User wants:
- Border around each tile so they can see where one ends
- Labels in the four corners, NS-mirrored (so N is at the
bottom and S at the top, matching the tile's own NS axis)
- Labels burned in to the canvas so they always show the tile
identity during flight (not just a live overlay)
Implementation:
- Thin dark border (rgba(0,0,0,0.55), 2px) via strokeRect just
inside the tile bounds
- S at top-left, N at bottom-left (NS mirrored) in large bold
text with white fill + black stroke for contrast
- y=NNN at top-right, x=NNN at bottom-right in smaller monospace
- All labels drawn directly on the canvas before texImage2D
upload, so they're part of the texture the shader samples
Richard Zink
07017cfac6