[android] Copy assets without blocking main thread

Carsten Hartenfelsrequested to merge
hartenfels/krita:feature/assetcopy into master

Krita copies a bunch of files from the Android assets to a normal-ish file system location on startup, since other code really expects that stuff to behave like on a real operating system. This could take so long that Android thinks the application is not responding and prompts the user to terminate it. This seems to happen with some frequency, as Play Console logs indicate.

With this commit, the copying now happens a little later, outside of the Android main thread in the Qt main thread. Since the startup application logo has disappeared from the screen at this point, we show a spinner in the middle of the screen so that the user doesn't just sit in front of a blank screen.

This also adds some additional defenses that may cause crashes: more try/catches around various points and a set to track already processed paths to avoid infinite recursion.

Test Plan

Start Krita on Android and look at it go.

Formalities Checklist

  • I confirmed this builds.
  • I confirmed Krita ran and the relevant functions work.
  • I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
  • I made sure my commits build individually and have good descriptions as per KDE guidelines.
  • I made sure my code conforms to the standards set in the HACKING file.
  • I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.
  • Does the patch add a user-visible feature? If yes, is there a documentation MR ready for it at Krita Documentation Repository?

Reminder: the reviewer is responsible for merging the patch, this is to ensure at the least two people can build the patch. In case a patch breaks the build, both the author and the reviewer should be contacted to fix the build. If this is not possible, the commits shall be reverted, and a notification with the reasoning and any relevant logs shall be sent to the mailing list, kimageshop@kde.org.

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