Developing C/C++ Applications with the KDevelop IDE

A sample implementation to help you get familiar with KDE's IDE and Qt Designer.
The Example Application

For this article, I've tried to come up with a useful example that will be simple to follow but still complex enough to provide the facilities to enhance it on you own at a later time.

To build something unique I thought about my early days with UNIX--I had a total lack of understanding of what an environment variable was. Every book maintained it, but I just didn't understand its simplicity.

Now, I don't want to make any assumptions about whether all readers know this, so, as a basic explanation, an environment variable is just a name that the shell, say bash, interprets as a synonym. A well-known variable is the PATH variable that contains all the directories containing programs that you want to call directly, without the directory name. Other good ones are the KDEDIR and QTDIR variables. To set these up permanently, edit your .bashrc (assuming your shell is the bash shell) located in your home directory. A little frontend that will give you an insight as to what your current values are, and being able to add or edit these and even to disable/enable them would be great.

Creating Projects

To start your very first project, select Project-->New Project from the menu. You'll then see the KDE Application Wizard (Figure 2).

Figure 2. KDE Application Wizard

Here, you're offered a whole variety of application templates. First, a whole set of KDE application and library types, a simple single-window application (KDE2-Mini), a full-featured framework application containing a menubar, toolbar and statusbar (KDE2-Normal), and another one using the MDI (multiple document interface) system. There are also templates for a KDE panel applet, a Konqueror/KParts plugin using the KDE 2 component system, and a KIO-Slave component that utilizes KDE 2's architecture to define a protocol and write a handling implementation based on the KIO library. Examples are the HTTP and the FTP I/O-slaves among others, but as a user you're already familiar with these if you're using, for example, KDE 2's filemanager and the Konqueror web browser.

Other project templates you'll find here are Qt-only application types, a GNOME template for programming with the GTK+ toolkit and plain C and C++ templates for writing console applications. Select the KDE 2 Mini application type as your first step in our example application; then click on the Next button on the bottom of the page to go to the next step. Here, enter the project name in the first edit line. As we want to write a good sample application that can be of some use later on, we should first think about a useful name.

As most KDE applications start with a K, like Konqueror or KMail, let's choose KEnvEdit as the project's name. The rest of the page should be filled out already; if not, please fill in the empty fields for your name and e-mail address. These should be filled out because all files will contain your name and address, so that everyone knows that this code is copyrighted by you. Press the Create button to generate the project. When the build process is finished, you can leave the wizard by selecting Exit.

KDevelop will now load the new project; in fact, you're ready to start off with actual code. As a short test, press the button that looks like a wheel on the toolbar; this will compile your application and run it for a test.

The compiler will show all the messages in the output window. This is important to know in case you run into compiling errors. When everything is working, either close the application window or press the Stop button in KDevelop. On the left you can see that your IDE contains a class browser that displays the contents of your source files sorted by their class and function names.

Make yourself comfortable with browsing the three files of your application that you already have: the KEnvEdit class declaration, the implementation heads for the constructor and destructor and the main() function.

Next, we will create the graphical user interface for our program. This is the fun part of application construction, so let's move on.

The Qt Designer

After you've finished with generating the project, your graphical user interface is far from being complete--it consists of a single, empty mainwindow. We will extend this by designing the user interface of the main dialogue with the Qt Designer, so please make sure that you have it installed and working (click on the Dialogeditor button for a test; the Designer should come up). Then, select File-->New in KDevelop. The new file dialogue will have some templates listed, among which you'll see a Qt Designer file. Select this entry and enter kenveditdlg.ui as the filename, then press OK.

The file is now generated for you, and the Qt Designer will show up with a dialogue to select a template for your dialogue. Choose Dialog and press OK. When you've reached this step, you're done for the most part--the GUI construction itself can even be done by someone who never even touched a C++ book. Now, you can see what our first dialogue will look like (Figure 3).

Figure 3. Qt Designer by Trolltech

The upper part of the dialog is the main window of our application; the lower one is a helper dialog that we also will have to create so that users can add new entries or change some of those that are already there. They are both shown here so you can play with Designer until you have the same look in your dialogue when following this tutorial.

What things should you watch out for especially? First of all, give the items that you need to access later with code useful variable names. Also, the dialogue's name item in the box on the left must be changed to KEnvEditDlg because that's the name of the class that will be generated out of this user interface by the template framework. Then, in KDevelop, change the inheritance of the class KEnvEdit from QWidget (the base class for all user interfaces in Qt/KDE) to KEnvEditDlg.

