FrameClock


Object Hierarchy:

Object hierarchy for FrameClock

Description:

public abstract class FrameClock : Object

A FrameClock tells the application when to update and repaint a window.

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.

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 FrameClock class for documentation of the phases. gdk_frame_clock_phase_update and the 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 get_monotonic_time, however, it is not the same as 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 update signal of the clock, they will stay exactly synchronized.


Namespace: Gdk
Package: gdk-3.0

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