Qt Creator shows up two times in Gnome 3 favorites bar

(edit: Sorry, I accidentally created this issue before finishing the description. The description is now finished.)

I added Qt Creator (installed via Qt online installer) as a favorite in Gnome 3 so that it is always shown in the launcher, even if it is not currently running. When I now start Qt Creator, an additional icon is shown in the launcher (see before.png). And when I click the first icon again, a second instance of Qt Creator is launched.

Expected behavior: Only one instance is launched, and it does not add an additional icon.

Fix: Add the following line to the .desktop file of Qt Creator, located in ~/.local/share/applications/DigiaQt-qtcreator-community.desktop:

StartupWMClass=qtcreator

Now, Gnome 3 can detect that the Qt Creator window belongs to the starter icon and switch to the running app instead of launching a new instance on click.

See also: http://askubuntu.com/questions/367396/what-represent-the-startupwmclass-field-of-a-desktop-file