Qt 3.0 adds a wide range of major new features as well as substantial

improvements over the Qt 2.x series. Some internals have undergone

major redesign and new classes and methods have been added.

The Qt version 3.x series is not binary compatible with the 2.x

series.  This means programs compiled with Qt version 2.x must be

recompiled to work with Qt 3.0.

In addition to the traditional Qt platforms Linux, Unix and the

various flavours of MS-Windows.  Qt 3.0 for the first time introduces a

native port to MacOS X. Like all Qt versions, Qt/Mac is source

compatible with the other editions and follows closely the platform's

native look and feel guidelines.

We have tried to keep the API of Qt 3.0 as compatible as possible with

the Qt 2.x series. For most applications, only minor changes will be

needed to compile and run them successfully using Qt 3.0.

One of the major new features that has been added in the 3.0 release

is a module allowing you to easily work with databases. The API is

platform independent and database neutral. This module is seamlessly

integrated into Qt Designer, greatly simplifying the process of

building database applications and using data aware widgets.

Other major new features include a plugin architecture to extend Qt's

functionality, for styles, text encodings, image formats and database

drivers. The Unicode support of Qt 2.x has been greatly enhanced, it

now includes full support for scripts written from right to left

(e.g. Arabic and Hebrew) and also provides improved support for Asian

languages.

Many new classes have been added to the Qt Library. Amongst them are

classes that provide a docking architecture (QDockArea/QDockWindow), a

powerful rich text editor (QTextEdit), a class to store and access

application settings (QSettings) and a class to create and communicate

with processes (QProcess).

Apart from the changes in the library itself a lot has been done to

make the development of Qt applications with Qt 3.0 even easier than

before. Two new applications have been added: Qt Linguist is a tool to

help you translate your application into different languages; Qt

Assistant is an easy to use help browser for the Qt documentation that

supports bookmarks and can search by keyword.

Another change concerns the Qt build system, which has been reworked

to make it a lot easier to port Qt to new platforms. You can use this

platform independent build system - called qmake - for your own

applications.

And last but not least we hope you will enjoy the revisited and widely

extended documentation.

Qt/Embedded

----------

Qt/Embedded 3.0 provides the same features as Qt 3.0, but currently

lacks some of the memory optimizations and fine-tuning capabilities of

Qt/Embedded 2.3.x. We will add these in the upcoming maintainance

releases.

If you develop a new product based on Qt/Embedded, we recommend

switching to 3.0 because of the greatly improved functionality.

However, if you are planning a release within the next two months and

require memory optimizations not available with Qt/Embedded 3.0, we

suggest using Qt/Embedded 2.3.x.

The Qt Library

========================================

A large number of new features has been added to Qt 3.0. The following

list gives an overview of the most important new and changed aspects

of the Qt library.

Database support

----------------

One of the major new features in Qt 3.0 is the SQL module that

provides cross-platform access to SQL databases, making database

application programming with Qt seamless and portable. The API, built

with standard SQL, is database-neutral and software development is

independent of the underlying database.

A collection of tightly focused C++ classes are provided to give the

programmer direct access to SQL databases. Developers can send raw SQL

to the database server or have the Qt SQL classes generate SQL queries

automatically.  Drivers for Oracle, PostgreSQL, MySQL and ODBC are

available and writing new drivers is straightforward.

Tying the results of SQL queries to GUI components is fully supported

by Qt's SQL widgets. These classes include a tabular data widget

(for spreadsheet-like data presentation with in-place editing), a

form-based data browser (which provides data navigation and edit

functions) and a form-based data viewer (which provides read-only

forms). This framework can be extended by using custom field editors,

allowing for example, a data table to use custom widgets for in-place

editing. The SQL module fully supports Qt's signals/slots mechanism,

making it easy for developers to include their own data validation and

auditing code.

Qt Designer fully supports Qt's SQL module. All SQL widgets can be

laid out within Qt Designer, and relationships can be established

between controls visually. Many interactions can be defined purely in

terms of Qt's signals/slots mechanism directly in Qt Designer.

Explicit linking and plugins

-------------------------

The QLibrary class provides a platform independent wrapper for runtime

loading of shared libraries.

Specialized classes that make it possible to extend Qt's functionality

with plugins: QStylePlugin for user interface styles, QTextCodecPlugin

for text encodings, QImageFormatPlugin for image formats and

QSqlDriverPlugin for database drivers.

