创建桌面notifications

Creating desktop notifications

Posted by Steve on Sun 18 Jun 2006 at 10:20

Tags: desktop, osd, programming

There are several times when you'll be writing a script, or a program, which needs to communicate with the desktop user and here we'll look at two of the more modern approaches.

On Screen Display

On-Screen display basically means that text is displayed over the top of your existing desktop - literally in your display, without a popup window of any type.

This might be familiar to you if you've used the xmms-osd-plugin plugin for XMMS.

Using the xosd-bin package it is very simple to send text to the screen:

droot@lappy:~# apt-get install xosd-binReading package lists... DoneBuilding dependency tree... DoneThe following extra packages will be installed:  libxosd2

Once installed you can show text by running the osd_cat command with some text to display:

skx@lappy:~$ echo -e "Test Message from Steve\nTesting more" | osd_cat 

If all goes well you should see your message on your root window in the top-left corner of your screen.

The position of the message, and the colour/font used can both be modified. Here is what I tend use:

echo "Test" | osd_cat --font='-b&h-lucida-medium-r-normal-*-34-*-*-*-p-*-iso10646-1' \   --color=green \   --pos=top \   --align=right \   --offset=50 \   --indent=50

The advantage of the xosd-bin package is that it is very simple to create a notification message without any real programming. The downside is that the message can't be dismissed early - or be interacted with by the user.

If you want your user to be able to cancel/respond to the message then you'll need something else. Something like the notification daemon.

notification-daemon

There is a new program which is intended to become the standard notification mediator which handles the display of popups and user interaction.

root@lappy:~# apt-get install libnotify1 notification-daemon dbus 

(Once installed you should probably logout + login again so that the dbus daemon is setup by your session manager.)

If you want to use the notification facilities in your code you'll need to install thelibnotify-dev package which contains the appropriate header files and a shared library to link against. You will also need the GTK headers and the GLib development files. Altogether these are quite a hefty download:

apt-get install libgtk2.0-dev libglib2.0-dev libnotify-dev

Once you've installed the requirements you can compile the following sample program (actually taken from the libnotify source package):

#include <libnotify/notify.h>#include <stdio.h>#include <unistd.h>int main(int argc, char * argv[] ) {    NotifyNotification *n;      notify_init("Basics");    n = notify_notification_new ("Summary",                                  "This is the message that we want to display",                                  NULL, NULL);    notify_notification_set_timeout (n, 5000); // 5 seconds    if (!notify_notification_show (n, NULL))     {        fprintf(stderr, "failed to send notification\n");        return 1;    }    g_object_unref(G_OBJECT(n));    return 0;}

Compile it by running:

skx@lappy:~$ gcc `pkg-config --cflags gtk+-2.0`\             `pkg-config --cflags glib-2.0` \             test-basic.c -lnotify -o test-basic 

Once compiled execute it by running:

skx@lappy:~$ ./test-basic

All being well an attractive notification dialog should popup and disappear after five seconds - or when you click it.

If you are interested in compiling, or testing, the system without installing the large build-dependencies you can cheat and use runtime-loading! The following code does that:

/*  * Dynamic loading + use of the libnotify library. * * Steve * -- * http://www.steve.org.uk/ */#include <stdlib.h>#include <stdio.h>#include <dlfcn.h>int main( int argc, char *argv[] ){  /* Library + notification handles */  void *handle, *n;  /* signatures of functions we're going to invoke dynamically. */  typedef void  (*notify_init_t)(char *);  typedef void *(*notify_notification_new_t)( char *, char *, char *, char *);  typedef void  (*notify_notification_set_timeout_t)( void *, int );  typedef void (*notify_notification_show_t)(void *, char *);  /* open the library */  handle= dlopen("libnotify.so.1", RTLD_LAZY);  if ( handle == NULL )  {    printf("Failed to open library\n" );    return 1;  }  /* Find the notify_init function and invoke it. */  notify_init_t init = (notify_init_t)dlsym(handle, "notify_init");  if ( init == NULL  )  {    printf("Library function not found: notify_init\n");    dlclose( handle );    return 1;  }  init("Basics");  /* Find the notify_notification_new function, and invoke it. */  notify_notification_new_t nnn = (notify_notification_new_t)dlsym(handle, "notify_notification_new");  if ( nnn == NULL  )  {    printf("Library function not found: notify_notification_new\n");    dlclose( handle );    return 1;  }  n = nnn("Test subject", "Test body with <b>bold</b>, and <i>italic</i>!", NULL, NULL);  /* Find the notify_notification_set_timeout function and invoke it. */  notify_notification_set_timeout_t nnst = (notify_notification_set_timeout_t)dlsym(handle, "notify_notification_set_timeout");  if ( nnst == NULL  )    {      printf("Library function not found: notify_notification_set_timeout\n");      dlclose( handle );      return 1;    }  /* invoke function, 3 second timeout. */  nnst(n, 3000 );  /* Finally shpow the notification. */  notify_notification_show_t show = (notify_notification_show_t)dlsym(handle, "notify_notification_show");  if ( init == NULL  )  {    printf("Library function not found: notify_notification_show\n");    dlclose( handle );    return 1;  }  /* invoke function, passing value of integer as a parameter */  show(n, NULL );  /* close the library and exit*/  dlclose(handle );  return 0;}

You can compile this with:

skx@lappy:~$ gcc dynamic.c -o dynamic -ldl skx@lappy:~$ ./dynamic

This program could be easily adapted to read the message, and title, from command line arguments, but as a simple sample it has probably already done its job.

Note:

To use this program you'll still need to install the notification daemon, dbus, and etc. But you dont need to install the GTK, Glib, and LibNotify development packages - note that you probably should, this is just a simple hack which works only until the API changes.

转载自：https://debian-administration.org/article/407/Creating_desktop_notifications