内容

• Qt Core 变化
• QStandardPaths
• 编译时校验信号槽连接
• Perl 兼容的正则表达式
• Qt GUI 变化
• 用于窗口和渲染的新类
• OpenGL 类
• QOpenGLPaintDevice
• Qt Network 变化
• QDnsLookup
• 更好地支持 IPv6 和双模网络
• 绑定 TCP 套接字
• SSL 证书
• 用于有缺陷 SSL 服务器的解决方案
• 支持不透明私钥
• Qt QML 变化
• QML 引擎
• 类型系统
• 其它
• Qt Quick 变化
• 新图形体系结构
• 视觉和图形类型
• 动画
• Text
• 用户输入
• 专用容器
• 位置器
• 模型和视图
• 粒子系统支持
• 实用类型
• Qt Multimedia 变化
• 新的类和函数
• 其它 Qt 5 发行的补充

Qt 5.0 的新功能

Qt Core 变化

QStandardPaths

QStandardPaths is a more powerful version of QDesktopServices that was present in Qt 4. Modeled after KStandardDirs from KDE 4, it contains additional features such as searching for all occurrences of a given file in the storage locations.

编译时校验信号槽连接

QObject now supports an additional syntax for connecting signals to slots, which forces the compiler to check whether the signal and the receiver exist and their arguments are compatible.

This syntax allows connecting a signal to any kind of C++ receiver, including C++11 lambdas, member functions, or static functions. The receivers no longer need to be declared as slots, but such declarations are still recommended for readability.

见 基于字符串的连接和基于函子的连接之间的差异 了解更多细节。

Perl 兼容的正则表达式

QRegularExpression is introduced to provide better support for regular expressions compatible with Perl. This class is more powerful and faster than QRegExp , and supports more features such as lazy and possessive quantifiers, lookbehinds, named capturing groups, and iteration of matches.

Qt GUI 变化

用于窗口和渲染的新类

A new set of enabler classes have been added, most importantly QWindow , QScreen , QSurfaceFormat ，和 QOpenGLContext . These are now used as backends for the Qt Widgets module and by Qt Quick 2.

OpenGL 类

Most of the useful Qt OpenGL classes have been polished and moved into Qt GUI . A few important ones are, QOpenGLFramebufferObject , QOpenGLShaderProgram , QOpenGLFunctions , and so on. For the complete list, refer to Qt GUI C++ 类 .

This change introduces QOpenGLContext as a replacement for QGLContext. This replacement class is more generic and decoupled from QWindow , making it to support more use cases such as using the same context for multiple surfaces.

QOpenGLPaintDevice

Instead of having QWindow and QOpenGLFramebufferObject be subclasses of QPaintDevice , you can now use QOpenGLPaintDevice . This new alternative can be created on the stack, makes it easier and flexible to render into the currently bound context using QPainter .

Qt Network 变化

QDnsLookup

It is now possible to lookup DNS records using the new QDnsLookup API. This does not replace QHostInfo , which is still the API to be used for resolving a host name to an IP address. QDnsLookup is mainly used for other types of DNS record, such as SRV, TXT and MX.

注意： This new class replaces the Q3Dns API, which is removed in Qt 5.

更好地支持 IPv6 和双模网络

Most applications using host names and network layer transparent protocols, will now gain IPv6 support transparently. This means, QTcpServer and QUdpSocket bound to QHostAddress::Any can now receive both IPv4 and IPv6 connections, although, QHostAddress::AnyIPv4 and QHostAddress::AnyIPv6 can be used to bind to only one protocol.

Outgoing http connections using QNetworkAccessManager will now attempt both IPv4 and IPv6 connections in parallel, and use the one that succeeds first.

绑定 TCP 套接字

QTcpSocket can be bound to an IP address before connecting, which is useful for limiting connection to a specific interface in a multi-homed environment.

SSL 证书

SSL certificate extensions can now be accessed to enable further development of SSL support in Qt.

Developers can also verify an SSL certificate chain programatically now.

