Module map 

Tilemaps: two 32 by 32 grids of tile indices.

One byte per cell, naming a tile the way tile describes. Which grid a layer reads is set on the layer, by bg::set_map and window::set_map; the two layers can share one. See https://gbdev.io/pandocs/Tile_Maps.html.

Wrapping

The grid is 32 cells square where the screen shows 20 by 18, and it wraps on both axes: cell 31 is followed by cell 0. Scrolling relies on that, so coordinates here are taken modulo 32 rather than checked. There is no out-of-range cell on a torus.

Structs

AttrAccesscgb

Proof that the attribute plane is the grid mapped at the tilemap addresses.

AttrGridcgb

A rectangle of attribute bytes, with the row stride of the grid it sits in.

TileGrid

A rectangle of tile indices, with the row stride of the grid it sits in.

Enums

Map

Which of the two tilemaps.

Constants

SIDE

Cells along one side of a tilemap.

Functions

edit_attrscgb

Map the attribute plane and leave it mapped for f.

fill

Put tile in every cell of a w by h rectangle.

set

Put tile in one cell.

write

Copy src in with its top left at (x, y).