Cross platform application development with Qt Daniel Rocha Sr. Technology Expert Forum Nokia

Contents Introduction Qt overview Qt for Nokia’s mobile platforms Hands-on demo

Introduction

Qt overview

Qt for Nokia’s mobile platforms

Hands-on demo

1. Introduction Qt is cute

Background Trolltech was founded in 1994 and first Qt release went live 1995 I n June 2008 Nokia acquired Trolltech ASA to enable the acceleration of their cross-platform software strategy for mobile devices and desktop applications, and to develop its Internet services business. On September 27, 2008 Nokia fully integrated Trolltech and named the new Nokia entity Qt Software. Nokia will keep the Qt cross platform focus. Nowadays ” Qt Development Frameworks ” http:// qt.nokia.com

Trolltech was founded in 1994 and first Qt release went live 1995

I n June 2008 Nokia acquired Trolltech ASA to enable the acceleration of their cross-platform software strategy for mobile devices and desktop applications, and to develop its Internet services business.

On September 27, 2008 Nokia fully integrated Trolltech and named the new Nokia entity Qt Software.

Nokia will keep the Qt cross platform focus.

Nowadays ” Qt Development Frameworks ”

Facts Easy to learn Comprehensive documentation with good examples Qt x mobile features In the first phase you will need to write Qt + native code Qt ’Mobility APIs’ Supports major desktop OSs + Nokia’s platforms Qt will be the main choice for developers cross-platform development and Nokia platforms http:// qt.nokia.com

Easy to learn

Comprehensive documentation with good examples

Qt x mobile features

In the first phase you will need to write Qt + native code

Qt ’Mobility APIs’

Supports major desktop OSs + Nokia’s platforms

Qt will be the main choice for developers cross-platform development and Nokia platforms

What is Qt? Pronounced “cute”. Qt is a cross platform application framework . All the tools you need to develop applications are offered free of charge. Qt offers APIs for C++ An application done with Qt can be run on all widely used desktop environments and also embedded environments like Windows CE, Maemo Linux (N900) and Symbian Apps are compiled to native applications . Qt is implemented starting from as low level as suitable instead of providing new API layers on top of existing high-level APIs. http:// qt.nokia.com

Pronounced “cute”.

Qt is a cross platform application framework .

All the tools you need to develop applications are offered free of charge.

Qt offers APIs for C++

An application done with Qt can be run on all widely used desktop environments and also embedded environments like Windows CE, Maemo Linux (N900) and Symbian

Apps are compiled to native applications . Qt is implemented starting from as low level as suitable instead of providing new API layers on top of existing high-level APIs.

Qt http:// qt.nokia.com

Qt versions Qt 4.5 is the latest stable version of Qt and was released in March 2009. Improvements include: Newest Qt WebKit Integration The WebKit browser engine included with Qt has the latest WebKit features: Support for full page zooming, with appropriate rescaling of images and fonts. The CSS-based transformation and animation features provided by a WebKit extension. Netscape plugin API Mac OS X Cocoa Support XML Transformations with XSLT http:// qt.nokia.com

Qt 4.5 is the latest stable version of Qt and was released in March 2009. Improvements include:

Newest Qt WebKit Integration

The WebKit browser engine included with Qt has the latest WebKit features:

Support for full page zooming, with appropriate rescaling of images and fonts.

The CSS-based transformation and animation features provided by a WebKit extension.

Netscape plugin API

Mac OS X Cocoa Support

XML Transformations with XSLT

Qt versions Qt 4.6 beta has been announced in October 2009. Improvements include: Symbian support Maemo support Animation framework State machine framework Multi touch support DOM access API: Web pages and XML Performance optimizations Graphics effects: blurring, colorizing, blooming. Qt 3D – simplifying Open GL http:// qt.nokia.com

Qt 4.6 beta has been announced in October 2009. Improvements include:

Symbian support

Maemo support

Animation framework

State machine framework

Multi touch support

DOM access API: Web pages and XML

Performance optimizations

Graphics effects: blurring, colorizing, blooming.

Qt 3D – simplifying Open GL

2. Overview Qt is easy

C++ Application Framework Qt provides easy C++ APIs Qt goes beyond C++ in the areas of inter-object communication and flexibility for advanced GUI development. Adds some features to C++: A very powerful mechanism for seamless object communication called signals and slots Queryable and designable object properties Powerful events and event filters Contextual string translation for internationalization Sophisticated interval driven timers that make it possible to elegantly integrate many tasks in an event-driven GUI Hierarchical and queryable object trees that organize object ownership in a natural way Guarded pointers (QPointer) that are automatically set to 0 when the referenced object is destroyed

Qt provides easy C++ APIs

Qt goes beyond C++ in the areas of inter-object communication and flexibility for advanced GUI development.

