MainLoopScheduler implements the Kanzi application main loop in form of a customizable sequence of stages, each consisting of a sequence of tasks, where a task is any callable, including functions, function objects, and lambdas. More...

#include <kanzi/core.ui/main_loop/main_loop_scheduler.hpp>

Classes
struct	TaskInfo
	TaskInfo is a structure containing information related to a task. More...

Public Types
Enumerations.
enum	TaskRecurrence { TaskRecurrence::Recurring, TaskRecurrence::OneTime }
	Enumeration for task recurrence options. More...

enum	TimerRecurrence { TimerRecurrence::Recurring, TimerRecurrence::OneTime }
	Enumeration for timer recurrence options. More...

Public types and aliases.
using	Task = function< void(chrono::nanoseconds)>
	Type alias for stage tasks. More...

using	TimerTask = function< void(chrono::nanoseconds, unsigned int)>
	Type alias for timer tasks. More...

using	Precondition = function< bool(void)>
	Type alias for stage precondition callbacks. More...

using	Callback = function< void(void)>
	Type alias for general callbacks. More...

using	OnSuspendCallback = function< optional< chrono::nanoseconds >(chrono::nanoseconds)>
	Type alias for on-suspension callbacks. More...

using	StageSequenceContainer = stable_vector< Stage * >
	Type alias for container of the execution sequence of the stages. More...

using	TaskInfoContainer = vector< TaskInfo >
	Alias for the vector of TaskInfo instances. More...

Public Member Functions
MainLoopTimerToken	appendTimer (const Stage &stage, FixedString name, TimerRecurrence recurrence, chrono::nanoseconds interval, TimerTask task)
	Adds a timer task to be executed after a stage in the main loop. More...

MainLoopTimerToken	appendTimer (const Stage &stage, MetadataGeneratedName name, TimerRecurrence recurrence, chrono::nanoseconds interval, TimerTask task)
	Adds a timer task to be executed after a stage in the main loop. More...

MainLoopTimerToken	prependTimer (const Stage &stage, FixedString name, TimerRecurrence recurrence, chrono::nanoseconds interval, TimerTask task)
	/name Timer. More...

MainLoopTimerToken	prependTimer (const Stage &stage, MetadataGeneratedName name, TimerRecurrence recurrence, chrono::nanoseconds interval, TimerTask task)
	Adds a timer task to be executed before a stage in the main loop. More...

bool	removeTimer (const MainLoopTimerToken &token)
	Removes a timer task from the main loop. More...

Constructors and destructor.
	MainLoopScheduler ()
	Constructor. More...

	~MainLoopScheduler ()
	Destructor. More...

	MainLoopScheduler (const MainLoopScheduler &)=delete

MainLoopScheduler &	operator= (const MainLoopScheduler &)=delete

	MainLoopScheduler (MainLoopScheduler &&)=delete

MainLoopScheduler &	operator= (MainLoopScheduler &&)=delete

Main loop entry points.
void	loopMain ()
	Executes the whole application main loop, along with automatic suspension and frame rate control. More...

void	loopRunning ()
	Executes the Running part of the main loop, along with automatic suspension and frame rate control. More...

bool	run ()
	Executes a single iteration of the main loop in the Running state, with elapsed duration observed using the internal clock. More...

void	loopPaused ()
	Executes the Paused part of the main loop. More...

void	suspend ()
	Puts the application thread into revocable suspension for the duration determined by the frame limit and callback set with setOnSuspendCallback(). More...

void	yield ()
	Puts the application thread into irrevocable suspension till the next frame border. More...

void	executeStage (const Stage &stage)
	Executes all tasks mapped to a stage of the main loop. More...

State control.
void	pause ()
	Pauses the main loop and changes its state to Paused. More...

void	resume ()
	Resumes the main loop and changes its state back to Running. More...

void	quit ()
	Quits the main loop and changes its state to Quitting. More...

MainLoopState	getState () const
	Gets the main loop scheduler state. More...

void	setCurrentFrameRendered ()
	Sets whether rendering was performed in the current frame. More...

bool	isCurrentFrameRendered () const
	Returns whether rendering was performed in the current frame. More...

