Class

CADisplayLink

A CADisplayLink object is a timer object that allows your application to synchronize its drawing to the refresh rate of the display.

Overview

Your application Object creation a new display link, providing a target object and a selector to be called when the screen is updated. Next, your application adds the display link to a run loop.

Once the display link is associated with a run loop, the selector on the target is called when the screen’s contents need to be updated. The target can read the display link’s timestamp property to retrieve the time that the previous frame was displayed. For example, an application that displays movies might use the timestamp to calculate which video frame will be displayed next. An application that performs its own animations might use the timestamp to determine where and how displayed objects appear in the upcoming frame. The duration property provides the amount of time between frames. You can use this value in your application to calculate the frame rate of the display, the approximate time that the next frame will be displayed, and to adjust the drawing behavior so that the next frame is prepared in time to be displayed.

Your application can disable notifications by setting the isPaused property to true. Also, if your application cannot provide frames in the time provided, you may want to choose a slower frame rate. An application with a slower but consistent frame rate appears smoother to the user than an application that skips frames. You can increase the time between frames (and decrease the apparent frame rate) by changing the frameInterval property.

When your application finishes with a display link, it should call invalidate() to remove it from all run loops and to disassociate it from the target.

CADisplayLink should not be subclassed.

Symbols

Creating Instances

init(target: Any, selector: Selector)

Returns a new display link.

Scheduling the Display Link to Send Notifications

func add(to: RunLoop, forMode: RunLoopMode)

Registers the display link with a run loop.

func remove(from: RunLoop, forMode: RunLoopMode)

Removes the display link from the run loop for the given mode.

func invalidate()

Removes the display link from all run loop modes.

Configuring the Display Link

var duration: CFTimeInterval

The time interval between screen refresh updates.

var isPaused: Bool

A Boolean value that states whether the display link’s notifications to the target are suspended.

var timestamp: CFTimeInterval

The time value associated with the last frame that was displayed.

Relationships

Inherits From

Conforms To