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343 lines
5.3 KiB
343 lines
5.3 KiB
INCLUDE "hardware.inc"
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INCLUDE "util.inc"
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SECTION "Map Data", WRAM0
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PAGEX:: DB
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PAGEY:: DB
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LAST_SCX:: DB
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LAST_SCY:: DB
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CURRENT_DATA_START::
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CURRENT_TILE_PTR:: DW
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CURRENT_TILE_SIZE:: DB
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CURRENT_MAP_PTR:: DW
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CURRENT_MAP_COLLISION:: DW
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CURRENT_MAP_WIDTH:: DB
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CURRENT_MAP_HEIGHT:: DB
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CURRENT_SPAWN_X:: DB
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CURRENT_SPAWN_Y:: DB
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CURRENT_CAMERA_X:: DB
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CURRENT_CAMERA_Y:: DB
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CURRENT_DATA_END::
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SECTION "Map Code", ROM0
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DEF INIT_SCX EQUS "((SCRN_VX - SCRN_X) / 2)"
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DEF INIT_SCY EQUS "((SCRN_VY - SCRN_Y) / 2)"
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DEF PAGE_SIZE EQU 2
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DEF STACK_OFFSET_ROW EQU 3
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DEF STACK_OFFSET_MAP EQU 1
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DEF STACK_OFFSET_LEFT EQU 0
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; Increments a 16-bit value located on the stack
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; \1 Stack offset
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MACRO INC_STACK16
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ld hl, sp + \1
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inc [hl]
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jr nz, .no_carry\@
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inc hl
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inc [hl]
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.no_carry\@:
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ENDM
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MACRO ZERO_ROW_TILE
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ld hl, sp + STACK_OFFSET_ROW
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ld a, [hl+]
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ld e, a
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ld d, [hl]
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xor a
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ld [de], a
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ENDM
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; Loads a map
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; @param hl Pointer to map metadata
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Map_Load::
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; Initialize scroll state
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ld a, INIT_SCX
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ld [rSCX], a
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ld [LAST_SCX], a
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ld a, INIT_SCY
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ld [rSCY], a
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ld [LAST_SCY], a
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ld a, 8
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ld [PAGEX], a
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ld [PAGEY], a
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; Store metadata
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ld bc, CURRENT_DATA_START
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ld d, CURRENT_DATA_END - CURRENT_DATA_START
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call memcpy
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; Write tiles to VRAM
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ld hl, CURRENT_TILE_PTR
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ld a, [hl+]
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ld c, a
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ld a, [hl+]
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ld b, a
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ld a, [CURRENT_TILE_SIZE]
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ld d, a
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ld hl, _VRAM
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MEMCPY hl, bc, d
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; Write initial map data
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ld hl, _SCRN0
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ld a, [CURRENT_CAMERA_X]
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sub INIT_SCX / 8
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ld b, a
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ld a, [CURRENT_CAMERA_Y]
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sub INIT_SCY / 8
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ld c, a
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ld d, SCRN_VY_B
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.write_rows:
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call write_map_row
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inc c
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dec d
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jr nz, .write_rows
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ret
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; Update map state based on SCX/SCY
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Map_Scroll::
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; If SCY = PAGEY, write map row
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; map coords = CURRENT_CAMERA_X, CURRENT_CAMERA_Y - 2
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; HL = _SCRN0 + 32 * (32 - page_y/8 - 2)
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ld hl, PAGEY
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ld a, [rSCY]
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cp [hl]
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jr nz, .scroll_down_check
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ld a, [rSCX]
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ld b, a
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ld a, [CURRENT_CAMERA_X]
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srl b
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srl b
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srl b
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sub b
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ld b, a
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ld a, [CURRENT_CAMERA_Y]
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cp 2
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jr c, .done
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sub 2
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ld c, a
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; a = scy/8 + (scy/8 < 2 ? 30 : -2)
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ld a, [rSCY]
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srl a
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srl a
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srl a
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cp 2
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jr nc, .loop0
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add 32
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.loop0:
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sub 2
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; hl = _SCRN0 + 32 * a
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ld e, a
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ld hl, _SCRN0
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.loop:
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ld a, e
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or a
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jr z, .write_up
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ld a, 32
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ADD16 hl
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dec e
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jr .loop
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.write_up:
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halt
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call write_map_row
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ld a, [PAGEY]
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sub 8
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ld [PAGEY], a
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jr .done
