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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><!-- /home/reggie/tmp/qt-3.0-reggie-5401/qt-x11-commercial-3.0.5/doc/changes.doc:37 --><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Key Features in Qt 3.0</title><style type="text/css"><!--h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm; }a:link { color: #004faf; text-decoration: none }a:visited { color: #672967; text-decoration: none }body { background: #ffffff; color: black; }--></style></head><body><table border="0" cellpadding="0" cellspacing="0" width="100%"><tr bgcolor="#E5E5E5"><td valign=center> <a href="index.html"><font color="#004faf">Home</font></a> | <a href="classes.html"><font color="#004faf">All Classes</font></a> | <a href="mainclasses.html"><font color="#004faf">Main Classes</font></a> | <a href="annotated.html"><font color="#004faf">Annotated</font></a> | <a href="groups.html"><font color="#004faf">Grouped Classes</font></a> | <a href="functions.html"><font color="#004faf">Functions</font></a></td><td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Key Features in Qt 3.0</h1> Qt 3.0 adds a lot of new features and improvements over the Qt 2.xseries. Some internals have undergone major redesign and new classesand methods have been added.<p> We have tried to keep the API of Qt 3.0 as compatible as possible withthe Qt 2.x series. For most applications only minor changes will beneeded to compile and run them successfully using Qt 3.0.<p> One of the major new features that has been added in the 3.0 releaseis a module allowing you to easily work with databases. The API isplatform independent and database neutral. This module is seamlesslyintegrated into Qt Designer, greatly simplifying the process ofbuilding database applications and using data aware widgets.<p> Other major new features include a plugin architecture. You can useyour own and third party plugins your own applications. The Unicode support of Qt 2.x has been greatly enhanced, it nowincludes full support for scripts written from right to left (e.g.Arabic and Hebrew) and also provides improved support for Asianlanguages.<p> Many new classes have been added to the Qt Library. Amongst them areclasses that provide a docking architecture(<a href="qdockarea.html">QDockArea</a>/<a href="qdockwindow.html">QDockWindow</a>), a powerful rich text editor(<a href="qtextedit.html">QTextEdit</a>), a class to store and access application settings(<a href="qsettings.html">QSettings</a>) and a class to create and communicate with processes(<a href="qprocess.html">QProcess</a>).<p> Apart from the changes in the library itself a lot has been done tomake the development of Qt applications with Qt 3.0 even easier thanbefore. Two new applications have been added: Qt Linguist is a tool tohelp you translate your application into different languages; QtAssistant is an easy to use help browser for the Qt documentation thatsupports bookmarks and can search by keyword.<p> Another change concerns the Qt build system, which has been reworkedto make it a lot easier to port Qt to new platforms. You can use thisplatform independent build system for your own applications.<p> <h2> The Qt Library</h2><a name="1"></a><p> A large number of new features has been added to Qt 3.0. The followinglist gives an overview of the most important new and changed aspectsof the Qt library. A full list of every new method follows theoverview.<p> <h3> Database support</h3><a name="1-1"></a><p> One of the major new features in Qt 3.0 is the <a href="sql.html">SQLmodule</a> that provides multiplatform access to SQL databases,making database application programming with Qt seamless and portable.The API, built with standard SQL, is database-neutral and softwaredevelopment is independent of the underlying database.<p> A collection of tightly focused C++ classes are provided to give theprogrammer direct access to SQL databases. Developers can send raw SQLto the database server or have the Qt SQL classes generate SQL queriesautomatically. Drivers for Oracle, PostgreSQL, MySQL and ODBC areavailable and writing new drivers is straightforward.<p> Tying the results of SQL queries to GUI components is fully supportedby Qt's SQL widgets. These classes include a tabular data widget(for spreadsheet-like data presentation with in-place editing), aform-based data browser (which provides data navigation and editfunctions) and a form-based data viewer (which provides read-onlyforms). This framework can be extended by using custom field editors,allowing for example, a data table to use custom widgets for in-placeediting. The SQL module fully supports Qt's signal/slots mechanism,making it easy for developers to include their own data validation andauditing code.