Adds some features to C++:

A very powerful mechanism for seamless object communication called signals and slots

Queryable and designable object properties

Powerful events and event filters

Contextual string translation for internationalization

Sophisticated interval driven timers that make it possible to elegantly integrate many tasks in an event-driven GUI

Hierarchical and queryable object trees that organize object ownership in a natural way

Guarded pointers (QPointer) that are automatically set to 0 when the referenced object is destroyed

Overview The Qt class library encompasses all the functions needed to build robust, high-end applications Separated into several modules, Qt’s intuitive API includes Core Classes GUI Classes SQL Database Classes XML Classes Networking Classes OpenGL ® Classes Qt WebKit Integration Multimedia classes And more

The Qt class library encompasses all the functions needed to build robust, high-end applications

Separated into several modules, Qt’s intuitive API includes

Core Classes

GUI Classes

SQL Database Classes

XML Classes

Networking Classes

OpenGL ® Classes

Qt WebKit Integration

Multimedia classes

And more

Signals and Slots in Core Module Unique inter-object communication mechanism provides Type-safe callback between objects Facilitates loose coupling / encapsulation Sender and receiver does not “know about” each other 1-to-many, many-to-1 communication between objects Works across threads Fully object-oriented A signal is emitted when a particular event occurs . A slot is a function that is called in response to a particular signal .

Unique inter-object communication mechanism provides

Type-safe callback between objects

Facilitates loose coupling / encapsulation

Sender and receiver does not “know about” each other

1-to-many, many-to-1 communication between objects

Works across threads

Fully object-oriented

A signal is emitted when a particular event occurs . A slot is a function that is called in response to a particular signal .

Qt GUI Classes All the UI components usually needed Customized components can be written and integrated with IDEs Provides rich set of GUI components and supporting functionality User interface components Simple to complex widgets and controls, dialogs Model-View-Controller (MVC) Item views Styles – ensuring native or custom look and feel on target platforms Font-aware layout system Accessibility classes Canvas component with Widget support

All the UI components usually needed

Customized components can be written and integrated with IDEs

Provides rich set of GUI components and supporting functionality

User interface components

Simple to complex widgets and controls, dialogs

Model-View-Controller (MVC) Item views

Styles – ensuring native or custom look and feel on target platforms

Font-aware layout system

Accessibility classes

Canvas component with Widget support

Qt Database Classes Provide platform and database- independent access functionality Driver Layer Low-level bridge between specific databases and the SQL API layer SQL API Layer Provide access to databases User Interface Layer Link data from a database to data-aware widgets Supports most major database drivers DB2, IBASE, MySQL, OCI, ODBC, PSQL, SQLITE, TDS QSqlDatabase db = QSqlDatabase::database("sales"); QSqlQuery query ("SELECT Lastname, City FROM Names", db);

Provide platform and database- independent access functionality

Driver Layer

Low-level bridge between specific databases and the SQL API layer

SQL API Layer

Provide access to databases

User Interface Layer

Link data from a database to data-aware widgets

Supports most major database drivers

DB2, IBASE, MySQL, OCI, ODBC, PSQL, SQLITE, TDS

Qt Networking Classes Provides TCP/IP networking functionality TCP sockets for clients and for servers Encapsulates TCP and UDP APIs SSL support HTTP 1.1 compliant asynchronous API FTP, DNS implementation & SSL support QHttp http; connect(http, SIGNAL(done(bool)), this, SLOT(done(bool))); http->get(“http://www.softafoorumi.com/amazingApi.jsp?action=doGreatThings”); void MyClass::done(bool error) { QString data = http->readAll(); //handle data }

Provides TCP/IP networking functionality

TCP sockets for clients and for servers

Encapsulates TCP and UDP APIs

SSL support

HTTP 1.1 compliant asynchronous API

FTP, DNS implementation & SSL support

QHttp http;

connect(http, SIGNAL(done(bool)), this, SLOT(done(bool)));

http->get(“http://www.softafoorumi.com/amazingApi.jsp?action=doGreatThings”);

void MyClass::done(bool error)

{

QString data = http->readAll();