It is possible to remove unused components from the Qt library, and

easy to extend any application with 3rd party styles, database drivers

or text codecs.

Qt Designer supports custom widgets in plugins, and will use the

widgets both when designing and previewing forms (QWidgetPlugin).

Rich text engine and editor

---------------------------

The rich text engine originally introduced in Qt 2.0 has been further

optimized and extended to support editing. It allows editing formatted

text with different fonts, colors, paragraph styles, tables and

images. The editor supports different word wrap modes, command-based

undo/redo, multiple selections, drag and drop, and many other

features.  The engine is highly optimized for proccesing and displaying

large documents quickly and efficiently.

Unicode

-------

Apart from the rich text engine, another new feature of Qt 3.0 that

relates to text handling is the greatly improved Unicode support. Qt

3.0 includes an implementation of the bidirectional algorithm (BiDi)

as defined in the Unicode standard and a shaping engine for Arabic,

which gives full native language support to Arabic and Hebrew speaking

people. At the same time the support for Asian languages has been

greatly enhanced.

The support is almost transparent for the developer using Qt to

develop their applications. This means that developers who developed

applications using Qt 2.x will automatically gain the full support for

these languages when switching to Qt 3.0. Developers can rely on their

application to work for people using writing systems different from

Latin1, without having to worry about the complexities involved with

these scripts, as Qt takes care of this automatically.

Docked and Floating Windows

---------------------------

Qt 3.0 introduces the concept of dock windows and dock areas. Dock

windows are widgets, that can be attached to, and detached from, dock

areas. The most common kind of dock window is a tool bar. Any number of

dock windows may be placed in a dock area. A main window can have dock

areas, for example, QMainWindow provides four dock areas (top, left,

bottom, right) by default. The user can freely move dock windows and

place them at a convenient place in a dock area, or drag them out of

the application and have them float freely as top level windows in

their own right. Dock windows can also be minimized or hidden.

For developers, dock windows behave just like ordinary widgets. QToolbar

for example is now a specialized subclass of a dock window.  The API

of QMainWindow and QToolBar is source compatible with Qt 2.x, so

existing code which uses these classes will continue to work.

Regular Expressions

-------------------

Qt has always provided regular expression support, but that support

was pretty much limited to what was required in common GUI control

elements such as file dialogs. Qt 3.0 introduces a new regular

expression engine that supports most of Perl's regex features and is

Unicode based. The most useful additions are support for parentheses

(capturing and non-capturing) and backreferences.

Storing application settings

----------------------------

Most programs will need to store some settings between runs, for

example, user selected fonts, colors and other preferences, or a list

of recently used files.  The new QSettings class provides a platform

independent way to achieve this goal. The API makes it easy to store

and retrieve most of the basic data types used in Qt (such as basic

C++ types, strings, lists, colors, etc). The class uses the registry

on the Windows platform and traditional resource files on Unix.

Creating and controlling other processes

----------------------------------------

QProcess is a class that allows you to start other programs from

within a Qt application in a platform independent manner. It gives you

full control over the started program.  For example you can redirect

the input and output of console applications.

Accessibility

---------------

Accessibility means making software usable and accessible to a wide

range of users, including those with disabilities. In Qt 3.0, most

widgets provide accessibility information for assistive tools that can

be used by a wide range of disabled users. Qt standard widgets like

buttons or range controls are fully supported. Support for complex

widgets, like e.g. QListView, is in development. Existing applications

that make use of standard widgets will become accessible just by using

Qt 3.0.

Qt uses the Active Accessibility infrastructure on Windows, and needs

the MSAA SDK, which is part of most platform SDKs. With improving

standardization of accessibility on other platforms, Qt will support

assistive technologies on other systems too.

XML Improvements

----------------

The XML framework introduced in Qt 2.2 has been vastly improved. Qt

2.2 already supported level 1 of the Document Object Model (DOM), a

W3C standard for accessing and modifying XML documents.  Qt 3.0 has

added support for DOM Level 2 and XML namespaces.

The XML parser has been extended to allow incremental parsing of XML

documents. This allows you to start parsing the document directly

after the first parts of the data have arrived, and to continue

whenever new data is available.  This is especially useful if the XML

document is read from a slow source, e.g. over the network, as it

allows the application to start working on the data at a very early

stage.

SVG support

-----------

SVG is a W3C standard for "Scalable Vector Graphics". Qt 3.0's SVG

support means that QPicture can optionally generate and import static

SVG documents. All the SVG features that have an equivalent in

QPainter are supported.

