gtkmm  4.8.0
Public Types | Public Member Functions | Static Public Member Functions | Related Functions | List of all members
Gdk::FrameClock Class Reference

Synchronizes painting to a surface. More...

#include <gdkmm/frameclock.h>

Inherits Glib::Object.

Public Types

enum class  Phase {
  NONE = 0x0 ,
  FLUSH_EVENTS = 1 << 0 ,
  BEFORE_PAINT = 1 << 1 ,
  UPDATE = 1 << 2 ,
  LAYOUT = 1 << 3 ,
  PAINT = 1 << 4 ,
  RESUME_EVENTS = 1 << 5 ,
  AFTER_PAINT = 1 << 6
}
 Used to represent the different paint clock phases that can be requested. More...
 

Public Member Functions

 FrameClock (FrameClock && src) noexcept
 
FrameClockoperator= (FrameClock && src) noexcept
 
 ~FrameClock () noexcept override
 
GdkFrameClock * gobj ()
 Provides access to the underlying C GObject. More...
 
const GdkFrameClock * gobj () const
 Provides access to the underlying C GObject. More...
 
GdkFrameClock * gobj_copy ()
 Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs. More...
 
gint64 get_frame_time () const
 Gets the time that should currently be used for animations. More...
 
void request_phase (Phase phase)
 Asks the frame clock to run a particular phase. More...
 
void begin_updating ()
 Starts updates for an animation. More...
 
void end_updating ()
 Stops updates for an animation. More...
 
gint64 get_frame_counter () const
 Gdk::FrameClock maintains a 64-bit counter that increments for each frame drawn. More...
 
gint64 get_history_start () const
 Returns the frame counter for the oldest frame available in history. More...
 
Glib::RefPtr< FrameTimingsget_timings (gint64 frame_counter)
 Retrieves a Gdk::FrameTimings object holding timing information for the current frame or a recent frame. More...
 
Glib::RefPtr< const FrameTimingsget_timings (gint64 frame_counter) const
 Retrieves a Gdk::FrameTimings object holding timing information for the current frame or a recent frame. More...
 
Glib::RefPtr< FrameTimingsget_current_timings ()
 Gets the frame timings for the current frame. More...
 
Glib::RefPtr< const FrameTimingsget_current_timings () const
 Gets the frame timings for the current frame. More...
 
void get_refresh_info (gint64 base_time, gint64 & refresh_interval_return, gint64 & presentation_time_return) const
 Predicts a presentation time, based on history. More...
 
double get_fps () const
 Calculates the current frames-per-second, based on the frame timings of frame_clock. More...
 
Glib::SignalProxy< void()> signal_update ()
 
Glib::SignalProxy< void()> signal_layout ()
 
Glib::SignalProxy< void()> signal_paint ()
 

Static Public Member Functions

static GType get_type ()
 Get the GType for this class, for use with the underlying GObject type system. More...
 

Related Functions

(Note that these are not member functions.)

Glib::RefPtr< Gdk::FrameClockwrap (GdkFrameClock * object, bool take_copy=false)
 A Glib::wrap() method for this object. More...
 

Detailed Description

Synchronizes painting to a surface.

A Gdk::FrameClock tells the application when to update and repaint a surface. This may be synced to the vertical refresh rate of the monitor, for example. Even when the frame clock uses a simple timer rather than a hardware-based vertical sync, the frame clock helps because it ensures everything paints at the same time (reducing the total number of frames). The frame clock can also automatically stop painting when it knows the frames will not be visible, or scale back animation framerates.

Gdk::FrameClock is designed to be compatible with an OpenGL-based implementation or with mozRequestAnimationFrame in Firefox, for example.

A frame clock is idle until someone requests a frame with request_phase(). At some later point that makes sense for the synchronization being implemented, the clock will process a frame and emit signals for each phase that has been requested. (See the signals of the Gdk::FrameClock class for documentation of the phases. Gdk::FrameClock::Phase::UPDATE and the signal_update() signal are most interesting for application writers, and are used to update the animations, using the frame time given by get_frame_time().

