:right-sidebar: True FrameClock =================================================================== .. currentmodule:: gi.repository.Gdk .. class:: FrameClock(**properties: ~typing.Any) :no-contents-entry: Superclasses: :class:`~gi.repository.GObject.Object` 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 :obj:`~gi.repository.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. :const:`~gi.repository.Gdk.FrameClockPhase.UPDATE` and the :obj:`~gi.repository.Gdk.FrameClock.signals.update` signal are most interesting for application writers, and are used to update the animations, using the frame time given by :obj:`~gi.repository.Gdk.FrameClock.get_frame_time`\. The frame time is reported in microseconds and generally in the same timescale as :func:`~gi.repository.GLib.get_monotonic_time`, however, it is not the same as :func:`~gi.repository.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 :obj:`~gi.repository.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 :obj:`~gi.repository.Gdk.FrameClock.get_frame_time` and the value inside the :obj:`~gi.repository.Gdk.FrameClock.signals.update` signal of the clock, they will stay exactly synchronized. Methods ------- .. rst-class:: interim-class .. class:: FrameClock :no-index: .. method:: begin_updating() -> None Starts updates for an animation. Until a matching call to :obj:`~gi.repository.Gdk.FrameClock.end_updating` is made, the frame clock will continually request a new frame with the :const:`~gi.repository.Gdk.FrameClockPhase.UPDATE` phase. This function may be called multiple times and frames will be requested until :func:`~gi.repository.Gdk.FrameClock.end_updating` is called the same number of times. .. method:: end_updating() -> None Stops updates for an animation. See the documentation for :obj:`~gi.repository.Gdk.FrameClock.begin_updating`\. .. method:: get_current_timings() -> ~gi.repository.Gdk.FrameTimings | None Gets the frame timings for the current frame. .. method:: get_fps() -> float Calculates the current frames-per-second, based on the frame timings of ``frame_clock``\. .. method:: get_frame_counter() -> int ``GdkFrameClock`` maintains a 64-bit counter that increments for each frame drawn. .. method:: get_frame_time() -> 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. .. method:: get_history_start() -> 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 :obj:`~gi.repository.Gdk.FrameClock.get_timings`\. The set of stored frames is the set from the counter values given by :obj:`~gi.repository.Gdk.FrameClock.get_history_start` and :obj:`~gi.repository.Gdk.FrameClock.get_frame_counter`\, inclusive. .. method:: get_refresh_info(base_time: int) -> ~typing.Tuple[int, 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``\. :param base_time: base time for determining a presentaton time .. method:: get_timings(frame_counter: int) -> ~gi.repository.Gdk.FrameTimings | 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 :obj:`~gi.repository.Gdk.FrameTimings.get_complete` and :obj:`~gi.repository.Gdk.FrameClock.get_history_start`\. :param frame_counter: the frame counter value identifying the frame to be received .. method:: request_phase(phase: ~gi.repository.Gdk.FrameClockPhase) -> None 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 :func:`~gi.repository.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 :const:`~gi.repository.Gdk.FrameClockPhase.UPDATE` phase for a period of time, you should use :obj:`~gi.repository.Gdk.FrameClock.begin_updating` instead, since this allows GTK to adjust system parameters to get maximally smooth animations. :param phase: the phase that is requested Signals ------- .. rst-class:: interim-class .. class:: FrameClock.signals :no-index: .. method:: after_paint() -> None The type of the None singleton. .. method:: before_paint() -> None The type of the None singleton. .. method:: flush_events() -> None The type of the None singleton. .. method:: layout() -> None The type of the None singleton. .. method:: paint() -> None The type of the None singleton. .. method:: resume_events() -> None The type of the None singleton. .. method:: update() -> None The type of the None singleton.