Now, back in Designer, connect the appropriate buttons with the connect signals/slots to the main window by dragging a line from the button to the main window. Both will be marked with a purple frame so you can see which item you connect to which widget. In the connections dialogue, you have to connect the signal clicked() with the appropriate functions (slots); as the dialogue template only offers two slots, accept and reject, we have to define our own. Use the name slotQuit(), for example, for the Quit button. An accelerator key (marked with an underline beneath the letter that you would use on the label of a button) can be set with an ampersand placed in front of the letter you are using.

So how is this supposed to work? In Designer, you're defining your user interface graphically and assigning functions to signals of items that you want to catch and react to. From the Designer file, the uic (UI compiler) will generate a C++ class that you should not edit, as it will be overridden when you change the dialogue again. Therefore, the slots you assigned to signals are declared virtual. In a class that inherits from your generated class, you're overriding these slots and filling in your code. What's left to do is to add another dialogue, KEnvAddDlg, in a ui file called kenvadddlg.ui, where you can add and edit values, a process shown in the Designer screenshot.

KDevelop in Action

More with KDevelop

Listing 1. Example Implementation Code

The example's implementation code is available in Listing 1. Some items that need to be finished that are not exactly trivial, but I'm sure you'll get to it--this is the challenge to take when everything else is done. Feel free to send me your code at nolden@kde.org. I'll probably make a KDE control center module out of it, and it will go into the KDE distribution--things like this make the project go on and improve what we have, as well as add more value to it. Maybe you'll have so much fun programming this KDE application that you'll show up on the KDE mailing lists and on #kde at our IRC server irc.kde.org.

Ralf Nolden has been addicted to KDE for years and currently is involved in quality management and PR for KDE as well as maintaining KDevelop. He is still a student of electrical engineering at the RWTH Technical University of Aachen, Germany.

______________________

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where is qt c++ help/manual/howtos?

WebFormSubmitter's picture

Does anybody know where is qt c++ help/manual/howtos?
I just started to learn KDevelop & C++, created a sample KDE+QT C++ app,
and don't know what QT classes/methods are available?

How to configure KDevelop Debugger for QT project.

Koushik's picture

Hello all,
i would like to know, is there any options to configure debugger for Kdevelop. presently i am working on QT based project so i would like to debug the errors but some how i cannot. it simply does nothing if i use debug which is present in the Kdevelop IDE. i dont know how to configure it. i need it to be like a visual C++ debugger so that i can debug my code line by line. please provide appropriate information on this. Thanks

regards,
Koushik P S R

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Kdevelop is great but it is very complex for beginners and people that doesn't develop KDE applications. I prefer to use Anjuta (http://anjuta.sourceforge.net) because it is more general and the syntax highlight is better than Kdevelop.

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Different from KDevelop which finishes all the tasks under linux, Magic C++ is a kind of visual remote unix and linux C/C++ IDE under windows.You can have a look at http://www.magicunix.com . It looks just like Visual C++ and supprots for editing, compiling, debugging etc.

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Where is figure 3?

Lost with debian woody + unstable

Anonymous's picture

Hi,

I've installed a Debian woody since Saturday (I'm new to Debian, i've used SuSE for several years) with some parts from unstale (kde within them).

I've downloaded kde-develop, I've also qt-designer installed but kdevelop seems to not be well configured.

First, documentation files... Where are the paths to them? I cannot build my KDE books, nor C/C++ reference...

Then, Qt-Designer; I've it installed, I can run it from outside KDevelop but after creating the sample application as KDE-Mini one there's no Form Dialog and not dialog editor button neither...

Well... Is there anyone here that can help me? Thanks a lot.

Re: Lost with debian woody + unstable

Anonymous's picture

Try to ask at #debian (/server irc.openprojects.net)

Re: Lost with debian woody + unstable

Anonymous's picture

apt-get install c-cpp-reference kdevelop kdevelop-data kdevelop-doc

all from unstable (attach /unstable to each package name)

Re: Lost with debian woody + unstable

Anonymous's picture

Thanks,

I did not installed c-cpp-reference and kdevelop-doc. Now I've it but Kdevelop still fails on setup. It says that "The documentation of the kde-library could not be found. It will be automatically generated in the next step". But then it ask me for the path of kdelibs and I can found them; it claims for the sources, that probably I've not installed but as I have now kdevelop-doc I think I'll no more need that sources... Could it be I can solve this later without installing that sources.

