Activities' future is a bit unclear at the moment. It overlaps with functionality provided by other services and the user story for how it fits into the desktop is unclear at best. However we also have to acknowledge that some people use activities to create a workflow that works for them. Rather than taking a sledgehammer to the concept, we're performing a more surgical approach of working out what use-cases people are trying to fix at finding the best solution to deliver that.
With that comes cleaning out some of the parts we don't like and one part decided at the Plasma sprint was dropping the activity based sub-session management.
What's changing
At the moment activities can be started and stopped at runtime.
This start/stop feature (pictured above) is being dropped.
In theory there is is XSMP code performs session management on a per-activity basis. When an activity is stopped, those applications are frozen, closed as running processes and restored when the activity next gets restarted.
It's a neat idea, but in practice this rarely happens, for a range of reasons:
- XSMP is not supported in an increasing amount of apps and toolkits. Subsessions even less so, and even more less so with Wayland.
- It is blocked in almost all Flatpak/Snap applications as there's a fundamental sandbox escape in the protocol.
The vast majority of apps just move to the neighbouring activity.
Even if it did work, there's a fundamental design flaw with the entire concept.
A window/app can be on two activities at once, if it should remain open on the other activity we can't suspend it. The concept of session restoration is at odds with the cardinality of windows to activities.
Many applications don't allow multiple instances; so if you resume an activity with the application already running, it won't do anything and that's unfixable.
The end result is one that's inconsistent and unpredictable which is a state worse than not existing so we're dropping this feature.
Will I see an impact?
Not much. If you do use activities you can still switch between them as before, just with no "stop" and "start" button.