用于有缺陷 SSL 服务器的解决方案

QSsl::SslOption enum now allows a QSslSocket -based code to access legacy systems by enabling bug workarounds.

注意： This change is also back-ported to Qt 4.8.

支持不透明私钥

This allows applications to read private keys from devices such as PKCS#11 dongles, as illustrated by the qsslkey example

Qt QML 变化

This is a new module in Qt 5 that provides the QML engine and the backend infrastructure.

QML 引擎

• v8 JavaScript 引擎
• Various parser and compiler optimizations have been implemented along with the new bindings optimizer.
• Loading/compilation can now be performed in a separate thread. This can be enabled by loading a loader object asynchronously through its source property, or by passing the Component.Asynchronous parameter to Qt.createComponent() .
• New QQmlEngine::trimComponentCache () function safely discards unused data in the engine’s component cache to free memory.

类型系统

• New var property type can hold JavaScript references.
• QML properties of type var and variant can now hold pixmaps.
• Value type improvements:
  • QColor is now a value type. The red, green, blue and alpha channels of a “color” property can now be accessed using “r”, “g”, “b” and “a” properties.
  • Improved support for QVector4D , now constructible in QML using Qt.vector4d() .
• Support for certain sequence types ( QList <int>, QList <qreal>, QList <bool>, QList < QUrl >, QList < QString > and QStringList ) has been improved. QObjects can define Q_PROPERTYs of these types which can be accessed from JavaScript.

其它

• JavaScript (.js) files can now import QML modules and other JavaScript files using the “import” statement.
• QQmlExpression can now be constructed directly (and more efficiently) from a QQmlScriptString .
• The component returned by Qt.createComponent() is no longer the owned by the engine. Be sure to hold a reference,or provide a parent.

Qt Quick 变化

This is a new module in Qt 5 which provides the visual canvas and scenegraph backend as well as the QtQuick QML module for QML-based application development.

The module replaces the QDeclarative* equivalents in QtQuick 1 with the following:

• QQuickView
• QQuickWindow
• QQuickItem
• QQuickPaintedItem

见 Qt Quick C++ 类 for the complete list.

QtQuick 2.0 QML module is a major update, and the following sections outline the features that come with it:

新图形体系结构

• Qt Quick 2.0 uses a dedicated OpenGL (ES) 2.0 based Qt Quick 场景图形 scene graph for all its rendering.

视觉和图形类型

• New Canvas type for drawing, provides a HTML5 canvas-like API along with the following additional features:
  • Two render targets: Canvas.Image and Canvas.FramebufferObject .
  • Background thread rendering.
  • Tiled canvas rendering.
  • Support for most of the HTML5 context2d APIs.
• Image type now has:
  • New horizontal and vertical alignment properties, horizontalAlignment and verticalAlignment .
  • Image.Pad enum value for fillMode property does not transform the image unlike the other fillMode 枚举值。
  • sourceSize.width and sourceSize.height now fits the image to size maintaining the aspect ratio.

动画

• New SpriteSequence type renders animated sprites and can transition between animations.
• New Sprite type that represents each animation in a SpriteSequence .
• New AnimatedSprite type for drawing single sprite animations.

Text

• Text :
  • AutoText format now switches to StyledText 而不是 RichText .
  • lineLaidOut signal is emitted for every line during the layout process to give the option of positioning and/or resizing text as they are laid out.
  • doLayout() method can now trigger the text layout from JavaScript.
  • ElideRight to support text that spans multiple lines.
  • fontSizeMode property now supports wrapping the text to the item size.
  • minimumPixelSize and minimumPointSize properties can be used to specify a lower bound when auto-fitting.
• TextEdit.textFormat property now defaults to PlainText 而不是 AutoText .
• TextInput 现在拥有 wrapMode and verticalAlignment properties.
• TextInput.positionAt() now takes y 值。

用户输入

• New MultiPointTouchArea type can process multi-point touches and provide information about the touch points including position, pressure and velocity.
• MouseArea type now:
  • Propagates wheel events.
  • Propagates clicked , doubleClicked and pressAndHold events differently to pressed . These events are propagated to the handler of the topmost MouseArea in the stack-order.
  • Can ignore the propagated events using the propagateComposedEvents . Such ignored events are propagated to the next MouseArea handler in the stack-order.

