Dr. Dobb's Journal - March 2008 - (Page 58)

State of the Art WT: A WEB TOOLKIT the browser. But the locale may also be changed at runtime, using WApplication::setLocale(locale). Here comes the nice part of the story. WApplication::setLocale() will invoke a refresh of the entire application, by calling WApplication::refresh(), which will propagate a WWidget::refresh() through the entire widget tree. During this Listing One class MyWidget : public WCompositeWidget { public: MyWidget(WContainerWidget *parent = 0) : WcompositeWidget(parent), { fumbleButton_ = new WPushButton("Fumble"); fumbleButton_->clicked.connect(SLOT(this, MyWidget::doFumble)); } private: WpushButton *fumbleButton_; void doFumble() { fumbleButton_->disable(); fumbleSome( ); } }; propagation, all widgets use the new locale to resolve their displayed text elements in the new locale, and any changes are caught by the usual Wt rendering mechanism to be reflected in the browser. This propagation requires no effort from you, even for application-defined widgets. Internationalization requires support for characters that go beyond the 8-bit western character sets. For this purpose, Wt provides Unicode support for both literal and localized strings. For literal strings, you may specify and access content through narrow, wide, and UTF8 encoded strings, and therefore allow interfacing with legacy code. For localized strings, Wt relies on the extensive support for Unicode and different character encodings available in XML. Server-Side Event Handling Wt’s signals and slots are implemented on top of the Boost.Signals package, which is part of the C++ Boost template libraries. All classes that inherit from WObject can use signals and slots with automatic care for connections when objects are destructed, because WObject inherits from boost::trackable. Wt makes all user interaction with HTML DOM elements available by emitting the corresponding Wt::Signal. These events include keyboard events (keyWentDown, keyWentUp, keyPressed), mouse events (clicked, doubleClicked, mouseMoved, and so on) and many others. The event is only propagated if the corresponding signal has any connections, and therefore avoids unnecessary communication. Unfortunately, without availability of JavaScript, the application may only react to click events. Wt is designed to be functional even when the client has no JavaScript support, and since the availability of JavaScript is indicated using WEnvironment::javaScript(), the absence of richer interaction may be worked around if required, by providing alternative methods for essential operations; for example, by adding extra buttons. Listing One illustrates a common Wt construct that instantiates a widget and reacts to some of its events (for brevity, we mix the implementation in the class declaration). In this example, a button is created as part of a new composite widget. When Listing Two class MyWidget : public WCompositeWidget { public: MyWidget(WContainerWidget *parent = 0) : WcompositeWidget(parent), { implementStateless(&MyWidget::disableFumbleButton); fumbleButton_ = new WPushButton("Fumble"); fumbleButton_ ->clicked.connect(SLOT(this, MyWidget::disableFumbleButton)); fumbleButton_->clicked.connect(SLOT(this, MyWidget::doFumble)); } private: WpushButton *fumbleButton_; void disableFumbleButton() { fumbleButton_->disable(); } void doFumble() { fumbleSome( ); } }; Listing Three class MyWidget : public WCompositeWidget { public: MyWidget(WContainerWidget *parent = 0) : WcompositeWidget(parent), { fumbleButton_ = new WPushButton("Fumble"); fumbleButton_ ->clicked.connect(SLOT(fumbleButton_, WPushButton::disable)); fumbleButton_->clicked.connect(SLOT(this, MyWidget::doFumble)); } private: WpushButton *fumbleButton_; void doFumble() { fumbleSome( ); } }; 58 Dr. Dobb’s Journal l www.ddj.com l March 2008 http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - March 2008

Dr. Dobb's Journal - March 2008 Contents Hmmmm Alia Vox Developer Diaries Developer’s Notebook Social Networks and Software Development Conversations Detecting Bugs in Safety-Critical Code Change Code Without Fear Continuous Integration and Performance Testing Wt: A Web Toolkit Automating Release Notifications The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - March 2008

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