//handle data

}

OpenGL is a standard API for rendering 3D graphics Allows you to build your user interface in Qt, display and manipulate 3D model in OpenGL ® Integrates OpenGL canvas with Qt Provides frame buffer and pixel buffer abstraction Supports accelerating 2D painting with OpenGL Mix 2D painting and 3D scenes Qt Open GL/3D Classes

OpenGL is a standard API for rendering 3D graphics

Allows you to build your user interface in Qt, display and manipulate 3D model in OpenGL ®

Integrates OpenGL canvas with Qt

Provides frame buffer and pixel buffer abstraction

Supports accelerating 2D painting with OpenGL

Mix 2D painting and 3D scenes

Qt XML Classes Core Module Simple XML stream reader and writer XML Module A well-formed XML parser using the SAX2 (Simple API for XML) interface Implementation of the DOM Level 2 (Document Object Model) XmlPatterns module An implementation of the XQuery standard Enable users to query XML files similar to SQL Semantics for value assignment, filtering, and simple operations Fully controllable output formatting Qt 4.5 adds XSLT support QXmlStreamReader xml; xml.addData( data ); while (!xml.atEnd()) { xml.readNext(); ... // do processing }

Core Module

Simple XML stream reader and writer

XML Module

A well-formed XML parser using the SAX2 (Simple API for XML) interface

Implementation of the DOM Level 2 (Document Object Model)

XmlPatterns module

An implementation of the XQuery standard

Enable users to query XML files similar to SQL

Semantics for value assignment, filtering, and simple operations

Fully controllable output formatting

Qt 4.5 adds XSLT support

QXmlStreamReader xml;

xml.addData( data );

while (!xml.atEnd())

{

xml.readNext(); ...

// do processing

}

Qt WebKit Integration An open source HTML rendering component integrated with Qt Based on webkit ( http://webkit.org ) that is also used by f.ex Safari, Google Chrome & iPhone Web standards compliant support for HTML, XHTML, XML, stylesheets, JavaScript, HTML editing, HTML canvas, AJAX, XSLT, XPath, some SVG. Deployable wherever Qt is: cross-platform/cross-version/cross-device Interact with Web environment, expose native objects NPAPI support with Qt 4.5 QWebView *view = new QWebView(parent); view->load(QUrl("http: // qt.nokia.com/")); view->show(); http://webkit.org

An open source HTML rendering component integrated with Qt

Based on webkit ( http://webkit.org ) that is also used by f.ex Safari, Google Chrome & iPhone

Web standards compliant

support for HTML, XHTML, XML, stylesheets, JavaScript, HTML editing, HTML canvas, AJAX, XSLT, XPath, some SVG.

Deployable wherever Qt is: cross-platform/cross-version/cross-device

Interact with Web environment, expose native objects

NPAPI support with Qt 4.5

QWebView *view = new QWebView(parent);

view->load(QUrl("http: // qt.nokia.com/"));

view->show();

Phonon Single, easy to use API (”Phonon”) for playback Provides possibility to play/synchronize multiple sound/video streams Will use native back-end format support DirectShow on Windows GStreamer on X11 QuickTime on Mac MMF on Symbian Plan to add more video and authoring support in the future Phonon::VideoPlayer *player = new Phonon::VideoPlayer(Phonon::VideoCategory, parentWidget); player->play(url);

Single, easy to use API (”Phonon”) for playback

Provides possibility to play/synchronize multiple sound/video streams

Will use native back-end format support

DirectShow on Windows

GStreamer on X11

QuickTime on Mac

MMF on Symbian

Plan to add more video and authoring support in the future

Phonon::VideoPlayer *player =

new Phonon::VideoPlayer(Phonon::VideoCategory, parentWidget);

player->play(url);

Qt Designer: GUI layout and forms builder Qt Creator : C ross-platform IDE for use with the Qt application framework Qt Linguist: Internationalization toolset Qt Assistant: Customizable documentation reader qmake: Cross-platform build tool Integration with Visual Studio ® and Eclipse ® IDEs – including Nokia’s Carbide.C++ For Symbian Integration with Maemo SDK in the works Development Tools

Qt Designer: GUI layout and forms builder

Qt Creator : C ross-platform IDE for use with the Qt application framework

Qt Linguist: Internationalization toolset

Qt Assistant: Customizable documentation reader

qmake: Cross-platform build tool

Integration with Visual Studio ® and Eclipse ® IDEs – including Nokia’s Carbide.C++ For Symbian

