Why do some running applications launch a new session when their icon is clicked in the launcher?

Question

Here is my problem. I locked a software's icon to the launcher. When I click it, programs run. When I click it again, it opens another session instead choosing running program. That happens virtualbox-ose, amsn, wireshark etc. How can I fix that?

Answer 1

Some of these applications detect that they are running and refer you to the open session of the software. The reasons are varied from such things as that's the way the software works to inability to share resources that need to be accessed. Virtualbox would be a good example, as it allows you start multiple VM's, or Wireshark would allow the monitoring of multiple interfaces if you could open multiple copies of the software. Hopefully this helps...

Answer 2

At the launching of an application, the launcher uses two variables to decide to start several instances of the same application or not. By example, if I install squirrel sql (a java application to browse a database) and create a launcher WITHOUT StartupWMClass, then the launcher will start several squirrel processes wich is VERY annoying !
In the file launcher that is used to start the application you can find :
StartupNotify and StartupWMClass
StartupNotify=true : we want the notification.
StartupWMClass : used to find a way to detect if the application was already started.
Please have a look at unity launcher log question