专用容器

• Flickable type now has:
  • a new rebound property that enables you to specify the transition type for the bounce back animation.
  • New topMargin , bottomMargin , leftMargin ，和 rightMargin properties allow extra margin space to be specified. This is useful to implement the pull-to-refresh functionality for a list.
  • New xOrigin and yOrigin properties provide the top left position of the content item.
  • New dragging , draggingHorizontally ，和 draggingVertically properties that provide information when the flickable area is dragged.

位置器

The following features are related to Row, Column, Grid, and Flow types:

• The “add” and “move” transitions can now access the ViewTransition attached property, and also animate arbitrary item properties (instead of being restricted to animating an item’s position).
• New Positioner.index , Positioner.isFirstItem and Positioner.isLastItem attached properties for items within a positioner.
• Grid type has new rowSpacing and columnSpacing 特性。
• All spacing properties on positioners now use real numbers instead of integers.

模型和视图

• ListView and GridView :
  • Transitions can be specified to animate the adding, removing and moving of items in a view. For details, see ViewTransition , ListView.add , ListView.addDisplaced , GridView.add ，和 GridView.addDisplaced .
  • New verticalLayoutDirection property enables items to be laid out from bottom-to-top using the BottomToTop 枚举值。
  • cacheBuffer property now has a non-zero default and delegates in the cacheBuffer are created asynchronously.
  • New headerItem and footerItem properties provide access to the instantiated header and footer items.
  • RightToLeft layout now also reverses the preferredHighlightBegin and preferredHighlightEnd .
• ListView 's new section.labelPositioning property can fix the current section label to the start of the view, and the next section label to the end of the view, so that labels do not scroll while section items are still in view.
• PathView has two new properties, curretnItem and maximumFlickVelocity .

粒子系统支持

新的 QtQuick .Particles 2.0 module provides support for the composition of a variety of 2D particle systems. See 使用 Qt Quick 粒子系统 了解更多细节。

实用类型

• New PathArc , PathCurve and PathSvg types:
  • PathArc and PathCurve support the construction of arcs and catmull-rom curves, respectively. PathSvg supports the construction of a path from an SVG string.
• Loader:
  • New asynchronous property allows components to be instantiated with a lower chance of blocking. With the asynchronous property set to true , the component is compiled in a background thread.
  • New active property delays instantiation of a Loader object’s item.
  • New setSource(JSObject) method to specify initial property values for the loaded item, similar to Component.createObject() .
  • sourceChanged signal is now only emitted when the source changes and the sourceComponentChanged signal is now emitted when the sourceComponent is changed. Ealier, these signals were emitted by the Loader only when one of the two properties had changed.
  • Loader type can now be used as a value source, and it can restore any previously set binding if its "when" clause becomes false .

Qt Multimedia 变化

Qt Multimedia is an essential module replacing the QtMultimedia library and Qt MultimediaKit mobility API in Qt 4.8. It features full support for Audio and Video playback, and recording. Support for web cameras is integrated.

Qt Multimedia uses the system’s native multimedia engine as a backend, and does not come with its own audio or video codecs. Thus the supported list of codecs is equivalent to the ones supported by the underlying OS.

It uses DirectShow and WMF on Windows, AVFoundation on Mac and gstreamer on Linux.

新的类和函数

The section provides a comprehensive list of all new classes and functions introduced in Qt 5.

• 新类
• 新成员函数
• 名称空间中的新函数
• 新全局函数
• 新宏
• 新枚举类型
• 新的 Typedef
• 新特性
• 新 QML 类型
• 新 QML 特性
• 新 QML 方法

新类