---
title: 3. Writing your first application
layout: docs
---

:doctitle: 3. Writing your first application
:notitle:

== Writing your first application

=== Building the QSkinny repository

In this chapter we will write a simple QSkinny application on Linux from scratch. As a prerequisite, a recent Qt version (>= 5.6) should be available and the directory of its `qmake` binary in the current `$PATH`. The we can build the QSkinny repository with the following commands:

[source,xml]
....
cd /home/user/dev/
git clone https://github.com/uwerat/qskinny.git
cd qskinny
qmake
make
....

This will produce the libraries `libqskinny.so` and others in the `qskinny/lib` directory. Optionally we could install the libraries to `/usr/local` via `make install`; for now we will use the ones from the local build at `/home/user/dev/qskinny/lib`. If you checked out the repository in another directory, you will have to adapt the include and library paths used below.

=== Compiling our first app

As a next step, we need to write our app. Let's start with a simple `main.cpp` file in a directory `myapp`:

.main.cpp
[source]
....
#include <SkinnyFont.h>
#include <QskWindow.h>

#include <QGuiApplication>

int main( int argc, char* argv[] )
{
    QGuiApplication app( argc, argv );

    SkinnyFont::init( &app );

    QskWindow window;
    window.show();

    return app.exec();
}
....

For now this will just create an empty window (the `QskWindow`) without any controls. Next, we need to create a `myapp.pro` file in our `myapp` directory:

.myapp.pro
[source,xml]
....
TEMPLATE = app
TARGET = myapp

INCLUDEPATH += /home/user/dev/qskinny/support \
               /home/user/dev/qskinny/src/common \
               /home/user/dev/qskinny/src/controls \
               /home/peter/temp/qskinny/src/layouts

LIBS += -L/home/user/dev/qskinny/lib -lqskinny -lqsktestsupport

SOURCES += \
    main.cpp
....

Now we can compile our app:

[source,xml]
....
cd myapp
qmake
make
....

When running the app we will have to supply the `LD_LIBRARY_PATH`:

[source,xml]
....
LD_LIBRARY_PATH=/home/user/dev/qskinny/lib ./myapp
....

This should show just an empty window.

=== Adding UI controls

Now that we have our app running, we can add some UI controls to it by extending the `main.cpp` file we created earlier. We will add some additional include directives, and then create a horizontal layout containing two push buttons. The layout with the two buttons will be shown in the window. Below is the complete updated source file:

.main.cpp
[source]
....
#include <SkinnyFont.h>
#include <QskWindow.h>
#include <QskLinearBox.h>
#include <QskPushButton.h>

#include <QGuiApplication>

int main( int argc, char* argv[] )
{
    QGuiApplication app( argc, argv );

    SkinnyFont::init( &app );

    auto* horizontalBox = new QskLinearBox( Qt::Horizontal );
    auto* button1 = new QskPushButton( "button 1", horizontalBox );
    auto* button2 = new QskPushButton( "button 2", horizontalBox );

    QskWindow window;
    window.addItem( horizontalBox );
    window.show();

    return app.exec();
}
....

Now the app is displaying the two buttons:

image::../images/writing-first-application.png[An app showing two buttons]

That's it; you just created a QSkinny application from scratch.

For information on how the controls and layouts above behave, see the next chapters.