How can I get apps to display a system tray icon?

[danirabbit]

Many 3rd party applications like Java, NodeWebkit, and Gtk2 applications don't seem to be able to display a system tray icon. Why is that? Is there a workaround?

[danirabbit]

elementary OS does not support GtkStatusIcon (commonly referred to as system tray), or the Ayatana Indicator API.

elementary OS shows indicator icons on the panel for system status and functions. This area is not intended to be extensible by third-party apps.

GtkStatusIcon (the old API for apps to place icons in the panel) has been deprecated since 2014 and is not implemented in elementary OS. As of 0.4 Loki, the panel no longer implements the Ayatana API either. It is recommended in the elementary HIG that apps not explicitly use the indicator area at all, as it is reserved for use by the system.

In addition, "system tray" APIs have always been optional and not implemented on all OSes; it was never guaranteed that a FreeDesktop operating system would implement it. As such, we recommend filing a report with application developers still using these APIs requesting that they make their app function without it.

App developers should instead use modern, cross-desktop APIs for platform integration

If you're an app developer, you can find lots of information about well-supported cross-desktop APIs for system integration, and read more on the elementary blog post about Backgrounding & System Integration. I also gave a talk at LAS 2019 about the motivations behind moving away from the system tray concept.