On the other hand, when I'm indexing the documentation (Qt only, as Kdevelop docs. are not found), it says that an 'htdig.conf' not were found... but I've htdig installed and an /etc/htdig/htdig.conf... I've tried linking that file from /etc/htdig.conf but it doesn't work... any ideas?

Thanks a million!

Re: Lost with debian woody + unstable

Anonymous's picture

apt-get install kdelibs3-doc

Re: Lost with debian woody + unstable

Anonymous's picture

p.s. try

apt-cache search kdelibs

to find packages related to kdelibs.

Re: Lost with debian woody + unstable

Anonymous's picture

p.s. try

apt-cache search kdelibs

to see packages related to kdelibs.

Now if it just had VIM..

Anonymous's picture

An IDE would be really nice if for nothing else than having a fast way to view classes in a program and bounce around between them, but without VIM as the editing component, it's too painful to bother with.

Re: Now if it just had VIM..

Anonymous's picture

The editor interface is generic so once kvim is completed you could use that :=)

Re: Now if it just had VIM..

Anonymous's picture

is anyone implementing kemacs to be used as a editor komponent on kdevelop?

Re: Now if it just had VIM..

Anonymous's picture

i'd love that too, but i don't really feel up to implementing it :)

Re: Now if it just had VIM..

Anonymous's picture

emacs 21 rocks. I use the viper-mode to get the good features of vi.

--

Only opinion

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

ehrm....

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Ralf, you're a KDevelop developer, have a KDE.org email address, and you claim thet 1.4 w/2.1.1 is the latest release of KDevelop??? I'm running debian/sid, with 2.2.2, and my KDevelop claims that it is 2.0.2. Anyways, good article, even it it looks like it should be dated March 6th, 2001 :-)

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

I am used to program in VB and i find it av very good short introduction.

regards RP

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

I am currently using VisualFoxPro 6.0 to develop inhouse applications at work. With the arrival of Qt 3 and its data-aware apps KDevelop / QtDesigner has reached the critical level of power that puts it in direct competition with VFP6+, VB, PB, etc... for ease of development and productivity.

As a test, I used QtDesigner to write an addressbook app that connected to my PostgreSQL database Addresses table. What was neat was that I didn't have to write a single line of code for it to work in the preview mode. I can easily flip back and forth between the dev mode and the preview mode, just as I do in VFP. Oh, the connection to the PostgreSQL database was handled by the supplied QPSQL7 driver.

Programming doesn't get any easier than this.

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

So did I, which is why I said that it was a good article...

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Score 0.... Assine comments. Did a small child write that? If you had looked at www.kdevelop.org, that the latest version is 2.1 Beta 2. Trying to sound cool you made yourself look like an idiot.

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Well, my comment made a lot more sense when this was originally posted, and Ralf had a comment about how the latest KDevelop was 1.4 that comes with 2.1.1. Now it appears to have been edited, and I'll admit I look like an ass :-) You'll note, however, that I didn't claim to be running the latest KDevelop, just that the version I *am* running was higher than what he *claimed* was the highest number. As it was obviously a typo of some sort (actually, I suspect at least a couple of the paragraphs were cut and paste from another source) my response was simply a slightly-humourous way of telling Ralf such. As for it appearing to have been written by a child, I mispelt one word. I assure you, many people who are not small children do that ;-)

P.S. *NO* I'm not saying Ralf is guilty of plagarism, just that he has undoutably written about KDevelop before, and simply lifted the introduction, rather than rewritting it. A very smart thing to do, unless you forget to proof-read it B)

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Anonymous, go buy some m$ stuff it should fit your need. Your reply to ralf is simply stupid.

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Anonymous, your reply to Anonymous is simply stupid. Please kill yourself now. Thank you.

Re: Developing C/C++ Applications with the KDevelop IDE

Anonymous's picture

Try to introduce yourself to Clint Eastwood,

very important

reem's picture

hi everybody i want to know how to make a program by kdevelop to run /stop /wait/ kill all process thanks please anyone answer me

Hello Chuck

Anonymous's picture

Hello Chuck, we are now on 3.3.1.

It rocks

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