The frame time is reported in microseconds and generally in the same timescale as g_get_monotonic_time(), however, it is not the same as g_get_monotonic_time(). The frame time does not advance during the time a frame is being painted, and outside of a frame, an attempt is made so that all calls to get_frame_time() that are called at a “similar” time get the same value. This means that if different animations are timed by looking at the difference in time between an initial value from get_frame_time() and the value inside the signal_update() signal of the clock, they will stay exactly synchronized.

Since gtkmm 3.24:

Constructor & Destructor Documentation

◆ FrameClock()

Gdk::FrameClock::FrameClock ( FrameClock &&  src)
noexcept

◆ ~FrameClock()

Gdk::FrameClock::~FrameClock ( )
overridenoexcept

Member Function Documentation

◆ begin_updating()

void Gdk::FrameClock::begin_updating ( )

Starts updates for an animation.

Until a matching call to end_updating() is made, the frame clock will continually request a new frame with the Gdk::FrameClock::Phase::UPDATE phase. This function may be called multiple times and frames will be requested until end_updating() is called the same number of times.

◆ end_updating()

void Gdk::FrameClock::end_updating ( )

Stops updates for an animation.

See the documentation for begin_updating().

◆ get_current_timings() [1/2]

Glib::RefPtr<FrameTimings> Gdk::FrameClock::get_current_timings ( )

Gets the frame timings for the current frame.

Returns
The Gdk::FrameTimings for the frame currently being processed, or even no frame is being processed, for the previous frame. Before any frames have been processed, returns nullptr.

◆ get_current_timings() [2/2]

Glib::RefPtr<const FrameTimings> Gdk::FrameClock::get_current_timings ( ) const

Gets the frame timings for the current frame.

Returns
The Gdk::FrameTimings for the frame currently being processed, or even no frame is being processed, for the previous frame. Before any frames have been processed, returns nullptr.

◆ get_fps()

double Gdk::FrameClock::get_fps ( ) const

Calculates the current frames-per-second, based on the frame timings of frame_clock.

Returns
The current fps, as a double.

◆ get_frame_counter()

gint64 Gdk::FrameClock::get_frame_counter ( ) const

Gdk::FrameClock maintains a 64-bit counter that increments for each frame drawn.

Returns
Inside frame processing, the value of the frame counter for the current frame. Outside of frame processing, the frame counter for the last frame.

◆ get_frame_time()

gint64 Gdk::FrameClock::get_frame_time ( ) const

Gets the time that should currently be used for animations.

Inside the processing of a frame, it’s the time used to compute the animation position of everything in a frame. Outside of a frame, it's the time of the conceptual “previous frame,” which may be either the actual previous frame time, or if that’s too old, an updated time.

Returns
A timestamp in microseconds, in the timescale of of Glib::get_monotonic_time().

◆ get_history_start()

gint64 Gdk::FrameClock::get_history_start ( ) const

Returns the frame counter for the oldest frame available in history.

Gdk::FrameClock internally keeps a history of Gdk::FrameTimings objects for recent frames that can be retrieved with get_timings(). The set of stored frames is the set from the counter values given by get_history_start() and get_frame_counter(), inclusive.

Returns
The frame counter value for the oldest frame that is available in the internal frame history of the Gdk::FrameClock.

◆ get_refresh_info()

void Gdk::FrameClock::get_refresh_info ( gint64  base_time,
gint64 &  refresh_interval_return,
gint64 &  presentation_time_return 
) const

Predicts a presentation time, based on history.

Using the frame history stored in the frame clock, finds the last known presentation time and refresh interval, and assuming that presentation times are separated by the refresh interval, predicts a presentation time that is a multiple of the refresh interval after the last presentation time, and later than base_time.

