Jan-Marek Glogowski authored Jul 15, 2019 and Jonas Ådahl committed Jul 17, 2019

LibreOffice is one big binary with explicit brandings for different
application modules. This is represented in X11 by a different
WM_CLASS setting for a window. The WM_CLASS is changed based on the
loaded document at runtime. As a result LibreOffice already offers
multiple desktop files with different icons, StartupWMClass
entries and application names.

This amendment of the set_app_id request just explicitly specifies
the use case to change a surfaces' app ID at runtime, so a compositor
implementor is made aware of it. Just as the WM_CLASS, a change of
the app ID should result in an update of the propertes of a surface
depending on the app ID, like the window icon specified in the
desktop file or a re-grouping of the surfaces in a task manager.

Signed-off-by: Jan-Marek Glogowski <glogow@fbihome.de>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Simon Ser <contact@emersion.fr>