Integration with Maemo SDK in the works

Qt Designer Qt Designer is a powerful, drag-and-drop GUI layout and forms builder Features Supports forms and dialog creation with instant preview Integrates with Qt layout system Extensive collection of standard widgets Support for custom widgets and dialogs Seamless integration with many IDEs Benefits Greatly speeds the interface design process Enables native look and feel across all supported platforms Developers work within the environment of their choice, leveraging existing skills

Qt Designer is a powerful, drag-and-drop GUI layout and forms builder

Features

Supports forms and dialog creation with instant preview

Integrates with Qt layout system

Extensive collection of standard widgets

Support for custom widgets and dialogs

Seamless integration with many IDEs

Benefits

Greatly speeds the interface design process

Enables native look and feel across all supported platforms

Developers work within the environment of their choice, leveraging existing skills

Qt Creator Lightweight, cross-platform IDE for Qt Advanced C++ code editor Integrated, context sensitive help system Integrated visual debugger (based on gdb) Integrated source code management Project and build management tools Integrated Qt development tools

Lightweight, cross-platform IDE for Qt

Advanced C++ code editor

Integrated, context sensitive help system

Integrated visual debugger (based on gdb)

Integrated source code management

Project and build management tools

Integrated Qt development tools

Code navigation tools Challenge Projects contain hundreds of source files Developers often don’t know name/location of file Solution Open files without knowing exact names or locations Search for classes, functions, symbols and files Follow symbols across several locations/files Switch between headers and source files Switch between declarations and definitions Quickly finding and opening classes.

Challenge

Projects contain hundreds of source files

Developers often don’t know name/location of file

Solution

Open files without knowing exact names or locations

Search for classes, functions, symbols and files

Follow symbols across several locations/files

Switch between headers and source files

Switch between declarations and definitions

Tailored to the needs of Qt cross-platform developers Challenge Qt is cross-platform, but IDEs/dev. environments are not Can be difficult to get up with a new framework Solution True cross-platform development environment for Qt Integrated Qt-specific features (i.e. Signals & Slots) Debugger aware of Qt class structures New developers get productive sooner Visualizing Qt class structures in Debug mode.

Challenge

Qt is cross-platform, but IDEs/dev. environments are not

Can be difficult to get up with a new framework

Solution

True cross-platform development environment for Qt

Integrated Qt-specific features (i.e. Signals & Slots)

Debugger aware of Qt class structures

New developers get productive sooner

Powerful C++ code editor Challenge Writing elegant, correct code can be time consuming Finding help often demands context switching Solution Syntax highlighting and automatic code completion Static code checking as you type Context sensitive help Code folding Parenthesis matching and parenthesis selection modes Advanced editing capabilities like block selection Code completion. Context-sensitive help.

Challenge

Writing elegant, correct code can be time consuming

Finding help often demands context switching

Solution

Syntax highlighting and automatic code completion

Static code checking as you type

Context sensitive help

Code folding

Parenthesis matching and parenthesis selection modes

Advanced editing capabilities like block selection

Available as part of complete SDK Qt Designer GUI Layout & Forms Tool Qt Assistant Help file/documentation browser Qt Linguist Translation/I18n Tool qmake Cross-platform build tool Qt Development Tools Qt Libraries Qt SDK Licensing Options: Commercial LGPL

3. Qt on Nokia’s mobile platforms Qt is mobile

Nokia + Ovi Developer Story | With the simplified toolchain you can tackle f. ex Maemo and Symbian-based devices Develop on PC, Mac or Linux Nokia’s Qt mobile offering

Qt for Symbian platform Qt Development Frameworks announced in October-08 the porting of Qt to Symbian OS, the world's leading, open smartphone platform Beta package available for download from Qt Development Frameworks website http://qt.nokia.com (http://qt.nokia.com/developer/qt-4.6-beta-for-symbian-developers). With the inclusion of the Symbian OS platform, developers have an additional 130 million target devices that they can support with their Qt-based applications.

Qt Development Frameworks announced in October-08 the porting of Qt to Symbian OS, the world's leading, open smartphone platform

Beta package available for download from Qt Development Frameworks website http://qt.nokia.com (http://qt.nokia.com/developer/qt-4.6-beta-for-symbian-developers).

With the inclusion of the Symbian OS platform, developers have an additional 130 million target devices that they can support with their Qt-based applications.

