Hello KDE

• This example, shown in Figure 12.16, is the same as the previous one except it is based on a KApplication object, rather than a QApplication object. Because the KApplication class is based on QApplication, there are no fundamental differences other than the addition of KDE facilities such as styles and themes, the capability to use KDE widgets, access to the standard KDE configuration, access to session management information, and the capability to launch the user's Web browser and e-mail client.

  Figure 12.16: A simple KDE program displaying text.

  
  • The KApplication object is defined in the header file kapp.h included on line 2. The kapp.h file includes the qapplication.h file, so every facility available to a Qt program is also available to a KDE program. The header files included on lines 3 and 4 hold the definitions of the QLabel and QString classes.
  • The KApplication object is created on line 8 by being passed the command-line arguments and a name for the application. This name can be used for such application-specific tasks as locating icons, receiving messages, and reading configuration information.
• Because a KDE object is being used in this program, it is necessary to include the KDE library that holds the object. There are some specialized KDE libraries, but the main two libraries are libkdecore and libkdeui.

  INCL= -I$(QTDIR)/include -I$(KDEDIR)/include/kde
  CFLAGS= -O2 -fno-strength-reduce
  LFLAGS= -L$(QTDIR)/lib -L$(KDEDIR)/lib -L/usr/X11R6/lib
  LIBS= -lkdecore -lkdeui -lqt-mt -lX11 -lXext -ldl
  CC=g++
  hellokde: hellokde.o
          $(CC) $(LFLAGS) -o hellokde hellokde.o $(LIBS)
  hellokde.o: hellokde.cpp
  clean:
          rm -f hellokde
          rm -f hellokde.o
  .SUFFIXES: .cpp
  .cpp.o:
          $(CC) -c $(CFLAGS) $(INCL) -o $@ $<
  

• The LIBS definition shows the inclusion of the libraries libkdecore.a, which contains the core functionality of KDE; and libkdeui.a, which contains all of the KDE widgets. KDE internally implements ODBC (Open Database Connectivity) by dynamically loading ODBC drivers, so it is also necessary to include the library libdl.a. The installation of KDE places these libraries in the default directory, so there is no need to add a new search path to LFLAGS.