Development/Tutorials/KIO Slaves/Hello World

Understanding

A kioslave allows you to represent any kind of storage in a way you want. As an example, the kio_http kioslave loads data from the network over the http (protocol) and shows it rendered as html. Technically, a kioslave is a shared object plus its description. E.g. the imap4 kioslave consist of the following files:

tweedleburg:/usr/local # find -iname "*imap4*"
./lib/kde4/kio_imap4.so
./share/kde4/services/imap4.protocol

The files

We want to write a "hello world" kioslave here. This can be seen as a learning exercise and as a template for future programming projects.

CMakeLists.txt

PROJECT( tutorial )
FIND_PACKAGE(KDE4 REQUIRED)
INCLUDE_DIRECTORIES( ${KDE4_INCLUDES} . )

set(kio_hello_PART_SRCS
   hello.cpp)

kde4_add_plugin(kio_hello ${kio_hello_PART_SRCS})

target_link_libraries(kio_hello ${KDE4_KIO_LIBS})

install(TARGETS kio_hello  DESTINATION ${PLUGIN_INSTALL_DIR})


########### install files ###############

install(FILES hello.protocol DESTINATION ${SERVICES_INSTALL_DIR})

hello.h

#ifndef HELLO_H
#define HELLO_H

#include <kio/slavebase.h>

/**
  This class implements a hello-world kioslave
 */
class hello : public KIO::SlaveBase
{
  public:
    void get( const KUrl &url );
    hello( const QString &pool, const QString &app );
};

#endif

hello.cpp

#include "hello.h"
#include <kdebug.h> 
#include <kcomponentdata.h>

extern "C" { int kdemain( int argc, char **argv ); }                                    

int kdemain( int argc, char **argv )
{                                   
  kDebug(7000) << "Entering function";
  KComponentData instance( "kio_hello" );

  if (argc != 4) 
  {
    fprintf( stderr, "Usage: kio_hello protocol domain-socket1 domain-socket2\n");
    exit( -1 );
  }
  hello slave( argv[2], argv[3] );
  slave.dispatchLoop();
  return 0;
}

void hello::get( const KUrl &url )
{
  kDebug(7000) << "Entering function";
  mimeType( "text/plain" );
  QString str( "Hello_world" );
  data( str.toAscii() );
  finished();
  kDebug(7000) << "Leaving function";
}

hello::hello( const QString &pool, const QString &app )
: SlaveBase( QByteArray("hello"), pool.toAscii(), app.toAscii() ) {}

hello.protocol

[Protocol]
DocPath=kioslave/kio_hello.html 
exec=kio_hello
input=none
output=filesystem
protocol=hello
reading=true

Compile the stuff

g++ -shared -lkdeui -lkio -lkdecore -fPIC -I/usr/local/include hello.cpp -o kio_hello.so

Install the stuff

Find out where your protocols are lying:

kde4-config --path services
/usr/share/kde4/services/

cp kio_hello.so /usr/local/lib/kde4/
cp kio_hello.so /usr/lib64/kde4/
cp kio_hello.protocol /usr/share/kde4/services/

Test it

Start kinfocenter, choose hello as protocol. If this is possible, start konqueror, type hello:/// into the URL bar.