Stage control.
void	setStageSequence (StageSequenceContainer stageSequence)
	Sets the sequence of execution of the main loop stages. More...

Task control.
MainLoopTaskToken	prependTask (const Stage &stage, FixedString name, TaskRecurrence recurrence, Task task)
	Adds a task to the front of a stage. More...

MainLoopTaskToken	prependTask (const Stage &stage, MetadataGeneratedName name, TaskRecurrence recurrence, Task task)
	Adds a task to the front of a stage. More...

MainLoopTaskToken	appendTask (const Stage &stage, FixedString name, TaskRecurrence recurrence, Task task)
	Adds a task to the back of a stage. More...

MainLoopTaskToken	appendTask (const Stage &stage, MetadataGeneratedName name, TaskRecurrence recurrence, Task task)
	Adds a task to the back of a stage. More...

bool	removeTask (const Stage &stage, const MainLoopTaskToken &token)
	Removes a task from a stage. More...

bool	replaceTask (const Stage &stage, const MainLoopTaskToken &token, Task task)
	Replaces a task in a stage with another one. More...

void	clearTasks (const Stage &stage)
	Removes all tasks in a stage. More...

TaskInfoContainer	getTaskInfo (const Stage &stage) const
	Returns a container with information about all tasks in a stage. More...

Task	getTask (const Stage &stage, const MainLoopTaskToken &token) const
	Return a task in a stage with given token. More...

Callbacks.
/}
void	setPrecondition (const Stage &stage, Precondition precondition)
	Sets a precondition for a stage. More...

void	setOnSuspendCallback (OnSuspendCallback callback)
	Sets the OnSuspend callback. More...

void	setOnPauseCallback (Callback callback)
	Sets the OnPause callback. More...

void	setResumeCheckCallback (Callback callback)
	Sets the ResumeCheck callback. More...

void	setOnResumeCallback (Callback callback)
	Sets the OnResume callback. More...

Event handle setters.
void	setTaskDispatcherEventHandle (NativeEventHandle nativeHandle)
	Sets the native event handle that is used in waiting for the task dispatcher. More...

void	setInputEventHandle (NativeEventHandle nativeHandle)
	Sets the native event handle that is used in waiting for user input. More...

Configurations.
void	setFrameRateLimit (optional< unsigned int > frameRate)
	Sets the frame rate limit of the application. More...

void	enableSuspendWhenIdle (bool suspendEnabled)
	Sets whether an application allows suspension. More...

bool	isSuspendWhenIdleEnabled () const
	Returns whether an application allows suspension. More...

bool	needsPolling () const
	Returns whether an event source needs polling. More...

Timing.
void	resetClock ()
	Resets all internal timestamps of MainLoopScheduler. More...

void	advanceFrame ()
	Advances the frame counter, and records last frame duration based on internal clock. More...

chrono::nanoseconds	getLastFrameDuration () const
	Returns the duration of the last frame: the amount of time that passed between the start of the previous frame and the start of the current frame. More...

optional< chrono::nanoseconds >	getSuspendDuration () const
	Suggests the duration of suspension based on configured frame limit, callback set with setOnSuspendCallback(), and the time elapsed since the start of frame based on the internal clock. More...

chrono::nanoseconds	getYieldDuration () const
	Suggests the yield duration, which is the remaining frame allotment, based on the frame limit and time elapsed since the start of frame as per the internal clock. More...

optional< chrono::nanoseconds >	getDurationUntilNextTimer () const
	Returns the time until the next timer task executes, based on internal clock. More...

void	setClockCallback (function< TimePoint()> callback)
	Sets the implementation of the time source. More...

Profiling.
void	initializeProfilerSampleBuffer (optional< size_t > sampleBufferSize)
	Initializes the sample buffer of main loop profiler. More...

MainLoopProfilerSharedPtr	getProfiler ()
	Gets the main loop profiler. More...

uint64_t	getFrameNumber ()
	Gets the current frame number in the main loop. More...

