iOS Device Display Summary

Table 2-1 summarizes the physical dimensions of iOS displays and how those pixels are mapped to the logical coordinate system in UIKit.

At runtime, use the bounds and scale properties of a UIScreen object to understand how UIKit present the display to your app, and the nativeBounds andnativeScale when you need to work with the exact number of pixels on the display.

If the native scale differs from the UIKit scale factor, then iOS first renders the content at the UIKit scale factor and then scales it to fit into the native number of pixels on the screen. For games and other apps that perform many calculations per pixel, rendering these additional pixels can be expensive. Instead, configure a view to render at the native scale instead. For more information on how to do this in Metal, see Native Screen Scale (iOS and tvOS).

Table 2-2 describes the ability to reproduce color and adapt the color display to the environment around the device.

The P3 Display color space has a larger color gamut than an sRGB color space, with more saturated reds and greens. For information on supporting wide color in your app, see WWDC 2016 - Session 712: Working with Wide Color.

A True Tone display uses advanced ambient light sensors to automatically adapt the color and intensity of the display to match the light in the surrounding environment. Different kinds of apps many need to react to these changes differently. To specify how the display should adapt when your app is frontmost, see UIWhitePointAdaptivityStyle.

Table 2-3 describes the rate at which the hardware can adjust the contents of the screen.

Under most circumstances, UIKit handles redrawing and animation for you, adjusting the frame rate as necessary to provide a good viewing experience with reasonable energy usage. However, when you configure a view animation, you can optionally specify a hint when you know that the animation should run at a higher or lower rate. For more information, see UIViewAnimationOptions.

In full screen apps and games, animation is often driven explicitly using a CADisplayLink object. Set the display link’s preferredFramesPerSecond property to the frame rate you want, ideally using one of the preferred values specified in Table 2-3. SpriteKit, SceneKit, or MetalKit also provide this property on the the SKView, SCNView, and MTKView classes. For more information on animating content in Metal, see Frame Rate (iOS and tvOS).

Table 2-4 summarize the how often the display register touches from fingers or Apple Pencil and delivers them to UIKit.

The display hardware periodically captures data from sensors embedded in the screen. When a user touches the screen, the sensor information is recorded, processed, and delivered to UIKit. On displays that support 3D Touch, additional information about how much pressure the user applied to the display is also recorded. Only some displays support Apple Pencil. On these displays, the capture rate is different when reading Apple Pencil events than the capture rate for finger touches, and additional stylus information, such as the azimuth, is also recorded in each event.

When the capture rate is higher than the delivery rate, multiple events are coalesced into one touch event whose location reflects the most recent touch. However, the additional touch information is available for apps that need more precision.

For more information on event handling, coalesced touches, 3D Touch, and Apple Pencil, see Event Handling Guide for iOS.

Display Features Overview

These subsections provide further details on the features listed in iOS Device Display Summary above.