What represents 'StartupWMClass' entry from a .desktop file in Ubuntu?

Question

I am very new in developing application under Linux.

I have a doubt regarding about the use of .desktop file to add an icon into the Ubuntu Unity toolbar.

I have the following .desktop file:

[Desktop Entry]
Type=Application
#Exec=/usr/share/ConnectDataSpace/appl/launcher.sh
Exec=/usr/share/XCloud/appl/launcher.sh
Type=Application
X-GNOME-Autostart-enabled=true
#Name[en_US]=Connect Data Space
Name[en_US]=XCloud
#Name=Connect Data Space
Name=XCloud
Comment[en_US]=
Comment=
StartupNotify=true
OnlyShowIn=GNOME;Unity;
#StartupWMClass=ConnectDataSpace
StartupWMClass=XCloud
#Icon=/usr/share/ConnectDataSpace/img/icoLauncher.png
Icon=/usr/share/XCloud/img/icoLauncher.png

My doubt is: What exactly represents the StartupWMClass=XCloud field of this file?

Folder

Answer 1

StartupWMClass - If specified, it is known that the application will map at least one window with the given string as its WM class or WM name hint (see the Startup Notification Protocol Specification for more details).

Source: Recognized desktop entry keys

Silicosis

mmm it still a litle obscure for me...so if I specify the value of this field what exactly happen in my toolbar? – Folder

@Folder It does not happen something specific (what you can see it). Think as that WM class or WM name is like a hint to detect an opened window (see, for example man xprop or man wmctrl). So, it can be used to customize window matching. Here is an example: wiki.go-docky.com/…. – Ascanius