The user wants the original tile content (map) to be readable
normally, not X-mirrored. The X-swap arrangement (canvasX = -perp
+ ...) places east tiles on the right of the screen, so X coordinates
read naturally left to right when scanning the corridor.
Combined state:
- Map content (image): drawn with normal orientation (no X-flip)
- Arrangement: east on right, west on left (X-swap)
- Labels: drawn in normal orientation in the corners
- Y-swap: north tiles (lng=+12) at canvas top -> screen top
Richard Zink
bac0397140