Update last_world_pos considerations

[KheirFerrum]

Summary

SUMMARY: Bugfixes "Update last_world_pos considerations"

Purpose of change

Several issues noted with current version, namely

• Saving the game and returning to the main menu does not update last_world_name properly
• last_world_pos returns wrong offset on deleting/creating a world.

First issue has been solved on DDA but I was unable to git blame the commit, though I was able to find the solution code. If someone is willing to step forward with the commit I will add them as co-author.

Second issue was solved on DDA as well, but produced more issues and in my opinion was inefficient.

• Update Load menu world selection on create/delete CleverRaven/Cataclysm-DDA#64795 and subsequently Fix nullptr-> crash when aborting world creation CleverRaven/Cataclysm-DDA#65124 solved it via making last_world_pos a class variable and incrementing/decrementing it on world create/delete

In general, I believe that derived indexes should only be regenerated instead of modified, as this prevents any risk of segfaults and keeps the code easy to follow.

In a similar vein, I don't believe that such indexes should be saved as class variables, as you will need to remember to update them every single time you code for dependent value changes instead of letting it be regenerated.

Describe the solution

Added code to update last_world_name and last_character_name on saving the game.

Added get_world_index() function using existing std::find code. Now last_world_pos is updated every redraw. The effect of this on performance should be negligible on any half decent phone/computer.

Describe alternatives you've considered

• Regenerate last_world_pos only when world is created/destroyed.
  • Would be more performant, but as I consider the boost to be generally negligible, I've elected against it.

Testing

• Create 5 worlds, and make a character in the third world. Save and return to the main menu.
• Check that pointer when in load menu defaults to the third world. Move to world tab and delete either world 1/2
• Check that it still defaults to the correct world when in load menu. Move to world tab and delete one of the last 2 worlds
• Check that it still defaults to the correct world when in load menu.
• Add worlds above and below the correct world (order is alphabetical). Check that it still defaults to correct world in load menu.

Additional context

[scarf005]

Tests

Create 5 worlds, and make a character in the third world. Save and return to the main menu.
Check that pointer when in load menu defaults to the third world.

created a new character in TestA

Move to world tab and delete either world 1/2
Check that it still defaults to the correct world when in load menu.

after removing world Event

Move to world tab and delete one of the last 2 worlds
Check that it still defaults to the correct world when in load menu.

after removing world TestB

Add worlds above

after adding world asdf

and below the correct world (order is alphabetical). Check that it still defaults to correct world in load menu.

after adding world zzz

LGTM