Detailed Description

MainLoopScheduler implements the Kanzi application main loop in form of a customizable sequence of stages, each consisting of a sequence of tasks, where a task is any callable, including functions, function objects, and lambdas.

It also provides the default Kanzi stages, along with platform specific mechanisms for automatic suspension, and frame rate control.

Application class owns an instance of MainLoopScheduler, and fills it with stage sequence and tasks. For more details, see the implementation of Application::initializeMainLoopTasks().

You can customize the application main loop by extending its stages with additional tasks, replacing existing tasks with your own implementations, or adding timer tasks to execute some functionality at regular intervals.

Examples

To modify contents of a stage:

    // You can add a task to the back of a stage, so that it is last in the sequence.
    // When you use this interface in the context of a task, and you add a task ahead
    // in the sequence of the executing stage, Kanzi executes that task in the same main loop iteration.
    // When you add a task, you must set the recurrence for that task.
    // For example, when you set the task to be a one-time task, Kanzi executes it once and then discards it.
    scheduler.appendTask(RenderStage,
                         kzMakeFixedString("PostRender"),
                         MainLoopScheduler::TaskRecurrence::OneTime,
                         [](chrono::nanoseconds lastFrameDuration) {
                             doSomething(lastFrameDuration);
                         });
    // You can add a task to the front of a stage, so that it is the first in the sequence.
    // All interfaces that add tasks to a stage return tokens. You can use these tokens to access
    // and modify the existing tasks in a stage.
    // When you set a task to Recurring, Kanzi executes it on every iteration of respective stage,
    // until you explicitly remove that task.
    MainLoopTaskToken tokenPreRender = scheduler.prependTask(RenderStage,
                                                             kzMakeFixedString("PreRender"),
                                                             MainLoopScheduler::TaskRecurrence::Recurring,
                                                             [](chrono::nanoseconds lastFrameDuration) {
                                                                 doSomething(lastFrameDuration);
                                                             });
    // You can replace a task using its token.
    scheduler.replaceTask(RenderStage,
                          tokenPreRender,
                          [](chrono::nanoseconds lastFrameDuration) {
                              doSomething(lastFrameDuration);
                          });
    // You can remove a task from its stage using its token.
    scheduler.removeTask(RenderStage,
                         tokenPreRender);
    // Clear an entire stage. For example, clear the stage when you want to implement
    // the entire stage in your own way.
    scheduler.clearTasks(RenderStage);

To observe contents of a stage:

    // You can observe the contents of a stage, including task names, recurrence, and tokens.
    // You can use this for debugging purposes.
    // You can also use the tokens retrieved in this way to remove or replace specific tasks.
    auto tasks = scheduler.getTaskInfo(RenderStage);
    for (const auto& task : tasks)
    {
        doSomething(task.name, task.recurrence, task.token);
    }

To add and remove a timer task:

    // When you want Kanzi to execute a task at regular time intervals, you can add that task as a timer before or after a stage of the main loop.
    // Use timer recurrence options to execute a timer only once or repeatedly.
    // When a recurring timer elapses multiple times in a single iteration of the main loop, Kanzi executes that timer only once.
    // Timer callback receives as arguments elapsed duration rounded down to a multiple of the interval of the timer and number of elapsed intervals.
    MainLoopTimerToken timerToken = scheduler.appendTimer(UserStage,
                                                          kzMakeFixedString("MyTimer"),
                                                          MainLoopScheduler::TimerRecurrence::Recurring,
                                                          chrono::seconds(1),
                                                          [](chrono::nanoseconds elapsedDuration, unsigned int repeatCount) {
                                                              doSomethingRepeatedly(elapsedDuration, repeatCount);
                                                          });
    // You can remove existing timers by using their token.
    scheduler.removeTimer(timerToken);

Member Typedef Documentation

using kanzi::MainLoopScheduler::Task = function<void(chrono::nanoseconds)>

Type alias for stage tasks.

Parameters

lastFrameDuration Time elapsed between start of last and current main loop iteration.

using kanzi::MainLoopScheduler::TimerTask = function<void(chrono::nanoseconds, unsigned int)>

Type alias for timer tasks.

