Crash detection & data restoration

[jupjohn]

As much as we try to build software that never falls over, it happens and it's usually produces one of two outcomes in chatterino:

1. The process dies, and the user restarts with everything as it was
2. The process dies, and something goes wrong with the settings files which causes them to be "reset" back to an initial state

While most crashes are harmless, chatterino still has ongoing issues with file-corrupting crashes and this annoying for users. "My chatterino died and now I've lost all of my commands/tabs" is something we've all heard.

I believe it would be worth implementing something to "handle" these file-corrupting crashes - either automatically, or with a bit of informed user intervention.

Current state

Currently, chatterino has backup files that are automatically generated (I'm not sure when). These files can be manually restored by users by copying them over, but the application doesn't actively recommend this/make it known to users.

[jupjohn]

If chatterino had some way to detect a bad shutdown, and also detect a corrupt/bad settings file(s), it could either automatically take the last backup and restore it over top; or show a popup to the user with resolution steps (directory link, what files to copy & check etc.)

[8thony]

If pajlada/settings#90 is implemented for all files (currently only window-layout.json #5647) the issue #3314 should be fixed.

If we want to go further with pajlada/settings#70 we don't save unnecessary files, so it should result in less corrupted files.

[Nerixyz]

currently only window-layout.json #5647

The other settings are backed up as well.

---

Related: #2751

[8thony]

The other settings are backed up as well.

Yes, the other settings are backed up as well, but with a different approach.

The issue #3314 describes that if no disk space is available, settings could end up with corrupt files using the old backup method.

The new backup API, writes into a tmp file first. If this fails, next time you open c2, the settings revert to the last successful save. (currently only window-layout.json)

[Nerixyz]

The new backup API, writes into a tmp file first. If this fails, next time you open c2, the settings revert to the last successful save. (currently only window-layout.json)

Both the window layout and the "regular" settings use the same API to save. The window layout doesn't use the settings library to manage the data, so we exposed the backup API for other types as well.

[8thony]

In my testing a while back on a full drive with c2 set to portable mode, all settings files got empty, and only the window layout stayed as it was before with an additional empty window layout tmp file in the same folder.
Probably I messed something up.