Qt for S60

Qt for S60 Mark Wilcox

What I’m Talking About

What is Qt?

Qt Modules

Qt for S60

Technology Previews

Porting Qt applications to S60

Example: CuteMaze

Porting other applications to Qt on S60

Example: GDAL Viewer

What is Qt?

A cross-platform (soon to be free) application framework

Developed by Trolltech (bought by Nokia -> Qt Software)

Aims to look native on every platform via GUI emulation

C++ code, highly modular

Qt Modules Phonon QtXml & QtXmlPatterns QtWebKit QtSvg QtSql QtScript QtOpenGL QtNetwork QtGui QtCore

QtCore

A base object class with built-in event driven programming support and a seamless object communication mechanism via signals and slots

Strings, arrays, characters, linked lists, stacks and queues

Atomic operations on integers and pointers

Guarded pointers (automatically zeroed when the object is destroyed)

Date & time access and timers

Files, streams and file system management

Containers – pairs, vectors, maps, hashes and sets

Threads, processes, mutexes, semaphores and shared memory

Exceptions that can be transferred between threads

Text handling and internationalization support

Platform independent application settings

Pattern matching using regular expressions

Convenience functions for handling URLs and XML

Support for loading libraries, plug-ins and resources

Basic geometry via points, lines, sizes and rectangles

Signals & Slots

Extension to C++ via code generated by the Qt Meta-Object Compiler (moc)

As part of class definition, declare signals that object will emit and slots that are targets for signals

A signal can also be connected to another signal so that emission of the first automatically causes the second to be emitted

Code examples…

#include <QObject> class Cell : public QObject { Q_OBJECT // This macro is required for all classes // that implement signals and slots public: Cell() { iValue = 0; } int value() const { return iValue; } public slots : void setValue(int value); signals : void valueChanged(int newValue); private: int iValue; }; void Cell::setValue(int value) { if (value != iValue) { iValue = value; emit valueChanged(value); } } Sender sender; Receiver receiver; QObject::connect(&sender, SIGNAL(send(int)), &receiver, SLOT(receive(int)));

QtGui

QPainter class (graphics context style interface, implementation in QPaintEngine subclasses) used to draw on any QPaintDevice instance

This includes QWidget – the base class for all widgets

There are lots of useful widgets:

Buttons, sliders and combo-boxes

Windows, dialogs, forms and frames

Scroll areas with scroll bars

Menus, tabs, toolbars and status bars

Splash screens and progress bars

Help search query and result

Single and multi-line text editors

List, table and tree views

Calendar

Qt UI Examples

QtNetwork

Portable and simple network programming classes for:

UDP, TCP, SSL and local sockets

Key and certificate handling for secure communications

HTTP and FTP protocol implementations

Host address lookup by name

A managed request and response mechanism

Proxies, authentication and cookie management

Local and remotely accessible (TCP) servers

QtOpenGL

Allows developers to combine a Qt UI with 3D graphics rendered using OpenGL

OpenGL ES used on embedded platforms

Module not yet available for Qt for S60

QtScript

Make your applications scriptable with Qt Script

Based on ECMAScript (JavaScript/JScript)

QScriptEngine class used to evaluate scripts that are:

Typed by the user

Loaded from disk

Downloaded from network

Can mix signals & slots between C++ and script and create dynamic connections from script (moc at work again!)

QtSql

Database integration module

3-layered architecture

Driver layer

SQL API layer

UI layer

Provides model classes for use in a model/view architecture in combination with data-aware widgets from the QtGui module

Not yet available for Qt for S60 but will integrate with sqlite

QtSvg

For displaying Scalable Vector Graphics

Currently only the static features of SVG Tiny version 1.2 are supported

Simply create a QSvgWidget and load an SVG file with it

QtWebKit

WebKit integration module

New in Qt 4.4

Download and display a web page in just 3 lines of code with QWebView widget:

QWebView *view = new QWebView(parent); view->load(QUrl("http://www.trolltech.com/")); view->show();

Provides bridge between JavaScript in the WebKit engine and QObject instances in Qt C++ code, very much like the QScript module

Not yet available for Qt for S60 (although WebKit already used in S60)

QtXml & QtXmlPatterns

Utility classes for reading and writing XML

SAX & DOM based parsers

XQuery/XPath language support

Not yet available in Qt for S60

Phonon

Cross-platform multimedia framework

Started as part of KDE and was then adopted into Qt

Actually just a common interface to various backends for different platforms

Helix backend being developed for Qt for S60 – not yet available

Qt for S60

Port of Qt to S60

Currently in a “technology preview” state

No commercial use allowed, GPL use and evaluation only until it’s officially released

Incomplete feature set and plenty of bugs still to be fixed

Actually fairly stable and usable already (with a few major issues where things aren’t implemented yet!)

Qt for S60 Architecture

Qt for S60 Builds

Qt uses a platform independent project file with a .pro extension

A Qt tool called qmake generates build files for each platform from the .pro files

So, on S60 the MMP, bld.inf and PKG files are generated by qmake – they should not be edited

An extension makefile is also generated by qmake to support Qt extensions to C++ (e.g. moc, uic – Qt Designer support, rcc – resources)

Implicit Sharing

Symbian/S60 developers likely to be concerned by apparently high levels of stack usage in Qt applications

It is higher than standard Symbian code but…

Many objects, including QString, are implicitly shared with copy-on-write semantics – only one copy of the data exists (allocated on the heap) with shallow copy performed and a reference count incremented until a change is made

This allows passing of such objects as arguments and returning them from functions without a significant performance penalty

Technology Previews

Qt Software open source philosophy of release early and often – get developer/customer feedback

Qt for S60 following this process

“ Pyramid” release in October – “just” QtCore, QtGui and QtNetwork

“ Temple” release in December – added new modules, bugfixes and toolchain improvements

“ Garden” release scheduled for Q109 – more modules and S60 UI integration planned (Qt apps to look like native apps)

Final release scheduled for Q309

Porting Qt Applications to S60

Even though Qt is cross-platform, a new layout is probably required for the smaller screen size of mobile platforms

Some UI design may need changing to work with keypad only input on many devices

We need to wait for the “Garden” release to know exactly how things are going to work (although we can get plenty of clues from the Windows CE port of Qt)

Known factors:

Applications will run “maximized” by default – you’ll still be able to see the status bar and softkey area

QMenuBar for an application’s main window will map onto the left softkey options menu (you can control which menu item also goes on the right (& centre?) softkey

Example: CuteMaze