopsis

Functions

• def defaultState ()

• def defaultTransition ()

• def historyType ()

• def setDefaultState (state)

• def setDefaultTransition (transition)

• def setHistoryType (type)

Detailed Description

A history state is a pseudo-state that represents the child state that the parent state was in the last time the parent state was exited. A transition with a history state as its target is in fact a transition to one or more other child states of the parent state. QHistoryState is part of The State Machine Framework .

Use the setDefaultState() function to set the state that should be entered if the parent state has never been entered. Example:

machine = QStateMachine()

s1 = QState()
s11 = QState(s1)
s12 = QState(s1)

s1h = QHistoryState(s1)
s1h.setDefaultState(s11)

machine.addState(s1)

s2 = QState()
machine.addState(s2)

button = QPushButton()
# Clicking the button will cause the state machine to enter the child state
# that s1 was in the last time s1 was exited, or the history state's default
# state if s1 has never been entered.
s1.addTransition(button.clicked, s1h)

If more than one default state has to be entered, or if the transition to the default state(s) has to be acted upon, the defaultTransition should be set instead. Note that the eventTest() method of that transition will never be called: the selection and execution of the transition is done automatically when entering the history state.

By default a history state is shallow, meaning that it won’t remember nested states. This can be configured through the historyType property.

class PySide2.QtCore.QHistoryState(type[, parent=None])

PySide2.QtCore.QHistoryState([parent=None])

param type:

HistoryType

param parent:

PySide2.QtCore.QState

Constructs a new history state of the given type , with the given parent state.

Constructs a new shallow history state with the given parent state.

PySide2.QtCore.QHistoryState.HistoryType

This enum specifies the type of history that a QHistoryState records.

Constant	Description
QHistoryState.ShallowHistory	Only the immediate child states of the parent state are recorded. In this case a transition with the history state as its target will end up in the immediate child state that the parent was in the last time it was exited. This is the default.
QHistoryState.DeepHistory	Nested states are recorded. In this case a transition with the history state as its target will end up in the most deeply nested descendant state the parent was in the last time it was exited.

PySide2.QtCore.QHistoryState.defaultState()

Return type:

PySide2.QtCore.QAbstractState

This property holds the default state of this history state.

PySide2.QtCore.QHistoryState.defaultTransition()

Return type:

PySide2.QtCore.QAbstractTransition

This property holds the default transition of this history state.

PySide2.QtCore.QHistoryState.historyType()

Return type:

HistoryType

This property holds the type of history that this history state records.

The default value of this property is ShallowHistory .

PySide2.QtCore.QHistoryState.setDefaultState(state)

Parameters:

state – PySide2.QtCore.QAbstractState

This property holds the default state of this history state.

PySide2.QtCore.QHistoryState.setDefaultTransition(transition)

Parameters:

transition – PySide2.QtCore.QAbstractTransition

This property holds the default transition of this history state.

PySide2.QtCore.QHistoryState.setHistoryType(type)

Parameters:

type – HistoryType

This property holds the type of history that this history state records.

The default value of this property is ShallowHistory .