Introduction to MeeGo Touch

About MeeGo Touch

MeeGo Touch is a cross-platform application and UI framework library built on top of Qt. The framework library makes use of the very latest Qt features to implement a specific UI style primarily targeting touch screen devices.

Using MeeGo Touch makes it easy to implement good looking, fully finger optimized applications that automatically take advantage of multitouch, device sensors, animations and transitions to create an iconic user experience on a range of platforms from handhelds to the desktop.

The MeeGo Touch style

The core of the MeeGo Touch style can be summarised as "direct manipulation of content". This places the focus of the applications squarely on the users' content, be that created by himself such as photos taken with the device itself, or content that is coming from the network. In a typical MeeGo Touch application the content therefore occupies the majority of the view, with the rest of the UI elements being de-emphasized.

The MeeGo Touch style discards many well known concepts from the desktop world such as file selection dialogs, scrollbars, tabs and so on. Due to the focus on touch, the user experience is highly tacticle with panning, flicking, dragging and pinching being common operations on wide variety of content. Instead of applications consisting of multiple windows as on a desktop, a MeeGo Touch application is typically divided into views and transitions between these.

Core to the concept of the MeeGo Touch style is the application canvas, a 2D pannable virtual area that extends beyond the physical borders of the screen. The use of a canvas as the foundation on which everything else is built breaks the limitations associated with traditional static UIs, be they Qt based or created with some other framework. For instance, any object on the canvas can be arbitrarily transformed, including rotated, scaled or perspective adjusted. Every object on the scene exposes a set of properties that can be animated, such as its current position, size, and opacity. Objects on the scene are also free to overlap and can be grouped into layers. All of this allows for the creation of highly fluid user interfaces where objects smoothly transition in and out of view, or where certain objects can detach from the rest of UI and stay pinned on the screen while all other content is replaced.

MeeGo Touch presents a programming interface that will seem familiar to developers with other UI frameworks such as Qt, most of the time it is therefore not necessary to understand the workings of the underlying canvas itself. However, if the developer so chooses he has the possibility of going beyond the ready made components provided in the MeeGo Touch style and taking direct advantage of the canvas in his application. In such cases MeeGo Touch also offers a set of lower level enablers to make his application themable and stylable for the scene.

Relationship with Qt

Qt by itself is already a mature cross-platform framework, providing a full set of traditional widgets that have been used in a number of successfull applications. In addition to this, Qt provides much of the necessary functionality for writing cross-platform applications in general, such as I/O, SQL & XML programming, threading, internationalization and so on.

In addition to this, Qt has recently come out with a number of new subsystems:

• The Graphics View Framework
• The Animation Framework
• The State Machine Framework
• Low-level 3D enablers

These new technologies serve as the basic enablers for next-generation user interfaces. However, as of Qt 4.6 these elements by themselves are still fairly low level and lacking the ties to any ready made UI components, including the existing Qt ones. MeeGo Touch takes these cutting edge components and implements a particular UI style optimized for touch devices and then, combined with a number of additional enablers that makes creating scene based applications easier, packages it together as a coherent UI framework library.

MeeGo Touch, like Qt, is also a cross-platform framework, capable of running wherever Qt does. From the point of view of a developer that wants to create a touch optimized application in the MeeGo Touch style, both Qt and MeeGo Touch are typically directly used; Qt for the application logic and MeeGo Touch for the scene based UI style.

The MeeGo Touch offering includes a set of ready made widgets implementing the MeeGo Touch style that specifically targets the Graphics View Framework, a set of pre-defined transitions and animations that can be themed and styled, and a set of features that makes writing scene based applications easier in general, such as automatic management of in-scene dialogs and windows, implicitly animated scene layouts and device orientation tracking. In addition to this MeeGo Touch exposes APIs necessary on mobile devices, such as power and memory management, that are not yet covered by either Qt or the Qt Mobility projects.

In the future, some of the functionality now provided through MeeGo Touch will migrate to Qt. In that sense, MeeGo Touch can be seen as the bleeding edge of Qt development, pushing the boundaries of next generation UI creation.