Exercise 5: Adding a user interface screen

Let us add a nice user interface screen to adjust the logger interval. Create a new file called /etc/e-smith/web/functions/loggerdemo, with the following contents:

#!/usr/bin/perl -wT
# vim: ft=xml:

# heading     : Demo
# description : Logger
# navigation  : 1000 1000

use strict;
use warnings;

use esmith::FormMagick::Panel::loggerdemo;

my $f = esmith::FormMagick::Panel::loggerdemo->new();


    <page name="First" pre-event="print_status_message()"


            options="'disabled' => 'DISABLED', 'enabled' => 'ENABLED'"

        <subroutine src="print_button('SAVE')" />

The file above describes the panel layout, which is written in FormMagick XML. Further details about FormMagick can be fiound in the Section called An overview of FormMagick in Chapter 10.

Another file provides the implementation, which goes into /usr/lib/perl5/site_perl/esmith/FormMagick/Panel/loggerdemo.pm:

#!/usr/bin/perl -w 
package esmith::FormMagick::Panel::loggerdemo;

use strict;
use warnings;
use esmith::ConfigDB;
use esmith::FormMagick;

our @ISA = qw(esmith::FormMagick Exporter);

our @EXPORT = qw();

our $VERSION = sprintf '%d.%03d', q$Revision: 1.1 $ =~ /: (\d+).(\d+)/;

our $db = esmith::ConfigDB->open or die "Couldn't open ConfigDB\n";

sub get_status
    return $db->get_prop("loggerdemo", "status");

sub get_interval
    return $db->get_prop("loggerdemo", "Interval");

sub change_settings
    my $fm = shift;
    my $q = $fm->{'cgi'};

    $db->set_prop('loggerdemo', 'status', $q->param("loggerdemo_status"));
    $db->set_prop('loggerdemo', 'Interval', $q->param("loggerdemo_Interval"));

    unless ( system ("/sbin/e-smith/expand-template", "/etc/crontab") == 0 )
        return undef;



Note: This code example calls expand-template. This is used for illustrative purposes only. All templates should be expanded by signalling events.

Similarly to events and actions, the /etc/e-smith/web/functions/ directory is a repository of potentially available functions. To make the new function actually show up in the user interface, create a symbolic link to it from the web manager cgi-bin directory, as follows:

    cd /etc/e-smith/web/panels/manager/cgi-bin
    ln -s ../../../functions/loggerdemo loggerdemo

Now, make sure the permissions and ownership are correct so that the web server can run your new function:

cd /etc/e-smith/web/functions
chown root:admin loggerdemo
chmod 4750 loggerdemo

We also need to run a program to rebuild the navigation bar. This is only required when adding or removing functions from the manager, and is normally handled automatically. Let's do it manually for now:


Try the server manager now, reloading the navigation bar in your browser, if necessary. You will see a new category called Demo and a new function within it called Logger. It will look a bit bare with some upper-case words which signify phrases which have not been localised. We'll fix that in a moment.

Try experimenting with it - it is a nice little user interface for playing with the logger customization. Every time you change the settings, notice that the /etc/crontab file is updated appropriately.

Adding localizations

The SME Server is designed to support localization into any language. This is done by small files which describe the mapping from the upper case tags (seen above) to the appropriate words for the local language. Enter the following into /etc/e-smith/locale/en-us/etc/e-smith/web/functions/loggerdemo

<lexicon lang="en-us">
    <!-- vim: ft=xml: 
        <trans>Logger demo</trans>








Now, re-select the Logger function and the tags should now be replaced by English phrases. We can very easily add translations for other languages by adding new locale files in the same hierarchy.

Note: The LABEL_LOGGERDEMO_INTERVAL tags has intentionally been left untranslated. Why don't you fix it now?