How to write applets for Wapanel

So you want to write applet for Wapanel, right?

You will need at least basic knowledge of C or/and C++, understanding of Meson build system will be useful too. But C/C++ knowledge should be enough.

Let’s start with creating directory for our applet in this guide I will name it example. Then create some basic files:

• meson.build

• example.c

They will be our basis for further operations.

meson.build should look something like this:

project('example', 'c')

library(
    'wapanel-applet-example',
    'example.c',
    dependencies: [
        dependency('gtk+-3.0'),
        dependency('wapanel-appletapi')
    ],
    install: true,
    install_dir: 'lib/wapanel/applets',
)

We have here our project name, source filename example.c, required dependencies gtk+3 and wapanel-appletapi (these two will be installed if you have wapanel in your system). Our install directory is lib/wapanel/applets that meson resolve to /usr/lib/wapanel/applets - in this directory all applets are installed system-wide. You can also install applets to:

• ~/.local/share/wapanel/applets

• besides binary in wapanel/applets directory

Let’s take a look at example.c

#include <wapanel-appletapi/appletapi.h>
#include <gtk/gtk.h>

// Called to get handy info about this applet.
wap_t_applet_info wap_applet_info() {
    wap_t_applet_info info = { .name = "example", .version = 1 };
    return info;
}

// Called when some panel need a new instance of your applet.
GtkWidget *wap_applet_new_instance(wap_t_applet_config applet_config) {
    return gtk_label_new("Hello, world!");
}

// Called when requested to remove all existing instances. GtkWidget should already be disposed by panel.
void wap_event_remove_instances() {}

// Called when panel exits.
void wap_event_exit() {}

There is slightly more code. Here is small explanation:

Includes:

• #include <wapanel-appletapi/appletapi.h>

  Include directive for applet API required for applets.

• #include <gtk/gtk.h>

  Just basic GTK include. You will need this anyways.

Callbacks:

• wap_t_applet_info wap_applet_info()

  This function sends information about your applet to panel.

• GtkWidget *wap_applet_new_instance(wap_t_applet_config applet_config)

  Panel calls this to get brand new GtkWidget, you can do some fancy stuff — remember to clean it up later.

• void wap_event_remove_instances()

  Here you can make cleaning of unspeakable things you done before.

• void wap_event_exit()

  You probably never need to write any code here.

When we have our source and build files we can make our project live! Make build directory, go to it and then call meson .. and ninja. Everything should build and you will be greeted with beautiful shared object file. Then you can put it in system path or local path as described above.

Congratulations! You just created your first applet!