gobject:object, common-lisp:standard-object, common-lisp:t

None

The gdk:frame-clock object 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.

The gdk:frame-clock object 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 the gdk:frame-clock-request-phase function. 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:frame-clock class for documentation of the phases. The :update value of the gdk:frame-clock-phase enumeration and the "update" signal are most interesting for application writers, and are used to update the animations, using the frame time given by the gdk:frame-clock-frame-time function.

The frame time is reported in microseconds and generally in the same timescale as the system 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 the gdk:frame-clock-frame-time function 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 the gdk:frame-clock-frame-time function and the value inside the "update" signal of the clock, they will stay exactly synchronized.

The "after-paint" signal

lambda (clock)    :run-last      

clock

The gdk:frame-clock object emitting the signal.

The signal ends processing of the frame. Applications should generally not handle this signal.

The "before-paint" signal

lambda (clock)    :run-last      

clock

The gdk:frame-clock object emitting the signal.

The signal begins processing of the frame. Applications should generally not handle this signal.

The "flush-events" signal

lambda (clock)    :run-last      

clock

The gdk:frame-clock object emitting the signal.

The signal is used to flush pending motion events that are being batched up and compressed together. Applications should not handle this signal.

The "layout" signal

lambda (clock)    :run-last      

clock

The gdk:frame-clock object emitting the signal.

The signal is 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.

The "paint" signal

lambda (clock)    :run-last      

clock

The gdk:frame-clock object emitting the signal.

The signal is emitted as the third step of toolkit and application processing of the frame. The frame is repainted. GDK normally handles this internally and emits GdkSurface::render signals, which are turned into GTK GtkWidget::snapshot signals.

The "resume-events" signal

lambda (clock)    :run-last      

clock

The gdk:frame-clock object emitting the signal.

The signal is emitted after processing of the frame is finished, and is handled internally by GTK to resume normal event processing. Applications should not handle this signal.

The "update" signal

lambda (clock)    :run-last      

clock

The gdk:frame-clock object emitting the signal.

The signal is emitted as the first step of toolkit and application processing of the frame. Animations should be updated using the gdk:frame-clock-frame-time function. Applications can connect directly to this signal, or use the gtk:widget-add-tick-callback function as a more convenient interface.