island-story/src/bg.s

INCLUDE "hardware.inc"
INCLUDE "png/map/intro.inc"

SECTION "BG Data", WRAM0

BG_COLLISION_DATA:: dw
BG_MAP_WIDTH:: db

SECTION "BG Code", ROM0

MACRO update_map_info
    ld hl, BG_COLLISION_DATA
    ld a, HIGH(\1)
    ld [hli], a
    ld a, LOW(\1)
    ld [hli], a

    ld a, \2
    ld [hli], a
ENDM

BG_Init::
    ; copy map
    ld e, intro_HEIGHT
    ld bc, _SCRN0
    ld hl, intro_MAP
.copy_map_row:
    ld d, intro_WIDTH
    call memcpy
    dec e
    jr z, .done
    ld d, 32 - intro_WIDTH
.skip:
    ; skip over trailing part in vram
    inc c
    jr nz, .nocarry
    inc b
.nocarry:
    dec d
    jr nz, .skip
    jr .copy_map_row
.done:

    ; copy tiles
    ld hl, intro_TILES
    ld bc, _VRAM
    ld d, intro_NUM_TILES
    call memcpy

    update_map_info intro_COLLISION, intro_WIDTH

    ret