Hemera::Qml::Settings::Display Class Reference

Display is the base QML object for defining Displays in a Hemera GUI Appliance. More...

#include <sources/qt5-sdk/plugins/qml/settings/hemeraqmldisplay.h>

Inheritance diagram for Hemera::Qml::Settings::Display:

Detailed Description

Display is the base QML object for defining Displays in a Hemera GUI Appliance.

Display enables a physical display or framebuffer, and associates an Orbit Handler to it. Display is not meant to be used directly: instead, you should use one of its subclasses, which defines the display server or painting device to be used.

At the moment, the following displays are available:

  • Wayland: Wayland is the most modern mechanism available, and meant to run on GL capable devices with Wayland support. Please enquire with your representative to find out if your device supports Wayland.
  • EGL Full Screen: EGL Full Screen, or EGLFS, tries to paint directly to an EGL framebuffer. It requires a GL capable device, and it is a good alternative to Wayland on those GL capable devices where Wayland isn't supported. Please note that running Widgets-based applications on EGLFS, although possibly working, it is not supported, and you are voiding your warranty when doing so. The advised choice is either LinuxFB or X11. Please enquire with your Hemera representative to learn more.
  • LinuxFB: LinuxFB paints directly to the Linux Framebuffer without any intermediary. It is the most compatible and lightweight method of painting to a screen, but it comes with a price: it works only with non-GL applications, and is unsuitable for complex use cases. It is the advised choice on those devices where GL is not available and only one application at a time is displayed on the screen, or there is no heavy multitasking need.
  • X11: X11 is the most popular solution for painting on a screen. It supports both GL and non-GL devices and applications depending on the driver, but carries a relevant overhead and requires a full-fledged server to be running. It is usually advised on those devices where compatibility issues suggest the usage of X11, or if applications require X11 to paint on the screen (Java is an example).
  • DirectFB: DirectFB is a lightweight alternative to X11. It is usually not advised, unless target device has explicit support for DirectFB.

Usually, your device will come with a recommended Display to be used, which will be the one of its default Developer Mode image. It is strongly suggested to stick with that choice, or to enquire with your representative to find out what works best for your use case.

Display is also a Sandbox: this is done for those cases, such as X11 and Wayland, where an additional component (server or compositor) is meant to be run. Usually, there's no need to specify any Sandbox-specific parameters to Display (besides name, which is compulsory), but in some cases it might be desirable to limit or allow the compositor to perform further actions.

Several concepts in Display are better explained in Base Hemera Concepts
See also