Spellcasting Monsters Misjudge Circular Distances

[worm-girl]

Describe the bug

Monsters who can cast spells do not appear to correctly be judging the distance to the player along diagonals. Spellcasting monsters are sort of rare and most monsters cast spells infrequently (moving up to melee if they flub a cast) so I'm not surprised this didn't get noticed.

Attach save file

N/A

Steps to reproduce

Make a new game with circular distances on.
Give a monster a spell via special_attacks with a fixed range. Set that monster's cooldown to 1, so that it will try to use the spell every turn.
Try standing at certain diagonal angles. The monster will stand just out of reach and try unsuccessfully to cast on you over and over again.
Set the distances to square and see that this does not happen.

Expected behavior

Monsters should not try to cast spells when they're out of range just because they can't do trigonometry.

Screenshots

No response

Versions and configuration

• OS: Windows
  • OS Version: 10.0.19045.3930 (22H2)
• Game Version: 0.G-7246-g7af851e7c2-dirty [64-bit]
• Graphics Version: Tiles
• Game Language: System language []
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food],
  Portal Storms Ignore NPCs [personal_portal_storms],
  Slowdown Fungal Growth [no_fungal_growth]
  ]

Additional context

I think the relevant code is at line 295 in mattack_actors.cpp

    // Bail out if the target is out of range.
    if( !spell_data.self && rl_dist( mon.pos(), target ) > spell_instance.range( mon ) ) {
        return false;
    }

I discovered this while working on #71584 . I'd fix it myself but I'm not actually sure what's wrong.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. Please do not bump or comment on this issue unless you are actively working on it. Stale issues, and stale issues that are closed are still considered.