Display Management Development Terminology

Display management development centers on two core concepts: logical screens and physical screens.

A logical screen cannot exist independently of a physical screen; each logical screen is mapped to a physical screen.

Physical screen attributes affect logical screen attributes. For example, when a foldable phone is folded or unfolded, the logical screen switches between the phone's inner screen and outer screen, and the width and height attributes of the logical screen are updated to the resolution of the corresponding screen.

Logical Screen

A continuous display space presented by the system to each application.

There are four types of logical screens: main screen, mirror screen, extended screen, and heterogeneous screen.

Main Screen

A logical screen that hosts the system's core UI (taskbar) and the default interaction focus.

Mirrored Screen

A logical screen that copies and displays content from another logical screen.

Common scenarios: wired screen projection, wireless screen projection, and screen recording.

Extended Screen

Serves as an extension of the main screen to increase the usable screen space.

Its relative position to the main screen can be set, and the mouse and windows can move between the main screen and the extended screen.

Heterogeneous Screen

A logical screen whose displayed content is completely independent of the main screen.

Common scenario: create a heterogeneous screen using a virtual screen to run an application. The application binds an XComponent to the virtual screen as the content output destination, thereby displaying the content generated by the application on the heterogeneous screen.

Physical Screen

A physical screen is the display unit to which the operating system outputs a complete image frame independently. It is the basic target object for composition and output in the graphics system.

A physical screen has its own frame buffer, which stores the complete image to be displayed on that screen.

Physical screens can be divided into two types: physical-hardware screens and virtual screens.

Physical-hardware Screen

A physical screen composed of physical hardware (such as LCD panel or OLED panel). Its image output is associated with a real, physically connected display.

Physical-hardware screens are further classified into built-in screens and external screens.

• Built-in screen: a physical-hardware screen integrated with the device

• External screen: a physical screen connected via a cable (such as HDMI or DP cable)

Virtual Screen

A software-simulated physical screen that has no corresponding physical display hardware. The image frames it generates are output to other destinations, such as being transmitted over a network (remote desktop sharing) or recorded into a video file (screen-recording software).

As a type of physical screen, a virtual screen can also be associated with a logical screen, for example, associating it with a mirrored screen for recording or projection, or associating it with a heterogeneous screen to run an application separately.