Parameters

elapsedDuration	The time since the last invocation or creation, rounded down to a multiple of the interval of the timer.
repeatCount	The number of elapsed intervals since the last invocation.

using kanzi::MainLoopScheduler::Precondition = function<bool(void)>

Type alias for stage precondition callbacks.

Returns: A boolean value that Kanzi uses to control the execution of the respective stage. Kanzi executes a Stage only if the return from its precondition is true, or no precondition is attached.

using kanzi::MainLoopScheduler::Callback = function<void(void)>

Type alias for general callbacks.

using kanzi::MainLoopScheduler::OnSuspendCallback = function<optional<chrono::nanoseconds>(chrono::nanoseconds)>

Type alias for on-suspension callbacks.

Parameters

remainingFrameAllotment The time remaining in the frame based on the configured frame rate limit and elapsed time as per internal clock.

Returns: Duration of suspension. Nullopt implies indefinite suspension.

using kanzi::MainLoopScheduler::StageSequenceContainer = stable_vector<Stage*>

Type alias for container of the execution sequence of the stages.

using kanzi::MainLoopScheduler::TaskInfoContainer = vector<TaskInfo>

Alias for the vector of TaskInfo instances.

Member Enumeration Documentation

enum kanzi::MainLoopScheduler::TaskRecurrence

strong

Enumeration for task recurrence options.

Enumerator
Recurring	Kanzi executes the task every time it executes the stage that owns this task, until you remove this task.
OneTime	Kanzi executes the task once and then discards it.

enum kanzi::MainLoopScheduler::TimerRecurrence

strong

Enumeration for timer recurrence options.

Enumerator

Recurring

Kanzi executes the timer tasks periodically at specified intervals.

When a recurring timer elapses multiple times in a single iteration of the Kanzi main loop, Kanzi executes that timer only once, but provides the number of elapsed intervals through its callback interface.

OneTime

Kanzi executes the timer once in a main loop iteration where the specified time since their addition has elapsed.

Constructor & Destructor Documentation

kanzi::MainLoopScheduler::MainLoopScheduler ( )

explicit

Constructor.

kanzi::MainLoopScheduler::~MainLoopScheduler ( )

Destructor.

kanzi::MainLoopScheduler::MainLoopScheduler ( const MainLoopScheduler & )

delete

kanzi::MainLoopScheduler::MainLoopScheduler ( MainLoopScheduler && )

delete

Member Function Documentation

MainLoopScheduler& kanzi::MainLoopScheduler::operator= ( const MainLoopScheduler & )

delete

MainLoopScheduler& kanzi::MainLoopScheduler::operator= ( MainLoopScheduler && )

delete

void kanzi::MainLoopScheduler::loopMain ( )

Executes the whole application main loop, along with automatic suspension and frame rate control.

void kanzi::MainLoopScheduler::loopRunning ( )

Executes the Running part of the main loop, along with automatic suspension and frame rate control.

An application exits this function only when it is no longer in the Running state.

bool kanzi::MainLoopScheduler::run ( )

Executes a single iteration of the main loop in the Running state, with elapsed duration observed using the internal clock.

Returns: A boolean value that marks whether rendering was performed in the current frame. The main loop uses this to determine whether to perform suspension or yielding. You can set this with the MainLoopScheduler::setCurrentFrameRendered().

void kanzi::MainLoopScheduler::loopPaused ( )

Executes the Paused part of the main loop.

An application exits this function only when it is no longer in the Paused state.

void kanzi::MainLoopScheduler::suspend ( )

Puts the application thread into revocable suspension for the duration determined by the frame limit and callback set with setOnSuspendCallback().

Input events and task dispatcher signals can revoke this suspension before the duration expires.

void kanzi::MainLoopScheduler::yield ( )

Puts the application thread into irrevocable suspension till the next frame border.

void kanzi::MainLoopScheduler::executeStage ( const Stage & stage )

Executes all tasks mapped to a stage of the main loop.

Passes the duration of the last frame to each task.