Multihead support

-----------------

Many professional applications, such as DTP and CAD software, are able

to display data on two or more monitors. In Qt 3.0 the QDesktopWidget

class provides the application with runtime information about the

number and geometry of the desktops on the different monitors and such

allows applications to efficiently use a multi-monitor setup.

The virtual desktop of Windows 98 and 2000 is supported, as well as

the traditional multi-screen and the newer Xinerama multihead setups

on X11.

X11 specific enhancements

-------------------------

Qt 3.0 now complies with the NET WM Specification, recently adopted

by KDE 2.0.  This allows easy integration and proper execution with

desktop environments that support the NET WM specification.

The font handling on X11 has undergone major changes.  QFont no longer

has a one-to-one relation with window system fonts.  QFont is now a

logical font that can load multiple window system fonts to simplify

Unicode text display.  This completely removes the burden of

changing/setting fonts for a specific locale/language from the

programmer.  For end-users, any font can be used in any locale.  For

example, a user in Norway will be able to see Korean text without

having to set their locale to Korean.

Qt 3.0 also supports the new render extension recently added to

XFree86. This adds support for anti-aliased text and pixmaps with

alpha channel (semi transparency) on the systems that support the

rendering extension (at the moment XFree 4.0.3 and later).

Printing

--------

Printing support has been enhanced on all platforms. The QPrinter

class now supports setting a virtual resolution for the painting

process. This makes WYSIWYG printing trivial, and also allows you to

take full advantage of the high resolution of a printer when painting

on it.

The postscript driver built into Qt and used on Unix has been greatly

enhanced. It supports the embedding of true/open type and type1 fonts

into the document, and can correctly handle and display Unicode.

Support for fonts built into the printer has been enhanced and Qt now

knows about the most common printer fonts used for Asian languages.

Networking

-----------

A new class QHttp provides a simple interface for HTTP downloads and

uploads.

Compatibility with the Standard Template Library (STL)

------------------------------------------------------

Support for the C++ Standard Template Library has been added to the Qt

Template Library (QTL).  The QTL classes now contain appropriate copy

constructors and typedefs so that they can be freely mixed with other

STL containers and algorithms.  In addition, new member functions have

been added to QTL template classes which correspond to STL-style

naming conventions (e.g., push_back()).

Qt Designer

========================================

Qt Designer was a pure dialog editor in Qt 2.2 but has now been

extended to provide the full functionality of a GUI design tool.

This includes the ability to lay out main windows with menus and

toolbars. Actions can be edited within Qt Designer and then plugged

into toolbars and menu bars via drag and drop. Splitters can now be

used in a way similar to layouts to group widgets horizontally or

vertically.

In Qt 2.2, many of the dialogs created by Qt Designer had to be

subclassed to implement functionality beyond the predefined signal and

slot connections. Whilst the subclassing approach is still fully

supported, Qt Designer now offers an alternative: a plugin for editing

code. The editor offers features such as syntax highlighting,

completion, parentheses matching and incremental search.

The functionality of Qt Designer can now be extended via plugins.

Using Qt Designer's interface or by implementing one of the provided

interfaces in a plugin, a two way communication between plugin and Qt

Designer can be established. This functionality is used to implement

plugins for custom widgets, so that they can be used as real widgets

inside the designer.

Basic support for project management has been added. This allows you

to read and edit *.pro files, add and remove files to/from the project

and do some global operations on the project. You can now open the

project file and have one-click access to all the *.ui forms in the

project.

In addition to generating code via uic, Qt Designer now supports the

dynamic creation of widgets directly from XML user interface

description files (*.ui files) at runtime. This eliminates the need of

recompiling your application when the GUI changes, and could be used

to enable your customers to do their own customizations. Technically,

the feature is provided by a new class, QWidgetFactory in the

UI-library.

Qt Linguist

========================================

Qt Linguist is a GUI utility to support translating the user-visible

text in applications written with Qt. It comes with two command-line

tools: lupdate and lrelease.

Translation of a Qt application is a three-step process:

  1) Run lupdate to extract user-visible text from the C++ source

     code of the Qt application, resulting in a translation source file

     (a *.ts file).

  2) Provide translations for the source texts in the *.ts file using

     Qt Linguist.

  3) Run lrelease to obtain a light-weight message file (a *.qm file)

     from the *.ts file, which provides very fast lookup for released

     applications.