Qt for Symbian platform - Total Offering Qt for Symbian – Qt 4.6 ported to S60 3 rd Edition FP 1 and FP 2, 5 th editions. Will be the only UI framework for Symbian Foundation devices in 2010. Carbide.c++ 2.0 supporting Qt/Symbian development. Fully integrated form editor ( Qt Designer ) Wizards for creating new Qt projects and classes Integrated .pro file editor Automated build setup for moc, uic, and rcc Examples and additional documentation available in Forum Nokia And more to come…

Qt for Symbian – Qt 4.6 ported to S60 3 rd Edition FP 1 and FP 2, 5 th editions.

Will be the only UI framework for Symbian Foundation devices in 2010.

Carbide.c++ 2.0 supporting Qt/Symbian development.

Fully integrated form editor ( Qt Designer )

Wizards for creating new Qt projects and classes

Integrated .pro file editor

Automated build setup for moc, uic, and rcc

Examples and additional documentation available in Forum Nokia

And more to come…

Current Release The release is called Colossus with following functionality QtCore - http://doc.trolltech.com/4.5/qtcore.html QtGui - http://doc.trolltech.com/4.5/qtgui.html QtNetwork - http://doc.trolltech.com/4.5/qtnetwork.html QtScript - http://doc.trolltech.com/4.5/qtscript.html QtSql - http://doc.trolltech.com/4.5/qtsql.html QtSvg - http://doc.trolltech.com/4.5/qtsvg.html QtTest - http://doc.trolltech.com/4.5/qttest.html QtWebKit - http://doc.trolltech.com/4.5/qtwebkit.html QtXml - http://doc.trolltech.com/4.5/qtxml.html Phonon - http://doc.trolltech.com/4.5/phonon-module.html Where to get it: http://pepper.troll.no/s60prereleases/

The release is called Colossus with following functionality

QtCore - http://doc.trolltech.com/4.5/qtcore.html

QtGui - http://doc.trolltech.com/4.5/qtgui.html

QtNetwork - http://doc.trolltech.com/4.5/qtnetwork.html

QtScript - http://doc.trolltech.com/4.5/qtscript.html

QtSql - http://doc.trolltech.com/4.5/qtsql.html

QtSvg - http://doc.trolltech.com/4.5/qtsvg.html

QtTest - http://doc.trolltech.com/4.5/qttest.html

QtWebKit - http://doc.trolltech.com/4.5/qtwebkit.html

QtXml - http://doc.trolltech.com/4.5/qtxml.html

Phonon - http://doc.trolltech.com/4.5/phonon-module.html

Where to get it: http://pepper.troll.no/s60prereleases/

Qt for Symbian releases FINAL P11 Garden P3-09 based on 4.5 Tower P6-09 based on 4.5 Pyramid P10 based on 4.4 QtNetwork QtXml QtGUI *) QtCore QtScript QtSql QtSvg http://pepper.troll.no/s60prereleases/ Beta late P9 QtXmlPatterns QtWebkit Phonon QtTest Colossus release focusing on HW acceleration and performance Bringing in QtSqt, QtWebkit (experimentary version) and phonon with MMF QtOpenGL Q3Support

Colossus release focusing on HW

acceleration and performance

Bringing in QtSqt, QtWebkit (experimentary version) and phonon with MMF

Qt Support in Carbide.c++ 2.0 Support for Qt development Carbide works with Qt projects .PRO editor for easy project configuration Package /deploy projects to phone Qt plug-ins are included in Carbide Qt project Wizard Support for Qt UI design tool Oh yeah, since Qt for Symbian is a Symbian application, you can use same tools for debugging, profiling etc.

Support for Qt development

Carbide works with Qt projects

.PRO editor for easy project configuration

Package /deploy projects to phone

Qt plug-ins are included in Carbide

Qt project Wizard

Support for Qt UI design tool

Oh yeah, since Qt for Symbian is a Symbian application, you can use same tools for debugging, profiling etc.

Qt for Maemo platform Maemo is an open-source development platform for Internet Tablets and maemo mobile computers (f.ex N900) 90% of source code is open-source Maemo 5 contains GSM and 3G functionality In maemo 5 GTK is still supported as development framework – not officially supported in maemo 6 anymore We’re bringing in Qt for maemo and encourage all developers to use Qt as the long term solution http://qt.nokia.com/developer/qt-for-maemo-developers

Maemo is an open-source development

platform for Internet Tablets and maemo

mobile computers (f.ex N900)

90% of source code is open-source

Maemo 5 contains GSM and 3G functionality

In maemo 5 GTK is still supported as development framework – not officially supported in maemo 6 anymore

