The Event Viewer is a tool which allows to display raw data and manipulate raw data from a web browser. It is ideal to develop new algorithms without recompiling any code or writing a new framework. The disadvantage is that it is quite tedious to install. Here are some instructions.



You need php installed. Otherwise, you will not be able to run the event viewer. In Ubuntu this is the package php.

Getting FACT++

First, you need to checkout FACT++ to get the tool getevent:

[0] svn checkout

Instructions how to compile FACT++ can be found here: InstallingFACT++. Compiling it with the TOOLS_ONLY option is enough. The web source code of the viewer is located now in FACT++/www/viewer.


To run the viewer, you need the V8 JavaScript engine installed. To be moe precise, you need the libraries and the development package (headers). A version of at least 5.6 is required. As most recent distributions ship with an older version. Tif you system uses apt (e.g. Ubuntu) you can check with

[1] apt list | grep libv8

libv8-3.14-dbg/xenial amd64
libv8-3.14-dev/xenial amd64
libv8-3.14.5/xenial,now amd64 [installed,automatic]
libv8-6.4/xenial 6.4.388.18-ppa1~xenial amd64
libv8-6.4-dbg/xenial 6.4.388.18-ppa1~xenial amd64
libv8-6.4-dev/xenial 6.4.388.18-ppa1~xenial amd64
libv8-6.5/xenial 6.5.144-ppa1~xenial amd64
libv8-6.5-dbg/xenial 6.5.144-ppa1~xenial amd64
libv8-6.5-dev/xenial 6.5.144-ppa1~xenial amd64
libv8-6.6/xenial,now 6.6.313-ppa1~xenial amd64 [installed]
libv8-6.6-dbg/xenial 6.6.313-ppa1~xenial amd64
libv8-6.6-dev/xenial,now 6.6.313-ppa1~xenial amd64 [installed]
libv8-dev/xenial,now amd64 [installed]

To install a newer version, you can either compile your own version (, go to Docs; see also or install some community maintained package. Here is an example:

[2] sudo add-apt-repository ppa:pinepain/libv8
[3] sudo apt-get update
[4] sudo apt install v8-6.6 v8-6.6-dev

This will install the headers and libraries into /opt/libv8-6.6.


Now you need the module which enables php to run V8Js ( Detailed installation instruction can be found in the README*.md files (Linux instructions:

If you have root rights, the easiest is to use pecl to install V8Js:

[5] sudo pecl install v8js

It will ask you for the installation directory of v8. In this example it is /opt/libv8-6.6.

Without root rights, the best is to do it also through pecl but locally:

[5] pecl bundle v8js
[6] cd v8js
[7] phpize
[8] ./configure --with-v8js=/opt/libv8-6.6
[9] make

You should now have a file modules/ in the v8js directory.

Local web-server

You can use a system web-server (apache2), but it might be difficult to configure. Some instruction will follow at the end of this document.

The easiest is to run a local web-server in user space. Fortunately, php comes with its own web-server exactly for this purpose. Its manual is available here

Start it in the veiwer directory with

[10] cd FACT++/viewer
[11] php -S localhost:5000

The viewer should now be accessible in your browser as http://localhost:5000/index.html.

If you get an error that V8Js is not properly installed, you might need to create a file php.ini with the following contents

If that does not work, you might have to use an relative or absolute path to

Start your web-server now with

[10] cd FACT++/viewer
[11] php -S localhost:5000 -c php.ini

Now your viewer should load without an error.


If you want to use a global web-server, you can install apache2, php and libapache2.mod-php.

Usually, the default directory for user web-content is /home/user/public_html. When you think you have identified where you can put web-contents, I suggest to test if everything works properly.

Put a file info.php with the following contents there.


Now, open your browser and browse that file through your web-server, e.g. http://localhost/~user/info.php. If you see the contents of the file, you still have to work on your configuration. If you see some nice table with php information, everything is ok.

In newer Ubuntu versions, php for local directories is turned off. You need to enable it by commenting the follwing in /etc/apache2/mods-enabled/php7.0.conf

# Running PHP scripts in user directories is disabled by default
# To re-enable PHP in user directories comment the following lines
# (from <IfModule ...> to </IfModule>.) Do NOT set it to On as it
# prevents .htaccess files from disabling it.
#<IfModule mod_userdir.c>
#    <Directory /home/*/public_html>
#        php_admin_flag engine Off
#    </Directory>

Then you have to configure apache to use the new extension by adding to your php.ini (in Ubuntu it is found at /etc/php/7.0/apache2/php.ini).

Now, reload the apache configuration

[5] sudo service apache2 reload

Event Viewer

To setup the event viewer, you have to provide the paths to getevent (part of FACT++) and to your data in index.php. Add that in the following lines (the paths are just an example and should be replaced with the correct paths on your system):

$getevent = "/home/user/FACT++/build/getevent";

$path = array(
              "cal" => "/home/user/data/",
              "raw" => "/home/user/data/",
              "mc"  => "/home/user/data/",

As Monte Carlo and Calibrated data needs special preparation, you will only want to look at raw data. You can just put the same path three times.

Last modified 19 months ago Last modified on Nov 12, 2018, 2:37:43 PM