Hello World Example

An example is worth a million words, so here is a simple one:

Example 1. Hello World applet

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#include <gtk/gtk.h>
#include <panel-applet.h>

static gboolean
hello_world_applet_start (PanelApplet *applet)
{
    GtkWidget *label;

    label = gtk_label_new ("Hello World");
    gtk_container_add (GTK_CONTAINER (applet), label);
    gtk_widget_show_all (GTK_WIDGET (applet));

    return TRUE;
}

static gboolean
hello_world_factory_callback (PanelApplet  *applet,
                              const gchar  *iid,
                              gpointer      data)
{
    gboolean retval = FALSE;

    if (g_strcmp0 (iid, "HelloWorldApplet") == 0)
        retval = hello_world_applet_start (applet);

    return retval;
}

PANEL_APPLET_OUT_PROCESS_FACTORY ("HelloWorldFactory",
                                  PANEL_TYPE_APPLET,
                                  hello_world_factory_callback,
                                  NULL)

Here are the few things that are important in this example:

While the previous example is simple, it can be useful to directly subclass the PanelApplet type. This makes it easy to have a per-applet instance private structure, among other benefits.

Example 2. Hello World applet, with a PanelApplet subclass

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#include <gtk/gtk.h>
#include <panel-applet.h>

#define HELLO_WORLD_TYPE_APPLET (hello_world_applet_get_type ())

typedef struct _HelloWorldApplet        HelloWorldApplet;
typedef struct _HelloWorldAppletClass   HelloWorldAppletClass;
typedef struct _HelloWorldAppletPrivate HelloWorldAppletPrivate;

struct _HelloWorldApplet {
    PanelApplet parent_object;

    /*< private >*/
    HelloWorldAppletPrivate *priv;
};

struct _HelloWorldAppletClass {
    PanelAppletClass parent_class;
};

struct _HelloWorldAppletPrivate
{
    GtkWidget *label;
};

static GType hello_world_applet_get_type (void) G_GNUC_CONST;

G_DEFINE_TYPE (HelloWorldApplet, hello_world_applet, PANEL_TYPE_APPLET);

static void
hello_world_applet_init (HelloWorldApplet *applet)
{
    applet->priv = G_TYPE_INSTANCE_GET_PRIVATE (applet, HELLO_WORLD_TYPE_APPLET,
                                                HelloWorldAppletPrivate);

    applet->priv->label = gtk_label_new ("Hello World");
    gtk_container_add (GTK_CONTAINER (applet), applet->priv->label);
    gtk_widget_show (applet->priv->label);
}

static void
hello_world_applet_class_init (HelloWorldAppletClass *klass)
{
  g_type_class_add_private (class, sizeof (HelloWorldAppletPrivate));
}

static gboolean
hello_world_applet_start (HelloWorldApplet *applet)
{
    gtk_widget_show (GTK_WIDGET (applet));

    return TRUE;
}

static gboolean
hello_world_factory_callback (HelloWorldApplet *applet,
                              const gchar      *iid,
                              gpointer          data)
{
    gboolean retval = FALSE;

    if (g_strcmp0 (iid, "HelloWorldApplet") == 0)
        retval = hello_world_applet_start (applet);

    return retval;
}

PANEL_APPLET_OUT_PROCESS_FACTORY ("HelloWorldFactory",
                                  HELLO_WORLD_TYPE_APPLET,
                                  (PanelAppletFactoryCallback) hello_world_factory_callback,
                                  NULL)