Introduction

This article contains guidelines for design and development of applications for YotaPhone, a dual-screen Android-based smartphone developed by Yota Devices.

It is intended for both beginners and experienced developers, and will cover the principles, prerequisites, and rules for making a new app from scratch. It will also attempt to explain the underlying philosophy of the device's distinguishing features and the encouraged user interaction flows.

Throughout this document we will be referring to Google's Android Developer manuals, as most concerns applicable to designing for other Android smartphones are also applicable to YotaPhone.

Glossary

Always-on Screen
Always-on Screen is the Electronic Paper Display (EPD) on the back side of YotaPhone.

Color Screen
Color Screen is the AMOLED front screen of YotaPhone.

Counter
An entity that displays the number of unattended events of a certain type (such as missed calls). It pulls its data from its parent application.

EPD
EPD stands for electrophoretic display, or electronic paper display, also commonly shortened to e-paper. The core features of this technology are paper-like appearance and significantly lower power consumption compared to traditional displays. YotaPhone's Always-on Screen uses this technology.

Fullscreen App
Unless stated otherwise, the term fullscreen App used in this document refers to fullscreen apps designed specifically for Always-on Screen, following the guidelines and principles contained further in this document. A fullscreen App that runs on YotaPhone's Always-on Screen or has a Widget designed for it can be considered an Application for YotaPhone.

Global update
One of the two modes of drawing to EPD; it updates the entire screen. All pixels are cycled to combat the ghosting effect, and the relevant ones change their color to the new values. This mode provides the best image quality. The disadvantage is that the entire screen tends to flash while pixels are cycled (white goes to black then back to white, and vice versa).

Local update
One of the two modes of drawing to EPD; it updates only those pixels that need to change color. As a result, the screen doesn't flash distractingly, but image artifacts will accumulate over time.

Touchscreen Gestures
A set of hand motions by which users interact with Android OS using a touchscreen. Please refer to Google's Android manual on Gestures to learn about the most common ones.

Waveform
A waveform is the sequence of voltage changes driving the EPD and supplying its pixels with new brightness data. Different modes of operation require usage of different waveforms for optimal image quality and performance.

Widget
Unless stated otherwise, the term Widget used in this document refers to YotaPhone's Always-on Screen Widgets—non-fullscreen application modules put on a Panel. A Widget pulls all of its content from its parent fullscreen application, and cannot exist without one. We have a section on Widgets further on in the document.

YotaCover
YotaCover is a special Panel that contains an image and/or notification counters and may be customized by user.

YotaHub
YotaHub is a Color Screen application that serves as a portal to YotaPhone's specific features and settings. It is the application used to set up YotaCovers, YotaPanels, and Widgets.

YotaPanel
YotaPanel, or simply Panel, is the term we use to refer to Home Screen-like pages of YotaPhone's Always-on Screen user interface. User can set up several YotaPanels, each containing Widgets and a navigation bar. For most intents and purposes they are analogous to Android Home Screen pages.