Development/Tutorials/Plasma4/GettingStarted

Creating your first Plasmoid

Tutorial Series	Plasma Tutorial
Previous	C++, Qt, KDE4 development environment
What's Next
Further Reading	CMake

Abstract

Where going to start creating a simple plasmoid in this tutorial, to keep things simple we will only create a static plasmoid, it will contain the following items.

• SVG Background
• Icon
• Some nice text

The Code

The .desktop file

Every Plasmoid needs a .desktop file to tell plasma how they should be started, and what name they carry.

plasma-applet-tutorial1.desktop [Desktop Entry] Encoding=UTF-8 Name=Tutorial 1 Comment=Plasma Tutorial 1 Type=Service ServiceTypes=Plasma/Applet

X-KDE-Library=plasma_applet_tutorial1 X-KDE-PluginInfo-Author=Bas Grolleman [email protected] X-KDE-PluginInfo-Name=plasma_applet_tutorial1 X-KDE-PluginInfo-Version=0.1 X-KDE-PluginInfo-Website=http://plasma.kde.org/ X-KDE-PluginInfo-Category= X-KDE-PluginInfo-Depends= X-KDE-PluginInfo-License=GPL X-KDE-PluginInfo-EnabledByDefault=true

The most important bits are the X-KDE-Library and X-KDE-PluginInfo-Name, they are the paste between your class and plasma, without it, nothing will start.

The header file

This is the example header file, I will add lot's of comment's in the code to explain everything.

plasma-tutorial1.h // Here we avoid loading the header multiple times

1. ifndef Tutorial1_HEADER
2. define Tutorial1_HEADER

// We need the Plasma Applet headers

1. include <Plasma/Applet>

// Define our plasma Applet class PlasmaTutorial1 : public Plasma::Applet {

   Q_OBJECT
   public:
       // Basic Create/Destroy
       PlasmaTutorial1(QObject *parent, const QStringList &args);
       ~PlasmaTutorial1();

       // This function returns the size of your applet
       QRectF boundingRect() const;
       // The paintInterface procedure paints the applet to screen
       void paintInterface(QPainter *painter, 
           const QStyleOptionGraphicsItem *option, QWidget *widget =0);

};

// This is the command that links your applet to the .desktop file K_EXPORT_PLASMA_APPLET(tutorial1, PlasmaTutorial1)

1. endif

Tip

If you have issues with your plasmoid leaving pixels behind when dragging this is almost always a result of a incorrect boudingRect()

Tip

The K_EXPORT_PLASMA_APPLET adds "plasma_applet_", please pay attention to this when setting up your .desktop file to avoid a name difference

The actual work file

Here is the body of the function, again with a lot of comments in between.

plasma-tutorial1.cpp

1. include "plasma-tutorial1.h"
2. include <QPainter>
3. include <QFontMetrics>
4. include <KIcon>
5. include <Plasma/Svg>

PlasmaTutorial1::PlasmaTutorial1(QObject *parent, const QStringList &args)

   : Plasma::Applet(parent, args)

{ }

PlasmaTutorial1::~PlasmaTutorial1() { }

QRectF PlasmaTutorial1::boundingRect() const {

   // In this tutorial we use a fixed size
   return QRectF(0,0,128,128);

}

void PlasmaTutorial1::paintInterface(QPainter *p,

   const QStyleOptionGraphicsItem *option, QWidget *widget)

{

   // First we create the objects to hold the icon and background image
   KIcon icon("document");
   Plasma::Svg* background = new Plasma::Svg("widgets/background",this);
   // Tell the Plasma/Svg object to use the whole image, 
   // instead of parts of it.
   background->setContentType(Plasma::Svg::SingleImage);

   // Now we draw the applet, starting with the background
   background->resize(boundingRect().width(),boundingRect().height());
   background->paint(p,boundingRect().left(),boundingRect().top());

   // The we place the icon and text
   p->drawPixmap(20, 0, icon.pixmap(boundingRect().width()-40));
   p->save();
   p->setPen(Qt::white);
   p->drawText(boundingRect(),Qt::AlignBottom+Qt::AlignHCenter,
       "Hello Plasmoid!");
   p->restore();

}

1. include "plasma-tutorial1.moc"