tt::detail::observable_base< T > Class Template Reference

#include <TTauri/Foundation/detail/observable_base.hpp>

Inheritance diagram for tt::detail::observable_base< T >:

Public Types
using	callback_type = std::function<void(T const &)>
using	time_point = typename hires_utc_clock::time_point
using	duration = typename hires_utc_clock::duration

Public Member Functions
	observable_base (observable_base const &)=delete
	observable_base (observable_base &&)=delete
observable_base &	operator= (observable_base const &)=delete
observable_base &	operator= (observable_base &&)=delete
	observable_base () noexcept
	Constructor.
T	previous_value () const noexcept
	Get the previous value.
time_point	time_when_last_modified () const noexcept
	Time when the value was modified last.
duration	duration_since_last_modified () const noexcept
	Duration since the value was last modified.
float	animation_progress (duration animation_duration) const noexcept
	The relative time since the start of the animation.
virtual T	load () const noexcept=0
	Get the current value.
T	load (duration animation_duration) const noexcept
	Get the current value animated over the animation_duration.
virtual bool	store (T const &new_value) noexcept=0
	Set the value.
size_t	add_callback (callback_type callback) noexcept
	Add a callback as a listener.
void	remove_callback (size_t id) noexcept
	Remove a callback.

Detailed Description

template<typename T>
class tt::detail::observable_base< T >

Observable abstract base class.

Objects of the observable_base class will notify listeners through callbacks of changes of its value.

This class does not hold the value itself, concrete subclasses will either hold the value or calculate the value on demand. In many cases concrete subclasses may be sub-expressions of other observable objects.

This object will also track the time when the value was last modified so that the value can be animated. Usefull when displaying the value as an animated graphic element. For calculating inbetween values it will keep track of the previous value.

Constructor & Destructor Documentation

observable_base()

template<typename T >

tt::detail::observable_base< T >::observable_base ( )

inlinenoexcept

Constructor.

Member Function Documentation

add_callback()

template<typename T >

size_t tt::detail::observable_base< T >::add_callback ( callback_type callback )

inlinenoexcept

Add a callback as a listener.

Parameters

callback

The callback to register, the new value is passed as the first argument.

Returns

The id of the callback, used to unregister the callback.

animation_progress()

template<typename T >

float tt::detail::observable_base< T >::animation_progress ( duration animation_duration ) const

inlinenoexcept

The relative time since the start of the animation.

The relative time since the start of the animation according to the duration of the animation.

Parameters

A	relative value between 0.0 and 1.0.

duration_since_last_modified()

template<typename T >

duration tt::detail::observable_base< T >::duration_since_last_modified ( ) const

inlinenoexcept

Duration since the value was last modified.

load() [1/2]

template<typename T >

virtual T tt::detail::observable_base< T >::load ( ) const

pure virtualnoexcept

Get the current value.

The value is often calculated directly from the cached values retrieved from notifications down the chain.

Implemented in tt::detail::observable_cast< T, OT >, tt::detail::observable_not< OT >, tt::detail::observable_value< T >, and tt::detail::observable_cast< std::string, tt::format10 >.

load() [2/2]

template<typename T >

T tt::detail::observable_base< T >::load ( duration animation_duration ) const

inlinenoexcept

Get the current value animated over the animation_duration.

previous_value()

template<typename T >

T tt::detail::observable_base< T >::previous_value ( ) const

inlinenoexcept

Get the previous value.

remove_callback()

template<typename T >

void tt::detail::observable_base< T >::remove_callback ( size_t id )

inlinenoexcept

Remove a callback.

Parameters

id	The id of the callback returned by the add_callback() method.

store()

template<typename T >

virtual bool tt::detail::observable_base< T >::store ( T const & new_value )

pure virtualnoexcept

Set the value.

The value is often not directly stored, but instead forwarded up the chain of observables. And then let the notifications flowing backward updated the cached values so that loads() will be quick.

Parameters

new_value

The new value

Returns

true if the value was different from before.

Implemented in tt::detail::observable_cast< T, OT >, and tt::detail::observable_value< T >.

time_when_last_modified()

template<typename T >

time_point tt::detail::observable_base< T >::time_when_last_modified ( ) const

inlinenoexcept

Time when the value was modified last.

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

• hikogui/src/TTauri/Foundation/detail/observable_base.hpp