1. Introduction

This document presents programming guidelines and graphical design guidelines for developers writing graphical applications for the control systems of the ELT.

This document is intended to serve as a one-stop for finding the standards, colours scheme and common graphical design patterns for control applications.

Chapter 3 gives a brief explanation of the intended users of Control UIs, their deployment locations, the software environment, and the visual guidelines.

Chapter 4 helps the user through case studies: how to recognize problematic situations, and their possible solutions.

Chapter 5 introduces coding notations, and examples of UI.

1.1. Scope

This document presents guidelines for developers writing applications with graphical user interfaces for the control systems of the ELT.

1.2. Definitions and Conventions

1.2.1. Abbreviations and Acronyms

The following abbreviations and acronyms are used in this document.

AR

Augmented Reality – A virtual reality paradigm which combines images from a virtual source, into a view of the real world, therefore, augmenting the experience with other sources of information, data, or graphical elements.

DPI

Dots per Inch – a measurement used to indicate resolution of a printed element. It is also misused to indicate PPI, or screen pixel density.

GUI

Graphical User Interface

ELT

Extremely Large Telescope

HCI

Science of Human Computer Interaction

KDE

K Desktop Environment – A Linux Desktop Environment compatible with X11 and Wayland, based on the Qt Framework.

MVC

Model-View-Controller implementation pattern

OpenGL

Open Graphics Library – An open 3D rendering engine specification.

OpenGL ES

Open Graphics Library for Embedded Systems – A subset of OpenGL with updates to cover use cases for embedded systems.

PPE

Personnel Protection Element

Qt

Qt Framework – A multiplatform C++ and Python application development framework, known for its UI solution.

Resolution, several terms

  • SD

Standard Resolution, or (normally) 480 interlaced scan lines. It is tied to older analog signal transmissions, so its actual resolution is determine by the standard used.

  • HD

1280x720 pixels, or 720 progressive scan lines. Also used to indicate quality of graphical representation, in contrast to SD

  • FullHD

1920x1080 pixels, or 1080 progressive scan lines.

  • UltraHD

See 4K. Also used to indicate the group in the 4k+ range

  • 3K

3000 lines of horizontal resolution, or 2880x1620

  • 4K

4000 lines of horizontal resolution, or 3840x2160

  • 8K

8000 lines of horizontal resolution, or 7680x4320

TBD

To Be Determined

TIO

Telescope Instrument Operator

UI

User Interface

VR

Virtual Reality - A graphical representation paradigm in which visual immersion is total; achieved by means of a headset. Virtual Reality presents a whole 360 degrees world to explore, and allows for 6 axis movement.

1.2.2. Definitions

The following terms are used in this document.

“em” unit

An “em”, is a DPI independent measurement unit. It is determined as the bounding rectangle around the uppercased letter “M”. In most fonts, the letter M, or the X are the ones used to set the bounding sizes of all other letters. Commonly used in webpages, but also in mobile user interfaces.

DPI

Dots per Inch, is a term used to describe the density of the pixel matrix of a screen. It is also used to describe the possible output or input resolution of a device.

Normal DPI

Screens that range from 19 to 27 inches in size, with resolutions from HD to FullHD.

GUI

A “GUI” is the graphical user interface part of an application. In this document, the terms “GUI” and “Application GUI” are used interchangeably, depending on context either referring to source code or screen display.

HighDPI

A term that groups several densities, it is informally used to refer to screens in the range of 23 to 32 inches, with resolutions of 3K or 4K. Please notice that Retina refers also to a distance needed, this doesn’t.

Persona

A construct used in design. It is a short description of a prototype user. Design should be done keeping this/these personas in mind.

PPI

Pixels Per Inch, a measurement used to indicate pixel density in screens.

Retina

A marketing term to describe, among other things, the amount of pixel density (300 DPI at 10-12 inches separation from eyes) needed for a screen to make individual pixels undiscernible to human vision.

System

The “System” (with uppercase spelling) refers to the ELT telescope, dome, and other systems needed for its operation.

Widget

A widget is an element of a graphical user interface (GUI) that displays information or provides a specific way for a user to interact with the operating system or an application.

Widgets include icons, pull-down menus, buttons, selection boxes, progress indicators, on-off check buttons, scroll bars, windows, window edges (that let you resize the window), toggle buttons, forms, and many other devices for displaying information and for inviting, accepting, and responding to user actions.