In the world of Linux, understanding the functionality and purpose of different fields in a .desktop file can be quite beneficial. One such field, the StartupWMClass, plays a crucial role in managing application windows. This article will delve into the StartupWMClass field, its purpose, and how it’s used.
The StartupWMClass field in a .desktop file is used to represent the class of the application window. It helps Linux desktop environments group windows of the same application together under a single launcher icon in the dock or taskbar.
Understanding .desktop Files
Before we dive into the specifics of the StartupWMClass field, it’s important to understand what a .desktop file is. A .desktop file is a type of file used by Linux desktop environments to launch applications. These files contain metadata about the application, such as its name, icon, and the command to start it. They are usually located in the /usr/share/applications/ directory.
The Role of the StartupWMClass Field
The StartupWMClass field in a .desktop file represents the class of the application window. It is used by modern Linux desktop environments, such as Gnome 3 and Ubuntu Unity, to group windows of the same application together under a single launcher icon in the dock or taskbar.
The value of the StartupWMClass field should match the WM_CLASS property of the application window. This allows the desktop environment to correctly associate windows with their corresponding launcher icon.
Determining the WM_CLASS Property
To determine the WM_CLASS of a window, you can use the xprop command in the terminal. The xprop command is a utility for displaying window and font properties in an X server. The WM_CLASS parameter is used to specify the window class.
Here’s how you can use it:
xprop WM_CLASSAfter running this command, you’ll need to click on the window you want to inspect. The output will display the WM_CLASS value.
The Limitations of StartupWMClass
It’s important to note that the StartupWMClass field is specific to X11-based systems and may not have any effect on systems that use Wayland as the default display server, such as Ubuntu 22+. In Wayland, the WM_CLASS property is not commonly used, so the StartupWMClass field may not have any impact.
Alternative Methods
Under different desktop environments, there are alternative methods to determine the WM_CLASS value. For example, under KDE/Kwin and Wayland, the xprop command may not work, and you can use qdbus to query the window information. In GNOME Shell, the built-in tool “Looking Glass” can be used to view the WM_CLASS value.
Conclusion
In summary, the StartupWMClass field in a .desktop file is a significant aspect of window management in Linux. It helps in grouping windows of the same application together, providing a more organized and streamlined user experience. However, its effectiveness may vary depending on the display server and desktop environment being used. Understanding its purpose and how to use it can greatly enhance your ability to manage and customize your Linux desktop environment.
The StartupWMClass field is used to represent the class of the application window and helps in grouping windows of the same application together under a single launcher icon in the dock or taskbar.
To determine the WM_CLASS property of a window, you can use the xprop command in the terminal. Simply run xprop WM_CLASS and click on the window you want to inspect. The output will display the WM_CLASS value.
The StartupWMClass field is specific to X11-based systems and may not have any effect on systems that use Wayland as the default display server, such as Ubuntu 22+.
Yes, under different desktop environments, there are alternative methods to determine the WM_CLASS value. For example, under KDE/Kwin and Wayland, you can use qdbus to query the window information. In GNOME Shell, the built-in tool "Looking Glass" can be used to view the WM_CLASS value.