Parameters

stage Stage to execute.

void kanzi::MainLoopScheduler::pause ( )

Pauses the main loop and changes its state to Paused.

void kanzi::MainLoopScheduler::resume ( )

Resumes the main loop and changes its state back to Running.

void kanzi::MainLoopScheduler::quit ( )

Quits the main loop and changes its state to Quitting.

MainLoopState kanzi::MainLoopScheduler::getState ( ) const

Gets the main loop scheduler state.

Returns: Current state of the main loop scheduler.

void kanzi::MainLoopScheduler::setCurrentFrameRendered ( )

Sets whether rendering was performed in the current frame.

Call this function from a task in the Render stage to inform the main loop that the task performed rendering. The main loop uses this as a precondition for executing the Present stage for a frame.

See also: MainLoopScheduler::setCurrentFrameRendered(), MainLoopScheduler::run().

bool kanzi::MainLoopScheduler::isCurrentFrameRendered ( ) const

Returns whether rendering was performed in the current frame.

The main loop uses this as a precondition for executing the Present stage for a frame.

See also: MainLoopScheduler::setCurrentFrameRendered(), MainLoopScheduler::run().

Returns: If rendering was performed in the current frame, true, otherwise false.

void kanzi::MainLoopScheduler::setStageSequence ( StageSequenceContainer stageSequence )

Sets the sequence of execution of the main loop stages.

Parameters

stageSequence Container of stage sequence.

MainLoopTaskToken kanzi::MainLoopScheduler::prependTask	(	const Stage &	stage,
		FixedString	name,
		TaskRecurrence	recurrence,
		Task	task
	)

Adds a task to the front of a stage.

Use this overload when you have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task. Must be a string literal.
recurrence	Recurrence choice for the task that you want to insert.
task	The task that you want to insert.

Returns: Token of the added task. You can use that token to remove or replace the task.

MainLoopTaskToken kanzi::MainLoopScheduler::prependTask	(	const Stage &	stage,
		MetadataGeneratedName	name,
		TaskRecurrence	recurrence,
		Task	task
	)

Adds a task to the front of a stage.

Use this overload when you do not have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task.
recurrence	Recurrence choice for the task that you want to insert.
task	The task that you want to insert.

Returns: Token of the added task. You can use that token to remove or replace the task.

MainLoopTaskToken kanzi::MainLoopScheduler::appendTask	(	const Stage &	stage,
		FixedString	name,
		TaskRecurrence	recurrence,
		Task	task
	)

Adds a task to the back of a stage.

Use this overload when you have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task. Must be a string literal.
recurrence	Recurrence choice for the task that you want to insert.
task	The task that you want to insert.

Returns: Token of the added task. You can use that token to remove or replace the task.

MainLoopTaskToken kanzi::MainLoopScheduler::appendTask	(	const Stage &	stage,
		MetadataGeneratedName	name,
		TaskRecurrence	recurrence,
		Task	task
	)

Adds a task to the back of a stage.

Use this overload when you do not have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task.
recurrence	Recurrence choice for the task that you want to insert.
task	The task that you want to insert.

Returns: Token of the added task. You can use that token to remove or replace the task.

bool kanzi::MainLoopScheduler::removeTask	(	const Stage &	stage,
		const MainLoopTaskToken &	token
	)

Removes a task from a stage.

Parameters

stage	Reference to the stage.
token	Token of the task.

Returns: If removal is successful, returns true. If the function cannot find the matching token, returns false.

bool kanzi::MainLoopScheduler::replaceTask	(	const Stage &	stage,
		const MainLoopTaskToken &	token,
		Task	task
	)

Replaces a task in a stage with another one.

Parameters

stage	Reference to the stage.
token	Token of the task.
task	The task with which to replace the current task.

Returns: If replacement is successful, returns true. If the function cannot find the matching token, returns false.

void kanzi::MainLoopScheduler::clearTasks ( const Stage & stage )

Removes all tasks in a stage.

Parameters

stage Reference to the stage.

TaskInfoContainer kanzi::MainLoopScheduler::getTaskInfo ( const Stage & stage ) const

Returns a container with information about all tasks in a stage.

Parameters

stage Reference to the stage.

Returns: Vector that contains the task information.