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.scroll_down_check:
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; If SCY = SCRN_Y - PAGEY, write map row
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; map coords = CURRENT_CAMERA_X, CURRENT_CAMERA_Y + 21
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; HL = _SCRN0 + 32 * ((32 - page_y) - 1)
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; TODO: Check math on these
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; If SCX = PAGEX, write map col
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; If SCX = SCRN_X - PAGEX, write map col
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.done:
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ld hl, LAST_SCY
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ld a, [rSCY]
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ld [hl], a
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ret
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; Write a row of map data into map RAM
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; @param b Map X coordinate (signed)
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; @param c Map Y coordinate (signed)
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; @param hl Start of the row to write
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write_map_row:
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push bc
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push de
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; If Y < 0, write a row of 0s
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bit 7, c
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jr nz, .zero_row
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; If Y >= MAP_HEIGHT, write a row of 0s
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ld a, [CURRENT_MAP_HEIGHT]
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dec a
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cp c
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jr nc, .begin_writing
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.zero_row:
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ld d, SCRN_VX_B
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xor a
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.zero_row_loop:
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ld a, [hl+]
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dec d
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jr nz, .zero_row_loop
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.zero_row_done:
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pop de
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pop bc
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ret
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.begin_writing:
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push hl
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; Allocate 2 bytes for map pointer
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; Allocate 1 byte for number of tiles left
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add sp, -3
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; left = number of tiles left to write
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ld hl, sp + STACK_OFFSET_LEFT
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ld [hl], SCRN_VX_B
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; HL = CURRENT_MAP_PTR + Y * CURRENT_MAP_HEIGHT
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ld a, [CURRENT_MAP_PTR]
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ld l, a
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ld a, [CURRENT_MAP_PTR + 1]
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ld h, a
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.compute_map_row:
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ld a, c
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or a
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jr z, .compute_map_row_done
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ld a, [CURRENT_MAP_HEIGHT]
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ADD16 HL
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dec c
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jr .compute_map_row
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; map = HL
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.compute_map_row_done:
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LD16 de, hl
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ld hl, sp + STACK_OFFSET_MAP
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ld a, e
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ld [hl+], a
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ld a, d
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ld [hl], a
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ld hl, sp + STACK_OFFSET_LEFT
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; While X < 0 and left > 0, write 0 to the row
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.pad_left:
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bit 7, b
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jr z, .copy_center
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ld a, [hl]
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or a
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jr z, .done
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; *row = 0
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ZERO_ROW_TILE
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; row++
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INC_STACK16 STACK_OFFSET_ROW
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; X++, left--
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inc b
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ld hl, sp + STACK_OFFSET_LEFT
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dec [hl]
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jr .pad_left
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; While X < MAP_WIDTH and [SP] > 0, copy from map
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.copy_center:
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ld a, [CURRENT_MAP_WIDTH]
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dec a
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cp b
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jr z, .pad_right
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ld a, [hl]
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or a
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jr z, .done
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; A = *map_ptr
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ld hl, sp + STACK_OFFSET_MAP
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ld a, [hl+]
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ld e, a
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ld d, [hl]
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ld a, [de]
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; map_ptr++
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INC_STACK16 STACK_OFFSET_MAP
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; *row = A
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ld hl, sp + STACK_OFFSET_ROW
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ld e, [hl]
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inc hl
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ld d, [hl]
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ld [de], a
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; row++
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INC_STACK16 3
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; X++, [SP]--
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.copy_center_inc:
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inc b
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ld hl, sp + STACK_OFFSET_LEFT
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dec [hl]
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jr .copy_center
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; While [SP] > 0, write 0 to the row
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.pad_right:
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ld a, [hl]
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or a
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jr z, .done
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; *row = 0
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ZERO_ROW_TILE
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; row++
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INC_STACK16 STACK_OFFSET_ROW
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; [SP]--
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.pad_right_inc:
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ld hl, sp + STACK_OFFSET_ROW
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dec [hl]
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jr .pad_right
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.done:
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add sp, 3
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pop hl
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pop de
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pop bc
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ret
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