Can't properly draw on tacmap with window scaling set to smaller windows

## Testmerges
#8676: 'Tgui update 1' by Kashargul at commit ac0e520c52
#8770: 'Sorokyne Strata - Complete revamp - Begone Snow!' by Zenith00000 at commit 75cf303759
#8624: 'Centralized Overwatch Console' by SpypigDev at commit d2507d9dc3
#8836: 'Refactors unleash_flame procs' by Nihisohel at commit 21664873ff
#8570: 'Sexier Sprites & The Soulening of Spitting' by BasilHerb at commit 0c3b23c586

## Round ID
27049

## Description of the bug
If you set your window scaling to smaller window in Preferences, you can't properly draw on the tacmap. The line you draw ends up being nowhere near where your cursor was, it's offset way up.

## What's the difference with what should have happened?
The line you draw on the tacmap should follow your cursor.

## How do we reproduce this bug?
1) Set window scaling to small windows in preferences
2) Try to draw on the tacmap canvas
3) The drawn line is nowhere near where your cursor was

## Attached logs
```
N/A
```

## Additional details
- Author: Goodwheatley
- Admin: Sgtmike
- Note: None