Task kanzi::MainLoopScheduler::getTask	(	const Stage &	stage,
		const MainLoopTaskToken &	token
	)		const

Return a task in a stage with given token.

Parameters

stage	Reference to the stage.
token	Token of the task.

Returns: If token is found, returns a copy of the task. If not found, returns invalid (default constructed) task.

MainLoopTimerToken kanzi::MainLoopScheduler::prependTimer	(	const Stage &	stage,
		FixedString	name,
		TimerRecurrence	recurrence,
		chrono::nanoseconds	interval,
		TimerTask	task
	)

/name Timer.

/{ Adds a timer task to be executed before a stage in the main loop. Use this overload when you have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task. Must be a string literal.
recurrence	Recurrence type of the task.
interval	The amount of time after which to execute the task.
task	The task.

Returns: Token of the added task. You can use this token to remove the task.

MainLoopTimerToken kanzi::MainLoopScheduler::prependTimer	(	const Stage &	stage,
		MetadataGeneratedName	name,
		TimerRecurrence	recurrence,
		chrono::nanoseconds	interval,
		TimerTask	task
	)

Adds a timer task to be executed before a stage in the main loop.

Use this overload when you do not have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task.
recurrence	Recurrence type of the task.
interval	The amount of time after which to execute the task.
task	The task.

Returns: Token of the added task. You can use this token to remove the task.

MainLoopTimerToken kanzi::MainLoopScheduler::appendTimer	(	const Stage &	stage,
		FixedString	name,
		TimerRecurrence	recurrence,
		chrono::nanoseconds	interval,
		TimerTask	task
	)

Adds a timer task to be executed after a stage in the main loop.

Use this overload when you have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task. Must be a string literal.
recurrence	Recurrence type of the task.
interval	The amount of time after which to execute the task.
task	The task.

Returns: Token of the added task. You can use this token to remove the task.

MainLoopTimerToken kanzi::MainLoopScheduler::appendTimer	(	const Stage &	stage,
		MetadataGeneratedName	name,
		TimerRecurrence	recurrence,
		chrono::nanoseconds	interval,
		TimerTask	task
	)

Adds a timer task to be executed after a stage in the main loop.

Use this overload when you do not have the task name available at compile time.

Parameters

stage	Reference to the stage.
name	Name for the task.
recurrence	Recurrence type of the task.
interval	The amount of time after which to execute the task.
task	The task.

Returns: Token of the added task. You can use this token to remove the task.

bool kanzi::MainLoopScheduler::removeTimer ( const MainLoopTimerToken & token )

Removes a timer task from the main loop.

Parameters

token Token of the task.

Returns: If removal is successful, returns true. If the function cannot find the matching token, returns false.

void kanzi::MainLoopScheduler::setPrecondition	(	const Stage &	stage,
		Precondition	precondition
	)

Sets a precondition for a stage.

Kanzi executes a Stage only if the return from its precondition is true, or no precondition is attached.

Parameters

stage	Reference to a stage.
precondition	Precondition for the stage.

void kanzi::MainLoopScheduler::setOnSuspendCallback ( OnSuspendCallback callback )

Sets the OnSuspend callback.

Kanzi executes this callback every time the main loop enters suspension, passing as argument the time remaining in frame, based on configured frame rate limit and elapsed time as per internal clock. The callback should return of the following:

Desired suspension duration in nanoseconds.
Nullopt for an indefinite suspend.
0 to cancel the suspend.
Parameters

callback The callback to use.

void kanzi::MainLoopScheduler::setOnPauseCallback ( Callback callback )

Sets the OnPause callback.

Kanzi executes this callback every time when the main loop enters the Paused state.

Parameters

callback The callback to use.

void kanzi::MainLoopScheduler::setResumeCheckCallback ( Callback callback )

Sets the ResumeCheck callback.

Kanzi executes this callback in every iteration of the Paused loop.

Parameters

callback The callback to use.

void kanzi::MainLoopScheduler::setOnResumeCallback ( Callback callback )

Sets the OnResume callback.

Kanzi executes this callback every time when the main loop exits the Paused state.

