Need better session management for apps

[Christopher Townsend]

This is the master bug for better session management for apps. All other bugs affected by this will be dup'ed to this bug.

Currently, if a user closes an app using the 'X' button on the window, many bad things can happen including data loss.

If a user is editing a document and accidentally hits the X while the data is not saved, the user will not be prompted to save and the data will be lost.

Another example is Libertine helper apps can crash when Xmir is killed.

[Christopher Townsend (townsend)]

For this, we should move the handling of starting and stopping Xmir into libertine-launch and out of ubuntu-app-launch.

Then, ubuntu-app-launch should send SIGTERM to the actual X app pid and wait for the Mir window(s) to be gone. When the windows are gone, but pids still exist, then u-a-l will send SIGKILL to any remaining pids.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Michał Sawicz (saviq)]

This actually affects all apps, not only Libertine ones.

We need UAL API to only send SIGTERM to the app (ideally only the main PID, if possible), in case it wants to pop a "Do you want to save..." dialog up. When that PID exits, we should also SIGTERM (and ultimately SIGKILL) all remaining processes in the group.

Separately, we need a "kill" method that would do SIGTERM and ultimately SIGKILL (or maybe SIGKILL directly, you asked to kill after all) the whole group.

[Daniel van Vugt (vanvugt)]

Whoa, hold on.... What does SIGTERM have to do with it?

Never mind. The problem described at the top here does not occur in Mir demo servers, only Unity8. Duplicate of bug 1671424.

[Michał Sawicz (saviq)]

No, not a duplicate - bug 1671424 is about *not* signalling the processes, but just closing the windows.

This bug is about quitting the whole app at once (not all its windows in sequence) or force-quitting it for whatever reason (say, misbehaving app).

With Unity8, an app is more than just the Mir client - it's the whole group of processes managed through UAL/systemd.