Dr. Dobb's Journal - March 2008 - (Page 55)

by Wim Dumon and Koen Deforche State of the Art Wt: A Web Toolkit Writing web applications using a C++ GUI programming style Wt is a freely available library and application server (www.webtoolkit.eu/wt) that lets C++ programmers write modern web applications using a familiar C++ GUI programming style. Wt then renders the C++ applications to the web browser. Figure 1, for instance, is a running Wt application—a functional look-alike of the GMail composer, fully AJAX enabled, and written entirely in C++ using CSS for the markup. Wim leads Sobicom nv, a software engineering consultancy company specialized in embedded systems design and bioinformatics. Koen is completing a Ph.D. in Medical Sciences. They can be contacted at wdumon@gmail.com and koen.deforche@ gmail.com, respectively. From a programmer’s perspective, the Wt API is similar to those offered by libraries such as Qt, Gtk, wxWindows, and the like. However, instead of rendering widgets to Windows/X11/ windows, Wt incrementally renders the widgets in web browsers. Wt completely hides the underlying web technologies (HTML, AJAX, XML, CGI, JavaScript, and DHTML), chooses a rendering and sessionmanagement strategy depending on browser capabilities, and deals with browser dialects. Browser-side events such as button clicks, mouse movements, and drag-and-drop events are transparently converted into serverside events using Wt’s signal/slot mechanism. Wt comes with a dynamic C++-to-JavaScript translation mechanism to avoid the high-latency server roundtrip for simple visual updates, while sticking to a single C++ specification of the event-handling code. While Wt’s rendering engine preferably uses AJAX for incremental rendering of updates made to the widget tree, Wt applications also work when AJAX or JavaScript are not available (or disabled). By exposing only a widget-level API, the library can guarantee protection against the most common cross-site scripting (XSS) attacks, by built-in and automatic filtering of displayed strings for malicious tags. Being a native C++ library, web applications developed with Wt typically enjoy greater efficiency and a smaller footprint than Java or Ruby solutions. As such, Wt lends itself to devices where efficiency and footprint matters, like in embedded applications. Library Overview A Wt session starts when users access the application URL, and ends when users quit the application explicitly, or implicitly by leaving the webpage. To programmers, session management is transparent and similar to other GUI applications on multiuser systems. In its most naïve configuration, for every new Wt session, a process is spawned and used for the duration of the session. A server with N sessions (logged-in users, for instance), shall therefore have N processes running. Wt can be configured to use cookies or URL rewriting to bind requests to the correct session. With this architecture, all sessions run in their own memory space (a crash of one process can never influence other processes), and sessions cannot communicate with each other unless explicit communication mechanisms are used, providing an additional security safeguard. Because this model is notappropriate or even desired for public web applications, Wt may also be configured to multiplex all sessions onto a limited number or even only one process. This saves server resources and is more resilient to Denial-of-Service attacks. These deployment choices offered by Wt do not affect your program March 2008 l www.ddj.com l Dr. Dobb’s Journal 55 http://www.webtoolkit.eu/wt 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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