Gdk.FrameClock¶

Subclasses:: None

Methods¶

Inherited:: GObject.Object (37)
Structs:: GObject.ObjectClass (5)

	`begin_updating` ()
	`end_updating` ()
	`get_current_timings` ()
	`get_fps` ()
	`get_frame_counter` ()
	`get_frame_time` ()
	`get_history_start` ()
	`get_refresh_info` (base_time)
	`get_timings` (frame_counter)
	`request_phase` (phase)

Virtual Methods¶

Inherited:: GObject.Object (7)

Properties¶

None

Signals¶

Inherited:: GObject.Object (1)

Name	Short Description
`after-paint`	This signal ends processing of the frame.
`before-paint`	Begins processing of the frame.
`flush-events`	Used to flush pending motion events that are being batched up and compressed together.
`layout`	Emitted as the second step of toolkit and application processing of the frame.
`paint`	Emitted as the third step of toolkit and application processing of the frame.
`resume-events`	Emitted after processing of the frame is finished.
`update`	Emitted as the first step of toolkit and application processing of the frame.

Fields¶

Inherited:: GObject.Object (1)

Class Details¶

class Gdk.FrameClock(**kwargs)¶

Bases:: GObject.Object
Abstract:: Yes
Structure:: Gdk.FrameClockClass

A GdkFrameClock 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.

GdkFrameClock 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 [method`Gdk`.FrameClock.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 GdkFrameClock class for documentation of the phases. Gdk.FrameClockPhase.UPDATE and the [signal`Gdk`.FrameClock::update] signal are most interesting for application writers, and are used to update the animations, using the frame time given by [method`Gdk`.FrameClock.get_frame_time].

The frame time is reported in microseconds and generally in the same timescale as GLib.get_monotonic_time(), however, it is not the same as GLib.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 [method`Gdk`.FrameClock.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 [method`Gdk`.FrameClock.get_frame_time] and the value inside the [signal`Gdk`.FrameClock::update] signal of the clock, they will stay exactly synchronized.

begin_updating()[source]¶

Starts updates for an animation.

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

end_updating()[source]¶

Stops updates for an animation.

See the documentation for [method`Gdk`.FrameClock.begin_updating].

get_current_timings()[source]¶

Returns:: the GdkFrameTimings for the frame currently being processed, or even no frame is being processed, for the previous frame. Before any frames have been processed, returns None.
Return type:: Gdk.FrameTimings or None

Gets the frame timings for the current frame.

get_fps()[source]¶

Returns:: the current fps, as a double
Return type:: float

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

get_frame_counter()[source]¶

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.
Return type:: int

GdkFrameClock maintains a 64-bit counter that increments for each frame drawn.

get_frame_time()[source]¶

Returns:: a timestamp in microseconds, in the timescale of of GLib.get_monotonic_time().
Return type:: int

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.

get_history_start()[source]¶

Returns:: the frame counter value for the oldest frame that is available in the internal frame history of the GdkFrameClock
Return type:: int

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

GdkFrameClock internally keeps a history of GdkFrameTimings objects for recent frames that can be retrieved with [method`Gdk`.FrameClock.get_timings]. The set of stored frames is the set from the counter values given by [method`Gdk`.FrameClock.get_history_start] and [method`Gdk`.FrameClock.get_frame_counter], inclusive.

get_refresh_info(base_time)[source]¶

Parameters:

base_time (int) – base time for determining a presentaton time

Returns:

refresh_interval_return:: a location to store the determined refresh interval, or None. A default refresh interval of 1/60th of a second will be stored if no history is present.
presentation_time_return:: a location to store the next candidate presentation time after the given base time. 0 will be will be stored if no history is present.

Return type:

(refresh_interval_return: int, presentation_time_return: int)

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.

get_timings(frame_counter)[source]¶

Parameters:: frame_counter (int) – the frame counter value identifying the frame to be received
Returns:: the GdkFrameTimings object for the specified frame, or None if it is not available
Return type:: Gdk.FrameTimings or None

Retrieves a GdkFrameTimings object holding timing information for the current frame or a recent frame.

The GdkFrameTimings object may not yet be complete: see [method`Gdk`.FrameTimings.get_complete] and [method`Gdk`.FrameClock.get_history_start].

request_phase(phase)[source]¶

Parameters:: phase (Gdk.FrameClockPhase) – the phase that is requested

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 Gdk.FrameClock.request_phase() will be combined together and only one frame processed. If you are displaying animated content and want to continually request the Gdk.FrameClockPhase.UPDATE phase for a period of time, you should use [method`Gdk`.FrameClock.begin_updating] instead, since this allows GTK to adjust system parameters to get maximally smooth animations.

Signal Details¶

Gdk.FrameClock.signals.after_paint(frame_clock)¶

Signal Name:: after-paint
Flags:: RUN_LAST
Parameters:: frame_clock (Gdk.FrameClock) – The object which received the signal

This signal ends processing of the frame.

Applications should generally not handle this signal.

Gdk.FrameClock.signals.before_paint(frame_clock)¶

Signal Name:: before-paint
Flags:: RUN_LAST
Parameters:: frame_clock (Gdk.FrameClock) – The object which received the signal

Begins processing of the frame.

Applications should generally not handle this signal.

Gdk.FrameClock.signals.flush_events(frame_clock)¶

Signal Name:: flush-events
Flags:: RUN_LAST
Parameters:: frame_clock (Gdk.FrameClock) – The object which received the signal

Used to flush pending motion events that are being batched up and compressed together.

Applications should not handle this signal.

Gdk.FrameClock.signals.layout(frame_clock)¶

Signal Name:: layout
Flags:: RUN_LAST
Parameters:: frame_clock (Gdk.FrameClock) – The object which received the signal

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.

Gdk.FrameClock.signals.paint(frame_clock)¶

Signal Name:: paint
Flags:: RUN_LAST
Parameters:: frame_clock (Gdk.FrameClock) – The object which received the signal

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

The frame is repainted. GDK normally handles this internally and emits [signal`Gdk`.Surface::render] signals which are turned into GtkWidget::snapshot signals by GTK.

Gdk.FrameClock.signals.resume_events(frame_clock)¶

Signal Name:: resume-events
Flags:: RUN_LAST
Parameters:: frame_clock (Gdk.FrameClock) – The object which received the signal

Emitted after processing of the frame is finished.

This signal is handled internally by GTK to resume normal event processing. Applications should not handle this signal.

Gdk.FrameClock.signals.update(frame_clock)¶

Signal Name:: update
Flags:: RUN_LAST
Parameters:: frame_clock (Gdk.FrameClock) – The object which received the signal

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

Animations should be updated using [method`Gdk`.FrameClock.get_frame_time]. Applications can connect directly to this signal, or use gtk_widget_add_tick_callback() as a more convenient interface.