Qt Linguist is a tool suitable for use by translators. Each

user-visible (source) text is characterized by the text itself, a

context (usually the name of the C++ class containing the text), and

an optional comment to help the translator. The C++ class name will

usually be the name of the relevant dialog, and the comment will often

contain instructions that describe how to navigate to the relevant

dialog.

You can create phrase books for Qt Linguist to provide common

translations to help ensure consistency and to speed up the

translation process. Whenever a translator navigates to a new text to

translate, Qt Linguist uses an intelligent algorithm to provide a list

of possible translations: the list is composed of relevant text from

any open phrase books and also from identical or similar text that has

already been translated.

Once a translation is complete it can be marked as "done"; such

translations are included in the *.qm file. Text that has not been

"done" is included in the *.qm file in its original form. Although Qt

Linguist is a GUI application with dock windows and mouse control,

toolbars, etc., it has a full set of keyboard shortcuts to make

translation as fast and efficient as possible.

When the Qt application that you're developing evolves (e.g. from

version 1.0 to version 1.1), the utility lupdate merges the source

texts from the new version with the previous translation source file,

reusing existing translations. In some typical cases, lupdate may

suggest translations. These translations are marked as unfinished, so

you can easily find and check them.

Qt Assistant

========================================

Due to the positive feedback we received about the help system built

into Qt Designer, we decided to offer this part as a separate

application called Qt Assistant. Qt Assistant can be used to browse

the Qt class documentation as well as the manuals for Qt Designer and

Qt Linguist. It offers index searching, a contents overview, bookmarks

history and incremental search. Qt Assistant is used by both Qt

Designer and Qt Linguist for browsing their help documentation.

qmake

========================================

qmake is a cross-platform make utility that makes it possible to build

the Qt library and Qt-based applications on various target platforms

from one single project description. It is the C++ successor of

'tmake' which required Perl.

qmake offers additional functionallity that is difficult to reproduce

in tmake. Qt uses qmake in its build system and we have released it as

free software.

Detailed changes

=============

Qt 3.0 went through 6 beta releases. These are the detailed changes

since Beta 6 only. For other changes, please see the changes notes

of the respective beta releases.

Qt 3.0 final is not binary compatible with Beta6; any programs linked

against Beta6 must be recompiled.

Below you will find a description of general changes in the Qt

Library, Qt Designer and Qt Assistant.  Followed by a detailed list of

changes in the API.

****************************************************************************

*			    General					   *

****************************************************************************

****************************************************************************

*			   Library					   *

****************************************************************************

- QApplication

	make sure we process deferred deletes before leaving the event

	loop. This fixes some ocassions of memory leaks on exit.

	win32: some improvements for modality and dockwindow handling

	x11 only: read non-gui QSettings when running without GUI.

- QCheckListItem

	Make the checkboxes respect the AlignCenter flag. Also make

	the boxes look better in case they are not placed in the first

	column.

- QComboBox

	if we have a currentItem and then we set the combobox to be

	editable then set the text in the lineedit to be of the

	current item.

- QCommonStyle

	QToolButton: spacing between a toolbutton's icon and its label.

	QProgressBar: text color fixed.

- QCursor

	added the What's This? cursor to the collection.

- QDataTable

	fixed broken context menus.

- QDate

	fixed addMonth() overflow.

- QDesktopWidget

	win32 only: works now also for cases where the card handles

	multiple monitors and GetSystemMetrics returns a single screen

	only.

- QDomAttr

	fixed a memory leak in setNodeValue()

- QDomNodeMap

	added count() as a Qt-style alias for length()

- QDragObject

	default to the middle of the pixmap as a hot spot, this looks

	nicer.

- QFileDialog (internal dialog)

	make viewMode() return the correct value even after the dialog

	is finished. Fixed getOpenFileName and getSaveFileName for

	non-existant directories. Make sure that when it's in

	directory mode that the filters reflect this, and change the

	label from file name to directory.

	win32 only: Improved modality when using the native file

	dialog.

- QFont

	x11 only: speed up fontloading with even more clever

	caching. Make sure we can match scaled bitmap fonts by

	default. Do not load a backup font for a script that is not

	default. Make sure the pixel size is correct, even for fonts

	that are unavailable. Try even harder to find a fontname that

	is not understood. Some RENDER performance optimizations.

- QFontDialog

	make sure the content is set up correctly when initializing

	the dialog.