Start showing a bouncing icon in the Dock

[probonopd]

Start showing an animated icon in the Dock from the time launch is about to start the application onwards.

The Dock is then responsible for stopping the animated icon and show the regular application icon in case the app has launched, or just remove the animated icon altogether after a timeout, or in case the application exits.

Is there already a protocol/standard for this?

[probonopd]

https://www.freedesktop.org/wiki/Specifications/startup-notification-spec/

Still at 0.1 after 18 years!
https://specifications.freedesktop.org/startup-notification-spec/startup-notification-0.1.txt

It uses "X messages", a mechanism for sending text strings between X
clients without the need for D-Bus. Interesting!

In the language of that spec, the launch command is called a "Launcher".

The startup notification protocol involves sending X messages with the
message_type atom _NET_STARTUP_INFO_BEGIN/_NET_STARTUP_INFO to the
root window.

[probonopd]

Possibly relevant code:

https://github.com/qtinsider/qt5-meego-platform-plugin/blob/ceb11993600bfcf7aecd0e5bc5e645e26556cb1f/mplatformscreen.cpp#L315-L339

[probonopd]

There is even a whole library for it:
https://github.com/freedesktop/startup-notification