KDE Platform

KDE Platform is a set of frameworks by KDE that serve as technological foundation for all KDE applications. Ever since KDE’s brand repositioning the Platform is released as separate product in sync with KDE’s Plasma Workspaces as part of the KDE Software Compilation 4. While the Platform is mainly written in C++, it includes bindings for other programming languages.^[1][2]

Technologies

• User Interface
  • Plasma – desktop and panel widget engine
  • KHTML – HTML rendering engine
  • KIO – extensible network-transparent file access
  • KParts – lightweight in-process graphical component framework
  • Sonnet – spell checker
  • XMLGUI – allows defining UI elements such as menus and toolbars via XML files
  • Goya

• Hardware and Multimedia
  • Phonon – multimedia framework
  • Solid – device integration framework

• Services
  • NEPOMUK
  • KNewStuff – KDE's "Hot New Stuff" classes
  • Policykit-KDE

• Communication
  • Akonadi

• Games
  • Gluon
  • KGGZ

• Other
  • ThreadWeaver – library to use multiprocessor systems more effectively
  • Kiosk – allows disabling features within KDE to create a more controlled environment
  • Kross
  • KConfig XT
  • ownCloud^[3]

Technologies superseded in KDE Platform 4

• aRts – sound server (replaced with Phonon)
• DCOP – inter-process communication system (replaced with D-Bus)

KJS

KJS is KDE's ECMAScript/JavaScript engine that was originally developed for the KDE project's Konqueror web browser by Harri Porten in 2000.

On June 13, 2002, Maciej Stachowiak announced on a mailing list that Apple was releasing JavaScriptCore, a framework for Mac OS X that was based on KJS.^[4] Through the WebKit project, JavaScriptCore has since evolved into SquirrelFish Extreme, a JavaScript engine that compiles JavaScript into native machine code.

External links

• KJS (KDE JavaScript/EcmaScript Engine) - api.kde.org
• KJSEmbed (allows you to access to QObjects from JavaScript)
• KJSEmbed Documentation
• OpenDarwin's Javascript engine based on KJS

KParts

KParts is the component framework for the KDE desktop environment. An individual component is called a KPart. KParts are analogous to Bonobo components in GNOME and ActiveX controls in Microsoft's Component Object Model. Konsole is available as a KPart and is used in applications like Konqueror and Kate.

Example uses of KParts:

• Konqueror uses the Okular part to display documents
• Konqueror uses the Dragon Player part to play multimedia
• Kontact embeds kdepim applications
• Kate and other editors use the katepart editor component
• Several applications use the Konsole KPart to embed a terminal

External links

• Creating and Using Components (KParts) (from KDE)
• Writing Plugins For KDE Applications (from KDE)
• Coding with KParts (from IBM)

Solid

Solid is a device integration framework for KDE Platform 4, the current release of KDE. It functions on similar principles to KDE's multimedia pillar Phonon; rather than managing hardware on its own, it makes existing solutions accessible through a single API. The current solution uses udev, NetworkManager and BlueZ (the official Linux Bluetooth stack). However, any and all parts can be replaced without breaking the application, making applications using Solid extremely flexible and portable.^[5][6] Work is underway to build a Solid backend for the Windows port of KDE based on Windows Management Instrumentation.^[7]

Solid is broken up into many hardware “domains” which operate independently. Domains may be added as needed. For instance, one domain may be Bluetooth, and another may be power management. Solid is used extensively within KDE 4 and its popular applications, making them more aware of hardware events and easier to develop.

External links

• Solid home page
• KDE dot article on Solid

Sonnet

Sonnet is a multilingual spell check program to be included in KDE 4. Sonnet is going to replace kspell2 that was created for KDE 3. The two main goals for Sonnet's development were a simpler API, wider language support and performance. Notable improvements in Sonnet over kspell2 are

• Automatic language detection, a language can be identified with as little as 20 characters of text. Even multiple languages in the same document can be detected and spell checked correctly
• Better performance
• Improvements in spell checking languages like Thai and Japanese
• Simpler design, kspell2 consisted of 7 components and a complicated API. Sonnet is a single component and aims to provide a simpler API
• The user can select a primary and backup dictionary, an example given was a doctor who frequently uses terms from a medical dictionary. Words that would not appear in a regular dictionary would be corrected by the backup dictionary that contains medical terms.

External links

• Article on Sonnet
• Developers blog

ThreadWeaver

ThreadWeaver is a programming library developed for KDE 4^[8] by Mirko Boehm that allows developers to easily take advantage of multicore processors.^[8] In Threadweaver the workload is divided into individual jobs, then relationship between jobs (what order they should be completed or which has a higher priority) from that Threadweaver will work out the most efficient way to execute them. Krita has implemented visual filter previews using ThreadWeaver to prevent GUI lockups.

Further reading

• Til Adam and Mirko Boehm (2009). "When the bazaar sets out to build cathedrals (§ ThreadWeaver)". In Diomidis Spinellis and Georgios Gousios. Beautiful Architecture: Leading Thinkers Reveal the Hidden Beauty in Software Design. O'Reilly Media, Inc.. pp. 303–314. ISBN 059651798X. 

Hello world example

#include <KApplication>
#include <KAboutData>
#include <KCmdLineArgs>
#include <KMessageBox>
#include <KLocale>
 
int main (int argc, char *argv[])
{
    KAboutData aboutData(
                         // The program name used internally.
                         "tutorial1",
                         // The message catalog name
                         // If null, program name is used instead.
                         0,
                         // A displayable program name string.
                         ki18n("Tutorial 1"),
                         // The program version string.
                         "1.0",
                         // Short description of what the app does.
                         ki18n("Displays a KMessageBox popup"),
                         // The license this code is released under
                         KAboutData::License_GPL,
                         // Copyright Statement
                         ki18n("Copyright (c) 2007"),
                         // Optional text shown in the About box.
                         // Can contain any information desired.
                         ki18n("Some text..."),
                         // The program homepage string.
                         "http://example.com/",
                         // The bug report email address
                         "submit@bugs.kde.org");
 
    KCmdLineArgs::init( argc, argv, &aboutData );
    KApplication app;
    KGuiItem yesButton( i18n( "Hello" ), QString(),
                        i18n( "This is a tooltip" ),
                        i18n( "This is a WhatsThis help text." ) );
    KMessageBox::questionYesNo( 0, i18n( "Hello World" ),
                                i18n( "Hello" ), yesButton );
    return 0;
}

References

External links

• TechBase, documentation for KDE developers
• API Reference, the reference guides for the KDE APIs
• Commit-Digest
• Source Cross Reference, Identifier search
• KDE Projects, overview of all projects within git.kde.org
• KDE quick Git source code browser
• ReviewBoard
• English Breakfast Network
• KDE Bug Tracking System
• KDE Developer's Journals