Chapter 1

In addition to the four C++ classes, you have to define elements of your application's GUI –
the menu, possibly some shortcut keys, and any string resources you might want to use
when localizing the application – in a resource file. In this chapter we'll briefly describe the
simple resource file used for hellogui: we'll take a closer look at resource files in Chapter
7.
Note
The stated design goal of Symbian OS is to make real, potentially large,
programs easier to write and understand. Compared with this aim,
programming a minimal application really isn't very important. As a
consequence, the document class in nonfile-based applications doesn't do
much, and the idea that the app UI is there to 'edit the document' is a bit
overengineered.
Let's have a look at how the classes in hellogui implement the requirements of APPARC,
Uikon, and CONE, and how the resource file is used to define the main elements of the GUI.
4.4 A Graphical Hello World
4.4.1 The Program
Our example program for this section is hellogui, a graphical version of 'Hello world!'. With
the aid of this example, you'll learn how to build an application for the Uikon GUI. Since the
application is intended to run on a P800 phone, I've used UIQ classes instead of Uikon ones,
but I'll point out the differences as they arise.
It will take more time to learn how a GUI program works and in this chapter we'll only briefly
comment on the C++ code itself. There's nothing particularly difficult about it, but it will be
easier to cover how such programs use C++ when we have seen more of how Symbian OS
C++ works. It's still worth getting to grips with the tools and techniques though, because we'll
be using GUI programs to show off some of the basics of Symbian OS in the next few
chapters.
Despite all the differences in the code, the build process is similar to that for hellotext: we
start with a .mmp file, turn it into the relevant makefile or project file, open up the IDE, build
the program for the emulator and check that it works. Then we rebuild for an ARM target,
copy to the target machine and run it there instead. There are, however, some important
differences:
� GUI programs must be built in such a way that Symbian OS can recognize them and
launch them. To ensure this, a program called hellogui must be built into a path such
as \system\apps\hellogui\ hellogui.app.
� GUI programs use the Symbian OS unique identifier (UID) scheme to verify that they
are Symbian OS GUI applications, and also to associate them, if necessary, with file
types identified by the same UID.
� GUI programs consist not only of the executable .app file, but also GUI data in a
resource file.
In this example, we'll start by looking at the project file for hellogui.app. We'll do a
command-line build for the emulator, to generate hellogui.app together with its resource
file, hellogui.rsc. Then we'll show how you can build the project from the IDE. Finally,
we'll build for an ARM target and transfer both files to a target machine using Symbian OS
Connect.
4.4.2 The Project Specification File