We’re bringing in Qt for maemo and encourage all developers to use Qt as the long term solution

http://qt.nokia.com/developer/qt-for-maemo-developers

Product evolution Internet Optimized Multimedia Computer Nokia N800 2 nd generation of Nokia Internet Tablets. Nokia N810 Taking the positioning of the Tablet Category from a predominantly ‘one-way’ surfing tool, to a genuine ‘two way’ communication device. With integrated slide keyboard N810 leads the richly connected pocketable Web 2.0 experience allowing you to connect to your content and experiences wherever you are. Nokia N810 WiMAX Edition Bringing WiMAX connection to strengthen the internet story. With wider wireless internet coverage, Internet will truly become personal and mobile. Nokia 770 1 st generation of Nokia Internet Tablets Easy access to the internet. High resolution touch screen.

Maemo 5 Linux based operating system for N900 Optimized for pocket sized devices and finger use Panorama desktop Multitasking with dashboard New UI style Animated UI Compositing window manager Accelerated graphics with OpenGL-ES2 http://www.forum.nokia.com/devices/N900 N900 WLAN IEEE 802.11b/g 32 GB internal storage Integrated GPS with A-GPS High definition camera support (integrated Image Signal Processor) 5 megapixel camera (2584 × 1938 pixels) HW acceleration for OpenGL ES 2.0 3.5 inch touch-screen 800 × 480 pixel resolution High-speed USB 2.0 HSPA/3G support – online anywhere 3G connectivity TI OMAP 3 processor, ARM Cortex-A8 600 MHz

Linux based operating system for N900

Optimized for pocket sized devices and finger use

Panorama desktop

Multitasking with dashboard

New UI style

Animated UI

Compositing window manager

Accelerated graphics with OpenGL-ES2

Hildon UI – simple and customizable Taskbar to navigate applications Status bar indicating device state Widgets and RSS feeds for up-to-date information Consistent controls across applications

Maemo software architecture ARM/OMAP-based Linux kernel GNOME Structured File Library System Libraries incl. GNU C, STD C++, OpenSSL, curl HTTP, etc Maemo SDK Qt Maemo UI and applications Debian Package Management System services such as D-Bus, DSM, MCE, BME, and SQLite DB GNOME Configuration Management Telepathy Communication Framework gStreamer Multimedia Framework E-D-S Calendar/ Contacts GNOME VFS File Access Maemo Launcher Maemo platform: Mostly open source except connectivity, power management and licensed software Mostly binary code for Nokia devices Hildon UI Framework GNOME/GTK+ Application Framework

Plus Qt Mobility APIs for Mobile Development First release planned Q4/2009 Supporting Symbian Maemo support under investigation Planned content Service Framework Contacts API Location API System Information API Messaging API Bearer Management Context Framework http:// labs.trolltech.com/page/Projects/QtMobility

First release planned Q4/2009

Supporting Symbian

Maemo support under investigation

Planned content

Service Framework

Contacts API

Location API

System Information API

Messaging API

Bearer Management

Context Framework

4. Demo Time to embarrass myself…

How to Get Started? http://qt.nokia.com

http://qt.nokia.com

Comments? Questions? Thank you! [email_address]

Back-up slides

Qt 4.5 Licensing

Licensing There have been lot of speculation and concerns of used licensing model. The current release is under Commercial Tech Preview license which allows evaluating and testing only. Qt 4.5 will be released under LGPL i.e no license fees for closed source commercial development On 14 January, Nokia announced that its Qt cross-platform user interface (UI) and application framework for desktop and embedded platforms will be available under the open source LGPL version 2.1 license from the release of Qt 4.5, scheduled for March 2009. In addition: Qt source code repositories will be made publicly available and will encourage contributions from desktop and embedded developer communities. Service offerings for Qt will be expanded to ensure that all Qt development projects can have access to the same levels of support, independent of the selected license.

There have been lot of speculation and concerns of used licensing model.

The current release is under Commercial Tech Preview license which allows evaluating and testing only.

Qt 4.5 will be released under LGPL i.e no license fees for closed source commercial development

On 14 January, Nokia announced that its Qt cross-platform user interface (UI) and application framework for desktop and embedded platforms will be available under the open source LGPL version 2.1 license from the release of Qt 4.5, scheduled for March 2009. In addition:

Qt source code repositories will be made publicly available and will encourage contributions from desktop and embedded developer communities.

Service offerings for Qt will be expanded to ensure that all Qt development projects can have access to the same levels of support, independent of the selected license.