Parameters

callback The callback to use.

void kanzi::MainLoopScheduler::setTaskDispatcherEventHandle ( NativeEventHandle nativeHandle )

Sets the native event handle that is used in waiting for the task dispatcher.

Parameters

nativeHandle Native event handle bound to the task dispatcher.

void kanzi::MainLoopScheduler::setInputEventHandle ( NativeEventHandle nativeHandle )

Sets the native event handle that is used in waiting for user input.

Parameters

nativeHandle Native event handle bound to input.

void kanzi::MainLoopScheduler::setFrameRateLimit ( optional< unsigned int > frameRate )

Sets the frame rate limit of the application.

This sets an upper limit on the number of frames rendered by Kanzi every second.

Parameters

frameRate The number of frames to render every second. To disable frame rate limit, use nullopt or 0.

void kanzi::MainLoopScheduler::enableSuspendWhenIdle ( bool suspendEnabled )

Sets whether an application allows suspension.

Parameters

suspendEnabled If the application allows suspension, use true, otherwise false.

bool kanzi::MainLoopScheduler::isSuspendWhenIdleEnabled ( ) const

Returns whether an application allows suspension.

Returns: If the application allows suspension, true, otherwise false.

bool kanzi::MainLoopScheduler::needsPolling ( ) const

Returns whether an event source needs polling.

Polling is needed when an event source does not have the capability to abort suspension.

Returns: When at least one event source needs polling, true.

void kanzi::MainLoopScheduler::resetClock ( )

Resets all internal timestamps of MainLoopScheduler.

A platform backend typically calls this interface when it switches the application from another state to Running state.

void kanzi::MainLoopScheduler::advanceFrame ( )

Advances the frame counter, and records last frame duration based on internal clock.

Additionally, records difference between the observed last frame duration and frame allotment based on set frame rate limit, which is used to compensate the allotment of subsequent frames.

chrono::nanoseconds kanzi::MainLoopScheduler::getLastFrameDuration ( ) const

Returns the duration of the last frame: the amount of time that passed between the start of the previous frame and the start of the current frame.

Returns: The duration of the last frame in nanoseconds.

optional<chrono::nanoseconds> kanzi::MainLoopScheduler::getSuspendDuration ( ) const

Suggests the duration of suspension based on configured frame limit, callback set with setOnSuspendCallback(), and the time elapsed since the start of frame based on the internal clock.

Returns: The duration of suspension in nanoseconds. When the application is suspended indefinitely, returns nullopt.

chrono::nanoseconds kanzi::MainLoopScheduler::getYieldDuration ( ) const

Suggests the yield duration, which is the remaining frame allotment, based on the frame limit and time elapsed since the start of frame as per the internal clock.

Additionally, adjusts the result based on the differences between the observed frame durations and the desired frame allotment based on set frame rate limit.

Returns: The duration of yield in nanoseconds.

optional<chrono::nanoseconds> kanzi::MainLoopScheduler::getDurationUntilNextTimer ( ) const

Returns the time until the next timer task executes, based on internal clock.

Returns: optional<chrono::nanoseconds> Time until the next timer task executes. If no timers are active, returns nullopt.

void kanzi::MainLoopScheduler::setClockCallback ( function< TimePoint()> callback )

inline

Sets the implementation of the time source.

Use this when you need precise control of time in unit testing.

Parameters

callback Callback to execute when the current time is needed.

void kanzi::MainLoopScheduler::initializeProfilerSampleBuffer ( optional< size_t > sampleBufferSize )

Initializes the sample buffer of main loop profiler.

Only effective in profiling builds.

Parameters

sampleBufferSize Optional size of sample buffer. If nullopt, Kanzi uses KZ_PROFILING_MAIN_LOOP.

MainLoopProfilerSharedPtr kanzi::MainLoopScheduler::getProfiler ( )

Gets the main loop profiler.

Returns: The pointer to the main loop profiler.

uint64_t kanzi::MainLoopScheduler::getFrameNumber ( )

Gets the current frame number in the main loop.

Returns: Frame number.

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

kanzi/core.ui/main_loop/main_loop_scheduler.hpp

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