<p> Qt Designer fully supports Qt's SQL module. All SQL widgets can belaid out within Qt Designer, and relationships can be establishedbetween controls visually. Many interactions can be defined purely interms of Qt's signals/slots mechanism directly in Qt Designer.<p> <h3> Plugins</h3><a name="1-2"></a><p> The <a href="qlibrary.html">QLibrary</a> class provides a platform independent wrapper for runtimeloading of shared libraries. QPluginManager makes it trivial to implementplugin support in applications. The Qt library is able to loadadditional styles, database drivers and text codecs from plugins. <p> Qt Designer supports custom widgets in plugins, and will use thewidgets both when designing and previewing forms.<p> See the <a href="plugins-howto.html">plugins documentation</a>.<p> <h3> Rich text engine and editor</h3><a name="1-3"></a><p> The rich text engine originally introduced in Qt 2.0 has been furtheroptimized and extended to support editing. It allows editing formattedtext with different fonts, colors, paragraph styles, tables andimages. The editor supports different word wrap modes, command-basedundo/redo, multiple selections, drag and drop, and many otherfeatures. The new <a href="qtextedit.html">QTextEdit</a> engine is highly optimized for proccesingand displaying large documents quickly and efficiently. <p> <h3> Unicode</h3><a name="1-4"></a><p> Apart from the rich text engine, another new feature of Qt 3.0 thatrelates to text handling is the greatly improved Unicode support. Qt3.0 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 speakingpeople. At the same time the support for Asian languages has beengreatly enhanced.<p> The support is almost transparent for the developer using Qt todevelop their applications. This means that developers who developedapplications using Qt 2.x will automatically gain the full support forthese languages when switching to Qt 3.0. Developers can rely on theirapplication to work for people using writing systems different fromLatin1, without having to worry about the complexities involved withthese scripts, as Qt takes care of this automatically.<p> <h3> Docked and Floating Windows</h3><a name="1-5"></a><p> Qt 3.0 introduces the concept of Dock Windows and Dock Areas. Dockwindows are widgets, that can be attached to, and detached from, dockareas. The commonest kind of dock window is a tool bar. Any number ofdock windows may be placed in a dock area. A main window can have dockareas, for example, <a href="qmainwindow.html">QMainWindow</a> provides four dock areas (top, left,bottom, right) by default. The user can freely move dock windows andplace them at a convenient place in a dock area, or drag them out ofthe application and have them float freely as top level windows intheir own right. Dock windows can also be minimized or hidden.<p> For developers, dock windows behave just like ordinary widgets. QToolbarfor example is now a specialized subclass of a dock window. The APIof QMainWindow and <a href="qtoolbar.html">QToolBar</a> is source compatible with Qt 2.x, soexisting code which uses these classes will continue to work.<p> <h3> Regular Expressions</h3><a name="1-6"></a><p> Qt has always provided <a href="qregexp.html#regular-expression">regular expression</a> support, but that supportwas pretty much limited to what was required in common GUI controlelements such as file dialogs. Qt 3.0 introduces a new regularexpression engine, <a href="qregexp.html">QRegExp</a>, that supports most of Perl's regexfeatures and is Unicode based. The most useful additions are supportfor parentheses (capturing and non-capturing) and backreferences.<p> <h3> Storing application settings</h3><a name="1-7"></a><p> Most programs will need to store some settings between runs, forexample, user selected fonts, colors and other preferences, or a listof recently used files. The new <a href="qsettings.html">QSettings</a> class provides a platformindependent way to achieve this goal. The API makes it easy to storeand retrieve most of the basic data types used in Qt (such as basicC++ types, strings, lists, colors, etc). The class uses the registryon the Windows platform and traditional resource files on Unix.<p> <h3> Creating and controlling other processes</h3><a name="1-8"></a><p> <a href="qprocess.html">QProcess</a> is a class that allows you to start other programs fromwithin a Qt application in a platform independent manner. It gives youfull control over the started program, for example you can redirectthe input and output of console applications.<p> <h3> Accessibility</h3><a name="1-9"></a><p> Accessibility means making software usable and accessible to a widerange of users, including those with disabilities. In Qt 3.0, mostwidgets provide accessibility information for assistive tools that canbe used by a wide range of disabled users. Qt standard widgets likebuttons or range controls are fully supported. Support for complex⌨️ 快捷键说明
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