Parameters
base_timeBase time for determining a presentaton time.
refresh_interval_returnA location to store the determined refresh interval, or nullptr. A default refresh interval of 1/60th of a second will be stored if no history is present.
presentation_time_returnA location to store the next candidate presentation time after the given base time. 0 will be will be stored if no history is present.

◆ get_timings() [1/2]

Glib::RefPtr<FrameTimings> Gdk::FrameClock::get_timings ( gint64  frame_counter)

Retrieves a Gdk::FrameTimings object holding timing information for the current frame or a recent frame.

The Gdk::FrameTimings object may not yet be complete: see Gdk::FrameTimings::get_complete() and get_history_start().

Parameters
frame_counterThe frame counter value identifying the frame to be received.
Returns
The Gdk::FrameTimings object for the specified frame, or nullptr if it is not available.

◆ get_timings() [2/2]

Glib::RefPtr<const FrameTimings> Gdk::FrameClock::get_timings ( gint64  frame_counter) const

Retrieves a Gdk::FrameTimings object holding timing information for the current frame or a recent frame.

The Gdk::FrameTimings object may not yet be complete: see Gdk::FrameTimings::get_complete() and get_history_start().

Parameters
frame_counterThe frame counter value identifying the frame to be received.
Returns
The Gdk::FrameTimings object for the specified frame, or nullptr if it is not available.

◆ get_type()

static GType Gdk::FrameClock::get_type ( )
static

Get the GType for this class, for use with the underlying GObject type system.

◆ gobj() [1/2]

GdkFrameClock* Gdk::FrameClock::gobj ( )
inline

Provides access to the underlying C GObject.

◆ gobj() [2/2]

const GdkFrameClock* Gdk::FrameClock::gobj ( ) const
inline

Provides access to the underlying C GObject.

◆ gobj_copy()

GdkFrameClock* Gdk::FrameClock::gobj_copy ( )

Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.

◆ operator=()

FrameClock& Gdk::FrameClock::operator= ( FrameClock &&  src)
noexcept

◆ request_phase()

void Gdk::FrameClock::request_phase ( Phase  phase)

Asks the frame clock to run a particular phase.

The signal corresponding the requested phase will be emitted the next time the frame clock processes. Multiple calls to request_phase() will be combined together and only one frame processed. If you are displaying animated content and want to continually request the Gdk::FrameClock::Phase::UPDATE phase for a period of time, you should use begin_updating() instead, since this allows GTK to adjust system parameters to get maximally smooth animations.

Parameters
phaseThe phase that is requested.

◆ signal_layout()

Glib::SignalProxy<void()> Gdk::FrameClock::signal_layout ( )
Slot Prototype:
void on_my_layout()

Flags: Run Last

Emitted as the second step of toolkit and application processing of the frame.

Any work to update sizes and positions of application elements should be performed. GTK normally handles this internally.

◆ signal_paint()

Glib::SignalProxy<void()> Gdk::FrameClock::signal_paint ( )
Slot Prototype:
void on_my_paint()

Flags: Run Last

Emitted as the third step of toolkit and application processing of the frame.

The frame is repainted. GDK normally handles this internally and emits Gdk::Surface::signal_render() signals which are turned into Gtk::Widget::signal_snapshot() signals by GTK.

◆ signal_update()

Glib::SignalProxy<void()> Gdk::FrameClock::signal_update ( )
Slot Prototype:
void on_my_update()

Flags: Run Last

Emitted as the first step of toolkit and application processing of the frame.

Animations should be updated using Gdk::FrameClock::get_frame_time(). Applications can connect directly to this signal, or use Gtk::Widget::add_tick_callback() as a more convenient interface.

Friends And Related Function Documentation

◆ wrap()

Glib::RefPtr< Gdk::FrameClock > wrap ( GdkFrameClock *  object,
bool  take_copy = false 
)
related

A Glib::wrap() method for this object.

Parameters
objectThe C instance.
take_copyFalse if the result should take ownership of the C instance. True if it should take a new copy or ref.
Returns
A C++ instance that wraps this C instance.